First application of multilayer graphene cantilever for laser photoacoustic detection

Abstract

The mechanical behaviours of multilayer graphene (MLG) membranes and cantilevers were investigated for the sensitive detection of acoustic waves in gases. The aim of this Work was to find sensors for laser photoacoustic spectroscopy with high sensitivity. The application of the MLG cantilever for photoacoustic detection was reported for the first time. MLG membranes and cantilevers were prepared from highly ordered pyrolytic graphite (HOPG) by multiple mechanical cleavages allowing simple adjustment of the membrane/cantilever thickness and relevant mechanical parameters. The MLG cantilevdr/membrane movements induced by pressure waves triggered by the absorption of the CO2 laser pulse in the gas-filled photoacoustic cell were detected by a He-Ne laser beam reflected from the cantilever/membrane to a position sensitive detector (optical microphone). The sensitivity of the MLG cantilevers for the photoacoustic detection of methanol vapours (testing gas) was more than one order of magnitude higher in comparison with a top class microphone (Bruel & Kjaer). The signal-to-noise ratio of 19, 61, and 70 together with the limits of detection of 0.75 ppm, 0.42 and 0.33 ppm were calculated for the condenser microphone, the MLG membrane, and the MLG cantilever, respectively. Additionally, the high sensitivity of both MLG elements for the photoacoustic detection is also promising thanks to the single layer graphene with very a small thickness on the nanometer scale.