Highly Sensitive Light-Induced Thermoelastic Spectroscopy Based on a Dual-Enhanced Quartz Crystal Tuning Fork via Gold Nanorods' LSPR Effect and High Thermal Conductivity.

We propose a novel, highly sensitive light-induced thermoelastic spectroscopy (LITES) detection scheme based on a quartz crystal tuning fork (QCTF), which features a dual enhancement mechanism driven by the localized surface plasmon resonance (LSPR) effect. Leveraging the inherent thermoelastic and piezoelectric effects of the QCTF, a thin layer of tailor-designed gold nanorods (AuNRs) was deposited onto the central region of the tuning fork. The dual synergistic enhancement and coupling effects originating from the LSPR response and superior thermal conductivity of AuNRs substantially improve the light absorption efficiency of the QCTF, which in turn gives rise to the enhanced sensitivity of gas detection. In this study, we first systematically investigated the LSPR mechanism of AuNRs and further synthesized AuNRs with tailored aspect ratios using the seed-mediated growth method. Subsequently, a full LITES detection system based on the AuNRs-modified QCTF was established for carbon dioxide (CO2) sensing. When the integration time is set to 331 s, the system demonstrates a normalized noise equivalent absorption (NNEA) coefficient as low as 1.33 × 10-10 cm-1·W·Hz-1/2. Featuring miniaturization and high sensitivity, the proposed system offers a novel technical route for environmental monitoring and industrial process analysis.