Synthesis of ultrathin platinum nanoplates for enhanced oxygen reduction activity.

Ultrathin Pt nanostructures exposing controlled crystal facets are highly desirable for their superior activity and cost-effectiveness in the electrocatalytic oxygen reduction reaction (ORR), and they are conventionally synthesized by epitaxial growth of Pt on a limited range of templates, such as Pd nanocrystals, resulting in a high cost and less structural diversity of the ultrathin Pt nanostructures. To solve this problem, we demonstrate that ultrathin Pt nanostructures can be synthesized by templating conveniently available Ag nanocrystals without involving galvanic replacement, which enables a much-reduced cost and controllable new morphologies, such as ultrathin Pt nanoplates that expose the {111} facets. The resulting ultrathin Pt nanoplates are ∼1-2 nm in thickness, which show an ∼22-fold increase in specific activity (5.3 mA cm-2), an ∼9.5-fold increase in mass activity (1.62 A mg-1) and significantly enhanced catalytic stability in the ORR, compared with the commercial Pt/C catalyst. We believe this strategy opens a door to a highly extendable family of ultrathin noble metal nanostructures, thus promising excellent activity and stability in a broad range of catalytic applications

High‑Throughput Electron Diffraction Reveals a Hidden Novel Metal–Organic Framework for Electrocatalysis

AbstractMetal‐organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X‐ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high‐throughput approach for structural analysis of MOF nano‐ and sub‐microcrystals by three‐dimensional electron diffraction (3DED). A new zeolitic‐imidazolate framework (ZIF), denoted ZIF‐EC1, was first discovered in a trace amount during the study of a known ZIF‐CO3‐1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF‐EC1 has a dense 3D framework structure, which is built by linking mono‐ and bi‐nuclear Zn clusters and 2‐methylimidazolates (mIm−). With a composition of Zn3(mIm)5(OH), ZIF‐EC1 exhibits high N and Zn densities. We show that the N‐doped carbon material derived from ZIF‐EC1 is a promising electrocatalyst for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications

Sisters.

"Sisters" is a final year project focussed on telling the story of sex workers in Singapore's Orchard Towers. Culminating in a film script as a final product, the story revolves around a pair of women connected to the sex work industry - a current sex worker and an ex-sex worker - and explores the intricacies of their interdependent relationship with each other. Based largely on real life events - a huge part of the scriptwriter's research and fieldwork - "Sisters" aims to let the audience have a glimpse of Orchard Tower's sex work industry and the problems sex workers face through the eyes of these two sisters, albeit non-biological. Along with their interactions with the people around them, when crisis strikes this pair of women and forces them to face the very elements that have turned them both in and out of this industry - will they be able to turn this crisis around to their advantage?Bachelor of Communication Studie

Amino/quaternary ammonium groups bifunctionalized large pore mesoporous silica for pH-responsive large drug delivery{

Mesoporous nanoparticles functionalized with amino groups on the pore surface and quaternary ammonium groups on the particle surface with particle sizes of 500-800 nm in length and 300-500 nm in diameter and a pore size of 7.2-7.4 nm, have been obtained through a post-synthesis and cocondensation method. Bleomycin (BLM) has been chosen as a model anti-cancer drug with a large molecular size, and the iron essential for organisms has been utilized for constructing NH 2 -Fe-BLM coordination bond architecture in the pore surface. The BLM was released under mildly acidic pH conditions by cleavage of the Fe-BLM coordination bond triggered by pH reduction. Cell assays show that mesoporous nanoparticles have good dispersity and good cell penetrating properties due to the positively charged quaternary ammonium groups on the outer surface of the nanoparticles. These organic functionalized large pore mesoporous materials can be utilized as carriers in the pHresponsive delivery of an anti-cancer drug with a large molecular size, opening up new opportunities for their further application in controlled release of biomacromolecules

Nanosized inorganic porous materials: fabrication, modification and application

International audienc

Synthesis of ultrathin platinum nanoplates for enhanced oxygen reduction activity.

Ultrathin Pt nanostructures exposing controlled crystal facets are highly desirable for their superior activity and cost-effectiveness in the electrocatalytic oxygen reduction reaction (ORR), and they are conventionally synthesized by epitaxial growth of Pt on a limited range of templates, such as Pd nanocrystals, resulting in a high cost and less structural diversity of the ultrathin Pt nanostructures. To solve this problem, we demonstrate that ultrathin Pt nanostructures can be synthesized by templating conveniently available Ag nanocrystals without involving galvanic replacement, which enables a much-reduced cost and controllable new morphologies, such as ultrathin Pt nanoplates that expose the {111} facets. The resulting ultrathin Pt nanoplates are ∼1-2 nm in thickness, which show an ∼22-fold increase in specific activity (5.3 mA cm-2), an ∼9.5-fold increase in mass activity (1.62 A mg-1) and significantly enhanced catalytic stability in the ORR, compared with the commercial Pt/C catalyst. We believe this strategy opens a door to a highly extendable family of ultrathin noble metal nanostructures, thus promising excellent activity and stability in a broad range of catalytic applications

Explaining the Size Dependence in Platinum-Nanoparticle-Catalyzed Hydrogenation Reactions.

Hydrogenation reactions are industrially important reactions that typically require unfavorably high H2 pressure and temperature for many functional groups. Herein we reveal surprisingly strong size-dependent activity of Pt nanoparticles (PtNPs) in catalyzing this reaction. Based on unambiguous spectral analyses, the size effect has been rationalized by the size-dependent d-band electron structure of the PtNPs. This understanding enables production of a catalyst with size of 1.2 nm, which shows a sixfold increase in turnover frequency and 28-fold increase in mass activity in the regioselective hydrogenation of quinoline, compared with PtNPs of 5.3 nm, allowing the reaction to proceed under ambient conditions with unprecedentedly high reaction rates. The size effect and the synthesis strategy developed herein may provide a general methodology in the design of metal-nanoparticle-based catalysts for a broad range of organic syntheses

Electrocatalytic water oxidation with manganese phosphates

Abstract As inspired by the Mn4CaO5 oxygen evolution center in nature, Mn-based electrocatalysts have received overwhelming attention for water oxidation. However, the understanding of the detailed reaction mechanism has been a long-standing problem. Herein, homologous KMnPO4 and KMnPO4•H2O with 4-coordinated and 6-coordinated Mn centers, respectively, are prepared. The two catalysts constitute an ideal platform to study the structure-performance correlation. The presence of Mn(III), Mn(IV), and Mn(V) intermediate species are identified during water oxidation. The Mn(V)=O species is demonstrated to be the substance for O−O bond formation. In KMnPO4•H2O, the Mn coordination structure did not change significantly during water oxidation. In KMnPO4, the Mn coordination structure changed from 4-coordinated [MnO4] to 5-coordinated [MnO5] motif, which displays a triangular biconical configuration. The structure flexibility of [MnO5] is thermodynamically favored in retaining Mn(III)−OH and generating Mn(V)=O. The Mn(V)=O species is at equilibrium with Mn(IV)=O, the concentration of which determines the intrinsic activity of water oxidation. This study provides a clear picture of water oxidation mechanism on Mn-based systems