Inorganic sensors oxygen

Even if few systems are proposed for inorganic compounds (with regard to the number of potential pollutants), instruments or sensors for parameters used for treatment process control are available UV systems for residual chlorine in deodorization, electrochemical sensors for dissolved oxygen (with nowadays a luminescent dissolved-oxygen probe utilizing a sensor coated with a luminescent material) and a colorimetric technique for residual ozone. 

Some bead materials possess porous structure and, therefore, have very high surface to volume ratio. The examples include silica-gel, controlled pore glass, and zeolite beads. These inorganic materials are made use of to design gas sensors. Indicators are usually adsorbed on the surface and the beads are then dispersed in a permeation-selective membrane (usually silicone rubbers). Such sensors possess high sensitivity to oxygen and a fast response in the gas phase but can be rather slow in the aqueous phase since the gas contained in the pores needs to be exchanged. Porous polymeric materials are rarer and have not been used so far in optical nanosensors. 

Nanowires and nanobelts of inorganic oxides have been fashioned into chemically sensitive semiconductor devices. These include tin and zinc oxides [9], and indium oxide [30], Once again, ammonia and NO2 gases were used for initial demonstrations. Oxygen had very little effect on the sensing action. Because of the low concentrations detected and the speed of the response, it was suggested that single-molecule response could be within reach with these ultraminiaturized sensors. 

Another class of dense inorganic membranes that have been used in membrane reactor applications are solid oxide type membranes. These materials (solid oxide electrolytes) are also finding widespread application in the area of fuel cells and as electrochemical oxygen pumps and sensors. Due to their importance they have received significant attention and their catalytic and electrochemical applications have been widely reviewed [94-98]. Solid materials are known which conduct a variety of cationic/anionic species [14,98]. For the purposes of the application of such materials in catalytic membrane reactor applications, however, only and conducting materials are of direct relevance. 

Since inorganic phosphate is indispensable for the nucleoside phosphorylase reaction, the phosphate concentration can be converted into an oxygen signal by using a nucleoside phosphorylase-xanthine oxidase sequence electrode (Watanabe et al., 1987 Watanabe, 1988). 2 mmol/1 of inosine has been shown to be necessary for optimal sensitivity to phosphate ion. The measuring range was 0.1-1 mmol/1 and the sensor could be used for 70 assays. 

The Inorganic 9. Calcium-doped cerium oxide (Ce02) is unsuitable as a solid electrolyte in a Nemst sensor Chemistry of for measuring the oxygen concentration and in a fuel cell. Why ... 

Mascell WC (1987) Inorganic solid state chemically sensitive devices electrochemical oxygen gas sensors. J Phys E Sci Instrum 20 1156-1168... 

Other inorganic materials were also studied by KP. Studies on gas sensitivity are reported for carbonates, especially BaCOj, being sensitive to CO and NO even at ambient temperature (Ostrick et al. 1999, 2000a, 2003), TiN (Ostrick et al. 2000b) as ammonia sensitive layers, and LaFj as oxygen (Cho et al. 1991 Choi et al. 1993) and ozone (Doll et al. 1996) sensing layers. The sensitivity of barium carbonate to CO in work-function-type gas sensors is due to the formation of bicarbonate... 

Application in catalyst and inorganic membranes preparation. J. Mater. Chem. 1999 9 55-65 Guizard C., Julbe A. Nanophase ceramic ion transport membranes for oxygen separation and gas stream enrichment. In Recent Advances in Gas Separation by Microporous Ceramic Membranes, Kanellopoulos N.K., ed., Amsterdam Elsevier, 2000, pp. 435-471 Guizard C., Barboiu M., Bac A., Hovnanian N. Hybrid organic-inorganic membranes with specific transport properties. Applications in separation and sensors technology. Separ. Purif. Technol. 2001 25 167-180... 

---