A single-walled carbon nanotube thin film-based pH-sensing microfluidic chip

Abstract

A novel microfluidic pH-sensing chip was developed based on pH-sensitive single-walled carbon nanotubes (SWCNTs). In this study, the SWCNT thin film acted both as an electrode and a pH-sensitive membrane. The potentiometric pH response was observed by electronic structure changes in the semiconducting SWCNTs in response to the pH level. In a microfluidic chip consisting of a SWCNT pH-sensing working electrode and an Ag/AgCl reference electrode, the calibration plot exhibited promising pH-sensing performance with an ideal Nernstian response of 59.71 mV pH⁻¹ between pH 3 and 11 (standard deviation of the sensitivity is 1.5 mV pH⁻¹, R² = 0.985). Moreover, the SWCNT electrode in the microfluidic device showed no significant variation at any pH value in the range of the flow rate between 0.1 and 15 μl min⁻¹. The selectivity coefficients of the SWCNT electrode revealed good selectivity against common interfering ions.