Synthesis of CdS Nanoparticles

SYNTHESIS OF CdS NANOPARTICLES USING IMMOBILIZED FUNGUS, C. VERSICOLOR... 

Ahmad, A., Mukherjee, R, and Mandal, D. 2002. Enzyme mediated extracellular synthesis of CdS nanoparticles by the fungus, Fusarium oxysporum. Journal of the American Chemical Society, 124 12108-9. 

The wet synthesis of CdS nanoparticles used in this work is based on the reaction between a dissolved cadmium salt (CdCl2) and a S-containing compound (thiourea (NH2)2CS) in an aqueous solution. Chemical deposition of CdS nanoparticles in the CdCl2 - NH3 - NaOH - (NH2)2CS - H2O bath was described elsewhere [3]. In the present work all the baths had the same composition and were prepared from solutions of cadmium chloride CdCl2 (0.005 mold-1), ammonia NH3-H2O (1.5 moll"1), sodium hydroxide NaOH (0.074 mold-1) and thiourea (NH2)2CS (0.025 mol-F1) using distilled water. The synthesis temperature was varied from 294 to 325 K. The primary concentrations of the precursors have been chosen according to the thermodynamic analysis [4]. A supersaturation of the solution with Cd(OH)2 takes place in the baths. It means that the mechanism of the cadmium sulfide formation could involve the stage of Cd(OH)2 formation. When the deposition process of CdS particles in the solution completed, the residue was filtered at an ambient pressure and dried at room temperature. 

The reactions of solvated electrons generated on y-irradiation of methanol (Equation 23.18) with thiophenol is of major interest for the synthesis of CdS nanoparticles in which HS is likely to be generated (Equation 23.28) similar to what was observed in aqueous thiols ... 

Synthesis of CdS nanoparticles can be performed easily and safely by freshmen students. Based originally on research by Agostiano (P), the procedure has been adapted to use reagents commonly available to a general chemistry laboratory (JO, 11). This experiment illustrates how intermolecular forces affect the formation of micelles and how surfactants behave in oil-water mixtures. The difference in color between the bulk and nanosized CdS is visibly obvious but students can also calculate the nanoparticle size with the aid of a UV/visible spectrophotometer. The explanation for the color difference is based on quantum confinement of electrons and holes in the particle s semiconductor lattice. 

As is the case in the synthesis of CdS nanoparticles, a surfactant (tetramethylammonium hydroxide) is used to prevent magnetite nanoparticle agglomeration. The hydroxide anions adsorb to the magnetite surface after the Fe304 particles have formed and the cations form a loose layer around them. Electrostatic repulsion reduces the number of collisions between the particles. 

New nanotechnology experiments for freshmen ean be found in recent issues of the science and engineering research literature. What were cutting edge syntheses a few years ago can now be performed by freshmen students in their general chemistry lab course, as is the ease for the synthesis of CdS nanoparticles described earlier in this chapter. Marty books have been published that introduce students and the general public to all areas of nanotechnology, from science to its impact on business and society. 

Various groups have employed a range of sonochemical approaches to s mthesize metal sulfate nanoparticles in aqueous solution. Wang et al. [194] have reported the sonochemical synthesis of CdS nanoparticles by irradiation of a mixture of cadmium chloride, sodium thiosulfate, and 2-propanol. Dhas et al. [191] have reported the surface synthesis of CdS nanoparticles on silica microspheres by using cadmium sulfate and thiourea as precursors. The mechanism of the sonochemical growth of metal particles consists of several steps. For example, ZnO/CdS core/shell-type composite particles are formed by four steps [195] ... 

Reaction Synthesis of CdS nanoparticles based on the precipitation reaction. 

Cadmium sulphide (CdS) is an II-VI semiconductor material with a direct band gap of 2.42 eV at room temperature with many outstanding physical and chemical properties, which has promising applications in photochemical catalysis, gas sensors, detectors for laser and infrared, solar cells, nonlinear optical materials, luminescence devices and optoelectronic devices [36-39]. CdS also exhibited excellent visible light detecting properties [40]. In the last decades, many techniques have been reported on synthesis of CdS nanoparticles [41-43]. 

N. Ghows, and M.H. Entezari, A novel method for the synthesis of CdS nanoparticles without surfactant, Ultrason. Sonochem. 18 (2011) 269-275. 

W. Wang, Z. Liu, C. Zhang, C. Xu, Y. Liu, G. Wang, Synthesis of CdS nanoparticles by a novel and simple one-step, solid-state reaction in the presence of a nonionic surfactant. Materials Letters 57 (2003) 2755-2760. 

P.Bansal, N. Jaggi, S.K. Rohilla, Green Synthesis of CdS nanoparticles and effect of capping agent concentration on crystallite size. Research Journal of Chemical Sciences 2 (2012) 69-71. 

