Fluorine sensors

Vasihev, A., Moritz, W., Filhpov, V, Bartholomaus, L.,Terentjev, A. and Gabusjan,T. (1998), High temperature semiconductor sensor for the detection of fluorine. Sensors and Actuators B, 49,133-8. 

Alberti G, Carbone A, Palombari R (2001) Solid state potentiometric sensor at medium temperatures (150-300 °C) for detecting oxidable gaseous species in air. Sens Actuators B 75 125-128 Bartholomaus L, Moritz W (2000) Super-sensitivity of an aU solid-state fluorine sensor mechemistic investigations. Solid State Ionics 132 31-37... 

The fluorine sensor is extensively used conunerdally. The fluorine content can also be detected by chemical sensing and the principle of this device also belongs to type II. The base material is lanthanum fluoride, which is an excellent fluorine conductor, and which is stable even in aqueous solution. A typical plication is to measure the fluorine content in test water solutions. The principle of fluorine detection is based on the F concentration cell method. The detection limit is as low as 10 M, which covers most F" concentrations in drinking water. A fast response is one of the typical characteristics of the type-II sensor it is less than 3 minutes even if the F content is as low as 10" M. 

In the Ion Selective Electrode (ISE) field, the most popular and extensively used sensor is the glass electrode whieh is sensitive to a hydrogen ion. One of the other commercial sensors is a fluorine sensor, whieh is not as well known as the glass electrode. 

Fluorine is widely distributed and found in sea waters, rocks, fossils, minerals and waste materials. Interest in the measurement of the fluorine content in these substances is related to the investigation of effects of fluorine ingestion over prolonged time periods. Furthermore, in the biomedical field, it is necessary to know the fluorine content in substances such as bone and tooth enamel after mineralization, and to monitor the uptake and metabolism in plants and animals in order to provide feedback to ongoing treatment. Therefore, the development of a simple and portable fluorine sensor, based upon the ISE, would be an important contribution in this field. 

However, in this fluorine sensor, the base electrolyte is composed of the lanthanum cation with the fluorine anion. In addition, one unusual property is that the sensor can operate even when directly immersed into aqueous solutions at room temperature. The realization of the application is greatly dependent on two facts Lap3 is stable in water and it shows an excellent fluorine conduction even at room temperature. These remarkable characteristics permit the use of Lap3 as a simple and portable sensor and have led to its commercial use on a worldwide scale. 

The second group of recently developed ionic liquids is often referred to as task specific ionic liquids in the literature [15]. These ionic liquids are designed and optimised for the best performance in high-value-added applications. Functionalised [16], fluorinated [17], deuterated [18] and chiral ionic liquids [19] are expected to play a future role as special solvents for sophisticated synthetic applications, analytical tools (stationary or mobile phases for chromatography, matrixes for MS etc.), sensors and special electrolytes. 

Figure 6.5 A fluorinated organically modified silicate doped with [Ru(dpp)3]2+ is a highly sensitive 02 sensor. Fluorine here ensures unprecedented sensitivity and a remarkable stability (2% drift over 6 months). The material has been implemented in sol-gel handheld oxygen sensors that are already commercialized. (Reproduced from ref. 6, with permission.)...

R. M. Bukowski, R. Ciriminna, M. Pagliaro and F. V. Bright, High-Performance Quenchometric Oxygen Sensors Based on Fluorinated Xerogels Doped with [Ru(dpp)3]2+, Anal. Chem., 2005, 77, 2670. 

Fluorinated polymers, especially polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) and perfluorinated alkyl vinyl ethers (PFAVE) as well as other fluorine-containing polymers are well known as materials with unique inertness. However, fluorinated polymers with functional groups are of much more interest because they combine the merits of pefluorinated materials and functional polymers (the terms functional monomer/ polymer will be used in this chapter to mean monomer/polymer containing functional groups, respectively). Such materials can be used, e.g., as ion exchange membranes for chlorine-alkali and fuel cells, gas separation membranes, solid polymeric superacid catalysts and polymeric reagents for various organic reactions, and chemical sensors. Of course, fully fluorinated materials are exceptionally inert, but at the same time are the most complicated to produce. 

Fluorinated alcohols are not only interesting as model systems for weak hydrogen bonds with implications in the life sciences [254] and as chemical sensor materials [255], but also provide excellent reaction media [256, 257] and peptide solvents [258 260] with conformation-modulating properties. In both cases, molecular aggregates are thought to play an important role. One of the most widely used fluorinated alcohols is 2,2,2-trifluoroethanol, which will be in the focus of the following section. 

Mike Sailor of the University of California, San Diego, has recently developed an element-specific fluorine detector to be used as a portable nerve gas sensor. What makes his instrument so different is that it has been presented to the scientific community (at an American Chemical Society meeting) before it is put into the hands of soldiers. This gives the opportunity for peer review and for corrections to the technology, if needed, to ensure that the instrument is useful and that money isn t wasted or lives aren t endangered. 

Room temperature sensors based on a V2O5-graphite cathode and a polyethylene oxide-based electrolyte were reported by Sathiyamoorthi etal. [55]. The gas is sampled through the porous cathode and for both chlorine and fluorine good sensitivity and rapid response times were observed. 

Abstract Pressure-sensitive paint (PSP) is applied to the areodynamics measurement. PSP is optical sensor based on the luminescence of dye probe molecules quenching by oxygen gas. Many PSPs are composed of probe dye molecules, such as polycyclic aromatic hydrocarbons (pyrene, pyrene derivative etc.), transition metal complexes (ruthenium(II), osumium(II), iridium(III) etc.), and metalloporphyrins (platinum (II), palladium(II), etc.) immobilized in oxygen permeable polymer (silicone, polystyrene, fluorinated polymer, cellulose derivative, etc.) film. Dye probe molecules adsorbed layer based PSPs such as pyrene derivative and porphyrins directly adsorbed onto anodic oxidised aluminium plat substrate also developed. In this section the properties of various oxygen permeable polymer for matrix and various dye probes for PSP are described. 

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