Electroreduction of CO2 on Au(310)@Cu High-index Facets.

The chemical selectivity and faradaic efficiency of high-index Cu facets for the CO2 reduction reaction (CO2 RR) is investigated. More specifically, shape-controlled nanoparticles enclosed by Cu {hk0} facets are fabricated using Cu multilayer deposition at three distinct layer thicknesses on the surface facets of Au truncated ditetragonal nanoprisms (Au DTPs). Au DTPs are shapes enclosed by 12 high-index {310} facets. Facet angle analysis confirms DTP geometry. Elemental mapping analysis shows Cu surface layers are uniformly distributed on the Au {310} facets of the DTPs. The 7 nm Au@Cu DTPs high-index {hk0} facets exhibit a CH4 : CO product ratio of almost 10 : 1 compared to a 1 : 1 ratio for the reference 7 nm Au@Cu nanoparticles (NPs). Operando Fourier transform infrared spectroscopy spectra disclose reactive adsorbed *CO as the main intermediate, whereas CO stripping experiments reveal the high-index facets enhance the *CO formation followed by rapid desorption or hydrogenation.

Low-Pt NiNC-Supported PtNi Nanoalloy Oxygen Reduction Reaction Electrocatalysts-In Situ Tracking of the Atomic Alloying Process.

We report and analyze a synthetic strategy toward low-Pt platinum-nickel (Pt-Ni) alloy nanoparticle (NP) cathode catalysts for the catalytic electroreduction of molecular oxygen to water. The synthesis involves the pyrolysis and leaching of Ni-organic polymers, subsequent Pt NP deposition, followed by thermal alloying, resulting in single Ni atom site (NiNC)-supported PtNi alloy NPs at low Pt weight loadings of only 3-5 wt %. Despite low Pt weight loading, the catalysts exhibit more favorable Pt-mass activities compared to conventional 20-30 wt % benchmark PtNi catalysts. Using in situ microscopic techniques, we track and unravel the key stages of the PtNi alloy formation process directly at the atomic scale. Surprisingly, we find that carbon-encapsulated metallic Ni@C structures, rather than NiNx sites, act as the Ni source during alloy formation. Our materials concepts offer a pathway to further decrease the overall Pt content in hydrogen fuel cell cathodes.

Isolating contiguous Pt atoms and forming Pt-Zn intermetallic nanoparticles to regulate selectivity in 4-nitrophenylacetylene hydrogenation.

Noble metals play a momentous role in heterogeneous catalysis but still face a huge challenge in selectivity control. Herein, we report isolating contiguous Pt atoms and forming Pt-Zn intermetallic nanoparticles as an effective strategy to optimize the selectivity of Pt catalysts. Contiguous Pt atoms are isolated into single atoms and Pt-Zn intermetallic nanoparticles are formed which are supported on hollow nitrogen-doped carbon nanotubes (PtZn/HNCNT), as confirmed by aberration-corrected high-resolution transmission electron microscopy and X-ray absorption spectrometry measurements. Interestingly, this PtZn/HNCNT catalyst promotes the hydrogenation of 4-nitrophenylacetylene to 4-aminophenylacetylene with a much higher conversion ( > 99%) and selectivity (99%) than the comparison samples with Pt isolated-single-atomic-sites (Pt/HNCNT) and Pt nanoparticles (Pt/CN). Further density functional theory (DFT) calculations disclose that the positive Zn atoms assist the adsorption of nitro group and Pt-Zn intermetallic nanoparticles facilitate the hydrogenation on nitro group kinetically.

Mesoporous Nitrogen-Doped Carbon-Nanosphere-Supported Isolated Single-Atom Pd Catalyst for Highly Efficient Semihydrogenation of Acetylene.

Semihydrogenation of acetylene in the ethylene feed is a vital step for the industrial production of polyethylene. Despite their favorable reaction activity and ethylene selectivity, the Pd-based intermetallic compound and single-atom alloy catalysts still suffer from the limitation of atomic utilization derived from the partial exposure of active Pd atoms. Herein, a hard-template Lewis acid doping strategy is reported that can overcome the inefficient utilization of Pd atoms. In this strategy, N-coordinated isolated single-atomic Pd sites are fully embedded on the inner walls of mesoporous nitrogen-doped carbon foam nanospheres (ISA-Pd/MPNC). This synthetic strategy has been proved to be applicable to prepare other ISA-M/MPNC (M = Pt and Cu) materials. This ISA-Pd/MPNC catalyst with both high specific surface area (633.8 m2 g-1 ) and remarkably thin pore wall (1-2 nm) exhibits higher activity than that of its nonmesoporous counterpart (ISA-Pd/non-MPNC) catalyst by a factor of 4. This work presents an efficient way to tailor and optimize the catalytic activity and selectivity by atomic-scale design and structural control.

