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

Abstract

Ag-adenine-templated CdS (Ag/CdS) nanohybrids have been synthesized and characterizedby transmission electron microscopy, selected area electron diffraction, x-ray diffraction,and optical, fluorescence and time resolved emission spectroscopy. Adenine serves as aneffective 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 ofthe Ag and CdS phase in the composite and also modifies the nature of electronictransition in CdS. For the nanohybrid containing a molar ratio of 0.1 of Ag/ CdS, CdSnanoparticles (2.5 nm) surround the Ag (6.5 nm) core. The excitation of these particles by340 nm light, where the absorption due to the Ag phase in the nanohybrid is negligiblysmall, results in the enhancement of fluorescence by a factor of 7 compared to that ofbare CdS. For the particles containing a molar ratio of Ag/CdS of unity, biggerclusters (14 nm) are produced causing the quenching of emission of CdS. In timeresolved 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 ofcharge within the surface states of varied energy from 180 to 370 eV. The observedchanges in fluorescence behavior in terms of intensity, lifetime and spectral shift areunderstood in terms of electronic interaction between Ag and CdS phases. Themanipulation of electronic and fluorescence properties in these nanohybrids couldbe exploited for optoelectronic, molecular-recognition and sensing applications.