Synthesis of metal–cadmium sulfide nanocomposites using jingle-bell-shaped core-shell photocatalyst particles (original) (raw)
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The Journal of Physical Chemistry B, 2004
Silica-coated cadmium sulfide nanoparticles (SiO 2 /CdS) having a jingle-bell structure were prepared via sizeselective photoetching and were used as photocatalysts for dehydrogenation of methanol. Irradiation of SiO 2 / CdS suspended in an aqueous solution containing methanol induced the liberation of hydrogen (H 2 ), the amount of which increased linearly with increase in the time of irradiation. The observed stable photocatalytic activity was attributed to the prevention of coalescence between CdS core particles by the surrounding SiO 2 shells during the photocatalytic reaction. The rate of H 2 liberation increased with decrease in the wavelength of irradiation light for the size-selective photoetching, that is, the smaller the size of the CdS core, the higher the rate of H 2 liberation, probably because of increased reduction and oxidation abilities of CdS as a result of decrease in their particle size, that is, size quantization effect. Rhodium photodeposited on SiO 2 /CdS worked as a cocatalyst for the enhancement of dehydrogenation. The photocatalytic activity was reduced by increase in shell thickness because of a decrease in the rate of penetration of chemical species or the transfer of electrons and holes through the SiO 2 layer. Also, the close contact between the core and shell retarded the photocatalytic reaction, indicating that the surface of the CdS core for methanol dehydrogenation was covered with a SiO 2 shell layer. The results indicate that the jingle-bell-shaped SiO 2 /CdS nanoparticles can be an efficient and stable photocatalyst with a flexibly tunable structure, in contrast to surface-modified CdS particles prepared by a conventional technique.
The CdS nanostructure undergoes photochemical dissolution, and hence, the photocatalytic activity deteriorates with light irradiation time. A thin layer of silica coating over CdS surface may prevent the photocorrosion and coalescence of quantum size CdS particles. Hence, we synthesized SiO 2 @CdS nanocomposites of different shapes and characterized them by XRD, HRTEM, EDX, SAED, BET surface area measurement and absorption and emission study. The dispersion of spherical CdS (Cd-2.62 at% and S-2.33 at%) nanoparticles of cubic crystal structure into thick amorphous SiO 2 (43.79 at%) matrix is demonstrated here. The fabrication of core (CdS)-shell (SiO 2 ) structure (SiO 2 @CdS) consisting of CdS nanorod (Cd-19.79 at% and S-22.90 at%) core (length 126nmandwidth126 nm and width 126nmandwidth6 nm) having characteristic lattice fringes of hexagonal crystals and thin SiO 2 (12.81 at%) shell (thickness = 1-1.4 nm) is successfully achieved for the first time. The surface area (21.2 m 2 /g) of CdS nanorod (aspect ratio = 21) is found to increase (42.3 m 2 /g) after SiO 2 coating. The photoluminescence of CdS nanosphere (485 nm) and nanorod (501 nm) is highly quenched after SiO 2 layer formation. The superior photocatalytic activity of SiO 2 @CdS composites for the benzaldehyde oxidation under UV irradiation has been displayed.
Small, 2006
Much interest has been shown in the design and preparation of chemical sensors using semiconductor nanoparticles as functional components. The detection of chemicals often employed in such sensors involves measurement of the structure-and concentration-dependent intensity of photoluminescence of the nanoparticles, which is based on adsorbing chemical species on their surfaces. Nanoparticles are advantageous for devices since they have relatively large specific surface areas to adsorb chemical species. However, it is also well known that such nanoparticles are unstable and tend to coalesce into larger particles because of their high surface energy, unless stabilizing agents (such as thiol compounds [3-8, 12, 13] or a trialkylphosphine oxide ) are strongly adsorbed onto the particles. However, for chemical sensing based on the photoluminescence properties of semiconductor nanoparticles, as well as for other de-vices utilizing the particle surface as a chemical reaction site, the presence of organic layers of stabilizing agents adsorbed on the surface is unfavorable because they may act as a barrier for the diffusion of target molecules from the solution phase to the surface of nanoparticles.
