Advances in nanoparticles: synthesis, characterization, theoretical modelling, and applications

Resume : Ever since “magic numbers” were discovered in the mass spectra of atomic clusters (nanoparticles) in the 1980's, it has been common to see images of the atomic structures of these typically sub-5nm model nanostructures. However these images are generally either archetypal structures or the results of computer modelling, i.e., very rarely have they emerged from direct experimental measurements. In the last decade the availability of aberration-corrected HAADF STEM has begun to transform this problem [1,2]. I will address the atomic structures of size-selected Au clusters, deposited onto standard carbon TEM supports from a mass-selected cluster beam source. Specific examples considered are the “magic number" clusters Au20 (20 atoms), Au55, Au309, Au561, and Au923. The results expose (i) the size range in which the bulk fcc motif emerges, (ii) the metastability of frequently observed structures, (iii) the nature of equilibrium for nanoparticle structures - specifically the first measurement of the energy difference between two competing isomers [3], (iv) the cluster surface and core melting points as a function of size and (v) the temperature the clusters reach under e-beam irradiation. The work also exploits an ultra-stable in situ MEMS heating stage (DENS Solutions). The approach can of course be extended to other kinds of nanoparticles, including binary nanoalloys of relevance to nanocatalysis and specifically the reduction of the usage of critical metals. [1] Z.Y. Li et al, Nature 451 46 (2008). [2] Z.W. Wang and R.E. Palmer, Phys. Rev. Lett. 108 245502 (2012). [3] D.M. Foster, R. Ferrando and R.E. Palmer, Nature Comms 9 1323 (2018).

Resume : Functionalized metallic nanoparticles (NPs) display complex electronic and optical properties. In the ligand-coated metallic NPs, the surface ligands determine the interactions of the NPs with the environment as well as modify their final properties. Despite the importance of understanding the interactions between ligand molecules and metallic NP surfaces, the search for experimental methodologies able to resolve spectral features, such as charge transfer modes or the vibrational structure of excited states of molecules from nanometric volumes near metals is still ongoing. Using a new generation of electron monochromators, for which the energy spread of the electron beam can now be reduced to achieve nominal energy resolutions less than 10 meV [1], the vibrational signatures of organic systems can be detected using an aloof beam configuration aimed at avoiding ionization damage [2] and adsorbed inorganic species can be identified at the surface of nanoparticles [3]. In this presentation, we will discuss the ability of EELS to map molecular coverages using higher energy vibrational bands in functionalized isolated NPs constructs as well as the capability of EELS to capture the vibronic fine structure of the excited electronic states of molecules. We will support our findings with spatially resolved VIS spectra acquired from equivalent samples and demonstrate the ability of EELS to probe electronic excitations of molecules at the vicinity of a metal surface where, typically, signals measured under UV-Vis excitation are dominated by scattering from the metal. References: [1] O.L. Krivanek et al, Nature 514 (2014), p. 209. [2] P. Rez et al, Nature Comm. 7 (2016), p. 10945 [3] P.A. Crozier, Ultramicroscopy 180 (2017), p. 104

Resume : Melting and crystallization are fundamental and practically important first-order phase transitions in condensed-matter physics, material science and climate change, yet a detailed understanding of their relevant kinetic pathways is still evolving [1,2]. To date, many theoretical models have been developed from homogeneous classical nucleation theory (CNT) model, but they rarely address the exact preferential nucleating sites and the potentially relevant role played by defects, surfaces, dimensionality and their combinations in phase transformations [3]. Recently, Samanta et al. conducted large-scale atomistic calculation of a phase transformation process of a metal from solid to liquid and predicted that the process takes place via multiple competing pathways involving the formation and migration of point defects or dislocations [4]. Although these calculations indeed provide a rare look at real phase transformations, much confusion still exists regarding the atomistic understanding of a dynamic process of a phase transformation due to the lack of direct experimental observations at the atomic scale as well as due to the experimental intricacies in tackling such a challenging topic. Bismuth (Bi) is an ideal inorganic model material suitable for gaining insights into nucleation dynamics due to its low melting point (even down to room temperature due to size effect). Recently, Wang et al. used conventional transmission electron microscopy (TEM) to investigate a phase transformation induced by point defects in supported Bi nanoparticles under high electron dose irradiation at room temperature, and highlighted the fundamental role of defects in the phase transformation [5]. Here, we report in-situ atomic-scale observations of a real dynamic process of melting or crystallization in supported Bi nanoparticles under heating or cooling conditions using a heating holder within an aberration-corrected (scanning) transmission electron microscope. We provide direct evidence that pre-nucleation in either melting or crystallization takes places via multiple intermediate state pathways involving the formation and migration of domain boundaries, dislocations and the ordering of interface and surface at the atomic scale. The pre-melting of the nanoparticles initiates at a grain boundary and expands to interfaces and dislocations and finally undergoes a catastrophic transformation from a solid-liquid structure to a liquid droplet as a whole in a rather short time when their size exceeds a threshold value. When the size is smaller than the threshold value, the melting of nanocrystals takes place via two barrier-crossing pathways, i.e. pre-melting at grain boundary and a catastrophic solid-liquid transformation. Interestingly, pre-crystallization in a droplet occurs first at a solid-liquid interface and subsequently at the liquid surface, and eventually the droplet undergoes a fast complete transformation to a solid nanocrystal when undercooled. Thus the ability to conduct in-situ atomic-scale observation of the evolutional pathways in phase transformations of supported nanoparticles represents a significant step forward in understanding microscopic mechanisms of phase transitions at the atomic scale. The findings in the present study demonstrate that the melting/crystallization processes cannot be viewed as a simple single barrier-crossing event but as a complex multiple intermediate state phenomenon, which enhances our general understanding of nucleation and growth, melting/crystallization phenomena, phase transformations and helps to clarify atomic origins of temperature dependent behaviours in other nanomaterials and thin films [6]. References [1] AM Alsayed et al, Science 309 (2005) p. 1207. [2] H Wang et al, Nat. Commun. 6 (2015) p. 6412. [3] A Tabazadeh, YS Djikaev and H Reiss, Proc. Natl. Acad. Sci. U. S. A. 99 (2002) p. 15873. [4] A Samanta, ME Tuckerman, TQ Yu, E Weinan, Science 346 (2014) p. 729. [5] Y Li et al, Nat. Commun. 8 (2017) p. 14462. [6] J Li, Z Wang and FL Deepak, J. Phys. Chem. Lett., 9 (2018) p. 961.

Resume : Branched gold nanoparticles (Au NPs) with sharp tips, known as nanostars (NSs), have gained significant attention as they are ideal substrates for surface-enhanced Raman scattering applications. A thorough understanding of the thermal instability and reshaping behaviour of such NSs below their melting point is indispensable for such applications since elevated temperatures are reached upon laser excitation. Up to date, most studies investigated the (photo)thermal stability of large ensembles of Au NPs. On the other hand, in-situ heating experiments in a transmission electron microscope enable the direct observation of temperature-induced changes of single NPs. However, such 2D studies are limited to the investigation of simple geometries such as rods or spheres. Extending such an investigation to 3D is hampered by the need for a long acquisition time. We propose a novel acquisition method where a tilt series of 2D projections is acquired within a few minutes. By continuously rotating the holder and simultaneously acquiring projections while focussing and tracking the NP, we were able to reduce the total acquisition time for a tilt series by a factor up to 10. Our results enabled us to quantify local volume decrease/increase and to measure the local curvature of the branches. With increasing temperature, the sharp tips reshaped towards shorter and more blunt tips, which confirms that curvature-induced surface diffusion is the driving mechanism of thermal reshaping of the Au NSs.

Resume : Nano-structured catalysts, e.g. nanoalloys, display highly promising properties for a range of electrochemical reactions, e.g. for the oxygen reduction and evolution reactions (ORR/OER) and for electroreduction of CO2 (CO2R) into fuels and chemicals. The activity, selectivity and stability of the catalysts depends specifically on the composition, structure and chemical ordering of the catalyst, and the ability to predict and optimize these properties in silico holds great potential. Here, we combine interatomic potentials and density functional theory (DFT) level calculations with genetic algorithms (GA) and machine learning (ML) to accelerate the search for new compositions and structures. We present examples for nanosheets, bi- and tri-metallic nanoalloys and core-shell particles, e.g. the identification of novel mixed core-shell particles for CO2RR. Where a traditional GA enables optimisation of a single variable, e.g. stability or activity, but we also present a new ML-GA approach, which allows for a multi-objective optimisation, where two or more variables can be searched simultaneously, yielding a substantial reduction in the number of minimization steps needed. Finally, a computationally fast approach to identify and correct for intrinsic DFT-errors is also presented. The approach, which utilizes an ensemble of different exchange-correlation functionals to identify errors associated with specific bonds, is demonstrated for CO2R and OER.

Resume : NH3 decomposition over Ru/Al2O3 catalyst for hydrogen and nitrogen production is studied theoretically and experimentally. A square-base pyramidal Ru30 cluster on γ-Al2O3 (100) surface, as a representative, is considered as a model structure catalyst used for the theoretical simulations. First-principles calculations is firstly performed to determine the adsorption of NHx (x=0-3) and N2H species, and identify the transition states of all considered reactions over Ru30/Al2O3 catalyst. Comparing with the two N atoms recombination reaction, the energy barrier of generation N2 molecule by the reaction of NH2 attacking N2H (N2H NH2 =N2 NH3) decreases greatly, ~1.20 eV. Thus, the N2 formation is not the rate determining step in the present study. Microkinetic modeling is further applied to estimate the temperature dependence of NH3 conversion according to the experimental conditions. The apparent activation energy obtained in this study (80.2 kJ/mol) is in good agreement with the previous experimental values (ranging from 79 to 122 kJ/mol).[1-3] The theoretical simulation results are further verified from our experimental investigation. References: [1] T.V. Choudhary, C. Svadinaragana, D.W. Goodman, Catal. Lett. 72 (2001) 197. [2] W. Zheng, J. Zhang, H. Xu, W. Li, Catal. Lett. 119 (2007) 311.

Resume : Exohedrally metal decorated carbon fullerene structures were proposed as a good hydrogen storage material. The geometry of the coverage of the decorating atoms play a key role in H2 adsorption. It is very difficult to predict stable low energy configurations of a fullerene decorated with M metal atoms, due to the huge number of possible structures. In this work, we have found new ground states of atom decorated C60 by employing an unbiased structure prediction method based on the Minima Mopping Method coupled to the BigDFT density functional code. Moreover, we present for the first time a fully ab-initio unbiased structure search of the configurational space of decorated C60 fullerenes in the presence of an electric field. The electric field reverses the energetic ordering of low energy structures and leads to an agreement with experimental measurements. We determine the energetically most stable configurations for a wide range of metal decorations and for a varying number of decorating atoms. An analysis of the electron localization function (ELF) suggests that we can predict the behaviour of decorating atoms on the C60 surface by just analysing the bonding of a single atom to the C60 .

