Immobilization using electrodeposition

However, the application of cobalt- oxide nanomaterials for immobilization of biomolecelus and biosensor fabrication is rare. Recently we used electrodeposited cobalt-oxide nanoparticles for immobilization of hemoglobin [67], The UV-visible spectrophotometric analysis and voltammetric studied indicates the immobilization of Hb onto cobalt-oxide nanoparticles (Figure 35). 

There has been an increasing number of studies of the UPD of main group elements, including S, Se, Te, I, Br, Cl, and As, on metal substrates, whereas studies of UPD processes on the surface of semiconductors and semimetal substrates are significantly less. Presently, most interesting in this connection is the combined use of photoexcitation of a semiconductor substrate and/or an immobilized precursor, and electrodeposition, as will be discussed in a subsequent paragraph. 

Various methods ofachieving preconcentration have been applied, including Hquid -hquid extraction, precipitation, immobihzation and electrodeposition. Most of these have been adapted to a flow-injection format for which retention on an immobihzed reagent appears attractive. Sohd, sihca-based preconcentration media are easily handled [30-37], whereas resin-based materials tend to swell and may break up. Resins can be modified [38] by adsorption of a chelating agent to prevent this. Sohds are easily incorporated into flow-injection manifolds as small columns [33, 34, 36, 39, 40] 8-quinolinol immobilized on porous glass has often been used [33, 34, 36]. The flow-injection technique provides reproducible and easy sample handhng, and the manifolds are easily interfaced with flame atomic absorption spectrometers. 

A biocomposite composed of a chitosan hydrogel, GOx and AuNPs immobilized onto a gold electrode via a single step electrodeposition was used to construct an... 

A PPy/PQQ modified GC electrode was used for amperometric detection of V-type nerve agent decomposition products. The electropolymerization of pyrrole was efficiently used for immobilization of the biocatalyst, PQQ. The introduction of CaCl2 as a supporting electrolyte during electrodeposition significantly improves the response of the sensor to DMAET and DEAET. Amperometric studies targeted to detection of DMAET and DEAET by PPy/PQQ electrode were performed at a constant potential set at 0.25 V, and the electrode characteristics such as sensitivity and the analyte detection limit were determined. 

Applications. A biotinylated GOX-based biosensor was developed based on a new electropolymerized material consisting of a pol3rp3uidyl complex of ruthenium(II) functionalized with a pyrrole group [90]. Because histidine, lysine and arginine functions also coordinate Os /Os , biosensors based on co-electrodeposited GOX, HRP, soybean peroxidase (SBP) and laccase with redox Os /Os polymer have been developed [89]. A metal chelate formed by nickel and nitrilotriacetic acid was used to modify a screen-printed electrode surface. The functionalized support allowed stable attachment of acetylcholinesterase and the resulting biosensor was used for sensitive detection of organophosphorus insecticides [91]. This method is attractive because it ensures a controlled and oriented enzyme immobilization, considerably improving the sensitivity and the detection limit. 

A vast amount of literature exists on enzyme-modified metal nanopartides. Crumbliss and co-workers pioneered the use of metal nanopartides for enzymatic sensors for various analytes such as H2O2, glucose, xanthine and hypoxanthine [156-158]. GCE or Pt electrodes are modified with enzyme-capped Au colloids, either by simple evaporation or electrodeposition. The nanopartides act as mediators, transferring electrons between the redox-active site on the immobilized biomolecule and the electrode and thus eliminating the need for external mediators. These sensors are classified as third generation biosensors . 

Schuhmann et al. introduced the use of electrodeposition paints (EDPs) as immobilization matrices for biosensors [17[. Following work enabled the incorporation of redox mediators into the polymer structure of EDPs [18. 146]. 

Electrodeposition Processes Hasse et al. [366] have used in situ AFM for the detection of silver nucleation at the three-phase junction of the type metal-sUver halide-electrolyte solution. At this phase boundary, electrochemical reduction of submicrometer size silver halide crystals immobilized on the surface of gold and platinum electrodes took place. Following nucleation, the reaction advanced until the entire surface of the silver halide crystals was covered with 20 atomic layers of silver. Then, reduction was terminated. The obtained silver layer could be oxidized and the next layer of silver halide crystals became accessible for further reduction. 

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