Cadmium sulfide (CdS) nanoparticles of three different sizes of 1.49, 2.0, and 2.1 nm were synthesized by the chemical method using thioglycerol as a capping agent. Optical absorption, wide angle x-ray scattering (WAXS), small angle x-ray scattering (SAXS), and high-resolution transmission electron microscopy (HRTEM) measurements revealed that nearly monodispersed particles of high quality could be obtained using a simple and straightforward method used in the present investigation. The nanoparticles were further used to fabricate heterojunctions with poly-phenylene-vinylene (PPV), and current-voltage characteristics were measured. A large forward current density of 21 mA cm−2 at 1 V is obtained for samples having the smallest average particle size and 13 mA cm−2 for the samples having the largest particle size among the samples investigated.

Nanocrystalline CdS particles have been synthesized and dispersed in a polystyrene (PS) medium in the form of thin composite films. X-ray reflectivity and atomic force microscopy (AFM) have been used to study the films. CdS particles are found to precipitate towards the bottom of the films giving rise to a continuous change in the electron density along the depth of the film. It is shown that previous knowledge about the realistic model of electron density profile is required for correct interpretation of the X-ray reflectivity data for systems where electron density changes continuously and independent information obtained from atomic force microscopic studies can be used conveniently for this purpose.

Cadmium sulfide nanoparticles were synthesized intracellularly by a Schizosaccharomyces pombe strain when challenged with 1 mM cadmium in solution. The nanoparticles, a known semiconducting material, exhibited an absorbance maximum at 305 nm. X-ray scattering data showed that the nanoparticles had a Wurtzite (Cd(16)S(20))-type hexagonal lattice structure and most of the nanoparicles were in the size range of 1-1.5 nm. The nanoparticles were used in the fabrication of a heterojunction with poly (p-phenylenevinylene). The diode exhibited approximately 75 mA/cm(2) current at 10 V when forward biased and the breakdown occurred at approximately 15 V in the reverse biased mode. These characteristics are considered ideal for a diode.

CdS, ZnS and ZnCdS nanoparticles of various sizes (1–10nm) are synthesized using a wet chemical route including passivation by organic capping molecules. The particles can also be doped with transition metal ions. The optical properties of the particles are investigated using UV absorption and photoluminescence spectroscopies. High resolution photoelectron spectroscopy using variable photon energy from a synchrotron source is performed to obtain detailed information about the nanoparticle surfaces. These investigations are able to reveal the termination of the nanoparticles and the nature of bonding between the surface atoms and stabilizing organic molecules.

Chemically capped CdS nanoparticles are embedded in porous silicon (PS) by a dip coating method. Atomic force microscopy measurements reveal that the PS surface is covered with CdS nanoparticles forming well-defined rectangular blocks of nearly uniform size (200×200 nm2). Photoelectron spectroscopy and energy dispersive x-ray analysis confirm the presence of CdS in PS. Optical and electrical properties of the heterojunctions so-formed are investigated. Junction characteristics show that the composite so-formed exhibits very high forward current density (145 mA cm-2) and high reverse breakdown voltage (15 V).

Extremely small 1.4-nm size mercaptoethanol-stabilized ZnS clusters have been synthesized with narrow size distribution. The structure of these clusters was studied by wide-angle X-ray scattering. The scattering curves were compared with the calculated scattered intensity of a variety of model clusters (ZnS)(N) and different defect types via Debye functions. In the as-received state the pattern is best described by a fragment of the zinc blende lattice, with N approximate to 30, and a defective stacking of three to four (111) planes. A large improvement of the simulation is gained by introducing liquidlike disorder to the model structure. This raises the unanswered question of a "real" liquid state of these small clusters at room temperature, The cluster matrix is thermally stable to 583 K. Above this temperature the primary cluster coalesce to form larger particles. Annealed at 1013 K the particles grow to > 4.0 nm with a highly defective zinc blende structure.

Nanoparticles of zinc sulphide have been synthesized by a chemical method. Mercaptoethanol is used to passivate the surface of the particles. Under certain conditions highly luminescent particles emitting blue light at ∼425 nm can be synthesized. This blue light emission in nanoparticles of zinc sulphide is observed to be completely quenched when doped with iron or nickel metal ions.