Time resolved emission studies of Ag-adenine-templated CdS (Ag/CdS) nanohybrids

Ag-adenine-templated CdS (Ag/CdS) nanohybrids have been synthesized and characterized by transmission electron microscopy, selected area electron diffraction, x-ray diffraction, and optical, fluorescence and time resolved emission spectroscopy. Adenine serves as an effective matrix for the stabilization of Ag/CdS through interaction of N(1), N(3) and -NH2 with Ag. The amount of Ag in the nanohybrid is observed to influence the organization of the Ag and CdS phase in the composite and also modifies the nature of electronic transition in CdS. For the nanohybrid containing a molar ratio of 0.1 of Ag/CdS, CdS nanoparticles (2.5 nm) surround the Ag (6.5 nm) core. The excitation of these particles by 340 nm light, where the absorption due to the Ag phase in the nanohybrid is negligibly small, results in the enhancement of fluorescence by a factor of 7 compared to that of bare CdS. For the particles containing a molar ratio of Ag/CdS of unity, bigger clusters (14 nm) are produced causing the quenching of emission of CdS. In time resolved emission spectroscopy the spectral shift from 415 nm (3.0 eV) to 550 nm (2.26 eV) monitored over a period of 1-220 ns is understood by the relaxation of charge within the surface states of varied energy from 180 to 370 eV. The observed changes in fluorescence behavior in terms of intensity, lifetime and spectral shift are understood in terms of electronic interaction between Ag and CdS phases. The manipulation of electronic and fluorescence properties in these nanohybrids could be exploited for optoelectronic, molecular-recognition and sensing applications.