Espresso Science: Laser-Based Diamond Thin-Film Waveguide Sensors for the Quantification of Caffeine

Diamond thin-film waveguides with a nanocrystalline diamond layer of approximately 20 mu m thickness were used in the mid-infrared regime in combination with quantum cascade lasers to detect the IR signature of caffeine. The diamond thin-film waveguides were fundamentally characterized with respect to their morphological properties via AFM and SEM. Theoretical simulations confirmed the feasibility of using a larger sensing area of approximately 50 mm2 compared to conventionally used strip waveguides. A comprehensive and comparative analysis confirmed the performance of the diamond thin-film-waveguidebased sensing system vs data obtained via conventional attenuated total reflection Fourier transform infrared spectroscopy using a single-bounce diamond internal reflection element. Hence, the utility of innovative diamond thin-film-waveguide-based sensors coupled with quantum cascade laser light sources has been confirmed as an innovative analytical tool, which may be used in a wide range of application scenarios, ranging from environmental to medical sensing, taking advantage of the robustness and inertness of nanocrystalline diamond.

Automated summary

Diamond thin-film waveguides with a nanocrystalline diamond layer were used to detect the IR signature of caffeine in the mid-infrared regime. The morphological properties of the waveguides were characterized using AFM and SEM, and theoretical simulations confirmed the feasibility of using a larger sensing area compared to strip waveguides. A comparative analysis confirmed the performance of the diamond thin-film-waveguide-based sensing system, indicating its potential for various applications.