Synthesis of Guanosine 5′-Monophosphate (GMP)-Mediated Ag/CdS Nanohybrids: Their Self-Assembly and Optoelectronic Properties

Guanosine 5'-monophosphate (GMP)-mediated Ag/CdS nanohybrids have been synthesized in the quantum-confined region. The presence of Ag in the nanohybrid and its binding with GMP has been ascertained by XRD, IR spectroscopy, and X-ray photoelectron spectroscopy (XPS) studies. GMP is attached to the surface of Ag/CdS through its various functionalities, namely, -NH2, -C=O, -NH-, -OH, N-7-C-8 + C-8-H, PO32-, P-O-5'-sugar, and sugar ring, through supramolecular interactions and brings a change in their optical and electronic properties. The presence of Ag at the interface of GMP-mediated CdS introduces several additional surface states at the interface of the two colloids, which enhances the radiative transition to cause an increase in the quantum efficiency of fluorescence from 0.005 in the absence of Ag to 0.039 in its presence. It is also evidenced by an increase in the fluorescence lifetime from 40 to 160 ns. In this time domain, different intermediates are understood to be produced by the relaxation of charge within the surface states of varied energies from 220-367 eV. The nature of the surface states could be controlled kinetically by optimizing the amount of Ag in the nanohybrid. Aging of the Ag/CdS nanohybrids induces self-assembly, which changes its morphology from quantum dots to nanowires over a period of one month unlike GMP-mediated CdS, which forms nanorods. These changes in morphology are also reflected by a significant increase in the rotational correlation time from 42.99 to 167 ns.