Abstract: Sample holders for transmission electron microscopy (TEM) based on micro-electro-mechanical systems (MEMS) have recently become popular for investigating the behavior of nanomaterials under in situ or environmental conditions. The accuracy and reproducibility of these in situ holders are essential to ensure the reliability of experimental results. In addition, the uniformity of an applied temperature trigger across the MEMS chip is a crucial parameter. In this work, it is measured the temperature homogeneity of MEMS-based heating sample supports by locally analyzing the dynamics of heat-induced alloying of Au@Ag nanoparticles located in different regions of the support through quantitative fast high-angle annular dark-field scanning TEM tomography. These results demonstrate the superior temperature homogeneity of a microheater design based on a heating element shaped as a circular spiral with a width decreasing outwards compared to a double spiral-shaped designed microheater. The proposed approach to measure the local temperature homogeneity based on the thermal properties of bimetallic nanoparticles will support the future development of MEMS-based heating supports with improved thermal properties and in situ studies where high precision in the temperature at a certain position is required. This schematic delineates an approach to quantifying potential localized temperature deviation within a nanochip. Employing two comparable nanoparticles as thermal probes in discrete nanochip regions, the alloying kinetics of these nanoparticles are monitorable using in situ quantitative high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography, thus enabling the precise estimation of local temperature deviations.image

Abstract: The increasing use of metallic nanoparticles (NPs) is significantly advancing the field of electrocatalysis. In particular, Cu/Ag bimetallic interfaces are widely used to enhance the electrochemical CO2 reduction reaction (eCO(2)RR) toward CO and, more recently, C-2 products. However, drastic changes in the product distribution and performance when Cu@Ag core-shell configurations are used can often be observed under electrochemical reaction conditions, especially during the first few minutes of the reaction. Possible structural changes that generate these observations remain underexplored; therefore, the structure-property relationship is hardly understood. In this study, we use electron tomography to investigate the structural transformation mechanism of Cu@Ag core-shells NPs during the critical first minutes of the eCO(2)RR. In this manner, we found that the crystallinity of the Cu seed determines whether the formation of a complete and homogeneous Ag shell is possible. Moreover, by tracking the particles' transformations, we conclude that modifications of the Cu-Ag interface and Cu2O enrichment at the surface of the NPs are key factors contributing to the product generation changes. These insights provide a better understanding of how bimetallic core-shell NPs transform under electrochemical conditions.

Abstract: In the present work, a method was utilized to control the in‐situ partial hydrolysis of a diphosphonate ester in presence of a titania precursor and in function of acid content and its impact on the hybrid nanoparticles was assessed. The hydrolysis degree of organodiphosphonate ester linkers during the formation of hybrid organic‐inorganic metal oxide nanoparticles, are relatively underexplored . Quantitative solution NMR spectroscopy revealed that during the synthesis of TiO2 nanoparticles, an increase in acid concentration introduces a higher degree of partial hydrolysis of the TEPD linker into diverse acid/ester derivatives of TEPD. Increasing the HCl/Ti ratio from 1 to 3, resulted in an increase in degree of partial hydrolysis of the TEPD linker in solution from 4% to 18.8% under the here applied conditions. As a result of the difference in partial hydrolysis, the linker‐TiO2 bonding was altered. Upon subsequent drying of the colloidal TiO2 solution, different textures, at nanoscale and macroscopic scale, were obtained dependent on the HCl/Ti ratio and thus the degree of hydrolysis of TEPD. Understanding such linker‐TiO2 nanoparticle surface dynamics is crucial for making hybrid organic‐inorganic materials (i.e. (porous) metal phosphonates) employed in applications such as electronic/photonic devices, separation technology and heterogeneous catalysts.

Abstract: The dehydrogenation of long-chain alkanes to olefins and alkylaromatics is a challenging endothermic reaction, typically requiring harsh conditions which can lead to low selectivity and coking. More favorable thermodynamics can be achieved by using a hydrogen acceptor, such as ethylene. In this work, the potential of heterogeneous platinum catalysts for the transfer dehydrogenation of long-chain alkanes is investigated, using ethylene as a convenient hydrogen acceptor. Pt/C and Pt–Sn/C catalysts were prepared<italic>via</italic>a simple polyol method and characterized with CO pulse chemisorption, HAADF-STEM, and EDX measurements. Conversion of ethylene was monitored<italic>via</italic>gas-phase FTIR, and distribution of liquid products was analyzed<italic>via</italic>GC-FID, GC-MS, and 1H-NMR. Compared to unpromoted Pt/C, Sn-promoted catalysts show lower initial reaction rates, but better resistance to catalyst deactivation, while increasing selectivity towards alkylaromatics. Both reaction products and ethylene were found to inhibit the reaction significantly. At 250 °C for 22 h, TON up to 28 and 86 mol per mol Pt were obtained for Pt/C and PtSn₂/C, respectively, with olefin selectivities of 94% and 53%. The remaining products were mainly unbranched alkylaromatics. These findings show the potential of simple heterogeneous catalysts in alkane transfer dehydrogenation, for the preparation of valuable olefins and alkylaromatics, or as an essential step in various tandem reactions.

