Optoelectronic sensors

Potential problems can result if monitoring well construction is such that the gravel pack and screened interval are not discretely terminated at the confining layer and its grouted annulus. 

---

Recovery well recharge test Dielectric well logging tool Optoelectronic sensor... 

Figure 11.33 Schematic of the optoelectronic sensor scheme. Sample and hold devices.

Nano-composites for optoelectronics Sensors using zeolite thin films Stereo-selective polymerization Contrast enhancement in MRl (e.g. Gd-Y)... 

On the other hand, the molecular recognition by enzymes, which are also applied in the form of organelles, microorganisms and tissue slices, is accompanied by chemical conversion of the analyte to the respective products. Therefore this type of sensor is termed a metabolism sensor2. The initial state is usually reached when the analyte conversion is complete. With metabolism sensors, under certain conditions cosubstrates, effectors, and enzyme activities can be measured via substrate determination. Amperometric and potentiometric electrodes and thermistors are the preferred transducers, but in some cases optoelectronic sensors have also been used. With biomimetic sensors physical signals such as sound, stress, or light are measured through their ability to... 

Chemical optoelectronic sensors use a reagent, R, which is immobi-... 

Fig. 8. Schematic of an optoelectronic sensor for the determination of human serum albumin by using immobilized bromocresol green. (Redrawn from Lowe et al., 1983).

Lowe et al. (1983) utilized the detection of protons produced during glucose oxidation by an optoelectronic sensor. Glucose oxidase was coupled to a transparent cellophane membrane together with the pH sensitive triphenylmethane dye bromocresol green. The membrane was... 

The direct fixation of the biocatalyst to the sensitive surface of the transducer permits the omission of the inactive semipermeable membranes. However, the advantages of the membrane technology are also lost, such as the specificity of permselective layers and the possibility of affecting the dynamic range by variation of the diffusion resistance. Furthermore, the membrane technology has proved to be useful for reloading reusable sensors with enzyme. In contrast, direct enzyme fixation is mainly suited to disposable sensors. This is especially valid for carbon-based electrodes, metal thin layer electrodes printed on ceramic supports, and mass-produced optoelectronic sensors. Field effect transistors may also be envisaged as basic elements of disposable biosensors. 

Test strips, which are available for the determination of about ten low-molecular mass substances (metabolites, drugs, and electrolytes) and eight enzymes [356], can be considered as precursors of optoelectronic biosensors. Efficient optoelectronic sensors based on immobilized dyes have been devised for the determination of glucose, urea, penicillin, and human serum albumin [357]. Other approaches use immobilized luciferase or horseradish peroxidase to assay ATP or NADH or, when coupled with oxidases, to measure uric acid or cholesterol. These principles have not yet been generally accepted for use in routine analysis. Thermistor devices involving immobilized enzymes or antibodies for a number of clinically relevant substances have also been described. Thermometric enzyme linked immunosorbent assays are being routinely employed for monitoring the production of monoclonal antibodies. 

The advanced level of a synthetic control for ZnS and other nanostructures and their rich morphologies at the nanoscale has provided the way to the unique applications in the fields of electronics, optoelectronics, sensors, life sciences, defense, energy, environmental science, and engineering. The recent achievements in ZnS nanostructures-based field emitters, field effect transistors and analysis of their carrier characteristics, p-type conductivity, catalytic activities, UV-light sensors, chemical sensors (including gas sensors), biosensors, and nanogenerators have been found to be very important. 

Goldfinch M.J. and Lowe C.R. (1984) Solid-phase optoelectronic sensors for biochemical analysis. Anal. Biochem, 138, 430-436. 

---