Core/shell-structured bimetallic nanocluster catalysts for visible-light-induced electron transfer

2000 ◽  
Vol 72 (1-2) ◽  
pp. 317-325 ◽  
Author(s):  
Naoki Toshima
Keyword(s):  
Electron Transfer ◽  
Visible Light ◽  
Hydrogen Generation ◽  
Cation Radical ◽  
Water Soluble ◽  
Core Shell ◽  
Metal Nanoclusters ◽  
Water Soluble Polymer ◽  
The Core ◽  
Bimetallic Nanoclusters

It has been found that the bimetallic nanoclusters often have so-called core/shell structure if they are prepared by alcohol-reduction of two kinds of noble metal ions in the presence of a water-soluble polymer like poly(N-vinyl-2-pyrolidone)(PVP), and that the core/ shell structured bimetallic nanoclusters have much higher catalytic activity than the corresponding monometallic nanoclusters. Here, several kinds of monometallic and bimetallic nanoclusters are synthesized by the similar method, and the catalyses are measured. Thus, the colloidal dispersions of Au, Pt, Pd, Rh, and Ru monometallic, and Au/Pt, Au/Pd, Au/Rh, and Pt/Ru bimetallic nanoclusters were synthesized and applied as the catalysts for visible-light- induced hydrogen generation. The core/shell structures are analyzed mainly by UV–vis spectra. The rate of electron transfer from the methyl viologen cation radical to the metal nanoclusters is proportional to the hydrogen generation rate at the steady state. All the electrons accepted by the metal nanoclusters are used for the hydrogen generation. Both electron transfer and hydrogen generation rates increase when the bimetallic nanoclusters are used in place of the corresponding monometallic nanoclusters. The most active catalysts were Au/Rh and Pt/Ru bimetallic nanoclusters.

Visible-light driven photocatalytic hydrogen generation by water-soluble all-inorganic core–shell silicon quantum dots

2020 ◽  
Vol 8 (31) ◽  
pp. 15789-15794
Author(s):  
Hiroshi Sugimoto ◽  
Hao Zhou ◽  
Miho Takada ◽  
Junichiro Fushimi ◽  
Minoru Fujii
Keyword(s):  
Quantum Dots ◽  
Visible Light ◽  
Quantum Confinement ◽  
Hydrogen Generation ◽  
Water Soluble ◽  
Core Shell ◽  
Photocatalytic Hydrogen Generation ◽  
Quantum Size ◽  
Visible Light Driven ◽  
Si Quantum Dots

Photocatalytic H2 generation by B,P-codoped Si quantum dots (QDs) with diameters in the quantum confinement regime is investigated. The H2 generation rate is enhanced by the increase of reduction ability of Si QDs owing to the quantum size effect.

scholarly journals Solubilization of Charged Porphyrins in Interpolyelectrolyte Complexes: A Computer Study

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 502
Author(s):  
Karel Šindelka ◽  
Zuzana Limpouchová ◽  
Karel Procházka
Keyword(s):  
Dissipative Particle Dynamics ◽  
Water Soluble ◽  
Coarse Grained ◽  
Core Shell ◽  
Computer Study ◽  
Interpolyelectrolyte Complex ◽  
The Core ◽  
Porphyrin Derivatives ◽  
Oppositely Charged ◽  
Positively Charged

Using coarse-grained dissipative particle dynamics (DPD) with explicit electrostatics, we performed (i) an extensive series of simulations of the electrostatic co-assembly of asymmetric oppositely charged copolymers composed of one (either positively or negatively charged) polyelectrolyte (PE) block A and one water-soluble block B and (ii) studied the solubilization of positively charged porphyrin derivatives (P+) in the interpolyelectrolyte complex (IPEC) cores of co-assembled nanoparticles. We studied the stoichiometric mixtures of 137 A10+B25 and 137 A10−B25 chains with moderately hydrophobic A blocks (DPD interaction parameter aAS=35) and hydrophilic B blocks (aBS=25) with 10 to 120 P+ added (aPS=39). The P+ interactions with other components were set to match literature information on their limited solubility and aggregation behavior. The study shows that the moderately soluble P+ molecules easily solubilize in IPEC cores, where they partly replace PE+ and electrostatically crosslink PE− blocks. As the large P+ rings are apt to aggregate, P+ molecules aggregate in IPEC cores. The aggregation, which starts at very low loadings, is promoted by increasing the number of P+ in the mixture. The positively charged copolymers repelled from the central part of IPEC core partially concentrate at the core-shell interface and partially escape into bulk solvent depending on the amount of P+ in the mixture and on their association number, AS. If AS is lower than the ensemble average ⟨AS⟩n, the copolymer chains released from IPEC preferentially concentrate at the core-shell interface, thus increasing AS, which approaches ⟨AS⟩n. If AS>⟨AS⟩n, they escape into the bulk solvent.

