Structural and Optical Tunability of Ag-ZnO Nanocomposite Thin Films For Surface-Enhanced Raman Studies.

The Ag-ZnO nanocomposite thin films of varying Ag contents were synthesized successfully using simultaneous RF- and DC-magnetron sputterings on quartz substrates. The as-prepared nanocomposites were then annealed in a mixture of hydrogen plus argon environment (95%Ar+5%H2) at a temperature of 300 °C. The pristine and annealed films were then subjected to synchrotron XRD to study for any possible structural modifications induced in the films. The crystalline behavior of the hexagonal wurtzite structure of ZnO, in the pristine and annealed samples of Ag-ZnO nanocomposites, was evident in samples prepared at low Ag content, but with increasing Ag content, the crystalline behavior of the hexagonal wurtzite structure was suppressed. FESEM utilized to study the formation of nanoparticles in the films revealed the non-uniform distribution and agglomeration of nanoparticles increases as the Ag content increases. A broad surface plasmon region in the range of 380–450 nm was observed for different compositions with remarkable blue and red shifts using UV-visible spectroscopy. These high-quality Ag-ZnO nanocomposite thin films with tunable optical properties were then used as surface-enhanced Raman spectroscopy (SERS) substrates for the detection of rhodamine B (RhB) at low concentrations of 10−6 M. The detection of RhB in trace amounts is important in the current scenario as wastewater discharge is a serious threat to our ecosystem. [ABSTRACT FROM AUTHOR]