Abstract
A series of semiconducting zinc sulfide (ZnS) nanoparticles were scalably, reproducibly,
controllably, and economically synthesized with anaerobic metal-reducing Thermoanaerobacter
species. They reduced partially oxidized sulfur sources to sulfides that extracellularly and
thermodynamically incorporated with zinc ions to produce sparingly soluble ZnS nanoparticles
with ~5 nm crystallites at yields of ~5 g l−1 month−1. A predominant sphalerite formation was
facilitated by rapid precipitation kinetics, low cation/anion ratio, higher zinc concentration, water
stabilization, or some combination of the four. The sphalerite ZnS nanoparticles exhibited
narrow size distribution, high emission intensity, and few native defects. Scale-up and emission
tunability using copper-doping were confirmed spectroscopically. Surface characterization was
determined using Fourier transform infrared and X-ray photoelectron spectroscopies, which
confirmed amine and carboxylic acid not only maintaining a nano-dimensional average
crystallite size, but also increasing aggregation. Application of ZnS nanoparticle ink to a
functional thin film was successfully tested for potential future applications.
