Abstract: An organic-inorganic hybrid material based on sol-gel derived SiO₂ and PVA has been obtained. Nitrate reductase is immobilized with this hybrid material on gold electrode surface and an amperometric nitrate reductase biosensor of high performance has been fabricated. The nitrate reduction reaction is driven by the enzyme and methyl viologen which is used as the electrontransfer mediator. The developed sensor is applied to detect nitrate with operating potential of -0.68V (vs. SCE). Optimum pH is 7.0 and enzymes loading are 7.2 mU. Under selective conditions the biosensor shows sensitivity of 2.53 nA/(μmol·L^-1) and a linear range of 0.01～0.36 mmol/L. The average response time is 12.1 s.

Key words: nitrate reductase sensor, modified electrode, methyl viologen, sol-gel, PVA, hybrid material