講演情報
[14a-K506-2]New Sensing Technique with Dual Probes of SERS/SEIRA: Raman and Infrared SPR Control on Tungsten Oxides
〇(D)Yan Ding1, Jiaqi Yang1, Tang Dang1, Hitoshi Tabata1, Hiroaki Matsui1 (1.The Univ. of Tokyo)
キーワード：
plasmonic materials、Cs-HTB、vibrational spectroscopy
Raman scattering and infrared absorption detections are limited by low cross-sections, but surface-enhanced techniques (SERS/SEIRA) enhance vibrational signatures for non-destructive, label-free molecular analysis. SERS and SEIRA differ in vibrational excitation, offering complementary insights, and simultaneous measurements enable comprehensive biological analysis. Optical advancements now enable simultaneous Raman and IR measurements. Current platforms have focused on Au nanostructures for dual resonances in the visible and IR range. Dual resonances rely on surface plasmon resonances (SPRs), where in-plane polarization and nano-gap control are crucial for excitation. However, these strategies often provide limited enhancement in either the visible or IR range, making it challenging to achieve comparable SPR performance across both optical regions.
Here we present the first dual spectroscopic platform using Cs-hexagonal tungsten bronze (Cs-HTB), enabling both SERS and SEIRA via charge transfer (CT) and SPRs. Cs-HTB films fabricated via pulsed laser deposition showed tunable optical properties by Cs doping, which enhanced CT efficiency for SERS in the visible range and free carriers for SPRs in the IR range. Preliminary SERS tests [Fig. 1a] on Rhodamine 6G demonstrated an enhancement factor (EF) ~104 and a detection limit (LOD) ~10-5 M for SERS, with the mechanism primarily driven by photoinduced CT through polaron states created by Cs doping, which enhance Raman signal by enabling efficient electrons transfer between Cs-HTB and probe molecules. By contrast, the SEIRA arises from SPRs induced by free carriers in Cs-HTB, as characterized by metallic dielectric functions in the mid-IR range. FDTD simulations of square microdot arrays structures demonstrated mid-IR SPR excitations on Cs-HTB [Fig. 1b].
Here we present the first dual spectroscopic platform using Cs-hexagonal tungsten bronze (Cs-HTB), enabling both SERS and SEIRA via charge transfer (CT) and SPRs. Cs-HTB films fabricated via pulsed laser deposition showed tunable optical properties by Cs doping, which enhanced CT efficiency for SERS in the visible range and free carriers for SPRs in the IR range. Preliminary SERS tests [Fig. 1a] on Rhodamine 6G demonstrated an enhancement factor (EF) ~104 and a detection limit (LOD) ~10-5 M for SERS, with the mechanism primarily driven by photoinduced CT through polaron states created by Cs doping, which enhance Raman signal by enabling efficient electrons transfer between Cs-HTB and probe molecules. By contrast, the SEIRA arises from SPRs induced by free carriers in Cs-HTB, as characterized by metallic dielectric functions in the mid-IR range. FDTD simulations of square microdot arrays structures demonstrated mid-IR SPR excitations on Cs-HTB [Fig. 1b].