The synthetic approach is very simple and does not require any special set up. In a typical room temperature reaction, 1.0 mL aqueous solution of cadmium chloride was added to 20 mL aqueous solution of soluble starch in a 50 mL one-necked round-bottom flask with constant stirring at room temperature. The pH of the solution was adjusted from 6 to 11 using 0.1 M ammonia solution. This was followed by a slow addition of 1.0 mL colourless selenide ion stock solution. The mixture was further stirred for 2 h and aged for 18 h. The resultant solution was filtered and extracted with acetone to obtain a red precipitate of CdSe nanoaprticles. The precipitate was washed several times and dried at room temperature to give a material which readily dispersed in water. The same procedure was repeated for the synthesis of PVA and PVP - capped CdSe nanoparticles by replacing the starch solution with the PVA and PVP polymers while the synthesis of elongated nanoparticles was achieved by changing the Cd Se precursor ratio from 1 1 to 1 2. The synthesis of polymer capped ZnSe nanoparticles also follows the same procedure except that ZnCb solution was used instead of CdCb solution. 

Qi, L. Colfen, H. and Antonietti, M. (2001). Synthesis and Characterization of CdS Nanoparticles Stabilised by Double Hydrophilic Block Copolymers. Nano Lett, 1, 61-65. 

Some miscellaneous examples of QD synthesis using surfactant systems are described below. A layer-by-layer [206] structure of dithiol self-assembled monolayers (SAM) and CdS mono- and multilayer nanoparticles were fabricated on a gold substrate covered with alkanedithiol. SAMs were formed by an alternate immersion of the substrate into ethanolic solutions of dithiol, and dispersion of CdS nanoparticles (ca. 3nm in diameter), the latter of which was prepared in A0T/H20/heptane w/o microemulsions. 

Agostiano A, Catalano M, Curri ML, Della Monica M, Manna L, Vasanelli L (2000) Synthesis and structural characterisation of CdS nanoparticles prepared in a four-components water-in-oil microemulsion. Micron 31 253-258... 

Synthesis and characterization of CdS nanoparticles embedded in a polymethylmethacrylate matrix was presented [165]. The assembly of CdS semiconductor nanoparticle monolayer on Au electrode was obtained, and its structural properties and photoelectrochemical applications were studied [166]. 

In this chapter we consider the feasibility of easily controlled and reproducible synthesis of CdS colloids. To provide control and restrain the growth rate of the CdS nanoparticles, we used the complex salt of a colloid-forming component (Cd2+) instead of its diluted solution actually, in this case the rate of colloid growth may be limited by the decay rate of the initial cadmium complex. 

Belcher etal. were able to isolate specific peptides able to direct the synthesis of crystal specific mefal sulfide (CdS and ZnS) nanoparticles through phage display." In this study, phages were panned against crystal surfaces, and those which bound were isolated and amphfied for further characterization. Two different peptide lengths were studied, a linear 7-mer peptide and a constrained 12-mer. Interestingly, this technique elucidated two different peptide sequences capable of directing the synthesis of CdS and ZnS, one set for each metal sulfide. The peptides specific for CdS did not bind ZnS and vice versa." ... 

An unusual reversible effect was observed in the synthesis of CdSe nanoparticles in the aqueous tertiary butanol solutions containing equimolar Cd[NH3l4SQ4 and Na2SeSQj by the high-energy... 

Further, Wu et al. (2004) exploited radiation chemical technique to synthesize CdS/polystyrene nanocomposite hollow spheres with diameters between 240 and 500 nm under ambient conditions in which the polymerization of styrene and the formation of CdS nanoparticles were initiated by y-irradiation. It was demonstrated that the walls of the hollow spheres were porous and composed of polystyrene containing homogeneously dispersed CdS nanoparticles (Figure 23.14). The quantum-confined effect of the CdS/polystyrene nanocomposite hollow spheres was confirmed by the ultraviolet-visible (UV-vis) and PL spectra. They proposed that the walls of these nanocomposite hollow spheres originated from the simultaneous synthesis of polystyrene and CdS nanoparticles at the interface of microemulsion droplets. 

Similarly, using the same particles as those used for the synthesis of CdS QDs (see Sect. 6.2, Fig. 36), silver nanoparticles could be deposited onto carboxylated poly(MMA-co-MAA) particles using silver salts as precursors [315, 316]. As for the case of CdS, periodic structures of polymer/silver hybrid colloids were elaborated. The method obviously opens a new avenue for production of optically responsive materials with a controlled periodicity. In another work using commercial llOnm carboxylate-functionalized PS particles as templates, Hao et al. reported the synthesis of silver nanodisks formed through chemical reduction of silver salts in DMF [332]. The composite particles obtained (Fig. 39) exhibited an intense electronic spectrum differing markedly from those of spheres. Still using... 

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