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Supported Au nanoparticles modified with basic Lindqvist-type [Nb6O19]8− clusters were fabricated by a simple adsorption method and exhibited efficient reduction activity for p-nitrophenol due to the base and reduction dual functional catalysis.

Recently, the creation of new heterogeneous catalysts using the unique electronic/geometric structures of small metal nanoclusters (NCs) has received considerable attention. However, to achieve this, it is extremely important to establish methods to remove the ligands from ligand‐protected metal NCs while preventing the aggregation of metal NCs. In this study, the ligand‐desorption process during calcination was followed for metal‐oxide‐supported 2‐phenylethanethiolate‐protected gold (Au) 25‐atom metal NCs using five experimental techniques. The results clearly demonstrate that the ligand‐desorption process consists of ligand dissociation on the surface of the metal NCs, adsorption of the generated compounds on the support and desorption of the compounds from the support, and the temperatures at which these processes occurred were elucidated. Based on the obtained knowledge, we established a method to form a metal‐oxide layer on the surface of Au NCs while preventing their aggregation, thereby succeeding in creating a water‐splitting photocatalyst with high activity and stability., The ligand‐desorption process during calcination was elucidated for metal‐oxide‐supported thiolate‐protected gold (Au) 25‐atom metal nanoculusters (NCs) using five experimental techniques. Furthermore, based on obtained knowledge, a method was established to form a metal‐oxide layer on the surface of Au NCs while preventing their aggregation, thereby succeeding in creating a water‐splitting photocatalyst with high activity and stability.

Efficient, robust and environmentally friendly cocatalysts for photocatalysts are important for large-scale solar hydrogen production. Herein, we demonstrate that a Rh–Zr mixed oxide is an efficient cocatalyst for hydrogen evolution. Impregnation of Zr and Rh precursors (Zr/Rh = 5 wt/wt%) formed RhZrOx cocatalyst particles on Al-doped SrTiO3, which exhibited 31× higher photocatalytic water-splitting activity than a RhOx cocatalyst. X-ray photoelectron spectroscopy proved that the dissociation of Cl− ions from preformed Rh–Cl–Zr–O solid led to formation of the active phase of RhZrOx, in which the Zr/Rh ratio was critical to high catalytic activity. Additional CoOx loading as an oxygen evolution cocatalyst further improved the activity by 120%, resulting in an apparent quantum yield of 33 (±4)% at 365 nm and a long durability of 60 h. Our discovery could help scale up photocatalytic hydrogen production., An efficient, robust and environmentally friendly Rh–Zr mixed oxide formed though the activation of Rh–Cl–Zr–O solid efficiently functions as a HER cocatalyst on Al-doped SrTiO3.

The atomic structures of Au25(SC2H4Ph)18, Au25(SePh)18, and Au144(SC2H4Ph)60, for which the crystal structures have been solved, were examined by aberration-corrected transmission electron microsco...

Hard X-ray excited optical luminescence is a unique property of materials, which makes them promising for biological imaging applications. However, the preparation of biocompatible contrast agents for hard X-ray excited optical luminescence remains a considerable challenge that has, to date, not been overcome. In this study, we investigated the luminescence properties of protein-directed Au∼20 clusters upon hard X-ray irradiation, both in solution and when embedded in films.

Ultrathin gold nanowires (AuUNWs) and nanorods (AuUNRs) with diameters smaller than the critical dimension for quantization (∼2 nm), are a new class of anisotropic nanostructures. Due to their uniq...

