Dioxygen sensors

Absorption and emission properties were similar to those of unattached [Re(phen)(CO)3 (py)]+ with high quantum efficiencies and long emission lifetimes. Quenching of the emission occurred in the presence of O2 suggesting their use for dioxygen sensors. 

Electrochemical sensors, the most ancient of which is the electrode, are currently undergoing development in that their prices are often low, they are easy to use and, most of all, they are easy to insert into a regulation system. In this respect, the most widely used today is the dioxygen sensor, which allows for combustion to be optimised thanks to the process of analysing the exhaust gases . Several million parts per year are produced, notably for the car industry. In the biomedical field, electrochemical sensors are also used to monitor glucose and pH, and to measure out certain cations. New developments are also being made in the field of pollutant analysis. 

During the past 40 years there have been numerous exciting extensions of electrochemistry to the field of analytical chemistry. A series of selective-ion potentiometric electrodes have been developed, such that most of the common ionic species can be quantitatively monitored in aqueous solution. A highly effective electrolytic moisture analyzer provides continuous online assays for water in gases. Another practical development has been the voltammetric membrane electrode for dioxygen (02), which responds linearly to the partial pressure of 02, either in the gas phase or in solution. The use of an immobilized enzyme (glucose oxidase) on an electrode sensor to assay glucose in blood is another extension of electrochemistry to practical analysis. 

The coordinative and/or dissociative adsorption of various probe molecules has been used to characterize the surface properties of Ti02) which finds applications as a catalyst, photocatalyst, and sensor. Among the molecules used as probes, we mention CO (37, 38, 563-576), C02 (563, 565, 577), NO (578,579), water (580,581), pyridine (582,583), ammonia (584,585), alcohols (586, 587), ethers (including perfluoroethers) (588), ozone (589), nitrogen oxide (590), dioxygen (591), formic acid (592-594), benzene (584), benzoic acid (595), and chromyl chloride (596). 

The molecule is very stable and can be sublimed [i]. Numerous metal phthalocyanines can reversibly bind molecules like, e.g., dioxygen at the metal ion. This can result in activation of internal bonds and subsequent facilitation of chemical reaction, in this case of dioxygen -> electroreduction. Thus these molecules have attracted attention as catalysts for various reactions, in particular dioxygen reduction in, e.g., fuel cells [ii], in general -> electrocatalysis [iii] and in -> sensors [iv]. Their strong coloration, which can be modified electrochemically by reduction/oxidation, suggests use in -> electrochromic devices [v]. 

The interaction of dioxygen with metals is important to these systems as well as to the development of O2 sensors plus fuel cells, batteries, and electrocatalysts see Electrochemistry Applications in Inorganic Chemistr Therefore, it is not surprising that studies of the interaction and activation of dioxygen at metal sites have occupied and fascinated researchers for quite some time. 

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