Cadmium compounds properties

Table 1. Physical and Chemical Properties of Selected Cadmium Compounds ...

Cadmium is a member of Group 12 (Zn, Cd, Hg) of the Periodic Table, having a filled d shell of electrons 4valence state of +2. In rare instances the +1 oxidation state may be produced in the form of dimeric Cd2+2 species [59458-73-0], eg, as dark red melts of Cd° dissolved in molten cadmium halides or as diamagnetic yellow solids such as (Cd2)2+ (AlCl [79110-87-5] (2). The Cd + species is unstable in water or other donor solvents, immediately disproportionating to Cd2+ and Cd. In general, cadmium compounds exhibit properties similar to the corresponding zinc compounds. Compounds and properties are listed in Table 1. Cadmium(TT) [22537 48-0] tends to favor tetrahedral coordination in its compounds, particularly in solution as complexes, eg, tetraamminecadmium(II) [18373-05-2], Cd(NH3)2+4. However, solid-state cadmium-containing oxide or halide materials frequently exhibit octahedral coordination at the Cd2+ ion, eg, the rock-salt structure found for CdO. 

Second order non-linear optical properties have been reported for a variety of TTF donor-acceptor compounds <02T7463> and the palladium complex 84 is a room-temperature semiconductor <02CL936>. Preparation of the zinc and cadmium compounds 85 has been reported <02CC1474> and aromatic fused TTFs such as 86 form thin films with useful electrical properties <02JAP265466>. A ferromagnetic interaction occurs in the salt of a TTF... 

Chemical properties PTFE is a iinear poiymer, free from branching. PTFE requires very high processing temperatures, around 380°C, which exciudesthe use of many pigments and additives. Inorganic cadmium compounds, iron oxides and ultramarines may be used. High chemical and solvent resistance. Epoxy, nitrile-phenolic and silicone adhesives can be used. 

More recently, the dangerous organometallic precursors (especially dimethylcad-mium) have been replaced by les s dangerous cadmium compounds, such as CdO [99] or Cd-acetate [260], both of which can be dissolved inTOPO or ODE in the presence of carboxylic or phosphonic acids. This makes the high-temperature synthesis of nanocrystals in organic solvents much easier (and therefore accessible), without losing any of the excellent optical properties of the particles. 

Quantum dots (QDs) are nanosized semiconductor particles of group II-VI or III-V main group elements with diameters of less than 10 nm [123]. These were first characterized in 1983 by Brus [124] as small semiconductor spheres in a colloidal suspension. QDs due to their nanoscale dimensions are subject to strong quantum confinement, which results in unique optical properties. Thus, in the last two decades, synthesis of QDs has attracted a lot of attention and generated a large number of publications [125]. A variety of methods have been proposed and implemented for synthesis of QDs. Of these methods, colloidal synthesis is the most accessible method for producing QDs suspended in solution. Colloidal synthesis of CdSe QDs is shown in Fig. 4. A cadmium compound is heated to 320°C... 

One other approach that was considered was ranking chemicals by groups according to their physical and chemical properties. A number of properties were selected, for example, LD50, bioaccumulation, and persistence as the main criteria for toxicity to the environment and humans. Substances were then classified according to the range they fell within (Ministers Advisory Panel, 1995). This approach was used for the Canadian Environmental Protection Act (CEPA) assessments. For example, polychlorinated dibenzodioxins, polycyclic aromatic hydrocarbons, inorganic cadmium compounds, benzidine, trichloroethylene, and a host of others were concluded to be toxic. Others, such as chlorobenzene, toluenes, xylenes, and dibutyl pthalate, were concluded to be nontoxic. Others, such as aniline, styrene, crankcase oils, and pentachlorobenzene, do not have sufficient information for classification. 

The properties of specific cadmium compounds are described in reference 5.5. 

Materials like the cadmium compounds of sulfur, selenium, and tellurium, which are, respectively, yellow, red, and black, exhibit color by a mechanism we have not examined previously. Since cadmium has a d ° electronic configuration, crystal field splitting cannot be the origin of the color, but the color can be explained with recourse to a look at semiconductor properties. 

The intermetallic compounds with Group 16 (VIA) elements including CdS, CdSe, and CdTe have interesting semiconductor properties for photoconductors, photovoltaic cells, and ir windows. Cadmium sulfide is widely used as a phosphor in television tubes. 

Substances which possess carcinogenic properties Mercury and its compounds Cadmium and its compounds... 

The corrosion reactions may be slowed down by using zinc alloys (with lead and cadmium, also improving the mechanical properties of zinc to simplify the production process) instead of the pure metal, or by amalgamating the inner surface of the can by adding a small amount of a mercury compound to the electrolyte. 

---