Resume : We perform first principles calculations to study the structure and properties of a Ti nanoparticle in various oxidation states.[1] We consider a decahedral morphology consisting of 181 Ti atoms with ten triangular (111) facets.[2] The most energetically stable oxidised nanoparticles are determined by systematic consideration of alternative configurations. First, we adsorb one, two, four and six oxygen atoms on the surface of nanoparticle to determine the stable structures. Linear Oad-Ti-Oad bonding configurations are found to be most stable. Next, we increase the oxygen content on the surface to 20, 40, 60, 80, 100 and 150 oxygen atoms. The results show that the average adsorption energies per oxygen atom are -5.79, -5.84, -588, -5.81, -5.75 and -5.48 eV, respectively. The 60 oxygen atom configuration has the most stable adsorption energy because it maximises the number of linear Oad-Ti-Oad bonds. The calculations also show the Ti lattice strain on the surface is increased from 2.0 to 8.2% with increasing oxygen coverage. In addition to the equilibrium configurations of the surface oxidised Ti nanoparticle, we also calculate the energy barrier to further oxidation by penetration of surface oxygen atoms into the nanoparticle subsurface. [3] We find that for higher oxygen coverages subsurface oxidation becomes more favourable driven by the increased lattice strain and occurs preferentially in the middle of the (111) facets. The energy barrier to diffusion decreases by around 0.1 eV for each 1% increase in surface strain. These results provide atomistic insights into the role of strain in nanoparticle oxidation. [1] Shih-Hsuan Hung and Keith P. McKenna, First-principles investigation of titanium nanoparticle oxidation, J. Phys. Chem. C, 2018, 122, 3107−3114 [2] Francesca Baletto and Riccardo Ferrando, Structural properties of nanoclusters: Energetic, thermodynamic, and kinetic effects, Rev. Mod. Phys., 2005, 77, 371-423 [3] Ji Liu,a Xiaofeng Fan, Changqing Suna and Weiguang Zhu, Oxidation of the titanium(0001) surface: diffusion processes of oxygen from DFT, RSC Adv., 2016, 6, 71311−71318

Resume : Bulk ZnO is a wide band gap semiconductor (Eg = 3.37eV, 298K), with a high excitonic binding energy (60 meV) making it a popular material in the photovoltaics industry. Carefully controlling impurity doping in ZnO can allow its properties to range from an insulator to an n-type semiconductor, with reports of p-type conductivity in ZnO crystals when doped with group V elements. ZnO, therefore, has many applications. While impurity doping is a well established method for band-gap tuning in ZnO, band-gap energetics has also been manipulated using quantum confinement effects (observed coupling between changes in atomic structure and electronic band-structure exhibited by nanoscale or low-dimensional materials). For quantum dots of ZnO, reports of band-gap values range from 3.64 eV to 4.72 eV for particles of radii 4.25nm and 2.17nm, respectively. Moreover, there are plenty of computational studies of even smaller particles of ZnO, so called nanoclusters, where the atomic structure does not resemble cuts from its bulk phase. Such studies also include the effect of doping; as in the bulk, Mg and Cd doped for Zn in these nanoclusters produces a red and blue shift, respectively. There are fewer computational studies for quasi-1D systems: most of these focus on nanotubes (NT)/and nanorods (NR), assuming an atomic structure analogous to that of carbon NT and NR. Reports from experiment and theory are not as consistent; however, there are reports that include SEM images showing ZnO NT cross-sections that are either hexagonal or circular. In this presentation I will show results from our exploration of the energy landscape for quasi-1D ZnO. Rather than constructing these structures, we have employed global optimisation techniques, and find not only the NT and NR, but other low energy minima. The energy landscape is too large for direct DFT exploration, so in this study we have developed suitable interatomic potentials that allowed us to filter out the suitable candidates. Materials software employed to evaluate each structure include GULP, Crystal, FHI-aims and Q-espresso. I will also describe the methodology developed (and implemented within G42+).

Resume : Nanotechnology has proposed in recent decades a huge variety of materials applicable in the field of nanomedicine. Among them dye-doped silica nanoparticles (DDSNs) offer all the required features to obtain very effective tools for diagnostic and therapeutic applications. Proper design and derivatization of DDSNs yield particularly stable, very bright nanosystems displaying multiple functions, for either photoluminescence (PL) or electrochemi-luminescence (ECL) sensing, labelling or imaging applications. [1-3] In this context, we have developed a direct micelle assisted strategy based on high molecular weight Pluronic surfactants yielding core-shell PEGylated silica nanoparticles endowed with very high monodispersity and colloidal stability in physiological media. These nanoparticles were recently reported with the acronym PluS NPs (Pluronic Silica NanoParticles) and have a silica core of about 10 nm, and an overall hydrodynamic diameter of about 25 nm [2-3]. PluS NPs can be tailored for optimization of processes such as directional energy transfer, providing systems with extremely valuable functions: high light-harvesting capability, signal-to-noise maximization, multiplexing, and signal amplification [3]. In particular, the use of coordination compounds, thanks to a deep knowledge of the mechanisms leading to signal generation, has allowed us to prepare very efficient systems as promising labels for ultrasensitive bioanalyses [4]. References [1] M. Montalti, L. Prodi, E. Rampazzo, N. Zaccheroni, “Dye Doped Silica Nanoparticles as Luminescent Organized Systems for Nanomedicine”, Chem. Soc. Rev., 2014, 43, 4243. [2] E. Rampazzo, S. Bonacchi, D. Genovese, R. Juris, M. Marcaccio, M. Montalti, F. Paolucci, M. Sgarzi, G. Valenti, N. Zaccheroni, L. Prodi., Coordination Chemistry Reviews, 2012, 256, 1664. [3] D. Genovese, E. Rampazzo, S. Bonacchi, M. Montalti, N. Zaccheroni, L. Prodi, “Energy transfer processes in dye-doped nanostructures yield cooperative and versatile fluorescent probes”, Nanoscale 2014, 6, 3022-3036. [4] G. Valenti, E. Rampazzo, S. Bonacchi, L. Petrizza, M. Marcaccio, M. Montalti, L. Prodi, F. Paolucci, "Variable Doping Induces Mechanism Swapping in Electrogenerated Chemiluminescence of Ru(bpy)32+ Core-Shell Silica Nanoparticles", J. Am. Chem. Soc., 2016, 138, 15935.

Resume : In recent years, functional nanoprobes with multiple imaging modalities have become an emerging field of biomedical research. In this study, we utilized a facile hydrothermal method for the preparation of magneto-fluorescent bimodal carbon dots doped with dysprosium (Dy-CDs). The prepared Dy-CDs have shown a good colloidal stability in a water solution and strong blue–green fluorescence, with a maximum at 452 nm. In addition, the excellent transverse relaxivity of the prepared Dy-CDs (r2 = 7.42 ± 0.07 mM−1s−1) makes them also suitable for T2-weighted magnetic resonance imaging (MRI). Thus, synthesized Dy-CDs could be potentially utilized for both MRI and fluorescence imaging of living cells.

Resume : Nanoprisms (NPrs) exhibit size-dependent optical properties and can be synthesized to exhibit strong absorption in the near-IR range, which corresponds to the ‘biological window’ and is the most suitable for biomedical applications.[1] Nowadays, the synthesis of NPrs does not produce a complete conversion of gold into anisotropic nanoparticles, and nanospheres are obtained as side product. This method often requires the use of cetyltrimethylammonium bromide (CTAB). CTAB is the most widely used and convenient surfactant for high-yielding syntheses of Au nanorods and nanoprisms even though it is known to be toxic. Previously, our group reported a high-yielding synthesis of NPrs which avoids the use of CTAB. [2] However, this protocol also generated nanospheres. Our contribution consists of the use of a small non-toxic additive for the selective quantitative precipitation of gold nanoprisms allowing for a fast CTAB-free scalable synthesis of gold NPrs. These materials have been characterized by several techniques (UV-vis-NIR spectroscopy, SEM, ζ-potential and electrophoresis gel) to compare their stability in different conditions and the influence of the purification method in the adsorption of proteins. References [1] Pelaz, B.; Grazu, V.; Ibarra, A.; Magen, C.; del Pino, P.; de la Fuente, J. M. Langmuir 2012, 28, 8965–8970. [2] Alfranca, G.; Artiga, A.; Stepien, G.; Moros, M.; Mitchell, S. G.; de la Fuente, J. M. Nanomedicine (Lond.) 2016, 11, 2903–2916

Resume : Metal phosphides, Zn3P2, Cd3P2, InP, are an important class of semiconductor quantum dots with applications ranging from light emitting diodes to biomedical imaging.1 The extreme sensitivity of metal phosphide quantum dots to air and moisture require the development of robust surface passivation strategies to truly harness their potential in the above applications.2 To create such robust surface passivation strategies, a thorough understanding of metal phosphide surface chemistry and interfaces is required.2 Our group has recently demonstrated the use of both solid and liquid state NMR as a tool to determine the chemical environment of the quantum dot surface, including the type of chemical species bound to the surface, and the level of oxidation.3-5 With lessons in hand we could go on to create oxide free InP nanocrystals, allowing us to study surface passivation strategies via a clean, native interface.6 Here I will discuss how an understanding of metal phosphide surface chemistry and interfaces leads to drastic improvements in the synthesis and optical properties of metal phosphide quantum dots. Synthetically size tunability towards previously unattainable size ranges for InP will be discussed. From an optical perspective, key optical properties (emission linewidth, quantum yield) for InP and Cd3P2 quantum dots will also be discussed. Highlighting the importance surface chemistry and interfaces play in unlocking the true potential of these emerging materials. 1) B. A. Glassy, B. M. Cossairt Small 2017, 13, 1702038. 2) M. A. Boles, D. Ling, T. Hyeon, D. V. Talapin Nat. Mater. 2016, 15 141-153. 3) A. Cros-Gagneux, F. Delpech, C. Nayral, A. Cornejo, Y. Coppel, B. Chaudret J. Am. Chem. Soc. 2010, 132, 18147-18157. 4) H. Virieux, M. Le Troedec, A. Cros-Gagneux, W.-S. Ojo, F. Delpech, C. Nayral, H. Martinez, B. 5) Chaudret J. Am. Chem. Soc. 2012, 134, 19701-19708. 5) W.-S. Ojo, S. Xu, F. Delpech, C. Nayral, B. Chaudret. Angew. Chem. Int. Ed. 2012, 51, 738-741. 6) E. A. Baquero, H. Virieux, R. A. Swain, A. Gillet, A. Cros-Gagneux, Y. Coppel, B. Chaudret, C. Nayral, F. Delpech Chem. Mater. 2017, 29, 9623-9627.

Resume : The issue of removing unwanted bacterial biofilms using conventional approaches (eg chlorine based chemicals) has prompted the development of new technologies. Amongst these, engineered nanoparticles (NPs) show some promise. While it has been already established that nanoparticles possess anti-bacterial properties, there is still a lack of fundamental understanding of the mechanisms involved in these actions, particularly concerning the role of the biofilm self-produced extracellular polymeric matrix (EPS). In this work we study how engineered NPs features (charge, size and hydrophobicity) combine with the EPS features (composition, density and structure) to determine NPs transport, uptake and accumulation within the biofilm. Epoxide-engineered fluorescent silica NPs were chosen as model NPs. The epoxide moieties were used as anchoring platform for further modification, aimed to change both surface charge and hydrophilicity/hydrophobicity (functionalisation with amine groups, PEG, benzoic acid or alkyl amines). Biofilms grown from two Pseudomonas strains were exposed to these NPs, and their interaction with the EPS assessed through several analytical techniques (confocal microscopy, UV-vis, IR and fluorescent spectroscopy, dynamic light scattering, Z-potential analysis). Significant differences are observed in the uptake and distribution as a function of NPs charge and surface groups, suggesting that the NPs selectively interact with biofilm EPS components.