Hard X-ray excited optical luminescence is a unique property of materials, which makes them promising for biological imaging applications. However, the preparation of biocompatible contrast agents for hard X-ray excited optical luminescence remains a considerable challenge that has, to date, not been overcome. In this study, we investigated the luminescence properties of protein-directed Au

We synthesized gold ultrathin nanorods (AuUNRs) by slow reductions of gold(I) in the presence of oleylamine (OA) as a surfactant. Transmission electron microscopy revealed that the lengths of AuUNRs were tuned in the range of 5-20 nm while keeping the diameter constant (∼2 nm) by changing the relative concentration of OA and Au(I). It is proposed on the basis of time-resolved optical spectroscopy that AuUNRs are formed via the formation of small (2 nm) Au spherical clusters followed by their one-dimensional attachment in OA micelles. The surfactant OA on AuUNRs was successfully replaced with glutathionate or dodecanethiolate by the ligand exchange approach. Optical extinction spectroscopy on a series of AuUNRs with different aspect ratios (ARs) revealed a single intense extinction band in the near-IR (NIR) region due to the longitudinal localized surface plasmon resonance (LSPR), the peak position of which is red-shifted with the AR. The NIR bands of AuUNRs with AR5 were blue-shifted upon the ligand exchange from OA to thiolates, in sharp contrast to the red shift observed in the conventional Au nanorods and nanospheres (diameter10 nm). This behavior suggests that the NIR bands of thiolate-protected AuUNRs with AR5 are not plasmonic in nature, but are associated with a single-electron excitation between quantized states. The LSPR band was attenuated by thiolate passivation that can be explained by the direct decay of plasmons into an interfacial charge transfer state (chemical interface damping). The LSPR wavelengths of AuUNRs are remarkably longer than those of the conventional AuNRs with the same AR, demonstrating that the miniaturization of the diameter to below ∼2 nm significantly affects the optical response. The red shift of the LSPR band can be ascribed to the increase in the effective mass of electrons in AuUNRs.

Terminal alkynes form a variety of interfacial structures with the clusters and nanoparticles of Au, Ag, Cu, Ru, Pd, and Pt. In order to extend the scope of modification by alkynes, we herein report the synthesis and structure characterization of Ir clusters protected by phenylacetylene (PA). Small, monodisperse PA-protected Ir clusters (1.3 ± 0.2 nm) were obtained by biphasic ligand exchange from ethylene glycol-stabilized Ir clusters (1.5 ± 0.2 nm). High-resolution transmission electron microscopy, extended X-ray absorption fine structure analysis, and powder X-ray diffraction analysis indicated that Ir clusters exhibit a face-centered cubic structure. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy indicated Ir atoms are almost in the zero valence state, which is in sharp contrast to the partial oxidation observed for Ir clusters stabilized by polymers. Absence of the terminal hydrogen of PA and red-shift of the C≡C stretching mode upon ligation observed by Fourier-transform infrared...

Recently, we have developed a synthetic method of ultrathin gold nanorods (AuUNRs) with a fixed diameter of ∼1.8 nm and variable lengths in the range of 6–400 nm. It was reported that these AuUNRs exhibited intense IR absorption assigned to the longitudinal mode of localized surface plasmon resonance and broke up into spheres owing to Rayleigh-like instability at reduced surfactant concentration and at elevated temperatures. In order to understand the structure–property correlation of AuUNRs, their atomic structures were examined in this work using aberration-corrected high-resolution transmission electron microscopy. Statistical analysis revealed that the most abundant structure observed in the AuUNRs (diameter ≈ 1.8; length ≈ 18 nm) was a multiply twinned crystal, with a periodicity of ∼1.4 nm in length. We propose that the AuUNRs are composed of cuboctahedral Au147 units, which are connected one-dimensionally through twin defects.

Ultrathin gold nanorods (AuUNRs; diameter ∼2 nm) stabilized by oleylamine (OA) were spheroidized when dispersed in chloroform containing a small amount of OA. Time-resolved optical spectroscopy and TEM analysis indicated that the AuUNRs were gradually shortened with the release of small Au nanospheres (AuNSs) because of Rayleigh instability, followed by transformation into plasmonic AuNSs (diameter >2 nm). The OA surfactants play an essential role in stabilizing the morphology of AuUNRs by suppressing the diffusion of Au surface atoms.

