Growing AuNRs in a single step with NIR plasmon for superior SERS and plasmonic photothermal performance

Au nanorods (AuNRs) with a variety of aspect ratios (ARs) are used in surface-enhanced Raman spectroscopy (SERS), thermal therapy, and similar applications. In this study, we report a seed-mediated synthesis of AuNRs to cover different ARs in a single step with diluted HCl. This process ensures the realization of longitudinal surface plasmon resonance (LSPR) from the visible to the near-infrared region (similar to 650-1150 nm), improved uniformity with negligible by-products, and a low amount of surfactant. With no extra organic component, a halide (Cl) that allows for the unique control of the LSPR is highlighted along with other growth-defining reagents. A comparative SERS of rhodamine and photothermal examinations were performed for halide- and non-halidegrown AuNRs with an AR of similar to 7. An excellent enhancement factor (3 x 10(8)) was achieved for the halidegrown AuNRs and was verified by a finite-difference time-domain (FDTD) simulation. Halide-grown AuNRs with a width of similar to 5 nm demonstrated a highly improved plasmonic photothermal temperature of 45 degrees C, compared with that of 35 degrees C obtained from non-halide-grown AuNRs at a laser power density of only 1.1 W/cm(2). The superior efficiency and photothermal effects of halide-grown samples in SERS are among the best reported, and significantly expand the scope of their application.

Automated summary

A seed-mediated synthesis method was used to prepare Au nanorods with different aspect ratios in a single step. The use of halide (Cl) as a growth-defining reagent allowed for unique control of the longitudinal surface plasmon resonance (LSPR), resulting in excellent SERS and photothermal effects.