Resume : Bacterial biofilms existing in natural and technical environments (e.g. wastewater treatment membranes and biomedical devices) consist in communities of microorganisms encased in a complex matrix of Extracellular Polymeric Substances (EPS). The EPS provides nutrients (proteins, polysaccharides, etc.) and a physical protection for bacterial cells, thus increasing bacterial resistance and making common bacterial eradication methods ineffective. In the quest for new effective antibiofouling strategies, the use of nanoparticles (NPs) has shown some promise. However, quantitative information on the NPs-biofilm interaction is still lacking, especially with regards to the role of the EPS. Here, fluorescently-labelled silica NPs were used to probe interactions in the biofilm matrix of Pseudomonas bacteria. Different NPs sizes were synthesized using both the Stober and the microemulsion method; subsequently surface functionalization with terminal groups such as amine and carboxylic acid was performed, and the effect of the different surface composition and charge in the nanoparticles uptake and diffusion into the biofilm was studied by Confocal Microscopy, Dynamic Light Scattering and Zeta Potential measurements. Amine-functionalized NPs were shown to have a stronger interaction with the biomolecules of the biofilm matrix and a better overall penetration. These preliminary results help to provide fundamental insight into NP-biofilm interactions.

Resume : Template-based wet-chemical fabrication provides a perfect approach for realizing large-scale arrays of nanostructures, mainly nanoparticles. We have developed nanostructuring techniques using anodic aluminum oxide (AAO) templates with scalable, parallel and fast processes.[1] Employing these techniques, regular arrays of surface nanoparticles and 1D nanostructures have been fabricated. The obtained nanostructures possess large-scale arrayed configuration, high structural density, perfect regularity and cost-effectiveness, and are highly desirable for constructing energy conversion and storage devices, including solar water splitting,[2-4] supercapacitors[5-6] and rechargeable sodium-ion batteries.[7-8] The device performances demonstrated that the obtained nanostructures benefit these applications through the precise control over the structural features enabled by the geometrical characteristics of the templates.[9-10] These achievements indicate the high potential and importance of template-based nanostructuring techniques for both basic research and device applications. Refs: [1] Y. Lei*, S. Yang, M. Wu, G. Wilde, Chem. Soc. Rev. 2011, 40, 1247. [2] Z. Wang, D. Cao, L.Wen, R. Xu, M. Obergfell, Y. Mi, Z. Zhan, Nasori, J. Demsar, Y. Lei*, Nat. Commun. 2016, 7, 10348. [3] Y. Mi, L. Wen, R. Xu, Z. Wang, D. Cao, Y. Fang, Y. Lei*, Adv. Energy Mater., 2016, 6, 201501496. [4] Xu R., Wen L., Wang Z., Zhao H., Xu S., Mi Y., Xu Y., Sommerfeld M., Fang Y., Lei Y.*, ACS Nano, 2017, 11, 7382. [5] H. Zhao, C. Wang, R. Vellacheri, M. Zhou, Y. Xu, F. Grote, Y. Lei*, Adv. Mater. 2014, 26, 7654. [6] R. Vellacheri, A. Al-Haddad, H. Zhao, W. Wang, C. Wang, Lei Y.*, Nano Energy, 2014, 8, 231. [7] L. Liang, Y. Xu, C. Wang, L. Wen, Y. Fang, Y. Mi, M. Zhou, H. Zhao, Y. Lei*, Energy Environ. Sci. 2015, 8, 2954. [8] Y. Xu, M. Zhou, X. Wang, C. Wang, L. Liang, F. Grote, M. Wu, Y. Mi, Y. Lei*, Angew. Chem. Int. Ed. 2015, 54, 8768. [9] H.P. Zhao, M. Zhou, L.Y. Wen, Y. Lei*, Nano Energy 2015, 13, 790. [10] Wen L.Y., Xu R., Mi Y., Lei Y.*, Nature Nanotechnology, 2017, 12 (3), 244-250.

Resume : In order to understand the size- and facet-dependent optical properties and photocatalytic activity of inorganic perovskite metal oxides, we have synthesized SrTiO3 particles with different fractions of {100} and {110} faces for the investigation of facet effects on the photodegradation of methylene blue and hydrogen evolution. SrTiO3 cubes were synthesized in aqueous solutions at 70 ºC in an oven. Particle size can be adjusted from 80 nm to 500 nm by tuning the amounts of ethanol added and precursor concentrations. SrTiO3 nanocrystals show optical size effect with smaller cubes giving a more blue-shifted absorption band. Replacing ethanol with hexanol and then heating the solution under 200 °C in autoclave gave all edge-truncated cubes, while use of ethylene glycol under the same reaction condition yielded {100}-truncated rhombic dodecahedra. UV-Vis spectra show clear optical facet effect; particles with a greater fraction of {110} facets have a more red-shifted absorption edge. SrTiO3 cubes are barely active catalyst. However, all edge-truncated cubes exposing large {110} faces show significant improvement toward both photodegradation of methylene blue and photocatalyzed hydrogen evolution in a water/methanol mixture. A modified band diagram with different band edge bending for different crystal surfaces could explain these observations.

Resume : The evaluation of metal oxides performance in terms of photocatalysis is expensive and time-consuming. Previous works have shown that a simple device based on a modified Grätzel cell is able to evaluate the photoelectric properties of oxides deposited on the cell anode. The current-voltage curve is the signature of the particle photoelectric activity. Therefore, this approach appears to be a time- and cost-effective solution to make a first discrimination between different materials proposed for photocatalytic applications, where the photoelectric charge generation is the key step. Hematite α-Fe2O3particles with controlled sizes and morphologies were synthesized following an original and environment-friendly microwave protocol. Selected morphologies were spindles, dendrites, cubes, rhombohedra, and 2D-sheets. In the spindles case, different aspect ratios were obtained by adjusting the concentration of a phosphate additive. The results have highlighted a significant effect of both particle shape and size on the photoelectric properties. The relationship between particle size and photoelectric effect has therefore been evaluated at constant morphology, only varying spindles length. Other morphologies were used to determine the relationship between particle shape and their photoelectric effect. A phenomenological model based on Lambert and Norde functions (equivalent circuit of cell) will be proposed to characterize the current-voltage curves in relation to particle shape.

Resume : Phenol is one of the organic compounds, which could be toxic with permanent health issues at high levels. The photocatalysis of phenol was studied using Cd-doped ZnO nanorods synthesized through mild hydrothermal method. The Cd-doped ZnO nanorod photocatalyst was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR), and UV-Vis spectroscopy. XRD patterns exhibit normal crystalline phase features indexed to the pure hexagonal wurtzite crystal structures, with the space group of P63mc. SEM images showed that the average particle size of synthesized Cd-doped ZnO nanoparticles was about 90 nm. Moreover, nanoparticles had less agglomeration and well-dispersed in the medium. FTIR analysis confirmed that application of surface modifier did not add any functional group on the nanoparticles synthesized. The effect of dopant on the bandgap energy reduction was confirmed. In addition, photocatalytic degradation of phenol was conducted considering the effect of various operational parameters including type of photocatalyst, pH, initial concentration of phenol, amount of photocatalyst, and irradiation time. The highest phenol removal efficiency achieved using 1% Cd-doped ZnO nanocatalyst for 20 mg/l of phenol at pH = 7, photocatalyst dosage = 3g/l, contact time= 120 min, and H2O2 = mmole. Keywords: Phenol; Cd-doped ZnO; doping; hydrothermal; photocatalyst; sunlight; pollutant

Resume : Quantum Dots (QDs) are an important class of materials that are extremely promising in the fields of photovoltaics, biological imaging, and efficient, high color purity lighting [1]. To date, the vast majority of industry uses cadmium selenide (CdSe) QDs. Their inherent toxicity, however, poses a threat to wide-scale implementation [2]. Indium phosphide (InP) and zinc phosphide (Zn3P2) are being studied as low toxicity replacements [3]. InP, although studied for several decades, still trails behind CdSe in terms of efficiency, and Zn3P2 is yet farther behind, having only recently been considered as viable. These Zn3P2 QDs could prove extremely valuable, as the reactants are nontoxic, and the constituent elements are both cheap and abundant, as a further benefit relative to InP. Both systems must see significant improvement in quantum yields and size distribution to be considered competitive with the current toxic option. We aim to understand, control, and optimize the chemistry of these less-understood alternatives by tuning precursor reactivity. Through elucidation of the reaction mechanism, and precise control of the surface chemistry as well as the ligand sphere, we have synthesized unprecedented high-quality and oxide-free InP and Zn3P2 QDs [4]. We illustrate our achievements with (i) a record low temperature synthesis of oxide-free InP QDs (150°C) and (ii) a Zn3P2 QD synthesis exhibiting size distributions and quantum yields far better than any thus far reported. Our precursor complexes show great promise in improving the safety and economy of the QD industry. 1. Boles et. al., Nat. Mater. 2016, 15, 141-153 2. Derfus et. al., Nano Lett., 2004 4, 11-18 3. Glassy et. al., Small, 2017, 13, 1702038 4. Baquero et. al, Chem. Mater., 2017, 29, 9623-9627

Resume : Yttrium aluminum garnet (Y3Al5O12 or YAG) phosphor is one of the best-known synthetic garnets with remarkable properties, but in this state it has a limited number of applications. However, by doping with different metal ions (transition metals or lanthanides) for YAG has found various applications in increasingly different areas, from jewelry, to optoelectronics, biotechnology to aerospace. In this work the bottom-up (co)precipitation process was used for the preparation of Ce-doped YAG nanopowders. The impact of the cerium dopant concentration on the morphostructural and optical properties was investigated. The quality of the YAG phosphors with different doping concentrations was studied from morphology, chemical structure and optical point of view. Shape, size, defects and agglomeration tendency of the YAG:Ce phosphor particles was studied using scanning electronic microscopy. FTIR spectrometry and X-ray diffraction showed the transformations from an amorphous to a crystalline phase, as well as purity of the garnet phase and lack of impurities. The variation of luminescent properties depending on dopant concentration was highlighted by fluorescence spectroscopy. After study of the influence of dopant concentration on the YAG properties, the cerium optimal concentration was determined in order to use YAG phosphors for applications in the field of emitting optoelectronics.

