NOVELTY - Gas sensing device has substrate having pair of conductive electrodes separated by a gap, functionalized nanomaterial. The functionalized nanomaterial bridges the gap between electrodes to form nanostructure network, and includes several gas sensitive nanoparticles distributed across portion(s) of surface.    USE - Device is used for sensing gas such as hydrogen, mercury vapor, hydrogen sulfide, nitrogen dioxide, methane, water vapor and/or ammonia, in environmental monitoring and process control for chemical refining, petroleum refining, rocket fuel production, fuel cell manufacturing, semiconductor processing and biomedical application such as hydrogen gas sensors.    ADVANTAGE - The device having high sensitivity, low detecting limits, fast response and durability is economical and safe.    DETAILED DESCRIPTION - Gas sensing device has substrate having pair of conductive electrodes separated by a gap, functionalized nanomaterial. The functionalized nanomaterial bridges the gap between electrodes to form nanostructure network, and includes several gas sensitive nanoparticles distributed across portion(s) of surface. The nanoparticles are made of material chosen from elemental metal, doped polyaniline and metal oxide, such as gold, palladium, camphor-sulfonic acid-doped polyaniline, chloride-doped polyaniline, perchlorate-doped polyaniline, acrylic acid-doped polyaniline, tetraethylammonium perfluoro octane sulfonate-doped polyaniline, para-toluene sulfonic acid-doped polyaniline and tin oxide, preferably palladium, gold, doped polyaniline, camphor-sulfonic acid-doped polyaniline or tin oxide. The nanomaterial is chosen from nanowires, single-walled carbon nanotubes, multi-walled carbon nanotubes, silicon nanowires, zinc oxide nanostructures, tin oxide nanowires, indium oxide nanowires, carbon boride nanotubes, boron-carbon-nitrogen (BxCyNz) nanotube structures. The device is manufactured using nanoparticles such as metal nanoparticles, doped polyaniline nanoparticles or metal oxide nanoparticles. The doped polyaniline nanoparticles are made from polyaniline and dopant chosen from camphor-sulfonic acid (CSA), chloride (Cl-), perchlorate (ClO4-), acrylic acid (C3H4O2), tetraethylammonium perfluoro octane sulfonate (TEAPFOS) and para-toluene sulfonic acid (CH3C6H4SO3H). An INDEPENDENT CLAIM is included for manufacture of gas sensing device.