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Here, we report the electrochemical synthesis of TiO(2) nanoparticles (NPs) using the potentiostat method. Synthesized particles have been characterized by using x-ray diffraction (XRD) studies, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results revealed that the TiO(2) film produced was mainly composed of rutile and that the particles are of a size in the range of 100 ± 50 nm. TiO(2) NPs were used for the modification of a screen printed carbon electrode (SPE). The resulting TiO(2) film coated SPE was used to immobilize flavin adenine dinucleotide (FAD). The flavin enzyme firmly attached onto the metal oxide surface and this modified electrode showed promising electrocatalytic activities towards the reduction of hydrogen peroxide (H(2)O(2)) in physiological conditions. The electrochemistry of FAD confined in the oxide film was investigated. The immobilized FAD displayed a pair of redox peaks with a formal potential of -0.42 V in pH 7.0 oxygen-free phosphate buffers at a scan rate of 50 mV s(-1). The FAD in the nanostructured TiO(2) film retained its bioactivity and exhibited excellent electrocatalytic response to the reduction of H(2)O(2), based on which a mediated biosensor for H(2)O(2) was achieved. The linear range for the determination of H(2)O(2) was from 0.15 × 10(-6) to 3.0 × 10(-3) M with the detection limit of 0.1 × 10(-6) M at a signal-to-noise ratio of 3. The stability and repeatability of the biosensor is also discussed.

Copper nanoparticles ͑Cu-NPs͒ have been electrochemically synthesized onto a poly͑o-phenylenediamine͒ ͑PoPD-͒ coated glassy carbon electrode ͑GCE͒. Electrochemical properties and surface characterizations were studied using cyclic voltammetry, atomic force microscopy ͑AFM͒, scanning electron microscopy ͑SEM͒, and X-ray diffraction ͑XRD͒ analysis. Cyclic voltammetry, AFM, SEM, and XRD confirmed the presence of Cu-NPs on the electrode surface. Cu-NPs are firmly stabilized by surface attachment of the PoPD functionality that can be attached to the electrode surface, thus becoming an integral part of the polymer backbone. The Cu-NPs-polymer film-coated GCE ͑Cu-NPs/PoPD/GCE͒ showed excellent electrocatalytic activity toward the reduction of hydrogen peroxide ͑H 2 O 2 ͒ and nitrite ͑NO 2 − ͒. Amperometry was carried out to determine the concentration of H 2 O 2 and NO 2 − at Ϫ0.3 V. The dependence of the current response on the H 2 O 2 concentration was explored under neutral conditions, and an excellent linear concentration range from 1.0 ϫ 10 −6 to 1.0 ϫ 10 −3 M was found. The Cu-NPs/PoPD/GCE allows highly sensitive, low working potential, stable, and fast amperometric sensing of H 2 O 2 and NO 2 − . This is promising for the future development of nonenzymatic sensors. The real-sample analysis of commercial H 2 O 2 samples was performed using the proposed method, and the obtained results are satisfactory.Electrodes modified with nanoscale materials are widely used for the fabrication of chemical and biosensors. Because our aim is to prepare a reliable, reproducible, selective, and fast monitoring sensor for a specific analyte, for this purpose, nanoparticles ͑NPs͒ are promising tools because they could facilitate electron-transfer reactions, and this could be coupled with ease of miniaturization of sensing devices to nanoscale dimensions. Nanoparticles are suitable for important applications in chemical/biochemical sensing because of their high surface-to-volume ratio and highly effective catalytic properties. 1-10