Resume : Resistive switching devices are promising alternative to existing memories which may offer a potential leap beyond the limits of Flash memories (with respect to write speed, write energies) and Dynamic random access memories DRAM (with respect to scalability, retention times). A conventional RRAM cell is composed of an insulating/dielectric layer sandwiched between two metallic layers. In this talk, an overview of physical and electrochemical processes which may be the origin of the switching phenomenon in various materials will be discussed. Furthermore, novel concepts (strategies) beyond classic doping will be discussed to control device properties like signal to noise ratios and power consumption. In our work, as a first strategy, we realize the superior bipolar resistive switching characteristics of CeO2:Gd-based resistive memory device by utilizing a unusual mean of UV radiation. This non-conventional tool provides us a new degree of freedom to manipulate the performance of a memory device. Our further investigations revealed that the prototype can deliver short term to long term memory transitions which is analogous to the forgetting process of human brain, which is a key biological synaptic function for information processing and data storage. In another strategy, a non-conventional and unique “chronoamperometry” approach contrary to classic voltammetry measurements was implemented to examine the bipolar resistive switching characteristics of ceria based memory cell. Configurable device functionalities such as; categorization of minimum threshold potential to prompt switching behaviour, tuneable on/off ratios with accessible multi-level data storage states can be achieved which are hard to realize in conventional measurement setups.

Resume : Dyes are widely used in various industries. Most of them are not readily biodegradable and are consisted as toxic, mutagenic, and carcinogenic compounds. Therefore, it is essential to remove them from effluent before their discharge to the environment. Therefore, the present study was aimed at evaluating the application of tungsten oxide-doped zinc oxide nanoparticles in the photocatalytic destruction of Direct Blue 15 dye in a sequencing batch reactor. ZnO nanoparticles were doped with WO3 using the hydrothermal synthesis method. To characterize the synthesized nanoparticles, scanning electron microscopy, X-ray diffraction, atomic force microscopy, zeta potential analysis, and ultraviolet-visible spectroscopy were used. The radiation source in this study was five 6W UV lamps. Finally, operational parameters affecting the process, namely pH, light intensity, dopant percentage, dye concentration, and contact time, were evaluated.The results of the present study revealed that the efficiency of the photocatalytic process for the destruction of organic dyes was higher with acidic pH values than with neutral or basic values. In addition, upon increasing the light intensity from 172 to 505 W/m2, the efficacy of dye destruction was enhanced from 27.8% to 73.5%. Also, increasing the concentration of the dopant percentage from 1% to 5% w/v increased the destruction efficacy from 30.69% to 73.1%. Finally, increasing the initial dye concentration from 20 to 100 mg/L decreased the destruction efficacy from 86.9% to 37.5%. In summary, photocatalytic process using WO3-doped ZnO nanoparticles fixed on a glass surface was shown a good efficiency for the destruction of organic dye from aquatic solution.

Resume : Under extreme heat fluxes due to ELM’s and plasma reaching the walls of the ITER fusion plasma reactor, vaporization and melting is most likely to occur. The behavior under extreme conditions of plasma facing components is of great interest. Tungsten (W), beryllium (Be) and carbon (C) need to be exposed and characterized mechanically, electrically and structurally. We present a new method which could be used in metallic thin film deposition. The method is based on the vaporization and ionization process of metal wires with microwave field. We used a 2.45 GHz frequency at 800 W microwave power source. A cylindrical cavity having the TM011 propagation mode accommodated a jigging device and the metallic wires were vaporized and ionized. The metallic wires used in this experiment were made of W, Be and C. The metallic wires having 0.5 mm diameter were vaporized and ionized in direct interaction with the microwave field from the cylindrical cavity. We investigate the dependence between the metal quantity which is vaporized and ionized by the microwave field and the microwave power. Electron temperature of metallic plasma produced using the microwave generator was estimated using the ratio of atomic emission lines acquired by a high definition optical multichannel spectrometer. The crystallographic orientation and the grain size of the thin films deposited on silicon substrates were determined using XRD low angle diffractometer, SEM and AFM and correlated with the processing parameters as microwave power, and the distance between wire and the substrate holder.

Resume : Metallic nanoparticles have been at the center of much research due to their exceptional physical properties, compared to those of bulk materials, leading to potential applications in magnetic data storage, catalysis, electronic devices, and biosensors. While bulk materials exhibit constant physical properties irrelevant to their size, those of nanoparticles are dramatically changed as a result of their large surface areas. Herein we report a metal nanoparticle synthesis method based on a physical vapor deposition process instead of the conventional wet process of chemical reactions in liquids. A narrow size distribution of synthesized gold nanoparticles was obtained using an ion coater on glycerin at low vapor pressure. The nanoparticle size could be modulated by controlling the sputtering conditions especially the discharge current. Due to the formation of gold nanoparticles, a surface plasmon resonance peak appeared at ~530 nm in the absorption spectrum. The surface plasmon resonance peak exhibited red-shift with increasing size of the gold nanoparticles. Our results provide a simple, environmental friendly method for the synthesis of metal nanoparticles by combine low-cost deposition apparatus and a liquid medium, which is free from toxic reagents.

Resume : Structural insight into glassy alloys1 excites scientist across all disciplines. Despite persistent experimental and computational efforts, the exact bonding environment could not yet be fully understood due to the absence of diffraction patterns in X-ray and electron microscopy.2 Here we demonstrate a novel combination of spectroscopy and mass spectrometry which allows to correlate properties of glassy alloys with structural information. Experimentally, mass spectrometry coupled with electrochemistry was used to electrolytically etch out ions of the glassy substance which resulted in the detection of the smallest building blocks as analyzed by electrospray ionization mass spectrometry (ESI MS). Here, the Pd80Si20 system3 was chosen which resulted in three distinct ions namely Pd+, PdSi+ and PdSi2+ suggesting specific bonding of Pd to Si. These specific bonds were further confirmed by Raman spectroscopy. To understand the coordination shell around Si, 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was applied which also supports the finding from ESI MS and Raman spectroscopy. Combining all these techniques to understand the structure has not been attempted before and will reveal the microscopic structure of amorphous systems in 3D with computational support in future. Reference: 1. J. Non-Cryst. Solids 1989, 113, 167-170 2. ACS Nano, 2016, 10, 3241-3247 3. Acta Materialia, 2016, 113, 284-292.

Resume : In this work we analyze the electrical characteristics of inorganic n-channel and p-channel thin-film transistors (TFTs) using either ZnO or CuO nanoparticles as active semiconducting material. The used nanoparticles are both dispersed in water-based solutions providing the opportunity of cost efficient and large-scale integration processes. All transistors were integrated in an inverted coplanar setup. Thus, the active semiconductor was deposited during the last process step, excluding chemical stress on the nanoparticulated film during the integration routine. A spin-coated high-k nanocomposite insulates the gate electrode from the channel region. For the gate electrode 50 nm aluminum followed by 7 nm titanium were evaporated under high-vacuum conditions. A common drain and source metallization is prevented by the different bandgaps of ZnO (3,3 eV) and CuO (1,2 – 1,6 eV) requiring various electrode materials. Therefore, two different templates providing aluminum (ZnO) or gold (CuO) as drain/source electrodes were fabricated. Finally, the nanoparticle layers were applied by doctor blade processes and annealed in a convection oven under ambient conditions. As the maximum temperature is 115°C the integration process is compatible to foil substrates. Single TFTs are characterized as well as inverter circuits in complementary technology. For this purpose, a p-channel TFT (CuO) is used in the pull-up network and an n-channel TFT (ZnO) is applied for the pull-down circuit.

Resume : The reference-free synchrotron-based Grazing Incidence X-Ray Fluorescence (GIXRF) methodology qualifies as a traceable reference for a quantitative characterization of both artificially fabricated nanoparticles and nanostructures and aerosol nanoparticles. Fully traceable quantification is achieved by the use of physically calibrated instrumentation, which is available in the PTB laboratory at the BESSY II electron storage ring. In GIXRF, an interference of incident and reflected radiation results in an X-Ray Standing Wave (XSW) field. This modulates the observed fluorescence intensities of elements within the XSW and thus, allows for both a dimensional and analytical characterization of nanoparticles and nanostructures. In addition, near-edge X-ray absorption fine structure (NEXAFS) measurements can be performed to investigate the chemical binding state of elements of interest. In this work, we will demonstrate the available characterization capabilities using various examples of artificially fabricated nanoparticles and –structures and of nanoparticles, which were deposited from the aerosol phase.

Resume : Small nanocluster catalysts have large surface-to-volume ratios that allow decreasing the catalyst loading while maintaining a high number of active sites. In addition, nanocatalysts exhibit unique catalytic properties in contrast to bulk catalysts. Oxidation of CO on Pt catalysts is one of the most studied catalytic reactions. One important step for this reaction is the adsorption of the reactants (CO and oxygen) on the Pt cluster surface. In this study, density functional theory was applied to investigate the variation of both adsorption energy and CO-stretching frequencies with the size and shape of the nanoparticle and the coordination number of the Pt atoms directly bonded to the adsorbates. A series of Pt nanoparticles with sizes of 0.8 nm to 2 nm has been considered. Moreover, all possible types of non-equivalent adsorption sites for a given size were investigated. We find that there is a systematic decrease of the CO adsorption energy as size increases on truncated octahedral clusters for sites with the same coordination number. Within the same cluster size on-top and bridge adsorption is preferred at low coordinated edge sites i.e., either between two (111) facets or between (111) and (100) facets. The CO-stretching frequencies are site specific and it is planned to use them for the identification of active sites. For this purpose, the influence of co-adsorbed oxygen on the frequencies is investigated.

Resume : A wide variety of 2D materials including, graphene, molybdenum disulfide, black phosphorous, and boron nitride have been reported. Heavier Group 14 elements (i.e., silicon and germanium) 2D structures are now of considerable interest because of their vast potential in optoelectronics, energy storage, and the semiconductor industry. The synthesis of germanium nanosheets (Ge-NSs) with well-defined surface chemistry will provide a convenient approach by which Ge-NSs electronic structure and properties may be controlled. This presentation will focus on our straightforward route to modify the surfaces of freestanding hydride-terminated Ge-NSs. Furthermore, we demonstrate that following functionalization, the crystal structure of the Ge-NSs remains intact and the introduction of organic moieties to the GeNS surfaces imparts improved thermal stability and solvent compatibility.

Resume : In this study, FePd magnetic nanoparticles (NPs) were developed as artificial enzymes with high biocompatibility and reusability, named ‘magnetozymes’, in a one-pot aqueous synthesis method using glutathione (GSH) and cysteine (Cys) as surfactants. The prepared hydrophilic FePd magnetozymes can be successfully re-dispersed in water and have high zeta potentials of 21.8 and 29.5 mV for Cys- and GSH-stabilized magnetozymes, respectively. The saturation magnetizations of the Cys- and GSH-conjugated magnetozymes, measured by a superconducting quantum interference device, are 4.7 and 41.4 emu g−1, with both magnetozymes exhibiting superparamagnetism at 300 K. The catalytic activities were tested by measuring the reduction of fluorescent dye and hydrogen peroxide by optical absorption measurements and electrochemical characterization. The Cys-FePd and GSH-FePd NCs exhibited significantly enhanced efficiency, with catalytic constants more than 2- and 7- fold higher than horseradish peroxidase (HRP), respectively. Furthermore, in vitro experiments reveal that the FePd NPs clearly behave like peroxidase to reduce ROS levels in mammalian cells. The cytotoxicity was analyzed by exposing the FePd magnetozymes to different cell lines for seven days, and they showed >90% viability at concentrations up to 20 μg mL–1. The FePd magnetozymes, having high saturation magnetizations and biocompatibility, enable a variety of possible catalytic and biological applications such as recyclable peroxidase-mimicking enzymes, antioxidant agents, and biosensors.

