Photothermal spectroscopy using multilayer cantilever for chemical detection

Photothermal spectroscopy is demonstrated using a high-aspect-ratio multilayer cantilever to measure adsorbed dimethyl methylphosphonate, which has an optical absorbance of ∼10−5 in the near infrared range. Detection sensitivity was 160 pW for a reed of 6 mm in length, 2 mm in width, and 10 μm. Sensitivity of the cantilever is compared to a thermal diffusion model that accounts for conduction loss through the cantilever clamp and to air along the length of the cantilever surface.