Effect of Ag-Cu Alloy Nanoparticle Composition on Luminescence Enhancement/Quenching

Metal enhanced/quenched luminescence was explored in the vicinity of AgxCu100-x, alloy nanoparticles at different compositions (x = 100, 67, 50, 30, and 0). These Ag-Cu nanoparticles were synthesized using the polyol process. It was observed that the luminescence of dyes was strongly dependent on the Ag-Cu nanoparticle composition. Highest luminescence enhancement of dye Cy 3, commonly used for biological applications, was achieved in the vicinity of pure silver nanoparticles. Enhancement effects were found to decrease as the percentage of copper was increased in the nanoparticles, leading to the quenching of fluorescence near pure copper nanoparticles. Theoretical calculations based on the corrected Gersten and Nitzan model(1) were carried out to predict the possible enhancement factors for spherical Ag-Cu nanoparticles for a range of compositions. Results of these calculations corroborate the experimental findings. Signal manipulation of luminescent dyes using the composition of alloy nanoparticles will extend applications of metal-enhanced luminescence to several fields ranging from optoelectronics to biological research.