Resume : We perform first-principles calculations to study Au nanoparticles (NPs) supported on ZnO nanowires. Our calculations aim to understand the equilibrium morphology of Au NPs and their reactivity for CO oxidation. We calculate the formation energies of low-index Au fcc surfaces ((100), (110) and (111)) and use the Wulff-construction to predict the equilibrium morphology of free Au NP (truncated-octahedral).[1] We also calculate the adhesion energies between the three Au surfaces and ZnO (1010) and (1120) surfaces.[2] For ZnO (1010), Au (111) has the most stable adhesion energy of -0.81 J/m2. While for ZnO (1120), Au (110) and (100) surfaces provides comparable adhesion energies of -0.43 J/m2. By using the Wulff-Kaishew construction, we model three different supported Au NPs on both ZnO (1010) and (1120) surfaces corresponding to different interface orientations. All the three morphologies are found to be consistent with experimental transmission electron microscopy images.[3] We also investigate the interaction of oxygen vacancy (VO) and zinc interstitial (Zni and charged Zni) defects in ZnO with surfaces and supported NPs. Finally, we investigate O2 molecule adsorption on the Au(NP)/ZnO systems and assess the energetics of CO oxidation (Au/ZnO O2(ad) CO → Au/ZnO O(ad) CO2, where the subscript ad represents the molecule or atom adsorption on Au/ZnO). [1] A. S. Barnard, X. M. Lin and L. A. Curtiss, Equilibrium morphology of face-centered cubic gold nanoparticles >3 nm and the shape changes induced by temperature, J. Phys. Chem. B 2005, 109, 24465-24472 [2] Yusuf V. Kaneti, Zhengjie Zhang, Jeffrey Yue, Quadir M. D. Zakaria, Chuyang Chen, Xuchuan Jiang and Aibing Yu, Crystal plane-dependent gas-sensing properties of zinc oxide nanostructures: experimental and theoretical studies, Phys. Chem. Chem. Phys., 2014, 16, 11471 [3] Xiaoyan Liu, Ming-Han Liu, Yi-Chia Luo, Chung-Yuan Mou, Shawn D. Lin, Hongkui Cheng, Jin-Ming Chen, Jyh-Fu Lee, and Tien-Sung Lin, Strong metal−support interactions between gold nanoparticles and ZnO nanorods in CO oxidation, J. Am. Chem. Soc. 2012, 134, 10251−10258

Resume : Rice straw, an agricultural bioresource, is utilized as a biotemplate in order to synthesize a hybrid TiO2-SiO2 structure, and the resulting products were used for removing hazardous methylene blue dye from aqueous solutions. Samples of the as-prepared hybrid TiO2-SiO2 structure are characterized by thermal gravity analysis, field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen gas adsorption/desorption measurement, and UV/vis spectroscopy. The results obtained show that the hybrid TiO2-SiO2 structure possesses both anatase and rutile phases, along with amorphous SiO2. Its specific surface area is determined to be 141.1 m2/g, and its pore size to be 3.77 nm. Light harvesting within the visible-light range is found to be enhanced by the use of this hybrid TiO2-SiO2 structure. Moreover, the photocatalytic activity and stability are also improved, as demonstrated by the degradation of methylene blue dye under UV irradiation.

Resume : Density functional theory calculations were performed on small 55-atom Pt-Ni nanoclusters to study their activity towards the hydrogen evolution reaction (HER). Two Pt-Ni compositions, Pt12Ni43 and Pt20Ni35, were studied in the gas phase and on a gamma-Al2O3 support. The critical hydrogen coverages were determined using the method based on the differential free energy of hydrogen adsorption. The free energy of hydrogen adsorption was used as a descriptor of the HER activity. Ni3 hollow sites were discovered to be the strongly binding sites for hydrogen. The clusters adsorb approximately four H atoms per facet before the hydrogen adsorption becomes endergonic, therefore the critical hydrogen coverages on the clusters are high. The obtained descriptor values are close to zero in the gas phase and on the support, suggesting that the clusters are catalytically active towards HER.

Resume : A large interest in semiconductors is observed due to their applications in electronics and renewable energy harvesting. Cu2ZnTiS4 and Cu2ZnTiSe4 are expected to show particularly appealing features which combined with their environmental harmlessness and low-cost production makes them promising materials for use in photovoltaics. Computational investigations show that these materials can have energy band gap approximately equal to that of kesterite Cu2ZnSnS4 while having about twice times higher absorption coefficient than Cu2ZnSnS4. In this study possibility of production of Cu2ZnTiS4 and Cu2ZnTiSe4 nanopowders – prepared by the high temperature reaction in solvent – have been investigated. The obtained materials have been characterized with powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy.

Resume : Often upconverting (UC) materials are referred as a very promising tool of visualization. Due to unique properties of luminescence emerging from combination of activator and sensitizer ions, UC nanomaterials has been considered as a replacement instead of conventional fluorophores in biomedicine. Excitation with a NIR (980 nm) laser is more advantageous for biological applications having deeper NIR light penetration into tissue. Moreover, UC nanoparticles are preferred for their high signal to noise ratio, photostability and low photodamage to biological samples. In this study we focused on substitution of Na+ ion with Li+ or K+ in order to investigate the impact of Na+ replacement on morphology and luminescence properties. Crystal phase of compounds containing various amounts of substituted ions in Na1-xGdF4:Lix (or Kx) was determined using XRD analysis. More detailed composition of synthesized Na1-xGdF4:Lix (or Kx) nanomaterials was investigated by ICP analysis. By adding different amounts of ions with smaller (Li+) and larger (K+) ionic radii a change in Yb-Er distance could be expected thus influencing UC luminescence. UC emission was recorded in VIS region and the ratio between emission of green and red emission bands was calculated. Furthermore, fluorescence lifetime and temperature measurements were carried out and the impact of Li+ and K+ dopants will be discussed in this study. Energy distance between 2H11/2 and 4S3/2 levels of Er3+ and sensitivity of Na1-xGdF4:Lix (or Kx) samples will be presented and discussed.

Resume : Organic-inorganic perovskite crystals have been aggressively applied to perovskite solar cells due to their attractive properties such as long carrier diffusion, am-bipolar conductivity, broad color-tunability, and their small exciton binding energy. These perovskite crystals have been also applied to various applications like light-emitting diodes (LED), photodetectors, field effect transistors, and lasers due to perovskite crystals can be simply prepared from low-cost precursors with simple solution processes1. These tremendous potential for various applications with high performance are based on perovskite electro-optical features and they are expected to be used as an alternative semiconductor material to silicon and compound materials. Recently, bright luminescence properties from methylammonium lead tri-bromide (MAPbBr3) perovskite quantum dots (PeQDs) have been reported owing to the development of methods for preparing these PeQDs. Zhang et al. developed a ligand-assisted reprecipitation (LARP) inspired by the reprecipitation method for preparing organic and nano / micro crystals. LARP can simply obtain MAPbX3 (X = I, Br, and Cl) PeQDs through mixing a solution dissolving precursors and poor solvent. Although synthesis methods representative for LARP with narrow size-distributions are of particular interest for the successful implementation of PeQDs into LED with narrow emission, size-controlled PeQDs by nanometers have not been developed. In this report, we propose Ostwald ripening as a size-tunable technique for MAPbBr3 PeQDs using ligand-assisted reprecipitation. In a typical Ostwald ripening process, large crystals absorb solute from small ones in dispersion, as a result, large crystals grow bigger, and small crystals shrink. MAPbBr3 PeQDs could be size-controlled from several tens of nanometer size to 4 nm and their PL peaks were consequently blue shifted from 514 nm to 457 nm, which demonstrates strong quantum confinement effects. To analyze size-dependence PL energy, it was find that these energy can be fitted by EPL = 2.34 + 2.43/d2, where is d is given in units of nanometers. This research suggests that Ostwald ripening can be expected to be an effective method for preparing PeQDs in the low nanometer size range.

Resume : There are numerous studies of its properties on calcium carbonate precipitation, however the exact path of CaCO3 nucleation is still unknown. In my research I focus on the spontaneous CaCO3 precipitation from aqueous solutions, which can be triggered by a combination of factors including supersaturation and the presence of foreign particulate matter, which may act as a nucleation point [1]. Calcium carbonate may nucleate either due to the so-called classical nucleation path or the alternative one. The general idea of the classical nucleation is based on the reversible process of adding ions to the precritical cluster, which can happen in a supersaturation solution. The postcritical nuclei obtained grow to the final crystals of CaCO3 (ion-by-ion attachment). Non-classical path involves the preliminary aggregation of the prenucleation clusters into amorphous CaCO3 nanoparticles (ACC) [2]. The sign and the magnitude of the ζ potential indicates on stability of colloidal dispersions. The amorphous phase of calcium carbonate can be stabilized by use of magnesium ions. The presence of Mg2+ influences transformation between amorphous calcium carbonate phase and CaCO3 polymorphs [3]. Experiments were performed using facile precipitation of CaCO3 by mixing aqueous solutions of CaCl2 with Na2CO3 in distilled water and adding MgCl2 to control calcium carbonate precipitation by various additions. Addition of Mg2+ ions stabilize ACC (nucleation inhibition: Mg2+ delays calcite nucleation by preventing the ACC dehydration. ¬¬¬___________________________________________________________ [1] Lioliou et al. Journal of Colloid and Interface Science, 2007, 421-428 [2] Politi et al. Science, 2004, 306, 1161−1164. [3] Nico et al., Chem. Rev., 2008, 108 (11), 4499–4550

Resume : Colloidal solutions of CdSe:Er nanoparticles (NPs) were prepared by using high-temperature pulse nucleation synthesis. The prepared NPs were investigated by means of the transmission electron microscopy and optical spectroscopy. CdSe:Er NPs with 1:2 atomic ratio of Er to Cd atoms were found to be tetragonal with ray’s length and cross-sectional diameter of about 25-30 and 3-4 nm, respectively. An influence of the doping with Er on the optical properties of CdSe NPs was revealed via the photoluminescence, linear optical absorption and time-resolved differential transmission measurements. NPs of CdSe:Er were observed to enhance the optical bleaching by 5 times in comparison with undoped CdSe NPs. This phenomenon is explained by the transformation of conduction band levels and by enhanced separation of the photo-induced charge carries in the tetrapod NPs with incorporated Er3+ ions.

Resume : Combination of the unique properties of aluminum nitride AlN and gallium nitride GaN in one material is anticipated to be advantageous for development of many optoelectronic and high power/frequency devices. Moreover, nanocrystalline forms of such materials can be suitable for sintering to yield high quality pellets for electronic applications. In this work, presented is a study on transamination/deamination chemistry of the mixed Ga/Al tris(dimethyl)amide system towards the binary metal nitride nanopowders. Both starting precursors were synthesized using the reaction of freshly prepared LiN(CH3)2 with Al or Ga chloride yielded the respective metal amide. The amides were then mixed (Al/Ga=1/1 (at.), and stirred 10 minutes or 24 h in a hexane solution at room temperature. Subsequently, the volatiles were evacuated and the solid binary metal amide mixture was reacted with liquid ammonia (-33 °C, 4 h). Upon ammonia removal, the resulting binary metal amide/imide mixture was isolated. The mixtures were individually nitrided at 800-1000 °C (4 h, NH3 flow) towards the final binary metal nitride nanopowders. The prepared materials and byproducts were investigated using powder XRD, FT-IR, and SEM/EDX. All final powders were found to be mixtures of nanocrystalline type h-GaN/AlN/(AlxGa1-xN). The amides stirring time was a key factor in the evolution of structural and chemical properties of the products. Acknowledgement. The study was supported by Polish NCN Grant No. 2017/25/B/ST5/01032.

