the chemicals are deposited and the In:S ratio can affect the optical band gap of the film. Single-walled indium sulfide nanotubes can be formed in the laboratory, by the use of two solvents (one in which the compound dissolves poorly and one in which it dissolves well). There is partial replacement of the sulfido ligands with O2−, and the compound forms thin nanocoils, which self-assemble into arrays of nanotubes with diameters on the order of 10 nm, and walls approximately 0.6 nm thick. The process mimics protein crystallization. Safety The β-In2S3 polymorph, in powdered form, can irritate eyes, skin and respiratory organs. It is toxic if swallowed, but can be handled safely under conventional laboratory conditions. It should be handled with gloves, and care should be taken to keep from inhaling the compound, and to keep it from contact with the eyes. Applications Photovoltaic and Photocatalytic There is considerable interest in using In2S3 to replace the semiconductor CdS (cadmium sulfide) in photoelectronic devices. β-In2S3 has a tunable band gap, which makes it attractive for photovoltaic applications, and it shows promise when used in conjunction with TiO2 in solar panels, indicating that it could replace CdS in that application as well. Cadmium sulfide is toxic and must be deposited with a chemical bath, but indium(III) sulfide shows few adverse biological effects and can be deposited as a thin film through less hazardous methods. Thin films β-In2S3 can be grown with varying band gaps, which make them widely applicable as photovoltaic semiconductors, especially in heterojunction solar cells. Plates coated with beta-In2S3 nanoparticles can be used efficiently for PEC (photoelectrochemical) water splitting. Biomedical A preparation of indium sulfide made with the radioactive 113In can be used as a lung scanning agent for medical imaging. It is taken up well by lung tissues, but does not accumulate there. Other In2S3 nanoparticles luminesce in the visible spectrum. Preparing In2S3 nanoparticles in the presence of other heavy metal ions creates highly efficient blue, green, and red phosphors, which can be used in projectors and instrument displays. References General references WebElements Sulfides Indium compounds Semiconductor materials