Medicated structural PVP/PEG composites fabricated using coaxial electrospinning

e-Polymers ◽  
2017 ◽  
Vol 17 (1) ◽  
pp. 39-44 ◽  
Author(s):  
Yong-Hui Wu ◽  
Deng-Guang Yu ◽  
Hai-Peng Li ◽  
Xiang-Yang Wu ◽  
Xiao-Yan Li
Keyword(s):  
Electron Microscope ◽  
Citric Acid ◽  
Shell Structure ◽  
Water Soluble ◽  
Working Fluid ◽  
Coaxial Electrospinning ◽  
Core Shell ◽  
The Core ◽  
Poorly Water Soluble ◽  
Core Shell Structure

AbstractA new type of medicated polymeric composite consisting of acyclovir (ACY), polyvinylpyrrolidone K60 (PVP) and polyethylene glycol 6000 (PEG) with core-shell structure were prepared by a coaxial electrospinning process. The composites could enhance the dissolution of the poorly water-soluble drug. The shell layers were formed from a spinnable working fluid containing the filament-forming PVP and citric acid while the core parts were prepared from an un-spinnable co-dissolving solution composed of ACY, sodium hydrate and PEG. Scanning electron microscope and transmission electron microscope observations demonstrated that the composites had a homogeneous linear topography with a slippery surface, a diameter of 670±130 nm, and an obvious core-shell structure. X-ray diffraction (XRD) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy results demonstrated that the drug and citric acid contained in the core and shell parts were in an amorphous status. In vitro dissolution experiments exhibited that ACY was able to be free within 1 min, and the dissolution media were neutral due to acid-basic action within the core-shell structures. The medicated nanocomposites resulted from a combined usage of hydrophilic polymeric excipients PVP and PEG could provide a new solution to the problem associated with the dissolution of poorly water-soluble drugs.

Ultra-thin C3N4 nanosheets for rapid charge transfer in the core–shell heterojunction of α-sulfur@C3N4 for superior metal-free photocatalysis under visible light

RSC Advances ◽  
2015 ◽  
Vol 5 (20) ◽  
pp. 15052-15058 ◽  
Author(s):  
Xueming Dang ◽  
Xiufang Zhang ◽  
Weiqiang Zhang ◽  
Xiaoli Dong ◽  
Guowen Wang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Visible Light ◽  
Core Shell ◽  
Photocatalytic Ability ◽  
Metal Free ◽  
The Core ◽  
Visible Light Driven

Enhanced visible-light-driven photocatalytic ability is obtained by fabricating an α-S@C3N4 heterojunction with ultra-thin C3N4 nanosheet as the means of rapid charge transfer.

Photocatalytic hydrogen generation from water under visible light using core/shell nano-catalysts

2010 ◽  
Vol 61 (9) ◽  
pp. 2303-2308 ◽  
Author(s):  
X. Wang ◽  
K. Shih ◽  
X. Y. Li
Keyword(s):  
Hydrogen Production ◽  
Visible Light ◽  
Production Rate ◽  
Hydrogen Generation ◽  
Nano Particles ◽  
Catalyst Loading ◽  
Core Shell ◽  
Hydrogen Production Rate ◽  
Photocatalytic Hydrogen Generation ◽  
Nano Catalysts

A microemulsion technique was employed to synthesize nano-sized photocatalysts with a core (CdS)/shell (ZnS) structure. The primary particles of the photocatalysts were around 10 nm, and the mean size of the catalyst clusters in water was about 100 nm. The band gaps of the catalysts ranged from 2.25 to 2.46 eV. The experiments of photocatalytic H2 generation showed that the catalysts (CdS)x/(ZnS)1−x with x ranging from 0.1 to 1 were able to produce hydrogen from water photolysis under visible light. The catalyst with x = 0.9 had the highest rate of hydrogen production. The catalyst loading density also influenced the photo-hydrogen production rate, and the best catalyst concentration in water was 1 g L−1. The stability of the nano-catalysts in terms of size, morphology and activity was satisfactory during an extended test period for a specific hydrogen production rate of 2.38 mmol g−1 L−1 h−1 and a quantum yield of 16.1% under visible light (165 W Xe lamp, λ > 420 nm). The results demonstrate that the (CdS)/(ZnS) core/shell nano-particles are a novel photo-catalyst for renewable hydrogen generation from water under visible light. This is attributable to the large band-gap ZnS shell that separates the electron/hole pairs generated by the CdS core and hence reduces their recombinations.

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