Chemistry

Prof. Challa V. Kumar
Fulbright Fellow (IISc) and Professor, Department of Chemistry, University of Connecticut Storrs CT USA.

Facile synthesis of white light-emitting, protein-based, metal-free, stable and pH sensitive nanoparticles (GlowDots) as alternatives to quantum dots are reported here. Controlled crosslinking of bovine serum albumin (BSA) molecules resulted in the facile formation of nanoparticles, which are then conjugated with three specific dyes in particular molar ratios to produce white-emitting particles. Chemical novelty is that the particle size, size distribution, stability, surface functions and absorption/emission peak positions are under reaction control. The particle size had a major size fraction of 36 nm (92 %) and minor size fraction 5 nm (8 %) as observed by dynamic light scattering and size has been confirmed by transmission electron microscopy. Particles were thoroughly characterized by gel electrophoresis, electron microscopy, and optical spectroscopy. These nanoparticles are biocompatible and non-toxic, as they are derived from edible proteins.  Due to their intense white-emission, they can be interrogated at multiple wavelengths for imaging and sensing applications. White fluorescence of GlowDots, for example, is strongly sensitive to the pH over a range of 2-13, and changes could be detected visually/quantitatively. The pH-induced emission color change is reversible when the pH was restored back. These are the very first reports of white-emitting nanoparticles that are bioderived and highly sensitive to pH over a wide range.