Resume : An approach to calculating integral conductivity of a model nanotube/dielectric composite system is discussed. Conductivity of random nanotube network formed in the dielectric medium is simulated considering tunneling conductivity between individual nanotubes being in close proximity and taking into account intrinsic conductivity of nanotubes. 3D model of a dielectric volume filled randomly with conductive nanotubes (nanotube/dielectric composite) is presented. Computer simulations performed in the frame of this model allowed us to calculate the total conductivity of such composite. The influence of tunneling distance parameter of the system conductivity was investigated. The results of the simulations coincide with experimental data obtained by other researchers and also indicate the difference for the cases of overlapping nanotubes (“soft core” model) and non-overlapping nanotubes (“hard core” model). The comparison with measured results shows that "hard core" model can be effectively used for predicting the parameters of fabricated composite being an important step towards the creation of the material with desired properties.

Resume : Optical chirality is a property of light that has been under studies in the past and which still attracts attention in the field of modern optics. Chirality is also property of certain natural or artificial materials, which enables their interaction with the spin angular momentum of the electromagnetic field. A chiral material senses the handedness of the light and this allows for a different interaction with left- and right-handed circularly polarized light. In this fashion such optical phenomena as polarization rotation or circular dichroism (CD) do appear. Creation of artificial structures, where chirality is controlled via shape and geometry, is enabled by modern micro- and nano-fabrication techniques. Relatively strong chiral response can be achieved in single or densely packed micro or nanoscopic helices. Optical response of single and clustered structures are controlled here via the size of a single helix, or with pitches and twists around their axis. A similar optical behavior can result also from purely geometrical properties of a three-dimensional arrangement of nanoobjects without chirality, such as nanospheres or nanodics. The optical response of the nanoparticle is strongly dependent both on the particle location in the focal plane and on the polarization state of the beam, and it differs notably from that of the classical Mie theory. Moreover, the optical response of a clustered nanospheres should be considered using the so-called T-matrix method or, alternatively, using the multiple scattering method. Here, we analyze a novel approach to optical chirality, which is observed in a clustered two-dimensional nanostructure, made from single nanospheres of different sizes and materials. The resulting chirality is induced here by the choice of heterogeneous material composition of a particle assembly, where individual properties of the cluster's constituents breaks the symmetry of the cluster. We report here on investigation of such planar clustered structures using numerical approaches.

Resume : For several years, graphene oxide has been enjoying unflagging popularity among scientists. Due to its unique properties, it can be used in areas such as electronics, fuel cell technology or medicine. There are two main synthesis approaches to obtain graphene oxide: “top-down” and “bottom-up” methods. The aim of this study was comparison of GO properties obtained by two methods: modified Hummers method and hydrothermal method from citric acid. We testes acid-base properties, fluorescence, chemical compound or size. Methods such as infrared spectroscopy, scanning electron microscopy, spectrophotometry, fluorometry or dynamic light scattering were investigated. The results indicate, that there are clear differences between these two types of GO. They differ in size, shape or optical properties. The duration of synthesis also plays an important role, especially in the case of “bottom-up” method. Due to these facts, the choice of synthesis method during research should be well thought out and adapted to the planned applications. Acknowledgments: This work has been supported by the National Science Centre, Poland, project registration number: 2015/19/B/ST8/02015

Resume : Organosilane modification on the surface of ZnO QDs is a possible means of fabricating hybrid nanomaterials with tuned optical and physico-chemical properties. We report here the synthesis, morpho-structural characterization and optical, photocatalytic and antibacterian properties of hybrid ZnO quantum dots (QDs) functionazed with variable amounts of the surfactant (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) (2, 5, 10 and 15% molar ratios of Si/Zn). This organosilane surfactant was chosen to evaluate its ability to both prevent the agglomeration of the nanoparticles and to tune the optical, photocatalytic and antibacterian properties of the resulting hybrid nanomaterials. The modified ZnO QDs were prepared using a precipitation method and the characterization was performed with X-ray diffraction, high-resolution transmission electron microscopy and UV-Visible spectrometry; their optical properties were studied by UV-visible spectrometry, photocatalytic activities were evaluated by measuring as a model organic compound, the degradation of methylene blue (MB) in water under UV irradiation and the antimicrobial activity of the modified ZnO QDs, determined by using the paper disc method on Mueller-Hinton agar against the Gram-negative bacteria, Escherichia coli (E. coli) and the Gram-positive bacteria, Staphylococcus aureus (S. aureus), was compared to that of unmodified ZnO QDs. Unmodified ZnO and GPTMS- functionalized ZnO QDs showed optical transmittance between 75 and 90% and low reflectance between 0 and 7% in the visible domain. A decrease in the band gap energies from 3.49 eV for unmodified ZnO to 3.29 eV for ZnO–GPTMS 15% was detected.

Resume : The catalytic performance and optical properties of bimetallic nanoparticles critically depend on the atomic distribution of the two metals in the nanoparticles. However, at elevated temperatures, during light induced heating or during catalysis atomic redistribution can occur. Measuring such metal redistribution in situ is challenging and a single experimental technique does not suffice. Furthermore, the availability of a well-defined nanoparticle system has been an obstacle for a systematic investigation of the key factors governing the atomic redistribution. In this study, we follow metal redistribution in precisely tunable, single-crystalline Au-Ag nanorods in situ, both at a single particle and ensemble averaged level, by combining in situ TEM with in situ EXAFS validated by ex situ measurements. We show that the kinetics of atomic redistribution in Au-Ag nanoparticles depend on the metal composition and particle volume, where a higher Ag-content or a larger particle size lead to significantly slower metal redistribution. We developed a simple theoretical model based on Fick’s first law which can correctly predict the composition and size dependent alloying behavior in Au-Ag nanoparticles as observed experimentally.

Resume : High-performance catalysts for the direct synthesis of hydrogen peroxide (H2O2) mostly utilize costly palladium (Pd), which makes the process commercially less viable. It is imperative to discover an inexpensive alternative. Here, we propose and demonstrate a new catalyst design strategy using nanoparticles (NPs) comprising immiscible elements. As a result, four novel H2O2-producing catalysts (i.e., RhAg, RhAu, PtAu, and IrAg NPs) were developed. In particular, Rh10Ag90, owing to its high Ag content, exhibits a 7.3-fold enhancement in the cost-to-productivity ratio compared to that of prototypic Pd; it may serve as an economical option. Using combinations of ab initio computations and experimental spectroscopies, we demonstrate that the observed productivities of these NPs are a result of the synergy between the two elemental domains at the interface. Our work stands in contrast to the traditional view that Pd is an essential component for efficient H2O2 productions, and thus will substantially increase the scope of future explorations of improved catalyst materials.

Resume : Au-Fe alloy nanoparticles reveal a wide field of application due to the combination of plasmonic and magnetic properties in one nanoparticle. Laser ablation in liquids generates solid solution (SS) and core shell (CS) nanoparticles with Au-rich shell and Fe-rich core [1]. The formation of CS or SS nanoparticles is ruled by the composition and the diameter of the nanoparticles. In situ scanning transmission microscopy heating experiments reveal the metastable character of the nanoparticles and the transformation into thermodynamically stable products. The final equilibrium ultrastructure predominantly depends on the composition of the nanoparticles, resulting in chemically homogeneous SS nanoparticles for Au50Fe50 and nanoparticles with cube-shaped Fe-rich core faceted by truncated Au-rich pyramids (tetrakis hexahedron) for Au20Fe80. The outstanding ultrastructure of tetrakis hexahedron is verified by combination of EDX elemental mapping and 3D models reconstructed by STEM tomography. Ex situ etching experiments result in nanoporous Au structures by dealloying of Au-Fe nanoparticles. The residual Au nanostructures give conclusions about the pristine Au-Fe ultrastructure and can be used for catalytic applications. [1] P. Wagener et al., “Solvent-surface interactions control the phase structure in laser-generated iron-gold core-shell nanoparticles,” Sci. Rep., vol. 6, p. 23352, Mar. 2016.

Resume : In this presentation, we demonstrate that metallic elements with widely differing physical-chemical properties (saturation vapor pressures, melting points, and densities) can be combined to form alloy nanoparticles using thermal plasma synthesis. We take a W-Ni-Fe ternary system as a model system to show that plasma-created alloy nanoparticles possess distinctive chemical and morphological features, which are related to a unique high-temperature plasma environment. Specifically, we present experimental evidence for an extensive alloying of component metals beyond the equilibrium solubility limits at low and moderate temperatures, encapsulation of a refractory component within lower-melting-point surface alloys, and formation of diffuse interfaces and smooth gradations in compositions. The compositional surveys that we present were obtained on different length scales using several characterization techniques with different spatial resolutions and depth sensitivities (STEM-EDX, FE-SAM, SEM-EDX, and XPS).

Resume : Industrial dyes and dye products are released into the water after they are being used for staining and dying. Elimination of these dyes from hydrosphere takes a prolonged period which remains a threat to many lifeforms. The need for a clean technology that is efficient and economical is necessary to eliminate this threat. To tackle this problem, Composite of Magnetic Iron Oxide (Fe3O4) - Manganese octahedral molecular sieve (OMS-2) was synthesized using OMS-2 via conventional reflux method and further explored as a photocatalyst for the degradation of Crystal Violet Dye. The synthesized Fe3O4-OMS-2 Composite was characterized by DLS, XRD, UV-Vis Spectroscopy, SEM and AFM for Structural, Photocatalytic, Electric and Magnetic Properties. The catalytic activity of the composite was observed by varying the amount of catalyst, time, pH of the medium and the concentration of the dye. The optimum conditions for the catalytic process were determined. Significant degradation was observed in the absence of light (67% in 60 minutes) and in the presence of sunlight (87% in 60 minutes) at 9 pH. It was observed that the catalyst can be reused multiple times by using external magnetic field due to its magnetic property. The reusability and recoverability of the catalyst were also studied. We discovered that Fe3O4/OMS-2 Nanocomposite was very effective for degrading the Crystal Violet Dye.

Resume : Ceria (CeO2) nanoparticles have shown great potential for use in solid oxide fuel cells, oxygen sensors, oxygen separation membranes, and as catalyst material owing to their high electronic and oxygen ion conductivity and high chemical stability. The particles exhibit high and reversible oxygen storage capacities, carried out by changing the valence state of Ce from 3+ to 4+, at intermediate temperatures (500 – 800 oC). Doping CeO2 with elements such as Pr and Tb, has shown to enhance its redox properties. A change in valency during oxidation or reduction can be mapped on the nanoscale using the fine structure of the Ce-M4,5 edge with electron energy loss spectroscopy (EELS). In our work, we have mapped the change in valency during reduction and oxidation on nanopartices of pure CeO2, as well as mesoporous thin films of the solid solution ZrO2-CeO2, in vacuum using a Protochips fusion heating holder and with a Protochips atmosphere holder, using an aberration-corrected FEI Titan G2 60-300 microscope with a Gatan GIF Quantum 965 EELS Spectrometer.

