Photophysical Aspects of Varying Zn2+/Pbse Nanostructures Mediated by Rna Leading to the Formation of Honeycomb-Like Novel Porous Morphology

This paper reports the effect of the addition of varied concentrations of Zn2+ on the photophysical properties of RNA-mediated PbSe nanostructures. An increasing addition of Zn2+ results in diminishing of the excitonic feature in the optical spectrum associated with a decrease in red emission with a simultaneous increase in the near-infrared (NIR) region up to 10 x 10(-5) mol dm(-3). It causes the emission lifetime to decrease from 255 to 208 ns at 770 nm and increase from 10.4 to 17.6 ns at 1000 nm. The addition of Zn2+ changes the nature of Q-PbSe from direct to indirect band gap semiconductor by creating different surface states within its band gap, inducing additional transitions. It is understood to facilitate the phonon-assisted relaxation populating the deeper traps responsible for enhanced NIR fluorescence. The adsorption capacity of aged Zn2+/PbSe is enhanced for Nile blue (NB) as compared to its fresh samples due to increased porosity. The excitation of PbSe with energy greater than the bandgap energy in NB-supported PbSe nanostructures results in an energy transfer from excited PbSe to NB involving multiple exciton generation per photon. The porosity, enhanced adsorption capacity with fairly high emission yield, and lifetime in the NIR region give Zn2+/PbSe significant potential as a synthesized nanosystem for tissue and bioimaging applications.