1,721,159 research outputs found
Guided formation of sub-5 nm interstitial gaps between plasmonic nanodisks
No full textTo achieve a reliable formation of a surface-enhanced Raman scattering (SERS) sensor with evenly distributed hot spots on a wafer scale substrate, we propose a hybrid approach combining physical nanolithography for preparing Au nanodisks and chemical Au reduction for growing them. During the chemical growth, the interstitial distance between the nanodisks decreased from 60 nm to sub-5 nm. The resulting patterns of the nanogap-rich Au nanodisks successfully enhance the SERS signal, and its intensity map shows only a 5% or less signal variation on the entire sample. This journal is © The Royal Society of Chemistry1231sciescopu
One-Pot Synthesis and Electrocatalytic Properties of Pd@Pt Core-Shell Nanocrystals with Tailored Morphologies
No full textPd@Pt core-shell nanocrystals consisting of well-defined Pd nanocube cores and dendritic Pt shells were prepared by a new facile aqueous one-pot synthetic method. The prepared Pd@Pt nanocrystals exhibited efficient catalytic activity and stability toward methanol electrooxidation, and their catalytic function was highly dependent on their Pt shell thickness due to the different synergism between Pt and Pd. Go nano! Pd@Pt core-shell nanocrystals consisting of well-defined Pd nanocube cores and dendritic Pt shells were prepared by a new facile aqueous one-pot synthetic method. The Pd@Pt nanocrystals exhibited efficient catalytic activity and stability toward methanol electrooxidation, and their catalytic function was highly dependent on their Pt shell thickness due to the different synergism between Pt and Pd (see scheme). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.121221sciescopu
One-pot synthesis of Au@Pd core-shell nanocrystals with multiple high- and low-index facets and their high electrocatalytic performance
No full textBimetallic nanocrystals (NCs) enclosed by high-surface energy facets have been of enormous interest due to their pronounced catalytic performance in numerous chemical and electrochemical reactions. However, it remains a significant challenge to develop a facile method to synthesize bimetallic NCs with high-surface energy facets in the form of finely tuned structures due to the difficulties in manipulating the nucleation and growth kinetics of NCs in the presence of multiple metal precursors. In the present work, a facile one-pot aqueous synthesis method is developed for the production of bimetallic Au@Pd core–shell NCs with an unusual truncated hexoctahedral (THOH) shape without pre-synthesized seeds. The THOH Au@Pd NCs are bound by multiple high- and low-index facets. The formation of this unique structure is realized through co-reduction of Au and Pd precursors under precisely controlled kinetic conditions. The prepared THOH NCs exhibit a prominent electrocatalytic performance for ethanol oxidation, which is attributed to their characteristic structural features. This study significantly expands the understanding of NC growth and will lead to fabricating novel nanomaterials with desired morphologies and functions.127281sciescopu
One-Pot Synthesis of CeO2-Supported Pd-Cu-Alloy Nanocubes with High Catalytic Activity
No full text118181sciescopu
Nitrogen-Doped Pt/C Electrocatalysts with Enhanced Activity and Stability toward the Oxygen Reduction Reaction
No full textRecently, nitrogen-doped carbon materials have proved to be
effective catalytic platforms for the oxygen reduction reaction
(ORR). Despite the recent synthetic advances for the preparation
of nitrogen-incorporated carbon materials, the low-temperature
and water-based synthesis of nitrogen-doped carbon
materials has rarely been explored due to the difficulties in nitrogen-
doping under such mild conditions. Here, nitrogendoped
Pt/C (Pt/NC) catalysts are prepared using a facile, lowtemperature,
aqueous-phase method. Hydrazine treatment of
a Pt/C catalyst successfully yields Pt/NC with controlled nitrogen
content. The as-prepared Pt/NC catalysts exhibit enhanced
electrocatalytic activity and stability toward ORR in comparison
to nitrogen-free Pt/C, and their ORR activities are highly dependent
on the level of nitrogen-doping. The Pt/NC catalyst containing
2.0 at% nitrogen results in the largest improvement of
ORR activity.1221sciescopu
Polyoxometalate-mediated one-pot synthesis of pd nanocrystals with controlled morphologies for efficient chemical and electrochemical catalysis
No full textPolyoxometalates (POMs), as inorganic ligands, can endow metal nanocrystals (NCs) with unique reactivities on account of their characteristic redox properties. In the present work, we present a facile POM-mediated one-pot aqueous synthesis method for the production of single-crystalline Pd NCs with controlled shapes and sizes. The POMs could function as both reducing and stabilizing agents in the formation of NCs, and thus gave a fine control over the nucleation and growth kinetics of NCs. The prepared POM-stabilized Pd NCs exhibited excellent catalytic activity and stability for electrocatalytic (formic acid oxidation) and catalytic (Suzuki coupling) reactions compared to Pd NCs prepared without the POMs. This shows that the POMs play a pivotal role in determining the catalytic performance, as well as the growth, of NCs. We envision that the present approach can offer a convenient way to develop efficient NC-based catalyst systems. Single-crystalline Pd nanocrystals with controlled shapes and sizes were synthesized by a polyoxometalate-mediated one-pot aqueous synthesis method. The prepared Pd nanocrystals exhibited enhanced catalytic properties toward electrochemical and chemical reactions (see figure). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim1881sciescopu
