Viral-templated gold/polypyrrole nanopeapods for an ammonia gas sensor

One-dimensional gold/polypyrrole (Au/PPy) nanopeapods were fabricated using a viral template: M13 bacteriophage. The genetically modified filamentous virus displayed gold-binding peptides along its length, allowing selective attachment of gold nanoparticles (Au NPs) under ambient conditions. A PPy shell was electropolymerized on the viral-templated Au NP chains forming nanopeapod structures. The PPy shell morphology and thickness were controlled through electrodeposition potential and time, resulting in an ultra-thin conductive polymer shell of 17.4 ± 3.3 nm. A post-electrodeposition acid treatment was used to modify the electrical properties of these hybrid materials. The electrical resistance of the nanopeapods was monitored at each assembly step. Chemiresistive ammonia (NH₃) gas sensors were developed from networks of the hybrid Au/PPy nanostructures. Room temperature sensing performance was evaluated from 5 to 50 ppm_v and a mixture of reversible and irreversible chemiresistive behavior was observed. A sensitivity of 0.30%/ppm_v was found for NH₃ concentrations of 10 ppm_v or less, and a lowest detection limit (LDL) of 0.007 ppm_v was calculated. Furthermore, acid-treated devices exhibited an enhanced sensitivity of 1.26%/ppm_v within the same concentration range and a calculated LDL of 0.005 ppm_v. (paper)