Abstract: Metal nanocrystals (NCs) display unique physicochemical features that are highly dependent on nanoparticle dimensions, anisotropy, structure, and composition. The development of synthesis methodologies that allow us to tune such parameters finely emerges as crucial for the application of metal NCs in catalysis, optical materials, or biomedicine. Here, we describe a synthetic methodology to fabricate hollow multimetallic heterostructures using a combination of seed-mediated growth routes and femtosecond-pulsed laser irradiation. The envisaged methodology relies on the coreduction of Ag and Pd ions on gold nanorods (Au NRs) to form Au@PdAg core-shell nanostructures containing small cavities at the Au-PdAg interface. The excitation of Au@PdAg NRs with low fluence femtosecond pulses was employed to induce the coalescence and growth of large cavities, forming multihollow anisotropic Au@PdAg nanostructures. Moreover, single-hollow alloy AuPdAg could be achieved in high yield by increasing the irradiation energy. Advanced electron microscopy techniques, energy-dispersive X-ray spectroscopy (EDX) tomography, X-ray absorption near-edge structure (XANES) spectroscopy, and finite differences in the time domain (FDTD) simulations allowed us to characterize the morphology, structure, and elemental distribution of the irradiated NCs in detail. The ability of the reported synthesis route to fabricate multimetallic NCs with unprecedented hollow nanostructures offers attractive prospects for the fabrication of tailored high-entropy alloy nanoparticles.

Abstract: Superstructures with nanoscale building blocks, when coupled with precise control of the constituent units, open opportunities in rationally designing and manufacturing desired functional materials. Yet, synthetic strategies for the large-scale production of superstructures are scarce. We report a scalable and generalized approach to synthesizing superstructures assembled from atomically precise Ce24O28(OH)8 and other rare-earth metal-oxide nanoclusters alongside a detailed description of the self-assembly mechanism. Combining operando small-angle X-ray scattering, ex situ molecular and structural characterizations, and molecular dynamics simulations indicates that a high-temperature ligand-switching mechanism, from oleate to benzoate, governs the formation of the nanocluster assembly. The chemical tuning of surface ligands controls superstructure disassembly and reassembly, and furthermore, enables the synthesis of multicomponent superstructures. This synthetic approach, and the accurate mechanistic understanding, are promising for the preparation of superstructures for use in electronics, plasmonics, magnetics and catalysis. Synthesizing superstructures with precisely controlled nanoscale building blocks is challenging. Here the assembly of superstructures is reported from atomically precise Ce24O28(OH)8 and other rare-earth metal-oxide nanoclusters and their multicomponent combinations. A high-temperature ligand-switching mechanism controls the self-assembly.

Abstract: The electroreduction of carbon dioxide (eCO2RR) to CO using Ag nanoparticles as an electrocatalyst is promising as an industrial carbon capture and utilization (CCU) technique to mitigate CO2 emissions. Nevertheless, the long-term stability of these Ag nanoparticles has been insufficient despite initial high Faradaic efficiencies and/or partial current densities. To improve the stability, we evaluated an up-scalable and easily tunable synthesis route to deposit low-weight percentages of Ag nanoparticles (NPs) on and into the framework of a nitrogen-doped ordered mesoporous carbon (NOMC) structure. By exploiting this so-called nanoparticle confinement strategy, the nanoparticle mobility under operation is strongly reduced. As a result, particle detachment and agglomeration, two of the most pronounced electrocatalytic degradation mechanisms, are (partially) blocked and catalyst durability is improved. Several synthesis parameters, such as the anchoring agent, the weight percentage of Ag NPs, and the type of carbonaceous support material, were modified in a controlled manner to evaluate their respective impact on the overall electrochemical performance, with a strong emphasis on operational stability. The resulting powders were evaluated through electrochemical and physicochemical characterization methods, including X-ray diffraction (XRD), N2-physisorption, Inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), SEM-energy-dispersive X-ray spectroscopy (SEM-EDS), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), STEM-EDS, electron tomography, and X-ray photoelectron spectroscopy (XPS). The optimized Ag/soft-NOMC catalysts showed both a promising selectivity (∼80%) and stability compared with commercial Ag NPs while decreasing the loading of the transition metal by more than 50%. The stability of both the 5 and 10 wt % Ag/soft-NOMC catalysts showed considerable improvements by anchoring the Ag NPs on and into a NOMC framework, resulting in a 267% improvement in CO selectivity after 72 h (despite initial losses) compared to commercial Ag NPs. These results demonstrate the promising strategy of anchoring Ag NPs to improve the CO selectivity during prolonged experiments due to the reduced mobility of the Ag NPs and thus enhanced stability.

