Protein conformation driven biomimetic synthesis of semiconductor nanoparticles

The present investigation demonstrates the role of protein conformation in synthesizing nanoparticles (NPs) through biomimetic route. Highly water-soluble and biocompatible CdS and CdSe nanoparticles in bovine serum albumin (BSA) matrix have been synthesized using a simple and controllable method at room temperature. Fourier transform infrared (FTIR) data are used to envisage the binding of the semiconducting particles with amide and OH groups of the protein molecule. Optical absorption and emission spectra confirm that particles formed lie within the size quantization regime. Circular dichroism spectroscopy reveals that BSA adopts different conformations at different pH which in turn controls the particle size. Further, addition of sodium borohydride (NaBH4) in BSA solution results in breakage of disulfide bonds generating increased number of thiolate groups which provide better stabilization and increased passivation of electronic defects on particle surface. In the process, better quality semiconductor NPs with higher quantum yield are produced. Thus, by modulating the protein conformation, the size and quality of the nanoparticles can be controlled.