Few-layer graphene Langmuir-Schaefer nanofilms for H2 gas sensing

Graphene nanofilms were deposited onto oxidized Si by modified Langmuir-Schaefer technique with the submerged substrate from the solution of few-layer graphene (FLG) which was obtained by sonication of expanded milled graphite. The films were characterized by SEM, AFM, HRTEM, XRD and Raman spectroscopy. The average FLG flake thickness and lateral dimension are 5 and 300 nm, respectively. The intensity of D vs. G Raman bands suggests a low defect density in our samples. The films were decorated by Pd nanoparticles (6 - 7 nm) using drop casting and centrifugation. The sensors were contacted by silver paste. The gas sensing was tested in mixtures of dry air with 10 -10 000 ppm of H-2. The sensor response at room temperature (RT) was 4 % at 10 ppm and 13.5 % at 1000 ppm of H-2. The optimum working temperature was 70 degrees C. Here the sensor response was doubled comparing with RT. The FLG film conductivity was of p-type.