TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The subjecting and isolating steps are performed as a single step process. Preferred Composition: (I) is of formula (Cu3-x-M1x-Sn-X4) (IA), (Cu2M1yM11-y-Sn-X4) (IB), or (Cu2M1zM12-z-Sn-X4) (IC). (IB) is preferably (Cu2FeyZn1-y-Sn-X4). (IC) is preferably (Cu2FezZn2-z-Sn-S4).M1 = at least one chalcophile metal other than Cu or Sn, such as 1-3 Fe, Zn, Cd (preferably), V, Cr, Mn, Co, Ni, Mo, W, Pd, Pt, Au, Ag, Hg, Ga, In, Tl, Ge, Pb, Sb or Bi;x = greater than 0 and less than 3;y = greater than 0 and less than 3; andz = greater than 0 and less than 2.Preferred Components: The chalcophile metal component comprises at least one metal consisting of copper, iron, zinc or cadmium. The non-metal component is comprised of at least one inorganic substance comprising sulfur-containing, selenium-containing or tellurium-containing inorganic substance. The non-metal component is comprised of at least one organic compound consisting of organosulfur, organoselenium or organotellurium compound. The organic compound is sulfur-containing, selenium-containing or tellurium-containing amino acids or nucleic bases. The nanoparticles exhibit at least one photoluminescent peak at 400-1500 nm. EXAMPLE - Cultures of Thermoanaerobacter strain M1 were cultured in iron sulfide medium. The electron donor was 10 mM glucose. Sodium selenite concentration was 5 mM. Metal stock solution consisted of cupric chloride, indium chloride, and gallium chloride in molar ratios of 2:1:1, so that a 0.2 M stock solution had 0.2, 0.1, and 0.1 M copper, indium and gallium, respectively. The enriched culture, including the electron donor and Thermoanaerobacter strain M1 was dosed with sodium selenite as a non-metal component and then several minutes to hours later the culture was additionally dosed with a solution containing metal component. Metals were typically added at the rate of 0.25 mM (copper basis) per day in order to avoid toxicity to the bacteria. Precipitated copper indium gallium selenide (CuIn(0.5)Ga(0.5)Se(2)) nanoparticles were harvested by repeated centrifugation followed by at least one time of washing with deionized water without lysing, then freeze-dried.