The reduction of toxic hexavalent chromium to its trivalent state at conducting polymers films was studied. The process is based on the capacity of conducting polymers to spontaneously donate electrons to the Cr(VI) species. Electrodes of polyaniline and polypyrrole, deposited as films on reticulated vitreous carbon (RVC), were prepared. The process of Cr(VI) reduction was studied under open and closed circuit conditions. It was observed that polyaniline was only suitable for use only under closed circuit conditions, whereas polypyrrole did not perform well under either open or closed circuit conditions. The electrocatalytic power of polyaniline for Cr(VI) reduction was demonstrated when the reaction rates for bare RVC and RVC/PANI were compared.
In this work, a highly sensitive electrochemical sensor for 4-nitrophenol (4-NP) was facilely constructed based on a Nafion modified glass carbon nanofilm electrode (Nafion-GCNFE). The GCNFE with high activity was quickly fabricated from a smooth GC surface in a blank electrolyte solution of H 2 SO 4 with square wave potential pulses (SWPPs), where the nanofilm formation might be related to repeated anodic oxidation coupled with SO 4 2− intercalation/deintercalation. Moreover, a Nafion modifier can improve the 4-NP adsorption on GCNFE, as confirmed by the Fourier transform infrared spectroscopy (FTIR), and hence increased the differential pulse voltammetry (DPV) response of 4-NP. The influence of pulse potential, pulse time, pulse frequency, and Nafion amount on the DPV signal of 4-NP was investigated in detail. Under an optimized detection condition, the electrochemical sensor based on Nafion-GCNFE exhibited excellent performances in sensing 4-NP with a wide linear range of 10 nM to 50 μM, a very low detection limit of 4 nM (3σ/slope), good reproducibility and reusability, high selectivity and long-term stability (over four weeks), which was successfully used for the 4-NP determination in real water samples with satisfied results.
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