Cadmium Selenide CdSe

If the electrolysis parameters (precursor concentrations, pH, temperature, cur-rent/potential, substrate) be defined in a precise manner, a self-regulated growth of the compound can be established, and highly (111 )-oriented zinc blende (ZB) deposits up to several p,m thickness are obtained at potentials lying at the anodic limit of the diffusion range (Fig. 3.3) [60]. Currently, the typical method of cathodic electrodeposition has been developed to yield quite compact and coherent, polycrystalline, ZB n-CdSe films of well-defined stoichiometry. The intensity of the preferred ZB(f 11) orientation obtained with as-deposited CdSe/Ni samples has been quite high [61]. 

Alkaline aqueous media containing selenosulfate ions (SeS03 ) and complexes of Cd with EDTA or nitrilotriacetate (NTA) have been successfully utilized to accomplish cathodic electrodeposition of nearly stoichiometric, wurtzite CdSe [62-64]. Similar results have been reported for seleno-cyanate (SeCN ) alkaline baths 

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Light detectors fall into two categories photoconductors and photodetectors. Photoconductors are devices whose resistance decreases upon exposure to light. Cadmium sulfide (CdS) and cadmium selenide (CdSe) are the most commonly used photoconductor materials in the visible spectrum. They are still mostly produced by sputtering but CVD is used increasingly (see Ch. 12, Sec. 4.0). 

Many colored pigments are based on cadmium compounds. For instance, cadmium sulfide (CdS) and cadmium selenide (CdSe) are used as pigments when a durable, nonfading color is required. Red is produced by CdSe, and bright yellow is produced by CdS. 

Gobet and Matijevic (17) produced monodisperse submicrometer-size particles of cadmium selenide (CdSe) and lead selenide (PbSe) by reversible release of selenide ions from selenourea in solutions of the corresponding metal salts. The equilibrium between selenourea and selenide ions is written as follows ... 

II-VI, such as cadmium selenide (CdSe) and other combinations of Group 12 and Group 16 ions... 

The color of the red glass in these traffic signals is due to cadmium selenide, CdSe. 

The estimates of radiative lifetime performed using Eq. (4) for lead selenide (PbSe) and cadmium selenide (CdSe) nanocrystals show a good agreement with experimental data". Although, expressions (3) and (4) are derived under assumption that the field variation is small on the nanociystal size scale, while the radiation field exhibits a strong angular dependence, more accurate computations give the same result. It is clear also that Eq. (4) should be essentially modified in the case of so called core-shell nanoeiystals with the dielectric permittivity s(r)= Score (0 < r < Aj), Ssheii (/ i < r < R2), where Ri is the core radius, and is the external radius of the shell. 

Aluminum selenide (Al2Se3) Ammonium selenite[(NH4)2Se03] Cadmium selenide (CdSe)... 

This section will consider in greater detail specific examples of particular types of nanomaterials interacting with different media in the environment. The fate and transport of carbon-based nanomaterials, including carbon nanotubes and fuUerenes, in aqueous environments and the properties of commercial oxide nanoparticles that affect their removal in water will be discussed. Nanomaterial exposure to soils and porous media, focusing on transport and retention, as well as environmental interactions of cadmium selenide (CdSe) quantum dots with biofilms will be presented. These specific examples provide an idea of the types of environmental interactions that must be considered, and illustrate that environmental impacts of nanomaterials cannot be generalized, but rather, are dependent on properties of the material in question and the environment to which it is exposed or transported. 

Estimate the number of intrinsic electrons, n, and holes, p, and the product np, for a crystal of cadmium selenide, CdSe, at 300 K, taking the effective mass of electrons to be 0.13me and holes as 0.45me. The band gap. Eg, is 1.70 eV. 

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