Surface-Anchored Poly(4-vinylpyridine)–Single-Walled\nCarbon Nanotube–Metal Composites for Gas Detection

Abstract

A platform for chemiresistive gas\ndetectors based upon single-walled\ncarbon nanotube (SWCNT) dispersions stabilized by poly­(4-vinylpyridine)\n(P4VP) covalently immobilized onto a glass substrate was developed.\nTo fabricate these devices, a glass substrate with gold electrodes\nis treated with 3-bromopropyltrichlorosilane. The resulting alkyl\nbromide coating presents groups that can react with the P4VP to covalently\nbond (anchor) the polymer–SWCNT composite to the substrate.\nResidual pyridyl groups in P4VP not consumed in this quaternization\nreaction are available to coordinate metal nanoparticles or ions chosen\nto confer selectivity and sensitivity to target gas analytes. Generation\nof P4VP coordinated to silver nanoparticles produces an enhanced response\nto ammonia gas. The incorporation of soft Lewis acidic Pd²⁺ cations by binding PdCl₂ to P4VP yields a selective and\nhighly sensitive device that changes resistance upon exposure to vapors\nof thioethers. The latter materials have utility for odorized fuel\nleak detection, microbial activity, and breath diagnostics. A third\ndemonstration makes use of permanganate incorporation to produce devices\nwith large responses to vapors of volatile organic compounds that\nare susceptible to oxidation.