A platform for chemiresistive gas detectors based upon single-walled carbon nanotube (SWCNT) dispersions stabilized by poly(4-vinylpyridine) (P4VP) covalently immobilized onto a glass substrate was developed. To fabricate these devices, a glass substrate with gold electrodes is treated with 3-bromopropyltrichlorosilane. The resulting alkyl bromide coating presents groups that can react with the P4VP to covalently bond (anchor) the polymer–SWCNT composite to the substrate. Residual pyridyl groups in P4VP not consumed in this quaternization reaction are available to coordinate metal nanoparticles or ions chosen to confer selectivity and sensitivity to target gas analytes. Generation of P4VP coordinated to silver nanoparticles produces an enhanced response to ammonia gas. The incorporation of soft Lewis acidic Pd2+ cations by binding PdCl2 to P4VP yields a selective and highly sensitive device that changes resistance upon exposure to vapors of thioethers. The latter materials have utility for odorized fuel leak detection, microbial activity, and breath diagnostics. A third demonstration makes use of permanganate incorporation to produce devices with large responses to vapors of volatile organic compounds that are susceptible to oxidation.
This work was supported by the National Science Foundation (DMR-1410718) and the King Abdullah University of Science and Technology. B.Y. acknowledges support from the National Research Foundation of Korea (2013R1A6A3A03023493). S.F.L. acknowledges support from the National Science Foundation Graduate Research Fellowship under Grant 1122374. The authors thank Dr. Maggie He [Massachusetts Institute of Technology (MIT)] for XPS measurements. B.Y. thanks Dr. Seung Goo Lee (MIT) for helpful discussions about organosilanization methods.