Biosynthesis of CdS nanoparticles through microbial induced calcite precipitation

The main objective of this study is to demonstrate the potential of microbial induced calcite precipitation (MICP) as rapid and effective process in the synthesis of fluorescent cadmium sulfide nanoparticles. A urease-producing bacterial isolate AX5, identified as Citrobacter braakii, from calcite rich shells of abalone that could tolerate cadmium at the concentration of 250mg/l was used. In order to investigate the role of MICP in enhancing the synthesis of CdS nanoparticles, the biomimetic synthesis was carried out by C. braakii in modified nutrient broth without amending any additional organic or toxic surfactants back into the environment. The large amount of monodispersed CdS nanoparticles was harvested and found to bind with biocalcite. XRD analysis confirmed the presence of CdS nanoparticles bound with biocalcite minerals in the precipitation. HRTEM and SEM micrographs showed spherical CdS nanoparticles of particle size in the range of 50–100nm. The other characteristics of harvested CdS nanoparticles were studied with UV–vis, PL spectra, FTIR, and fluorescence microscopy. The findings of present study have important insights into the application of MICP as a promising mechanism for the biosynthesis of CdS nanoparticles.