Amperometric detection sensing layer

So far SECM applications have been considered where enzymes immobilized at a surface catalyze redox reactions of low molecular weight compounds. The reaction products are detected at the ultramicroelectrode tip under diffusion-controlled conditions. This approach requires that the biochemically active layer continuously generate or consume redox active (for amperometric detection) or charged (for potentiometric detection) species. Since the tip signal depends on the diffusion coefficients and/or convective effects as well as the local concentration, it is possible to image localized mass transport phenomena instead of localized chemical fluxes (Chapter 9). In a general sense it is a process that is recorded with lateral resolution. 

Amperometric Detection, Fig. 4 (A) Illustration of the cross section of a unit cell. The surface of the LSI was modified by metal (Au/Pt/Ti) and insulated by epoxy polymer (SU-8 3005) to define the electrode area exposed to the solution, (a) Contact hole to expose A1 pad. b) Sensing point. (B) Microgram of unit cells. A1 pads a) can be seen under the Au layer. The size of a sensing point... 

Modification of the electrode started with academic studies on physical and chemical adsorption, i.e., with the appearance of fundamental researches on adsorption of different species on electrode surfaces, both under polarization and at open circuit potential [3]. The properties of similar chemically modified electrodes , in which the modifier consists of a monolayer of a variety of chemical species with different characteristics, possessing (or not) particular properties, were initially studied in a purely electrochemical context, aimed at the collection of fundamental physico-chemical data. A small group of electrochemists were among those involved in these basic studies, envisioning the perspectives opened by the novel systems. In the first, really fascinating, work with similar monomolecular layers, cobalt porphyrin and phthalocyanine, as well as deliberately synthesized dicobalt face-to-face porphyrins were adsorbed on Pt or C surfaces to catalyze molecular oxygen reduction [4]. However, similar systems were not always used or adequately tested in proper amperometric sensing by researchers more interested in electroanalysis dicobalt face-to-face porphirins still constitute a rare example of tailored materials for selective amperometric detection. 

An acid phosphatase (AP) hybrid biosensor was developed using a thin layer of potato tissue coupled to an amperometric GOD-based biosensor based on internal sensing of H202. The reversible inhibition of AP was utilized for the determination of malathion, paraoxon methyl, paraoxon, and aldicarb with limits of detection of 0.5 ppb for paraoxon methyl, and 40 ppb for aldicarb. The tissue-based biosensor exhibited a longer shelf life and abetter reliability on the amperometric results than a bi-enzymatic sensor with purified AP and GOD. A similar biosensor was also developed using a potato layer with a Clark-type dissolved oxygen electrode. ... 

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