Resume : Designing novel ceria nanomaterials which are stable at high temperatures is important for their further development in many catalytic applications, such as automotive three-way catalysis and dry reforming of methane. The use of two-dimensional graphene oxide flakes offers a promising potential method to produce high surface area nanostructured ceria catalysts. In this work, graphene oxide is used as a sacrificial template during the synthesis of ceria particles to replicate its two-dimensional morphology, resulting in the production of nanoflakes consisting of <10nm nanoparticles arranged in two dimensions. Compared with untemplated ceria particles, these nanoflakes retain a higher surface area and more reducible surface after high-temperature calcination, demonstrating improved resistance to sintering. Additionally, ceria nanoflakes can be used as a catalyst support material for nickel nanoparticles, with enhanced metal dispersion and metal-support interaction compared with untemplated nickel-ceria catalysts. Because of this, ceria nanoflakes demonstrate better catalytic performance for carbon monoxide oxidation (ceria catalyst) and dry reforming of methane (nickel-ceria catalyst) in comparison to untemplated ceria particles. These results show the advantage of using graphene oxide as a sacrificial template to produce sintering-resistant nanocatalysts for high-temperature applications.

Resume : Colloidal Cu2-xS nanocrystals (NCs) have attracted increasing attention for application in photovoltaics, biomedical sensing and photocatalysis. Ligand exchange procedures are essential to make the NCs suitable for these applications. In colloidal Cu2-xS NC synthesis, thiols are often used as organic ligand and sulfur source as they yield high quality NCs. However, thiol ligands on Cu2-xS NCs are extremely difficult to exchange, limiting the applications of these NCs. Here, we present successful ligand exchange procedures of 1-dodecanethiol (DDT) on Cu2¬ -XS NCs for mercaptopropionic acid (MPA), 11-mercaptoundecanoic acid (MUA) at high pHs (>9), and Na2S in formamide. The product hydrophilic Cu2-xS NCs have excellent colloidal stability in formamide. Furthermore, the size and shape of the NCs are not significantly affected by the ligand exchange procedures. In addition, water-dispersible Cu2-xS NCs can be easily obtained by precipitation of the NCs, followed by redispersion in water. Interestingly, the ligand exchange rates for DDT-capped Cu2-XS NCs depended on the preparation method; being much slower for Cu2-xS NCs prepared via heating-up than by hot-injection synthesis. XPS studies reveal that the differences in the ligand exchange rates can be attributed to the surface chemistry of the Cu2-xS NCs.

Resume : The choices in synthesising nanoparticles (NPs) with different sizes, chemical composition and shapes, are nowadays so extensive to be almost limitless. The NPs shape has shown to play a relevant role in driving biological processes[1-2] and being able to capture and quantify shape control parameters on a scale that is meaningfully related to the biology is an urgent requirement.[3] Despite some effort have been made in order to propose a nomenclature strategy for this plethora considering some NPs characteristics,[4] still there are no obvious high-level methods to describe the NPs shape. For non-geometrical shaped NPs, for example, fancy names are often used, sometime borrowed from similar looking objects.[5-6] Since the NPs nomenclature process in not yet regulated by any official organization (as in the case of IUPAC for chemical compounds) therefore it might happen that nanostructures with different shapes are named the same, as well as two NPs with the very same nanostructure are called with different fancy names, leading to confusion, scarce searchability and impossibility to relate those parameters to biological impacts. Herein we propose the use of a platform that captures NPs structures in digital form so that they can be analysed, stored and processed objectively. The process involves conventional TEM imaging and data processing by Fourier Transform in order to capture key shape descriptors. Following a specific preparation protocol, we can deposit the NPs on the TEM grid homogenously dispersed to clearly distinguish a particle form another, being able to extract xy coordinates of their 2D projections. The contours extracted from the TEM images are then compared using the normalized complex coordinate signature.[7] On a practical side this work will allow a NPs “user/producer” to identify if the produced nanostructure already exist, beyond chemical-physical parameters, on the base of its shape and to evaluate the batch quality compared to existing (standard) ones stored in a database. Our approach aim not only to identify the likeness of a shape to existing morphologies, but also to set the basis for “in batch” and “batch-to-batch” quality control in a semi-quantitative manor. In addition, we set the basis to develop and explore the concepts of geometrical identity. The concepts outlined in this work will be of interest for the whole NPs and nanomedicine community, opening to new approaches for a more systematic NPs identification and classification. References 1. Chen, X.; Yan, Y.; Müllner, M.; Ping, Y.; Cui, J.; Kempe, K.; Cortez-Jugo, C.; Caruso, F., Shape-dependent activation of cytokine secretion by polymer capsules in human monocyte-derived macrophages. Biomacromolecules 2016, 17 (3), 1205-1212. 2. Talamini, L.; Violatto, M. B.; Cai, Q.; Monopoli, M. P.; Kantner, K.; Krpetic, Z.; Perez-Potti, A.; Cookman, J.; Garry, D.; P. Silveira, C., Influence of size and shape on the anatomical distribution of endotoxin-free gold nanoparticles. ACS nano 2017. 3. Castagnola, V.; Cookman, J.; De Araujo, J.; Polo, E.; Cai, Q.; Silveira, C.; Krpetić, Ž.; Yan, Y.; Boselli, L.; Dawson, K., Towards a classification strategy for complex nanostructures. Nanoscale Horizons 2017. 4. Gentleman, D. J.; Chan, W. C., A systematic nomenclature for codifying engineered nanostructures. Small 2009, 5 (4), 426-431. 5. Liang, H.; Rossouw, D.; Zhao, H.; Cushing, S. K.; Shi, H.; Korinek, A.; Xu, H.; Rosei, F.; Wang, W.; Wu, N., Asymmetric silver “nanocarrot” structures: Solution synthesis and their asymmetric plasmonic resonances. Journal of the American Chemical Society 2013, 135 (26), 9616-9619. 6. Zhao, L.; Ji, X.; Sun, X.; Li, J.; Yang, W.; Peng, X., Formation and stability of gold nanoflowers by the seeding approach: the effect of intraparticle ripening. The Journal of Physical Chemistry C 2009, 113 (38), 16645-16651. 7. Sokic, E.; Konjicija, S. In Novel fourier descriptor based on complex coordinates shape signature, Content-Based Multimedia Indexing (CBMI), 2014 12th International Workshop on, IEEE: 2014; pp 1-4.

Resume : Research activities on entropy dominated crystal structural stabilisation have flourished since the discovery of high entropy alloys (HEAs) [1]. HEAs, which are solid solution of five or more metallic elements in near equiatomic ratios, have shown better properties than many of the conventional principal elemental alloys. Recently, this concept was extended to oxide systems [2] and termed high entropy oxides (HEOs). HEOs have already gained significant research interest since their discovery. One of the main reasons behind this growing attention is the fact that a large number of cations in equiatomic amounts can be incorporated into a single lattice structure, overcoming the common enthalpy dominated phase separation often encountered in doped oxides. Several compositions along with different crystal structures (such as rocksalt, fluorite, spinel and perovskite) are possible for HEOs [3,4,5,6]. The role of configurational entropy in structural stabilisation is clearly evident in some of the HEOs, like the rocksalt based systems [3]. Even highly complex perovskite systems containing 10 different cations in equiatomic amounts, can be stabilised into a single orthorhombic phase due to the high configurational entropy [6]. While, in case of the rare earth based HEOs (RE-HEOs), factors other than entropy are found to stabilise the single phase [4]. Apart from the compelling structural features, the distinct design concept allows for the fine tailoring of the functional properties of HEOs. Different types of HEOs show distinct properties, some examples of such tailorable properties in the transitional metal based HEOs (TM-HEOs) are high room temperature Li+ conductivity, colossal dielectric constant, etc [7]. In our recent studies TM-HEOs were used as electrode material for secondary Li-ion batteries. High capacities (above 550 mAh/g) along with substantial stability (over 500 cycles) were observed when the TM-HEOs were cycled against Li as counter electrode. The RE-HEOs on the other hand, showed interesting optical properties like narrow band gaps (around 2 eV) [8], which can be reversibly tuned by heat treatments under different atmospheres. The combination of these studies can help to find practical applications for this new class of oxide systems. References 1. Yeh, J.-W. et al., Adv. Eng. Mater. 6, 299–303 (2004). 2. Rost, C. M. et al., Nat. Commun. 6, 8485 (2015). 3. Sarkar, A. et al., J. Eur. Ceram. Soc. 37, 747–754 (2017). 4. Djenadic, R. et al., Mater. Res. Lett. 5, 102–109 (2017). 5. Dąbrowa, J. et al., Mater. Lett. 216, 32–36 (2018). 6. Sarkar, A., J. Eur. Ceram. Soc. 38, 2318–2327 (2018). 7. Bérardan, D., J. Mater. Chem. A 4, 9536–9541 (2016). 8. Sarkar, A. et al., Dalt. Trans. 46, 12167–12176 (2017).

Resume : Nanoclusters are of interest due to a large number of applications ranging from catalysis to data storage. To be able to utilise individual nanoclusters, they should usually be encapsulated by some material or ligands, or supported on some substrate. Graphene is a very strong candidate for such a substrate. As such, the goal is to model the anchoring, structural changes and properties of nanoclusters which are supported on graphene. In this work we have developed interatomic potentials to meet this goal. In particular, barium oxide clusters were chosen here as barium cations are very large and therefore atomic-resolution microscopy techniques can be used to draw comparison between theory and experiment. In simulation, one of the key problems is structure prediction, often addressed by global optimisation techniques. In this work, structures of nanoclusters of alkali earth oxides including barium oxide were first predicted in vacuo using an evolutionary algorithm and data mining coupled with density functional theory and interatomic potentials. It was found that barium, strontium and calcium oxide clusters generally resemble rocksalt cuts, with magnesium oxide clusters forming equivalent configurations at sizes above 30 atoms, while smaller clusters prefer barrel-like structures (nanotubes)[1,2]. The question then is how formation and stability of this different phase is altered when the clusters are graphene-supported and whether the phase transition occurs at a different size and size-selection differs from the unsupported case. To be able to address this, we parametrised new interatomic potentials from DFT data to model the clusters' interactions with graphene. This was then used to investigate adsorption behaviour on graphene, in particular changes in structure and properties of the nanoclusters and differences in relative stability compared to in vacuo. [1] S.G.E.T. Escher, T. Lazauskas, M.A. Zwijnenburg and S. M. Woodley, Comp. Theor. Chem. 1107, 74-81 (2017) [2] S.G.E.T. Escher, T. Lazauskas, M.A. Zwijnenburg and S. M. Woodley, Inorganics 6, 29 (2018)

