Phosphomolybdic acid nano-aggregates immobilized nafion membrane modified electrode for selective cysteine electrocatalytic oxidation and anti-dermatophytic activity

• An elegant chemically modified electrode for low potential electrocatalytic oxidation of cysteine in pH 7.
• The system characterized using TEM, XRD, FTIR and UV–vis.
• Electrochemical characterization by Fe(CN)63− and Ru(bpy)32+ reveals metal like surface behavior of the working electrode.
• The {Nafion + PMo12} composite showed marked anti-dermatophytic activity against Trichophyton rubrum organism.

Phosphomolybdic acid (PMo12) stabilized Nafion (Nf) membrane colloidal solution ({Nf-PMo12}) modified glassy carbon electrode (GCE/{Nf-PMo12}-CME) has been demonstrated as a new and efficient electrocatalyst for cysteine (CySH) oxidation in pH 7 phosphate buffer solution. Physico-chemical characterizations of the {Nf-PMo12} by TEM, XRD, FT-IR and UV–vis spectroscopy techniques revealed stabilization of the PMo12 as 5–60 nm sized nano-aggregates within the sulphonic acid micro-channels of Nafion without any changes in the crystal structure. Electrochemical characterization of the GCE/{Nf-PMo12}-CME with Fe(CN)63− and Ru(bpy)32+ indicates metal like surface feature of the working electrode. The GCE/{Nf-PMo12}-CME showed highly stable CySH electrochemical oxidation current signal at 0.58 ± 0.02 V vs. Ag/AgCl in pH 7 with 150 mV reduction in the response and about 8 times higher the peak current than that of the respective unmodified electrode. Amperometric i–t response of CySH at an applied potential of 0.58 V vs. Ag/AgCl yielded current sensitivity and regression coefficient values of 0.011 μA/μM and 0.9998 respectively without any interference from xanthine, hypoxanthine, nitrite, uric acid and other sulphur containing biochemicals; methionine and taurine, except ascorbic acid. Calculated detection limit value is (signal-to-noise ratio, S/N = 3) 25 μM. In particular, the PMo12 and {Nf-PMo12} systems showed marked anti-dermatophytic activity against Trichophyton rubrum organism, and the activity is comparable with standard fluconazole drug.

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