Chemiresistive hydrogen gas sensors from gold-palladium nanopeapods

Gold-palladium (Au-Pd) nanopeapod-based H-2 chemiresistors were fabricated using a gold binding M13 viral template. Peptides displayed along the length of this biological template served as affinity binding sites to direct gold nanoparticle assembly under ambient conditions in an aqueous environment. In addition, the geometry of this filamentous biomolecule readily facilitated the formation of the highly anisotropic nanopeapod structure. Pd electroless deposition controlled peapod diameter, as well as electrical resistance. Sensor performance was determined by overall peapod morphology. Thicker nanopeapods (i.e., similar to 15 nm Pd layer) with fully encapsulated Au nanoparticle seeds showed strong evidence of oxygen inclusion during or after Pd deposition, and a modest response (i.e., 0.04%-2.6%) at 2000 ppm(v) H-2 after device conditioning through extended H-2 exposure. Thinner nanopeapods (i.e., similar to 5 nm Pd layer) with discontinuous Au nanoparticle coverage showed superior performance with a response of 117% at 2000 ppm(v) H-2 in air, a 70% response time (t(70%)) within 1min, and a low detection limit of 25 ppm(v). The bio-directed formation of these unique thin-shelled, Au-Pd peapod nanostructures and the development of a highly sensitive H-2 detector advance both the fields of nanoassembly and gas sensing. (C) 2014 AIP Publishing LLC.