Carbon Nanotube Sensors for Gas and Organic Vapor Detection

TLDR

A gas sensor fabricated by casting single‑walled carbon nanotubes on an interdigitated electrode is presented for room‑temperature detection of gases and organic vapors. The extended detection capability arises from direct charge transfer in individual semiconducting SWNTs and additional electron hopping across intertube junctions via physically adsorbed molecules. The sensor exhibits linear responses from sub‑ppm to hundreds of ppm, with detection limits of 44 ppb for NO₂ and 262 ppb for nitrotoluene, responds within seconds and recovers in minutes, and shows less than 6 % sensitivity variation across devices, matching commercial metal‑oxide or polymer sensors while retaining room‑temperature sensitivity and manufacturability.

Abstract

A gas sensor, fabricated by the simple casting of single-walled carbon nanotubes (SWNTs) on an interdigitated electrode (IDE), is presented for gas and organic vapor detection at room temperature. The sensor responses are linear for concentrations of sub ppm to hundreds of ppm with detection limits of 44 ppb for NO2 and 262 ppb for nitrotoluene. The time is on the order of seconds for the detection response and minutes for the recovery. The variation of the sensitivity is less than 6% for all of the tested devices, comparable with commercial metal oxide or polymer microfilm sensors while retaining the room-temperature high sensitivity of the SWNT transistor sensors and manufacturability of the commercial sensors. The extended detection capability from gas to organic vapors is attributed to direct charge transfer on individual semiconducting SWNT conductivity with additional electron hopping effects on intertube conductivity through physically adsorbed molecules between SWNTs.