Tunable Near-Infrared II Photosensitive Platforms of Plasmonic Ring Nanocone Arrays

Abstract

A well-ordered metal tip array reveals prominent absorption at 1000-1550 nm. Near-infrared II-gold ring nanocone arrays (NIR II-GRNA) were prepared on conical anodic aluminum oxide structures. Plasmonic substrates were prepared via multistep anodization and pore-widening processes followed by metal sputtering. The NIR II-GRNA substrates were prepared on the conical tip by depositing gold layers using a vacuum coater. The controllable structures of the D-25, D-30, and D-35 substrates in terms of tip diameters and gap distances were found to tune optical properties by adjusting the sputtering conditions. The plasmonic charge transfer between the conductive bridges in NIR II-GRNA predicted an additional absorbance mode in the second NIR II region using a finite element method. The NIR II-GRNA substrate exhibited high sensitivity and repeatability of surface-enhanced Raman scattering (SERS) owing to its water repellence and the resonance modes of its absorbance spectra. Poly(N-isopropylacrylamide) was introduced to demonstrate the photosensitive temperature-dependent SERS platform triggered by the NIR II light irradiation. The D-25 substrate exhibited enhanced cancer cell killing upon NIR II irradiation at 1550 nm. Plasmonic nanocone materials can have the potential for NIR II applications.