Abstract: The success of colloidal semiconductor nanocrystals (NCs) in science and optoelectronics is inextricable from their surfaces. The functionalization of lead halide perovskite NCs1-5 poses a formidable challenge because of their structural lability, unlike the well-established covalent ligand capping of conventional semiconductor NCs6,7. We posited that the vast and facile molecular engineering of phospholipids as zwitterionic surfactants can deliver highly customized surface chemistries for metal halide NCs. Molecular dynamics simulations implied that ligand-NC surface affinity is primarily governed by the structure of the zwitterionic head group, particularly by the geometric fitness of the anionic and cationic moieties into the surface lattice sites, as corroborated by the nuclear magnetic resonance and Fourier-transform infrared spectroscopy data. Lattice-matched primary-ammonium phospholipids enhance the structural and colloidal integrity of hybrid organic-inorganic lead halide perovskites (FAPbBr3 and MAPbBr3 (FA, formamidinium; MA, methylammonium)) and lead-free metal halide NCs. The molecular structure of the organic ligand tail governs the long-term colloidal stability and compatibility with solvents of diverse polarity, from hydrocarbons to acetone and alcohols. These NCs exhibit photoluminescence quantum yield of more than 96% in solution and solids and minimal photoluminescence intermittency at the single particle level with an average ON fraction as high as 94%, as well as bright and high-purity (about 95%) single-photon emission. Phospholipids enhance the structural and colloidal integrity of hybrid organic-inorganic lead halide perovskites and lead-free metal halide nanocrystals, which then exhibit enhanced robustness and optical properties.

Abstract: The efficiency of a catalytic process is assessed based on conversion, yield, and time effectiveness. However, these parameters are insufficient for evaluating environmentally sustainable research. As the world is urged to shift towards green catalysis, additional factors such as reaction media, raw material availability, sustainability, waste minimization and catalyst biosafety, need to be considered to accurately determine the efficacy and sustainability of the process. By combining the high porosity and versatility of metal organic frameworks (MOFs) and the activity of gold nanoparticles (AuNPs), efficient, cyclable and biosafe composite catalysts can be achieved. Thus, a composite based on AuNPs and the nanometric flexible porous iron(III) aminoterephthalate MIL-88B-NH2 was successfully synthesized and fully characterized. This nanocomposite was tested as catalyst in the reduction of nitroarenes, which were identified as anthropogenic water pollutants, reaching cyclable high conversion rates at short times for different nitroarenes. Both synthesis and catalytic reactions were performed using green conditions, and even further tested in a time-optimizing one-pot synthesis and catalysis experiment. The sustainability and environmental impact of the catalytic conditions were assessed by green metrics. Thus, this study provides an easily implementable synthesis, and efficient catalysis, while minimizing the environmental and health impact of the process.

Abstract: A thorough and quantitative understanding of the fate of excitons in covalent–organic frameworks (COFs) after photoexcitation is essential for their augmented optoelectronic and photocatalytic applications via precise structure tuning. The synthesis of a library of COFs having identical chemical backbone with impeded conjugation, but varied morphology and surface topography to study the effect of these physical properties on the photophysics of the materials is herein reported. The variation of crystallite size and surface topography substantified different aggregation pattern in the COFs, which leads to disparities in their photoexcitation and relaxation properties. Depending on aggregation, an inverse correlation between bulk luminescence decay time and exciton binding energy of the materials is perceived. Further transient absorption spectroscopic analysis confirms the presence of highly localized, immobile, Frenkel excitons (of diameter 0.3–0.5 nm) via an absence of annihilation at high density, most likely induced by structural torsion of the COF skeletons, which in turn preferentially relaxes via long‐lived (nanosecond to microsecond) excimer formation (in femtosecond scale) over direct emission. These insights underpin the importance of structural and topological design of COFs for their targeted use in photocatalysis.

Abstract: Metal halide perovskite (MHP) quantum dots (QDs) offer immense potential for several areas of photonics research due to their easy and low-cost fabrication and excellent optoelectronic properties. However, practical applications of MHP QDs are limited by their poor stability and, in particular, their tendency to aggregate. Here, we develop a two-step double-solvent strategy to grow and confine CsPbBr3 QDs within the three-dimensional (3D) cavities of a mesoporous SBA-16 silica scaffold (CsPbBr3@SBA-16). Strong confinement and separation of the MHP QDs lead to a relatively uniform size distribution, narrow luminescence, and good ambient stability over 2 months. In addition, the CsPbBr3@SBA-16 presents a high activity and stability for visible-light-driven photocatalytic toluene C(sp(3))-H bond activation to produce benzaldehyde with similar to 730 mu mol g(-1) h(-1) yield rate and near-unity selectivity. Similarly, the structural stability of CsPbBr3@SBA-16 QDs is superior to that of both pure CsPbBr3 QDs and those confined in MCM-41 with 1D channels.