A new route for the formation of Au nanowires and application of shape-selective Au nanoparticles in SERS studies

Abstract

A new route for the formation of shape-selective Au nanoparticles (NPs) has been demonstrated. The reduction of Au(III) ions was done with alkaline 2,7-DHN in CTAB micellar media under 30 min of continuous UV-irradiation. The reaction results in uniform Au nanospheres and Au nanowires. With the change in Au(III) ion to CTAB molar ratio, the particles’ size and shape can be tuned. Au nanorods and nanoprisms are synthesized via seed mediated growth and microwave heating methods and the particles are characterized by several spectroscopic tools. The shape effects of the four different types of Au NPs were investigated using surface enhanced Raman scattering (SERS) studies. The results showed that the SERS intensity increases with the change in NPs’ shape from nanospheres to nanorods to nanowires to nanoprisms. The highest enhancement observed for the nanoprisms is due to the presence of a maximum number of sharp edges or surface active rough surfaces compared to the smooth surfaces of the nanospheres. This high enhancement factor (EF) of these multiple shaped Au NPs might find potential application in detection of single molecules or in many other fields like detection of bio-molecules, bioassays, bio-diagnosis or even clinical diagnostics and in medical therapy.