Graphene-enhanced quartz tuning fork for laser-induced thermoelastic spectroscopy

A novel, highly sensitive gas sensing system that uses a graphene-coated quartz tuning fork (QTF), based on light-induced thermoelastic spectroscopy (LITES) is developed. Graphene films with different thicknesses are deposited on commercially available QTF to improve the light absorption and thermoelastic effect. The optimum coating thickness is obtained experimentally and used for gas detection. CO2 is selected as the target analyte for performance verification, and a gain factor of 1.8 and 1.7 is attained for the sensitivity and SNR, respectively, when compared to traditional LITES using bare QTF. A minimum detection limit of 0.06% was obtained corresponding to a normalized noise equivalent absorption coefficient of $5.78\times 10^{-10}{\mathrm {cm}}^{-1}\cdot \text{W}\cdot {\mathrm {Hz}}^{-1/2}$ , and a measurement precision of approximately 0.1 ppm was achieved with an integration time of 300 s. The method of spin coating film on a commercially available QTF exhibits the advantages of low-cost, simplicity, and ease of operation; moreover, the strong UV to THz light absorption of graphene offers a promising strategy for sensitive trace gas analysis and ultra-broad band optical detection.