Novel pH sensing redox wire based on a polyamide homopolymer of L-tryptophan

The redox profile obtained from an electrochemically oxidised polyamide homopolymer containing L-tryptophan is shown to serve as a versatile molecular wire for monitoring pH. The transformation of the polypeptide is examined and the optimisation of the electrode-redox wire interface was conducted in order to enhance the electrochemical signature. Voltammetric interrogation of the modified polymer reveals the creation of quinoid functionality which can be efficiently addressed through interaction with nanofractured carbon surfaces. Preliminary voltammetric and XPS characterisation was conducted and a Nernstian response (−0.060 V/pH) was observed (pH 3–8) and as such could be used as a key component in the design of new pH probes.