Highly enhanced photocatalytic activity of Au nanorod–CdS nanorod heterocomposites
Journal of Molecular Catalysis A: Chemical, 2013
This paper signifies the importance of different shapes of Au and CdS-nanoparticles for fabricating Au-CdS heterocomposites {prepared by mixing or impregnation of Au-nanosphere (9.1 nm), Aunanorod (20 nm × 8.6 nm; L × W), CdS-nanosphere (10-12 nm) and CdS-nanorod (126 nm × 5.5 nm)} onto the photoluminescence and photocatalytic study. Second derivative absorption spectra's exhibit precise onset at 441 nm (CdS-nanosphere) and 469.5 nm (CdS-nanorod) that are significantly redshifted to 509 nm (Au-nanosphere-CdS-nanosphere), 485 nm (Au-nanosphere-CdS-nanorod), 520 nm (Au-nanorod-CdS-nanosphere) and 485.5 nm (Au-nanorod-CdS-nanorod) depending upon interfacial contact-area. XRD patterns reveal the hexagonal phase of pure and Au-CdS nanocomposites. Photoluminescence of CdS nanorods has been effectively inhibited by modifying its surface with Au-nanoparticles (0.002-0.04 wt%). Relaxation lifetime of photoexcited charge-carriers found to be improved ca. 12.5 s for Au-nanosphere-CdS-nanorod and 34 s for Au-nanorod-CdS-nanorod due to effective charge transfer kinetics at the interface, in contrast to prompt charge-recombination (2.7 s) in CdS. Under UV light (10.4 mW/cm 2) irradiation, Au-nanorod-CdS-nanorod exhibits the best photocatalytic activity for the oxidation of salicylic acid (86%, k = 9 × 10 −3 min −1) and reduction of p-nitrophenol to p-aminophenol (53%) as a function of improved stability and better current-voltage (I-V) characteristics suitable for rapid charge transfer process during photoreaction.
Chemical Engineering Journal, 2014
The high purity Au-CdS hybrid plasmonic nanoparticles were prepared by spray pyrolysis technique. The in-situ growth process of Au in CdS is unique gives plasmonic effect is discussed. The effect of Au loading in CdS on optical and photocatalytic properties is investigated. Au 0.15-CdS shows the best degradation efficiency of 90% for MB dye. The CoSP method has potential to prepare number of other M-S hybrid materials. g r a p h i c a l a b s t r a c t Various Au-CdS hybrid nanoparticles have been synthesized in-situ by using simple inexpensive CoSP technique. They have been shown the color tuning, enhancement in the absorption/extinction, PL quenching and enhanced Photocatalytic properties in the visible and NIR regions.
Ionics, 2020
A simple sol-gel method was adopted to synthesize SiO 2 /TiO 2 (ST) composite spheres decorated with CdS nanostars. Two types of photocatalyst were synthesized; one is SiO 2-CdS (S-CdS) and the other is SiO 2 /TiO 2-CdS (ST-CdS) composite spheres. The synthesized SiO 2-CdS and SiO 2 /TiO 2-CdS composite spheres were extensively characterized using different techniques. The photocatalytic activities of the as-synthesized catalysts were evaluated by the degradation of Congo red (CR) dye under visible light irradiation. The ST-CdS composite spheres showed better photocatalytic activity in the visible light irradiation by providing more active sites for dye adsorption, and by reducing the recombination of electrons and holes. The simulation model was consistent with the absorption results which established the UV and visible light photocatalyst activity. The results showed that the CdS nanostar decorated SiO 2 /TiO 2 spheres showed better photocatalytic activity under visible light irradiation compared with the SiO 2-CdS composite spheres. Keywords Dye degradation. CdS nanostar. Visible light irradiation. FDTD model. SiO 2 /TiO 2 composite * Ja-Hon Lin
Room temperature synthesis of CdS nanoflakes for photocatalytic properties
Journal of Materials Science: Materials in Electronics, 2014
Herein, we report, preparation of cadmium sulphide (CdS) nanoflakes at room temperature by simple arrested precipitation method. The synthesized CdS nanoflakes were characterized by various techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Fourier transform-infrared spectroscopy, and UV-Visible spectrophotometer. Nanoflakes of CdS were found to be a mixed-phases composed of cubic and hexagonal with average crystallite size of 20 nm. Surface morphology of CdS seems to be nanoflakes. The absorption spectrum was slightly shifted to blue region as compared to the bulk, this indicates that synthesized material is smaller in size. The band gap energy was found to be 2.48 eV. The photocatalytic results reveals that CdS nanoflakes exhibits excellent photocatalytic performance for methyl orange (20 ppm) degradation, under sunlight and UV within 120 min (83 and 95 % respectively).
Synthesis, Characterisation and Photocatalytic Activity of Cadmium Sulphide Nanoparticles
Chemical Science Transactions, 2016
Cadmium sulphide (CdS) nanoparticles were synthesized using thiourea as a source for sulphide ion in the presence of disodium succinate. The prepared nanoparticles were characterized by IR spectroscopy, x-ray diffraction and scanning electron microscopy. The photocatalytic activity of CdS was tested for degradation of methylene blue and rhodamine B. CdS catalyst shows high activity for the photocatalytic degradation of methylene blue dye.
Separation and Purification Technology, 2013
Cadmium sulphide (CdS) nanostructures were synthesized via a simple chemical precipitation method by using Mercaptoethylamine hydrochloride (MEA) as a capping agent. Fine tuning of the nanosized CdS material was carried out by controlling the amount of the capping agent. The synthesized CdS nanostructures were characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and UV-Vis diffuse reflectance spectroscopy (DRS). Optical absorption spectroscopy was mainly used to measure the band gap and size of the CdS nanostructures. The photocatalytic activities of the synthesized samples were investigated for degradation of methylene blue (MB) under blue LED (3 W) and solar light irradiation.