Preparation of oriented cadmium sulfide nanocrystals

Abstract

Cadmium sulfide (CdS) particulate films, composed of highly oriented, rod-like nanocrystals have been generated in situ by the exposure of stearic acid (SA) Langmuir monolayer-coated aqueous CdCl 2 solutions to hydrogen sulfide (H 2 S). The SA-coated CdS particulate films were transferred to a solid substrate and examined by transmission electron microscopy ( TEM) and Auger electron energy spectroscopy. It was found for the first time that the electron diffraction pattern was a composite one with six sets of diffraction patterns which were contributed by the different oriented CdS nanocrystals in these particulate films system. The epitaxial growth of rod-like CdS nanocrystals has been rationalized in terms of matching the d 220 spacing of the cubic CdS crystals and the d 101´0 spacing of the hexagonal closed-packed SA monolayer. The presence of a negatively charged monolayer at the air/water interface was an essential requirement for the oriented growth of CdS nanocrystals. This leads to a novel means of fabrication of highly oriented semiconductor quantum wires.

Cryo-Transmission Electron Microscopy Confirms Controlled Synthesis of Cadmium Sulfide Nanocrystals within Lecithin Vesicles

“…The anisotropy and orientation of the nanocrystals is somewhat consistent with the observed anisotropy of CdS nanocrystals grown under Langmuir monolayers of stearic acid (SA) . These experiments revealed a preferred direction of growth of rodlike CdS nanocrystals corresponding to templating between the {220} lattice plane of cubic CdS and the (101̄0) plane of the hexagonal close-packed SA monolayer.…”

Cadmium removal at high concentration in aqueous medium: mediated by Desulfovibrio alaskensis

“…(20 mg/L), D. vulgaris (11 mg/L), D. magneticus (1.3 mg/L), D. desulfuricans (56 mg/L) (Arakaki et al 2002;Naz et al 2005). Although, D. alaskesis 6SR is an anaerobic bacterium that could be a drawback for its cultivation and manipulation, this presents a great advantage in the sense that an anaerobic culture produces scarce biomass and its simple mechanism of removal allows an easy recovery of cadmium sulfide, which has an added value, e. g., in the manufacture of solar cells (Pan et al 1997). On the other hand, microalgae are considered as excellent biosorption agents due to their great surface extension and their ability to remove concentrations [200 mg/L of cadmium, and other microalgae can accumulate intracellularly this metal (Aksu and Donmez 2006;Igwe and Abia 2006), in both cases a large amount of biomass is required as well as special growth conditions.…”

“…For this reason, SRB such as D. alskensis 6SR have a positive influence on the process called bioprecipitation for the removal of heavy metals, also this kind of mechanism allows for the easy recovery of metals by non-expensive physical methods. Besides, metal sulfides are also of interest as nanocrystals due to their special applications as semi-conductors, solar radiation absorbers, polymer surface coatings, cathode materials, solar cell components, electro-luminescent devices, and multilayer dielectric filters (Pan et al 1997).…”