NOVELTY - Producing (M1) non-oxide semiconductor nanoparticles involves subjecting a combination of reaction components to conditions conducive to microbially-mediated formation of non-oxide semiconductor nanoparticles, where the combination of reaction components comprises e.g. anaerobic microbes, culture medium suitable for sustaining the anaerobic microbes, and chalcophile metal component containing at least one type of metal ion; and isolating the non-oxide semiconductor nanoparticles, which contain at least one of the metal ions and at least one of the non-metals.    USE - For production of non-oxide semiconductor nanoparticles (claimed) used in numerous emerging applications such as electronics (e.g. transistors and diode lasers), light-emitting diode (LED) displays, photovoltaics (e.g. solar cells), and medical imaging.    ADVANTAGE - The method provides non-oxide semiconductor nanoparticles having a size of 1-500 (preferably 1-200, more preferably 1-100, most preferably 1-20, especially 1-10) nm; produces a variety of semiconductor nanoparticle compositions on a commercially (i.e. bulk) viable scale at a non-prohibitive cost; produces semiconductor nanoparticles of a particular particle size, morphology, electronic or photonic characteristic, dopant composition, or doping level; and also provides substantially pure semiconductor nanoparticle product bereft of microbial matter, thereby reducing or eliminating separation and washing steps.    DETAILED DESCRIPTION - Producing non-oxide semiconductor nanoparticles involves subjecting a combination of reaction components to conditions conducive to microbially-mediated formation of non-oxide semiconductor nanoparticles, where the combination of reaction components comprises anaerobic microbes, a culture medium suitable for sustaining the anaerobic microbes, a chalcophile metal component containing at least one type of metal ion, a non-metal component containing at least one non-metal selected from sulfur, selenium, tellurium, and arsenic, and at least one electron donor that provide donatable electrons to the anaerobic microbes during consumption of the electron donor by the anaerobic microbes; and isolating the non-oxide semiconductor nanoparticles, which contain at least one of the metal ions and at least one of the non-metals. An INDEPENDENT CLAIM is included for a nanoparticulate semiconductor composition (C1) comprising single crystals having an average size of 1-20 nm, at least one metal, and non-metals selected from arsenic, sulfur, selenium and tellurium, where the semiconductor composition has a photoluminescence peak indicated by a full-width half maximum value of less than 20 nm.