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Cu(I)-catalyzed azide-alkyne cycloadditions (CuAAC) have gained increasing interest in the selective labeling of living cells and organisms with biomolecules. However, their application is constrained either by the high cytotoxicity of Cu(I) ions or the low activity of CuAAC in the internal space of living cells. This paper reports the design of a novel Cu-based nanocatalyst, water-soluble thiolated Cu30 nanoclusters (NCs), for living cell labeling via CuAAC. The Cu30 NCs offer good biocompatibility, excellent stability, and scalable synthesis (e.g., gram scale), which would facilitate potential commercial applications. By combining the highly localized Cu(I) active species on the NC surface and good structural stability, the Cu30 NCs exhibit superior catalytic activities for a series of Huisgen cycloaddition reactions with good recyclability. More importantly, the biocompatibility of the Cu30 NCs enables them to be a good catalyst for CuAAC, whereby the challenging labeling of living cells can be achieved via CuAAC on the cell membrane. This study sheds light on the facile synthesis of atomically precise Cu NCs, as well as the design of novel Cu NCs-based nanocatalysts for CuAAC in intracellular bioorthogonal applications. [ABSTRACT FROM AUTHOR]

Metal nanoclusters (NCs) with precise structure and ultrasmall size have attracted great interests in catalysis. However, the poor stability has limited its large-scale use. Herein, we proposed the "covalence bridge" strategy to effectively connect atomically precise metal NCs and metal-organic frameworks. Benefiting from the covalent linkage, the synthesized UiO-66-NH2-Au25(L-Cys)18 showed outstanding stability after 16 h photocatalysis. Moreover, the covalence bridge created a strong metal-support interaction between the two components and provided an effective charge transport channel and thereby enhanced photocatalytic activity. UiO-66-NH2-Au25(L-Cys)18 displayed an exceptional photocatalytic H2 production rate, which is 21 and 90 times higher than that of UiO-66-NH2/Au25(PET)18 (made by physically combination) and bare UiO-66-NH2, respectively. Thermodynamic and kinetic studies demonstrated that UiO-66-NH2-Au25(L-Cys)18 exhibited higher charge transfer efficiency, lower overpotential of water reduction and activation energy barrier compared with its counterparts. [ABSTRACT FROM AUTHOR]

Achieving superior performance of nanoparticle systems is one of the biggest challenges in catalysis. Two major phenomena, occurring during the reactions, hinder the development of the full potential of nanoparticle catalysts: sintering and contamination with carbon containing species, sometimes called coking. Here, we demonstrate that Ir nanocrystals, arranged into periodic networks on hexagonal boron nitride (h-BN) supports, can be restored without sintering after contamination by persistent carbon. This restoration yields the complete removal of carbon from the nanocrystals, which keep their crystalline structure, allowing operation without degradation. These findings, together with the possibility of fine tuning the nanocrystals size, confer this nanoparticle system a great potential as a testbed to extract key information about catalysis-mediated oxidation reactions. For the case of the CO oxidation by O2, reaction of interest in environmental science and green energy production, the existence of chemical processes not observed before in other nanoparticle systems is demonstrated. [ABSTRACT FROM AUTHOR]

Hydrogenation of p-nitrophenol (PNP) towards the conversion to p-aminophenol (PAP) by metal catalysis is known as a simple and eco-friendly technique for the production of corresponding industrial and pharmaceutical intermediates. While continuous efforts are paid for more sustainable and greener procedures by using transition metal catalysts, atomic-precise reaction mechanism for the PNP-to-PAP is still illusive to be fully understood. Utilizing a dry-wet combined strategy, here we have synthesized water-soluble Pd8 nanoclusters (NCs) with mercaptosuccinic acid (H2SMA) as the ligand, and the Pd8 NCs found high catalytic performance for the conversion of PNP-to-PAP, as identified by the electrospray ionization mass spectrometer (ESI-MS) measurement. The gradual changes over time of ultraviolet–visible (UV–vis) spectra of PNP really display the catalytic reduction by NaBH4 in presence of Pd8 NCs. Further, in-depth charge transfer interactions between PNP and the Pd8 clusters at the proton-rich conditions are investigated by natural bond orbital (NBO) analysis and electron density difference (EDD) analysis. The exothermic and kinetic-favorable reaction pathways are addressed, based on successive PNP hydrogenation and H2O removal processes, clarifying the reaction mechanism of Pd catalysts. It is worth noting that this solid-state synthetic route for such Pd8 clusters enables gram-scale quantity of production in likely practical use. [ABSTRACT FROM AUTHOR]

