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ELECTROCHEMICAL BEHAVIOR OF MIXED SILVER-COPPER SULFIDE TOWARD H2O2: ANALYTICAL APPLICABILITY FOR BIOSENSING SYSTEMS

Comparative study of electrochemical behaviors of mixed silver-copper sulfides and silver sulfide has been made in order to investigate its analytical applicability as mediators in biosensing systems (containing oxidases or peroxidases). X-ray diffractometry (XRD) of prepared powder of mixed silver-copper sulfide revealed that beside ternary sulfides (AgCuS and Ag 1.2 Cu 0.8 S) also metallic silver can be found. The electrocatalytical activities of sulfides were evaluated towards the detection of hydrogen peroxide (H 2 O 2 ) at various pH values. Cyclic voltammetry was carried out to determine the exact reduction (0 V) and oxidation (0.25 V) potentials for the electrochemical reaction of H2O2 on carbon paste electrode modified with mixed silver-copper sulfide or silver sulfide. Tentative electrochemical reaction mechanisms for observed phenomenon are proposed. The amperometric studies revealed that the mixed copper-silver sulfide modified carbon paste electrode performed well by attaining a wide linear response range toward H 2 O 2 from 1 µM to 3 mM with detection limit 0.14 µM and the sensitivity of 350 µA mM -1 . In addition, good selectivity, rapid and stable response towards H 2 O 2 is obtained. Obtained results suggest promising paths for selective and sensitive application of sulfide modified electrode in biosensing system.

hydrogen peroxide, silver-copper sulfide, carbon paste, electroanalytical, biosensing.

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