Investigation of Various Types of Nanorods as Sensitive Surface-Enhanced Raman Scattering Substrates.

Core-shell-isolated nanorods can be used to amplify the signals of target cancer antigen molecules. Recent research has suggested that these nanorods feature surface-enhanced Raman scattering (SERS) signals superior to those of nanoparticles. In this study, nanorod geometrical models based on core-shell-isolated nanocapsule morphology were employed to analyze the scattered power density in three-dimensional spaces. Superior to the conventional cross-section field analysis method, the average scattered power density based method in this presentation could verify the enhancement effects from all possible positions on the nanorod surface. The numerical results in this study were also compared with the experimental results described in the literature. The resonance scattering power reached the maximal value when the radius of the Au/SiO2 and Ag/SiO2 nanorods was 20 nm. At an incident wavelength of 751 nm, the Au/SiO2 and Au/Al2O3 nanorods achieved maximal scattered power density when spacing d=30 nm. Conversely, the Au/TiO2 nanorods achieved maximum scattered power density when spacing d=40 nm. When the core was Au, nanorods with shell thickness h of 1 nm produced a resonant scattering intensity same as it by the nanorods without shells. The numerical results also indicated a stronger resonance peak when the incident ray illuminated the major-axis plane of the Au/SiO2 nanorods. When the incident ray illuminated the curvature plane of the nanorods, the resonance wavelength clearly shifted toward the UV wavelength range. The four Au/SiO2 nanorods with symmetric arrangement achieved the highest resonance peak when the nanorod spacing was 30 nm. This presentation can serve as a key reference for the design of core-shell-isolated nanorods as highly sensitive SERS substrates.