Chemical alcohol sensors

In recent years further concepts have been developed for the construction of polymer-based diodes, requiring either two conjugated polymers (PA and poly(A-methyl-pyrrole) 2 > or poly(A-methylpyrrole in a p-type silicon wafer solid-state field-effect transistor By modifying the transistor switching, these electronic devices can also be employed as pH-sensitive chemical sensors or as hydrogen or oxygen sensors 221) in aqueous solutions. Recently a PPy alcohol sensor has also been reported 222). 

Most microhotplate-based chemical sensors have been realized as multi-chip solutions with separate transducer and electronics chips. One example includes a gas sensor based on a thin metal film [16]. Another example is a hybrid sensor system comprising a tin-oxide-coated microhotplate, an alcohol sensor, a humidity sensor and a corresponding ASIC chip (Application Specific Integrated Circuit) [17]. More recent developments include an interface-circuit chip for metal oxide gas sensors and the conccept for an on-chip driving circuitry architecture of a gas sensor array [18,19]. 

Adsorption temperature, effect on TPD spectra of oxygen on Pd-doped tin(IV) oxide, 74,75 Airborne chemicals, detection and identification, 299-307 Alcohol sensors, general discussion, 333... 

Chen J, Naglak T, and Wang HY (1992) An amperometric alcohol sensor on chemically permeabilized methylo-tropic microorganisms. Biotechnology Progress 8 161-164. 

Mohr G. Citterio D., Demuth C., Fehlmann M., Luzi J., Lohse C., Moradian A., Nezel T., Rothmaier M. Spichiger U.E., Reversible chemical reactions as the basis for optical sensors used to detect amines, alcohols and humidity, Journal of Materials Chemistry 1999 9 2259. 

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. 

D. C. Sundberg, Z. Zhujun, Y. Zhang, M. Wangbai, R. Russell, Z. M. Shakhsher, C. L. Grant, and W. R. Seitz, Poly(vinyl alcohol) as a substrate for indicator immobilization for fiber-optic chemical sensors, Anal. Chem. 61, 202-205 (1989). 

Alcohol vapor, tin oxide sensor responses, 63,64-65f Algorithms, computer, detection and identification of airborne chemicals, 305-307... 

In general, EC reactions are typically observed according to the following general rank order (by relative ease of oxidation) o,p-quinol and o,p-aminophenol > tertiary amine > m-quinol rv phenol rv arylamine > secondary amine thiol > thioether primary amines, aliphatic alcohols. (HDVs) each redox active metabolite are obtained from the response across adjacent EC-Array sensors. These data are a reflection of the kinetic and thermodynamic components of electron transfer reactions. Since chemical structure is a critical determinant of an analyte s redox behavior, the intrinsic generation of an HDV with EC-Array provides qualitative information for each species. 

Electrochemical transducers work based on either an amperometric, potentio-metric, or conductometric principle. Further, chemically sensitive semiconductors are under development. Commercially available today are sensors for carbohydrates, such as glucose, sucrose, lactose, maltose, galactose, the artificial sweetener NutraSweet, for urea, creatinine, uric acid, lactate, ascorbate, aspirin, alcohol, amino acids and aspartate. The determinations are mainly based on the detection of simple co-substrates and products such as 02, H202, NH3, or C02 [142]. 

Chemically binding enzymes to nylon net is very simple and gives strong mechanically resistant membranes (135). The nylon net is first activated by methylation and then quickly treated with lysine. Finally, the enzyme is chemically bound with GA. The immobilized disks are fixed direcdy to the sensor surface or stored in a phosphate buffer. GOD, ascorbate oxidase, cholesterol oxidase, galactose oxidase, urease, alcohol oxidase (135), and lactate oxidase (142) have been immobilized by this procedure and the respective enzyme electrode performance has been established. 

Reversible, optically active interactions between ZnTTBPc and alcohols at low vapor concentration were studied by quantum chemical calculations and x-ray absorption spectroscopy, while the irreversible crystallization of the ZnTTBPc films was observed in the films exposed to saturated alcohol vapor. Further investigation into the factors that initiate this irreversible transformation will be beneficial to improving the stability of organic gas sensors. 

Price J B 1973 Anisotropic etching of silicon with KOH-H20-isopropyl alcohol Semicoruluctor Silicon (Electrochemical Society Symposium Series) ed H R Huff and R R Burgess (Pennington, NJ ECS) pp 339-53 Harrison J J, Seiler K, Manz A and Fan Z 1992 Chemical analysis and electrophoresis systems integrated on glass and silicon chips Tech. Digest Solid-State Sensor and Actuator Workshop (Hilton Head Island, SC) (New York IEEE) pp 110-13... 

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