Experimental Studies and Modeling of Starlike Plasmonic Nanostructures for SERS Application

This work describes fabrication and characterization of two types of surface-enhanced Raman scattering (SERS) substrates based on starlike gold nanoparticles (NPs). Type I SERS substrates are formed by adsorption of gold nanoparticles from chemically synthesized colloidal solution onto the modified glass substrates. Type II SERS substrates are fabricated by the direct nucleation and growth of Au NPs on the modified glass substrates immersed in the precursors solution. Morphology, optical, and SERS characteristics of both types of substrates are studied. Study shows that by varying the diameters of nanostars cores and the lengths of their spikes during the synthesis one can tune the plasmon absorption peak position from visible to near-infrared and achieve the resonance with most of common laser wavelengths. The measured SERS enhancement factors are equal to 10(5) and 10(6) for the substrates of type I and type II, respectively. The modeling of the electric field distribution in the vicinity of nanoparticles are done for exciting laser wavelengths varied in the range from 400 to 1000 nm. Calculated electric field distribution in the vicinity of Au NPs at different lambda(exc) correlates with the SERS enhancement factors obtained experimentally.