Microsensor Based on Gold Nanoparticles for Fast and Sensitive Ortho-Xylene Detection

Abstract

Miniaturization of gas sensors carries added benefits of better portability, lower costs, and allowing for multianalyte detection by integrating various sensors in one device. In this study, laser writing technology is proposed to fabricate a micro gas sensor based on 11-mercaptoundecanoic acid functionalized gold nanoparticles, which are assembled and deposited over the spacing between two electrodes. During the response process to volatile organic compounds (VOCs), conductivity change is dominated by interparticle properties, such as dielectric constant, interparticle spacing. The microsensor showed the maximum response to ortho-xylene among seven target analytes. The microsensor exhibited larger response ( $\Delta \text{R}/\text{R}_{a}= 0.412$ ) than the drop-cast film ( $\Delta \text{R}/\text{R}_{a} = 0.044$ ) at 5000 ppm for ortho-xylene. The response time of the microsensor was 57 s, shorter than the drop-cast film of 127 s. Improved sensitivity and shorter response time were also observed for other VOCs (toluene, ethanol, benzene, methanol, acetone, chloroform). The better sensing performance can be attributed to the larger surface-volume ratio brought by the rough surface and the miniaturization of device. Therefore, the shorter response time and higher response were obtained by laser writing technology.