NIR LSPR-coupling of Ag nanorices and W18O49 nanowires: Application of LRET and SERS

Abstract

Broadband plasmonic nanomaterials working in the near-infrared (NIR) region which can concentrate and transfer the low-energy NIR light in the upconversion system are desired. However, single plasmon regulation often fails to meet requirement. Herein, a new type of Ag/W18O49 binary composite film composed of a metal domain (Ag nanorices) and a semiconductor domain (W18O49 nanowires) is designed and fabricated, which exhibits a broad and strong localized surface plasmon resonance (LSPR) across visible to NIR wavelengths, arising from interactions between the two nanostructure domains. The experimental and theoretical studies demonstrate that the localized electric field is dramatically amplified due to an NIR-driven strong plasmonic coupling of LSPR. In particular, the resonance excitation of plasmonic coupling in the Ag/W18O49 composite film induces remarkable enhancement of upconversion via the LSPR effect, and simultaneously provides ultrasensitive surface-enhanced Raman scattering (SERS) by the enhanced electromagnetic field. This work demonstrates a new strategy for accurate molecular detection by assembling upconversion nanoparticles (UCNPs) on Ag/W18O49 composite film, and the so-formed NaYF4/Ag/W18O49 multilayer film can support both the quantitative detection by luminescence resonance energy transfer (LRET) and the qualitative detection by SERS.