Temperature-Controlled Selectivity of Hydrogenation and Hydrodeoxygenation in the Conversion of Biomass Molecule by the Ru1/mpg-C3N4 Catalyst.

Hydrogenation and hydrodeoxygenation are significant and distinct approaches for the conversion of biomass and biomass-derived oxygenated chemicals into high value-added chemicals and fuels. However, it remains a great challenge to synthesize catalysts that simultaneously possess excellent hydrogenation and hydrodeoxygenation performance. Herein, we report a catalyst made of isolated single-atom Ru supported on mesoporous graphitic carbon nitride (Ru1/mpg-C3N4), fabricated by a wet impregnation method. The as-prepared Ru1/mpg-C3N4 catalyst shows excellent hydrogenation and hydrodeoxygenation performance. First-principles calculations reveal that the Ru atom is mobilized, and the active site is induced by adsorption of the reactants. A systematic reaction mechanism is proposed, suggesting that vanillyl alcohol is the deoxygenation prohibited product, while 2-methoxy- p-cresol is the deoxygenation allowed product. Thus, the excellent selectivity for the hydrogenation or hydrodeoxygenation of vanillin at different temperatures results from switching between the two types of products.

Carbon nitride supported Fe2 cluster catalysts with superior performance for alkene epoxidation.

Sub-nano metal clusters often exhibit unique and unexpected properties, which make them particularly attractive as catalysts. Herein, we report a "precursor-preselected" wet-chemistry strategy to synthesize highly dispersed Fe2 clusters that are supported on mesoporous carbon nitride (mpg-C3N4). The obtained Fe2/mpg-C3N4 sample exhibits superior catalytic performance for the epoxidation of trans-stilbene to trans-stilbene oxide, showing outstanding selectivity of 93% at high conversion of 91%. Molecular oxygen is the only oxidant and no aldehyde is used as co-reagent. Under the same condition, by contrast, iron porphyrin, single-atom Fe, and small Fe nanoparticles (ca. 3 nm) are nearly reactively inert. First-principles calculations reveal that the unique reactivity of the Fe2 clusters originates from the formation of active oxygen species. The general applicability of the synthesis approach is further demonstrated by producing other diatomic clusters like Pd2 and Ir2, which lays the foundation for discovering diatomic cluster catalysts.

Strain Engineering to Enhance the Electrooxidation Performance of Atomic-Layer Pt on Intermetallic Pt3Ga.

Strain engineering has been a powerful strategy to finely tune the catalytic properties of materials. We report a tensile-strained two-to-three atomic-layer Pt on intermetallic Pt3Ga (AL-Pt/Pt3Ga) as an active electrocatalyst for the methanol oxidation reaction (MOR). Atomic-resolution high-angle annular dark-field scanning transmission electron microscopy characterization showed that the AL-Pt possessed a 3.2% tensile strain along the [001] direction while having a negligible strain along the [100]/[010] direction. For MOR, this tensile-strained AL-Pt electrocatalyst showed obviously higher specific activity (7.195 mA cm-2) and mass activity (1.094 mA/µgPt) than those of its unstrained counterpart and commercial Pt/C catalysts. Density functional theory calculations demonstrated that the tensile-strained surface was more energetically favorable for MOR than the unstrained one, and the stronger binding of OH* on stretched AL-Pt enabled the easier removal of CO*.

Isolated Single-Atom Pd Sites in Intermetallic Nanostructures: High Catalytic Selectivity for Semihydrogenation of Alkynes.

Improving the catalytic selectivity of Pd catalysts is of key importance for various industrial processes and remains a challenge so far. Given the unique properties of single-atom catalysts, isolating contiguous Pd atoms into a single-Pd site with another metal to form intermetallic structures is an effective way to endow Pd with high catalytic selectivity and to stabilize the single site with the intermetallic structures. Based on density functional theory modeling, we demonstrate that the (110) surface of Pm3̅m PdIn with single-atom Pd sites shows high selectivity for semihydrogenation of acetylene, whereas the (111) surface of P4/mmm Pd3In with Pd trimer sites shows low selectivity. This idea has been further validated by experimental results that intermetallic PdIn nanocrystals mainly exposing the (110) surface exhibit much higher selectivity for acetylene hydrogenation than Pd3In nanocrystals mainly exposing the (111) surface (92% vs 21% ethylene selectivity at 90 °C). This work provides insight for rational design of bimetallic metal catalysts with specific catalytic properties.