The facet-dependent enhanced catalytic activity of Pd nanocrystals
No full textA systematic study of heterogeneous Buchwald–Hartwig amination using shape-controlled Pd nanocrystals with distinctly different surface facets is presented.122221sciescopu
Designed Synthesis of Well-Defined Pd@Pt Core-Shell Nanoparticles with Controlled Shell Thickness as Efficient Oxygen Reduction Electrocatalysts
No full textImproving the electrocatalytic activity and durability of Pt-based catalysts with low Pt content toward the oxygen reduction reaction (ORR) is one of the main challenges in advancing the performance of polymer electrolyte membrane fuel cells (PEMFCs). Herein, a designed synthesis of well-defined Pd@Pt core–shell nanoparticles (NPs) with a controlled Pt shell thickness of 0.4–1.2 nm by a facile wet chemical method and their electrocatalytic performances for ORR as a function of shell thickness are reported. Pd@Pt NPs with predetermined structural parameters were prepared by in situ heteroepitaxial growth of Pt on as-synthesized 6 nm Pd NPs without any sacrificial layers and intermediate workup processes, and thus the synthetic procedure for the production of Pd@Pt NPs with well-defined sizes and
shell thicknesses is greatly simplified. The Pt shell thickness could be precisely controlled by adjusting the molar ratio of Pt to Pd. The ORR performance of the Pd@Pt NPs strongly depended on the thickness of their Pt shells. The Pd@Pt NPs with 0.94 nm Pt shells exhibited enhanced specific activity
and higher durability compared to other Pd@Pt NPs and commercial Pt/C catalysts. Testing Pd@Pt NPs with 0.94 nm Pt shells in a membrane electrode assembly revealed a single-cell performance comparable with that of the Pt/C catalyst despite their lower Pt content, that is the present NP catalysts
can facilitate low-cost and high-efficient applications of PEMFCs.163651sciescopu
Synthesis of chestnut-bur-like palladium nanostructures and their enhanced electrocatalytic activities for ethanol oxidation
No full textWe report a facile method for the synthesis of Pd nanostructures with highly open structure and huge surface area by reducing Na2PdCl 4 with ascorbic acid and using cetylpyridinium chloride (CPC) as a surfactant in an aqueous solution. The prepared Pd nanostructures had an average overall size of 70 nm and were composed of dozens of needle-like thin arms, originating from the same core, with an average thickness of 2.3 nm; the arms looked like chestnut-burs. Time evolution of Pd nanostructures implied that small Pd particles generated at the early stage of the reaction by fast reduction grew via the particle attachment growth mechanism. The morphology and size of the Pd nanostructures could be readily controlled by varying the concentration of CPC; depending on the amount of CPC, the reduction rates varied the morphology of the Pd nanostructures. Because of the huge surface area and possible catalytically active sites, the prepared chestnut-bur-like Pd nanostructures exhibited greater electrocatalytic activity toward ethanol electrooxidation compared to other Pd nanocatalysts, including cubic and octahedral Pd nanocrystals, and even commercial Pd/C. © the Partner Organisations 2014.121201sciescopu
The effective nuclear delivery of doxorubicin from dextran-coated gold nanoparticles larger than nuclear pores
No full textTo date, gold nanoparticles (AuNPs) have been investigated for diverse bioapplications. Generally, AuNPs are engineered to possess surface coating with organic/inorganic shells to increase colloidal stability in biological solutions and to facilitate chemical conjugation. In the present study, we developed a strategy to prepare dextran-coated AuNPs with control over its size by simply boiling an aqueous solution of Au salt and dextran, in which dextran serves as both reducing agent for AuNP (Au(0)) formation from Au(III) and AuNP surface coating material. The prepared dextran-coated AuNPs (dAuNPs) maintained its colloidal stability under high temperature, high salt concentration, and extreme pH. Importantly, the dAuNP remarkably improved efficacy of an anti-cancer agent, doxorubicin (Dox), when harnessed as a Dox delivery carrier. The half-maximal inhibitory concentration (EC50) of Dox-conjugated dAuNP with diameter of 170 nm was w9 pM in HeLa cells, which was 1.1 105 times lower than that of free Dox and lower than any previously reported values of Dox-nanoparticle complex. Interestingly, smaller AuNPs with 30 and 70 nm showed about 10 times higher EC50 than 170 nm AuNPs when treated to HeLa cells after conjugation with Dox. To achieve high cytotoxicity as cancer therapeutics, Dox should be delivered into nucleus to intercalate with DNA double helix. We show here that Dox-AuNPs was far more efficient as an anti-cancer drug than free Dox by releasing from AuNPs through spontaneous degradation of dextran, allowing free diffusion and nuclear uptake of Dox. We also revealed that larger AuNPs with lower degree of dextran crosslinking promoted faster degradation of dextran shells.148541sciescopu
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