Fabrication of a SnO2–graphene nanocomposite based electrode for sensitive monitoring of an anti-tuberculosis agent in human fluids

Abstract

We demonstrated a simple and one step optimized preparation of a tin oxide–reduced graphene oxide (SnO₂–Gr) nanocomposite through simultaneous oxidation and reduction of SnCl₂ and graphene oxide (GO). The crystal structure, chemical composition, oxidation state, surface morphology and the average size of the SnO₂ nanoparticles in the nanocomposite were discussed. The extent of defects present in the nanocomposite was calculated from the I_D/I_G ratio. Further, the electrochemical properties of the SnO₂–Gr nanocomposite modified glassy carbon (SnO₂–Gr/GC) electrode were studied by CV, which showed high electrocatalytic activity and enhanced electrochemical detection ability towards the anti-tuberculosis agent isoniazide (INH). The as fabricated SnO₂–Gr/GC electrode reduces the overpotential of 610 mV when compared to the bare GC electrode. The potential of the optimized amperometric signal exhibited a linear relation with the concentration of INH in the range from 1.0 × 10⁻⁷ M to 8.5 × 10⁻⁴ M with a sensitivity of 0.0187 μA μM⁻¹ and the limit of detection (LOD) was found to be 60 nM. The pulse optimized square wave voltammogram revealed a linear concentration range between 1.9 × 10⁻⁸ and 7.2 × 10⁻⁶ M with a high sensitivity of 1.098 μA μM⁻¹ and the LOD was found to be 7 nM. Moreover, the SnO₂–Gr/GC electrode was used to analyze INH in human urine samples and pharmaceutical tablets in the presence of coexisting interference substances; the SnO₂–Gr/GC electrode also exhibited good repeatability, reproducibility and stability. The observed results confirm that the proposed sensor electrode was suitable for INH sensing.