Intermetallic Nix My (M = Ga and Sn) Nanocrystals: A Non-precious Metal Catalyst for Semi-Hydrogenation of Alkynes.

Intermetallic Nix My (M = Ga and Sn) nanocrystals with uniform particle size and controlled composition are successfully synthesized via a solution-based co-reduction strategy. The as-obtained nanocrystals are crystalline and structurally ordered. The active-site isolation and modified electronic structure are responsible for the excellent catalytic performance for alkyne semi-hydrogenation of the as-obtained non-precious catalysts.

Silver nanowire-based electrochemical immunoassay for sensing immunoglobulin G with signal amplification using strawberry-like ZnO nanostructures as labels.

The quick development of nanoscience and nanotechnology has paved the way for ultrasensitive biosensing and analysis. In this work, an ultrasensitive electrochemical immunosensor was developed for the detection of human immunoglobulin G (IgG) by combining with a newly designed trace tag on a disposable immunosensor array. The array was prepared by immobilizing captured antibodies on ultralong Ag nanowires, whilst the trace tag was prepared by loading horseradish peroxidase (HRP)-labeled goat anti-human IgG (HRP-anti-IgG) on thionine (TH)-doped mesoporous ZnO nanostrawberries (MP-ZnO). With a sandwich-type immunoassay format, mainly due to crystalline framework and high surface area of the mesoporous (MP) materials, as well as the superconductivity of silver nanowires, the electrochemical signal was significantly amplified. The linear range of the developed immunosensor is 0.01-200 ng mL(-1) and the detection limit is 4 pg mL(-1) IgG, which make the hierarchically nanostructured composites very promising candidates for the next-generation sandwich-type electrochemical immunoassays.

Ultrathin CdSe nanosheets: synthesis and application in simultaneous determination of catechol and hydroquinone.

Ultrathin crystalline CdSe nanosheets have been synthesized through a facile solution processes. Their application to simultaneous electrochemical determination of catechol and hydroquinone is demonstrated. The few-layer single crystalline CdSe modified electrode exhibits strong electrocatalytic activity toward the oxidation of a mixture of catechol and hydroquinone. The excellent analytical performance makes the ultrathin CdSe nanomaterials promising for the development of electrochemical sensors for potential applications in medicine, biotechnology and environmental chemistry.

Suppression subtractive hybridization analysis of gene expression during late kidney development identifies the developmentally regulated gene rPEA3.

BACKGROUND: While early kidney development has been studied exhaustively, the later stages of nephrogenesis that occur after birth in the rodent are relatively poorly understood. To gain insight into this process, we detected the alterations in gene expression in rat kidney at two postnatal stages, P0 (0 day after birth), the time at which nephrogensis is still active, and P21 (21 days after birth), when nephrogenesis is complete. METHODS: Sprague-Dawley rats were mated, and appearance of a vaginal plug was designated as E0. Kidneys were dissected from embryos at E13, E15, E17 and E19, and from postnatal days P0, P7, P14, P21 and adult rats. Suppression subtractive hybridization (SSH) analysis was performed and highly expressed genes were evaluated as molecular markers by real-time reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, immunofluorescence, and Western blot. RESULTS: Several differentially expressed genes were identified, including rPEA3, a member of the PEA3 subfamily of Ets domain transcription factors. Real time RT-PCR analysis revealed that rPEA3 exhibited dynamic developmental regulation, with high levels of expression from embryonic day E15 until birth, and declining levels thereafter. By in situ hybridization, rPEA3 mRNA was detected in the ureteric bud (UB) and surrounding metanephric mesenchyme of the kidneys from E15 until birth, but was undetectable in mature kidneys. Double-immunofluorescence staining showed that both rPEA3 and WT1 expressed in the condensed mesenchymal cells at E15 and E17; and later from E19 to P7, both expressed in the epithelial cells of ureteric bud and their branches. CONCLUSIONS: These studies provide compelling evidence that SSH is an effective method for identifying genes that are regulated during renal development, and suggest that the newly identified gene rPEA3 may play an important role in kidney development and differentiation.