Reliable detection of o-nitrophenol and p-nitrophenol based on carbon nanotubes covalently functionalized with ferrocene as an inner reference

Abstract

Developing an accurate and sensitive method for the detection of environmental pollutants is of great significance. However, traditional single signal based electrochemical sensors are usually susceptible to external and internal effects. To overcome these influences, in the present work, ferrocene (Fc) was covalently functionalized on multi-walled carbon nanotubes (MWNTs) to fabricate a facile electrochemical sensor for the detection of o-nitrophenol (o-NP) and p-nitrophenol (p-NP). With an increase in the concentration of both the nitrophenols, the peak currents of nitrophenols increased while the peak current of Fc remained constant. Thus, Fc can be used as an inner reference element to obtain a ratiometric signal by dividing nitrophenol current by Fc current, which endowed the sensor with a built-in correction of environmental effects. Moreover, Fc can effectively separate the reduction peaks of o-NP and p-NP, which made it possible to detect o-NP and p-NP individually and simultaneously. Due to the self-calibration based on the ratiometric strategy and the good conductivity of MWNTs, the prepared sensor showed high accuracy, reliability, and sensitivity for o-NP and p-NP detection with the linear range of 1.0 × 10⁻⁷ to 1.0 × 10⁻⁴ M. The facile, low cost, and sensitive sensor reported here has promising potential for accurate and reliable detection of other compounds.