Development of low-cost and high-performance catalysts for hydrogen generation via hydrolysis of ammonia borane (NH3BH3, AB) is a highly desirable pathway for future hydrogen utilization. In this work, Ni nanocatalysts doped with CeOx and supported on graphene (Ni-CeOx/graphene) were synthesized via a facile chemical reduction route and applied as robust catalysts for the hydrolysis of AB in aqueous solution at room temperature. The as-synthesized Ni-CeOx/graphene nanocomposites (NCs) exhibited excellent catalytic activity with a turnover frequency (TOF) as high as 68.2 min−1, which is 49-fold higher than that for a simple Ni nanoparticle catalyst and is among the highest values reported for non-noble metal catalysts in AB hydrolysis. The development of efficient and low-cost Ni-CeOx/graphene catalysts enhances the feasibility of using ammonia borane as a chemical hydrogen storage material, which may find application ina hydrogen fuel-cell based economy. [ABSTRACT FROM AUTHOR]

Nanoparticles of catalytically important transition metals, such as Pd, Pt, Rh, and Ru have been prepared by the well-known 'digestive ripening' (DR) and 'modified digestive ripening' (mDR) methods. In the traditional DR process, a polydisperse colloidal dispersion is refluxed in the presence of a surface-active molecule, such as alkanethiol. The mDR method involved a small modification in the procedure, wherein refluxing was performed with an alkanethiol and a tetra-alkylammonium bromide surfactant. This minor modification led to a dramatic change in the final particle size distributions, giving access to nanoparticles in the <3 nm size regime; this was not possible with the traditional DR process. Bromide ions, which are present during refluxing, proved to be an important ingredient in the modification process. These bromide ions are revealed to act as etchants, resulting in ultra-small nanoparticles. All transition metal nanoparticles investigated displayed catalytic activity in the reduction reaction of p-nitro phenol. Pd nanoparticles, synthesized by a modified digestive ripening method, exhibited the best catalytic activity among the systems investigated. [ABSTRACT FROM AUTHOR]

Matryoshka-caged gold nanorods (mCGNRs) were successfully synthesized by alternating between a seed-mediated silver-coating method and galvanic replacement reactions (GRRs). As the number of matryoshka layers of the mCGNRs increased, the plasmon resonance peak broadened and was red-shifted, and the catalytic activity towards the reduction of 4-nitrophenol (4-NTP) increased. When mCGNRs with 6 layers were used as nanocatalysts in the reduction of 4-nitrophenol, the reaction rate coefficient was 5.2- and 3.7-times higher than that of the gold-nanorod- and caged-gold-nanorod-catalyzed reductions of 4-nitrophenol, respectively. In addition, the surface-plasmon-resonance-based absorption of light enhanced the catalytic performance of the mCGNRs. With the support of a polyurethane foam, the mCGNRs synthesized in this study can be applied as recyclable heterogeneous catalysts for the reduction of 4-nitrophenol. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

eterogeneous catalytic reactions involve the use of highly dispersed active phases such as metal, metal oxide, or metal sulphide nanoparticles on thermally stable supports. Fluctuations of the reaction temperature during the reactions can induce sintering of the particles. The stability of such small particles represents a crucial parameter in the development of new families of catalysts with high activity in many fields. Here we report the stability of platinum nanoparticles (2-3 nm) on a few-layer graphene (FLG) surface as studied by in situ high temperature transmission electron microscopy. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Monodisperse Au nanoparticles (NPs) have been synthesized at room temperature via a burst nucleation of Au upon injection of the reducing agent t-butylamine-borane complex into a 1, 2, 3, 4-tetrahydronaphthalene solution of HAuCl4·3H2O in the presence of oleylamine. The as-synthesized Au NPs show size-dependent surface plasmonic properties between 520 and 530 nm. They adopt an icosahedral shape and are polycrystalline with multiple-twinned structures. When deposited on a graphitized porous carbon support, the NPs are highly active for CO oxidation, showing 100% CO conversion at −45 °C. [ABSTRACT FROM AUTHOR]