Resume : Colloidal semiconductor nanocrystals (NCs) are the subject of intense research due to their electronic and physicochemical properties that can be exploited for applications such as catalysis, electronics, photovoltaics, and biomedicine. For years, scientists have demonstrated a strong and continuous interest in the design of materials that possess specific functions. This can be achieved by exploiting and fine tuning the surface properties of desired materials. In this regard, the surface-ligand interface plays a crucial role in the control of both the characteristics and functions of nanocrystals. Due to their biocompatibility and intrinsic physicochemical properties, ZnO-based nanomaterials represent a highly desired alternative for heavy-metal based nanostructures.[1,2] Two types of ZnO-based nanomaterials were obtained, one via an original one-pot self-supporting organometallic method (OSSOM) that enables strict control over the size and shape of the formed NCs and the other by direct hydrolysis. Both bare and ligand-coated nanocrystals were characterized with a broad range of analytical methods including IR, PXRD, TGA and TEM to confirm the desired structures. In this presentation, I will focus on Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP) combined with advanced solid-state Nuclear Magnetic Resonance spectroscopy that was adapted to enable a comprehensive atomic-scale insight into the dynamic surface chemistry and structure of the synthesized quantum dot systems. It will be shown that this technique enables a multinuclear and multidimensional approach that can provide a highly detailed description of the surface giving insights not only into the surface morphologies but also distinct bridging ligand coordination modes. For 17O ssNMR spectroscopy, a new, quick, efficient, inexpensive, and straightforward isotopic labelling strategy will be introduced. The presented methodology has a great potential to enable further descriptions of surface features and surface-ligand interfaces for a wide range of nanosystems. [1] M. Wolska-Pietkiewicz, K. Tokarska, A. Grala, A. Wojewódzka, E. Chwojnowska, J. Grzonka, P. Cywiński, K. Kruczała, Z. Sojka, M. Chudy, J. Lewiński, Chemistry – a European Journal, 2018, 24, 4033-4042 [2] A. Grala, M. Wolska-Pietkiewicz, Z. Wróbel, T. Ratajczyk, J. Kuncewicz, J. Lewiński, Mater. Chem. Front., 2018, Advance Article , DOI: 10.1039/C7QM00586E

Resume : Oxide dispersion strengthened (ODS) steels have emerged as promising materials for high-temperature applications such as jet turbines and advanced nuclear reactors. Their ability to resist irradiation damage, corrosion, and high-temperature creep comes from nanoscale oxide particles which are dispersed in the material and inhibit the motion of defects such as dislocations and interstitials. Although a uniform distribution of dispersoids is considered important for the strengthening of the material, the effects of non-uniform dispersoid distribution are not well understood. Here, ODS steel tubes made of Fe-14Cr ODS steels with yttrium oxide dispersoids were studied using miniaturized flat tensile specimens. Creep experiments were performed in vacuum at temperatures of 750 and 850°C under uniaxial loading. Subsequently, by employing synchrotron X-rays we imaged the chemical microstructure of the specimen. The X-ray measurements were carried out at the microXAS beamline of the Swiss Light Source using X-ray fluorescence (XRF) scanning microscopy. The X-rays were focused to a micrometer spot size which allowed us to spatially resolve cracks present in the creep-tested specimen. We observe a correlation between chemical distribution and physical fracture characterized by regions depleted in Y (but not in Fe or Cr) indicating an absence of dispersoids at the location of a crack. The ability to map the chemical landscape on the micrometer scale provides a powerful tool to evaluate the integrity of materials and predict the formation and propagation of cracks.

Resume : This work presents a study on the intercalation of carbon dioxide (CO2) into fluorohectorite clays. Intercalation of water in smectite clays occurs naturally and has been extensively studied with a wide range of techniques, among them neutron [1] and X-ray scattering [2]. Recent experiments and simulations have shown that also CO2 can intercalate in smectite clays in gaseous and liquid form [3]. We have recently demonstrated that under certain conditions of pressure and temperature, fluorohectorite clays are able to capture a large amount of CO2, depending on the type of interlayer cation [4][5]. We have investigated fluorohectorite clays with three different cations (Na, Ni and Li), showing that Li-fluorohectorite clay is able to retain CO2 up to a temperature of 35°C, at ambient pressure, and that the captured CO2 can be released by heating above this temperature. These conditions are highly relevant for mapping out, and understanding, the mechanisms involved in CO2 capture and retention by smectite clays, either in geological formations, or in CO2 capturing elements. Here we present results on the study of CO2 intercalation into synthetic fluorohectorite clays using a Sieverts apparatus varying the pressure from 0 to 50 bar for the three studied cations. REFERENCES: [1] Martins (2014), Appl Clay Sci 96:22; [2] Hansen (2012), Sci Rep 2: 618; [3] Giesting (2012), Environ. Sci. Technol. 46: 5623; [4] Hemmen (2012), Langmuir 28: 1678; [5] Michels (2015), Sci Rep, 5:8775.

Resume : Metal-organic frameworks, a relatively new class of porous inorganic-organic hybrid materials, have been highlighted as prospective scaffolds for supporting guest materials on the nanoscale and beyond. [1-4] Though of major relevance for the geometry control of the guest materials, the underlying host-guest chemistry is still not completely understood. We have recently shown that strong specific interactions between the guest materials and the supporting scaffolds decorated with organic functional groups determine the size of the guest particles, as nanoclusters [5], atom clusters [6] or single atoms [7]. In this work I will review design strategies and our latest results in a combined experimental-theoretical approach. References [1] Chem. Soc. Rev. 2013:1807 [2] Eur. J. Inorg. Chem. 2010:3701 [3] CrystEngComm. 2015:199 [4] J. Mater. Chem. 2012:10102 [5] Chem. Commun. 2016:5175 [6] in preparation [7] J. Mater. Chem. A, 2017, 2017:15559

Resume : The performance of platinum (Pt)-impregnated NaY zeolite electrocatalyst has been evaluated for small molecule oxidation and reduction. The Cyclic Voltammetry (CV) measurement has provided a contradicting trend of electrochemical oxidation and reduction activity of methanol (CH3OH) and formic acid (HCOOH) on Pt impregnated zeolite electrocatalyst, where the HCOOH has shown a similar level of oxidation and reduction activity to those observed on Pt zeolite electrocatalyst made by ion exchange method, whilst a decrease of CH3OH oxidation and reduction was detected by using Pt impregnated zeolite catalyst. This may be associated to Pt nanoparticle size and Pt surface distribution on zeolite. The en-situ Extended X-Ray Adsorption Fine Structure (EXAFS) analysis has shown Pt particle size is smaller for those made by impregnation method than by ion exchange process (1) at same Pt loading on zeolite. The X Ray Diffraction (XRD) measurement reveals there is a reduction of zeolite crystallinity under calcinations and reduction process with correspondent to 50% decrease of zeolite pores, which was confirmed by Brunauer Emmett and Teller (BET) surface measurement.

Resume : The high hydrophobicity of fullerenes and the resulting formation of aggregates in aqueous solutions hamper the possibility of their exploitation in many technological applications. Noncovalent bioconjugation of C60 with proteins is an emerging approach for their dispersion in water. Contrary to covalent functionalization, bioconjugation preserves the physicochemical properties of the carbon nanostructures. The unique photophysical and photochemical properties of fullerenes are then fully accessible for applications in nanomedicine, sensoristic, biocatalysis and materials science fields. Using lysozyme and C60 as model systems and NMR chemical shift perturbation analysis, a protein-C60 binding pocket was identified unambiguously in aqueous solution. Lysozyme forms a stoichiometric 1:1 adduct with C60 and conserves its tridimensional structure upon binding. Only few residues, localized in a well-defined protein binding pocket, are perturbed. AFM, cryo-TEM and high resolution X-ray powder diffraction show that the C60 dispersion is monomolecular. The adduct is biocompatible, stable in physiological and technologically-relevant environments, and easy to store. Hybridization with lysozyme preserves the photophysical and electrochemical properties of C60. The non-covalent bioconjugation of C60 with different proteins offers a palette of carriers for fullerenes for all pH ranges. [1] ACS Nano 2014, 8, 1871 [2] Nanoscale 2018 DOI: 10.1039/c8nr02220h

Resume : An incredible variety of synthetic strategies have been developed in the last 10 years in the production of shaped gold nanoparticles (GNPs).[1-3] In particular, branched GNPs have shown to be of interest for their physicochemical properties (SERS, NIR-SPR) and potential in the biological/biomedical field.[4-5] However, from the synthetic point of view there is a lack of understanding on how these branched features are generated and the synthesis still suffer of high in-batch and batch-to-batch variability both in terms of size and shape distribution therefore limiting the translation of these materials to biomedical applications. The use of microfluidic reactors has been proposed as a way to ensure higher control of the thermal and chemical environment, leading to an improved control in the nanoparticles uniformity.[6-9] In this work, we propose the use of microfluidic synthesis in continuous flow to generate high quality and reproducible branched gold NPs with minimum human interference and we analyse the mechanism behind the formation of a NP, especially in relation to the chosen reducing agent. Commonly the mechanism behind NPs formation is regulated by thermodynamic processes (known as nucleation and growth) but also by kinetic processes, which limit the level of control on the NPs properties. The microfluidic approach allows us to isolate kinetic intermediates in order to investigate the shape evolution over time. We demonstrated how, in some case, the growth pathway of gold nanostructures might involve unexpected differently shaped reaction intermediates. The evolution study of GNPs allowed not only to elucidate reaction mechanisms, but also to develop synthetic strategies for the production of a number of new and diverse complex gold nanostructures. We believe that the approach adopted in this work represents a key step toward the development of a more regulated and controllable synthesis of NPs necessary for their application in the field of nanomedicine. References 1. Grzelczak, M.; Pérez-Juste, J.; Mulvaney, P.; Liz-Marzán, L. M., Shape control in gold nanoparticle synthesis. Chemical Society Reviews 2008, 37 (9), 1783-1791. 2. Hao, E.; Schatz, G. C.; Hupp, J. T., Synthesis and optical properties of anisotropic metal nanoparticles. Journal of Fluorescence 2004, 14 (4), 331-341. 3. Bakr, O. M.; Wunsch, B. H.; Stellacci, F., High-yield synthesis of multi-branched urchin-like gold nanoparticles. Chemistry of materials 2006, 18 (14), 3297-3301. 4. Talamini, L.; Violatto, M. B.; Cai, Q.; Monopoli, M. P.; Kantner, K.; Krpetic, Z.; Perez-Potti, A.; Cookman, J.; Garry, D.; P. Silveira, C., Influence of size and shape on the anatomical distribution of endotoxin-free gold nanoparticles. ACS nano 2017. 5. Chithrani, B. D.; Ghazani, A. A.; Chan, W. C., Determining the size and shape dependence of gold nanoparticle uptake into mammalian cells. Nano letters 2006, 6 (4), 662-668. 6. Zhao, C.-X.; He, L.; Qiao, S. Z.; Middelberg, A. P., Nanoparticle synthesis in microreactors. Chemical Engineering Science 2011, 66 (7), 1463-1479. 7. Song, Y.; Hormes, J.; Kumar, C. S., Microfluidic synthesis of nanomaterials. Small 2008, 4 (6), 698-711. 8. Wagner, J.; Köhler, J., Continuous synthesis of gold nanoparticles in a microreactor. Nano letters 2005, 5 (4), 685-691. 9. Nightingale, A. M.; Phillips, T. W.; Bannock, J. H.; de Mello, J. C., Controlled multistep synthesis in a three-phase droplet reactor. Nature communications 2014, 5.