The present work describes the characterization by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques of ITO modified electrodes with electrostatic assemblies (Polycation/Quantum Dots) and their use in the electro- and photoelectrocatalytic reduction of CO2. These assemblies were prepared with polycations poly-diallyldimethylammonium (PD) and poly-(2-trimethylammonium) ethyl methacrylate (PM) and nanocrystals of CdTe of 2.77 nm (Q2). The size of the nanocrystals was controlled by the synthesis reflux time and incorporated by electric field directed Layer-by-Layer assembly method (EFDLA). The polycations were characterised by NMR measurements; showing important effects on the electrostatic assemblies. PM modified electrodes, with its lower rigidity, exhibited less roughness than the PD modified electrodes, 8.0 nm versus 32.8 nm, and higher heterogeneity in its surface composition. Higher resistance to the charge transfer and time constants were obtained with PMQ2 modified electrode, 63.8 Ω cm−2 and 2.69 ms versus 49.30 Ω cm−2 and 1.3 ms for PDQ2. The electro- and photoelectro properties for CO2 reduction were studied through j-E curves and potential controlled electrolysis. Modified surfaces were active toward the reduction of CO2, with a positive shift of the activity between darkness and irradiation conditions, 0.050 V with PDQ2 and 0.450 V with PMQ2. The main product of the CO2 reduction was CH3OH, with traces of CO and HCOOH. The PM modified electrodes with QDs of 2.77 nm presented a selective behaviour for the production of CH3OH.

4-(Fluorophenyl)thiolate-protected Ag44 clusters (Ph4P)4[Ag44(SC6H4F)30] were calcined on mesoporous carbon (MPC) under vacuum at 300–500 °C for 2 h. X-ray absorption spectroscopy, transmission electron microscopy, and thermal-desorption mass spectrometry revealed that sulfur-free Ag44 clusters were successfully produced by the calcination of [Ag44(SC6H4F)30]4– at 300 °C, in sharp contrast to the formation of silver sulfide nanoparticles by the calcination of dodecanethiolate-protected Ag nanoparticles (3.0 ± 0.6 nm). Ag44/MPC was applied in the catalytic dehydrogenation of ammonia–borane (NH3BH3) as a test reaction. It turned out that the Ag44/MPC catalysts produced 1 equiv of H2 from NH3BH3 but only in the presence of O2 (turnover frequency 1.9 × 103 h–1 Ag atom–1). Given that nanoparticles of other metals (Pt, Pd, Rh, Ni, or Ru) produced 3 equiv of H2 under an inert atmosphere, this result indicates that the Ag44/MPC-catalyzed dehydrogenation of NH3BH3 proceeds by a different mechanism from that on oth...

Supported Au25 clusters were prepared through the calcination of Au25(SC12H25)18 on hierarchically porous carbon nanosheets under vacuum at temperatures in the range of 400–500 °C for 2–4 h. TEM and EXAFS analyses revealed that the thiolate coverage on Au25 gradually decreased with increasing calcination temperature and period and became negligibly small when the calcination temperature exceeded 500 °C. The catalysis of these Au25 clusters was studied for the aerobic oxidation of benzyl alcohol. Interestingly, the selectivity for benzaldehyde formation was remarkably improved with the increase in the amount of residual thiolates on Au25, while the activity was reduced. This observation is attributed to the dual roles of the thiolates: the reduction of the oxidation ability of Au25 by electron withdrawal and the inhibition of the esterification reaction on the cluster surface by site isolation.

We synthesized and measured optical extinction spectra of Au ultrathin (diameter: ∼1.6 nm) nanowires (UNWs) and nanorods (UNRs) with controlled lengths in the range 20–400 nm. The Au UNWs and UNRs exhibited a broad band in the IR region whose peak position was red-shifted with the length. Polarized extinction spectroscopy for the aligned Au UNWs indicated that the IR band is assigned to the longitudinal mode of the surface plasmon resonance.