As reported in Nanotechnology, Gu Feng and colleagues applied a simple protocol for polymer nanotube fabrication to CuTAPc, a commonly used industrial dye, to form their surface modified device. A high surface area to volume ratio was obtained by modifying the nanotube structure on a platinum layer, which helped the team to realize a sensor with high sensitivity and a fast response towards NO.

High sensitivities and improved linear ranges were achieved through well established measurements such as differential pulse voltammetry (DPV) and differential potential amperometry (DPA). Detection limits as low as 10 nM were obtained in common voltammetric analysis with the ultra-high response current in the microamp range.

Meanwhile, electrochemical impedance spectroscopy (EIS) was introduced to determine the sensitivity of the device to variations in polymer conductivity. By comparing the data with values obtained from an equivalent circuit model simulation, it was found that the resistance of poly-CuTAPc nanotubes decreased proportionally with the NO concentration exclusively at the oxidation potential, which points towards the possibility of determining the NO concentration in the nanometre range.

In addition, a de-doping process was applied to the sensors to increase the porosity of the nanotubes, which further lowers the detection limit. This is probably because high porosity provides more active sites and/or surface area through the expulsion of embedded anions.

The scientists are currently planning to fabricate sensors that can detect more chemicals such as dopamine, hydrazine and glucose, to further extend the applications in human and environmental studies.