Room-Temperature Methanol Gas Sensor Based on PEDOT:Tosylate Thin Films: Enhanced Sensitivity through Urea Surface Treatment

Tosylate (PEDOT:Tos), a conducting polymer, has emerged as a versatile material, yet its potential for gas sensing remains unexplored. This study presents the first investigation of pristine PEDOT:Tos as a chemiresistive gas sensor for detecting methanol (MeOH), at room temperature. We demonstrate that pristine PEDOT:Tos can detect methanol down to 5 ppm. Furthermore, we examine the influence of a simple urea surface treatment, which significantly enhances the sensor's performance. The urea-modified sensor exhibits an ∼3.7 times increase in response to 100 ppm MeOH (from ∼6 to ∼22% relative resistance change) and achieves a calculated limit of detection of 1.19 ppm. While the treatment improves response magnitude, it also increases the response and recovery times to 17 min and 8 h, respectively, suggesting strong analyte interaction suitable for cumulative sensing applications, such as long-term environmental or agricultural monitoring. Complementary density functional theory calculations confirm a charge transfer mechanism underpinning the sensing response. This work establishes PEDOT:Tos as a promising and easily modifiable material for room-temperature gas sensing, paving the way for new applications in industrial safety and environmental science. Furthermore, the demonstrated ease of surface modification offers a pathway for tuning electrical properties, enabling broader applicability.