Scalable economic extracellular synthesis of CdS nanostructured particles by a non-pathogenic thermophile Ji-Won MoonIlia N. IvanovChad E. DutyLonnie J. LoveAdam J. Rondinone • Wei WangYi-Liang LiAndrew S. MaddenJennifer J. MosherMichael Z. Hu • Anil K. SureshClaudia J. RawnHyunsung JungRobert J. LaufTommy J. Phelps

Abstract We report microbially facilitated synthesis ofcadmium sulfide (CdS) nanostructured particles (NP) usinganaerobic, metal-reducing Thermoanaerobacter sp. Theextracellular CdS crystallites were \10 nm in size withyields of *3 g/L of growth medium/month with demon-strated reproducibility and scalability up to 24 L. Duringsynthesis, Thermoanaerobacter cultures reduced thiosulfateand sulfite salts to H 2 S, which reacted with Cd 2? cations toproduce thermodynamically favored NP in a single step at65 C with catalytic nucleation on the cell surfaces. Pho-toluminescence (PL) analysis of dry CdS NP revealed anexciton-dominated PL peak at 440 nm, having a narrow fullwidth at half maximum of 10 nm. A PL spectrum of CdSNP produced by dissimilatory sulfur reducing bacteria wasdominated by features associated with radiative excitonrelaxation at the surface. High reproducibility of CdS NPPL features important for scale-up conditions was con-firmed from test tubes to 24 L batches at a small fraction ofthe manufacturing cost associated with conventional inor-ganic NP production processes.Keywords CdS nanostructured particles Nano-biotechnology Thermoanaerobacter Fermentation Photoluminescence Scalable synthesisIntroductionElectro-optical properties of nanostructured particles (NP)including semiconducting quantum dots have been applied