Sensing ethanol

Zeolite membranes and films have been employed to modify the surface of conventional chemical electrodes, or to conform different types of zeolite-based physical sensors [49]. In quartz crystal microbalances, zeolites are used to sense ethanol, NO, SO2 and water. Cantilever-based sensors can also be fabricated with zeolites as humidity sensors. The modification of the dielectric constant of zeolites by gas adsorption is also used in zeolite-coated interdigitaled capacitors for sensing n-butane, NH3, NO and CO. Finally, zeolite films can be used as barriers (for ethanol, alkanes,...) for increasing the selectivity of both semiconductor gas sensors (e.g. to CO, NO2, H2) and optical chemical sensors. 

These effects can be attributed mainly to the inductive nature of the chlorine atoms, which reduces the electron density at position 4 and increases polarization of the 3,4-double bond. The dual reactivity of the chloropteridines has been further confirmed by the preparation of new adducts and substitution products. The addition reaction competes successfully, in a preparative sense, with the substitution reaction, if the latter is slowed down by a low temperature and a non-polar solvent. Compounds (12) and (13) react with dry ammonia in benzene at 5 °C to yield the 3,4-adducts (IS), which were shown by IR spectroscopy to contain little or none of the corresponding substitution product. The adducts decompose slowly in air and almost instantaneously in water or ethanol to give the original chloropteridine and ammonia. Certain other amines behave similarly, forming adducts which can be stored for a few days at -20 °C. Treatment of (12) and (13) in acetone with hydrogen sulfide or toluene-a-thiol gives adducts of the same type. 

An elimination reaction is, in a sense, the reverse of an addition reaction. It involves the elimination of two groups from adjacent carbon atoms, converting a saturated molecule into one that is unsaturated. An example is the dehydration of ethanol, which occurs when it is heated with sulfuric acid ... 

Ethanol Electrodes The reliable sensing of ethanol is of great significance in various disciplines. The enzymatic reaction of ethanol with the cofactor nicotinamide-adenine dinucleotide (NAD+), in the presence of alcohol dehydrogenase (ADH)... 

A very recent example of the first case is presented by Vilaseca et al. [71] where an LTA coating on a micromachined sensor made the sensor much more selective to ethanol than methane. Moos et al. [72, 73] report H-ZSM5 NH3 sensor based on impedance spectroscopy using the zeolite as active sensing material. At elevated temperatures (>673 K) NH3 still adsorbs significantly in contrast to CO2, NO,... 

Li, Y Su, X., Jian, J. and Wang, J. (2010) Ethanol sensing properties of tungsten oxide nanorods prepared by microwave hydrothermal method. Ceramics International, 36, 1917-1920. 

Porous ultrafine tin oxide ethanol gas sensors92 in the form of a thin film have been prepared from tin alkoxide by the sol-gel process. The microstructural evolution of the tin oxide films, which affected the ethanol gas-sensing properties of the films, was investigated as a function of firing temperature and solution concentration. Theoretically, it was expected that ethanol gas sensitivity would increase monotonically with decreasing film thickness, but experimental results showed a maximum sensitivity at about 70 nm. The sudden decrease of the sensitivity below the thickness of 70 nm seemed to be due to the sudden decrease of film porosity, i.e., the sudden decrease of the number of the available sites for the oxidation reaction of ethanol molecules. Thus, it seemed that below the thickness of 70 nm, the sensitivity was governed by microstructure rather than by film thickness. 

A series of unsymmetrical porphyrazines with thio-ethoxy(ethoxy) ethanol groups (S-polyetherol) appended to the periphery, which both coordinate metals and impart solubility to the macrocycle have been reported (50). These macrocycles show selective optical changes in response to specific metal ions, thus are of potential use in metal ion sensing. 

The (—) and racemo forms were also prepared. The CD spectrum of the (+) and (—) polymers in ethanol showed negative and positive bisigned profiles respectively, indicating main-chain helical screw sense chirality. The origin of... 

Microwave spectroscopy is probably the ultimate tool to study small alcohol clusters in vacuum isolation. With the help of isotope substitution and auxiliary quantum chemical calculations, it provides structural insights and quantitative bond parameters for alcohol clusters [117, 143], The methyl rotors that are omnipresent in organic alcohols complicate the analysis, so that not many alcohol clusters have been studied with this technique and its higher-frequency variants. The studied systems include methanol dimer [143], ethanol dimer [91], butan-2-ol dimer [117], and mixed dimers such as propylene oxide with ethanol [144]. The study of alcohol monomers with intramolecular hydrogen-bond-like interactions [102, 110, 129, 145 147] must be mentioned in this context. In a broader sense, this also applies to isolated ra-alkanols, where a weak Cy H O hydrogen bond stabilizes certain conformations [69,102]. Microwave techniques can also be used to unravel the information contained in the IR spectrum of clusters with high sensitivity [148], Furthermore, high-resolution UV spectroscopy can provide accurate structural information in suitable systems [149, 150] and thus complement microwave spectroscopy. 

In normal air, the Sn02 can adsorb oxygen species of O2, and on the surface, vhich increased the resistance ofthe Sn02 nanostructured film [63[. Sensing of ethanol vapors vas completed in a 300 °C environment. At this temperature the ethanol vapor reacts with the oxygen species on the surface ofthe Sn02 and removes... 

Electrolytes are ubiquitous and indispensable in all electrochemical devices, and their basic function is independent of the much diversified chemistries and applications of these devices. In this sense, the role of electrolytes in electrolytic cells, capacitors, fuel cells, or batteries would remain the same to serve as the medium for the transfer of charges, which are in the form of ions, between a pair of electrodes. The vast majority of the electrolytes are electrolytic solution-types that consist of salts (also called electrolyte solutes ) dissolved in solvents, either water (aqueous) or organic molecules (nonaqueous), and are in a liquid state in the service-temperature range. [Although nonaqueous has been used overwhelmingly in the literature, aprotic would be a more precise term. Either anhydrous ammonia or ethanol qualifies as a nonaqueous solvent but is unstable with lithium because of the active protons. Nevertheless, this review will conform to the convention and use nonaqueous in place of aprotic .]... 

We then designed model studies by adsorbing cinchonidine from CCU solution onto a polycrystalline platinum disk, and then rinsing the platinum surface with a solvent. The fate of the adsorbed cinchonidine was monitored by reflection-absorption infrared spectroscopy (RAIRS) that probes the adsorbed cinchonidine on the surface. By trying 54 different solvents, we are able to identify two broad trends (Figure 17) [66]. For the first trend, the cinchonidine initially adsorbed at the CCR-Pt interface is not easily removed by the second solvent such as cyclohexane, n-pentane, n-hexane, carbon tetrachloride, carbon disulfide, toluene, benzene, ethyl ether, chlorobenzene, and formamide. For the second trend, the initially established adsorption-desorption equilibrium at the CCR-Pt interface is obviously perturbed by flushing the system with another solvent such as dichloromethane, ethyl acetate, methanol, ethanol, and acetic acid. These trends can already explain the above-mentioned observations made by catalysis researchers, in the sense that the perturbation of initially established adsorption-desorption equilibrium is related to the nature of the solvent. 

In sharp contrast with the remaining transition metals, Group 6 allenylidenes [M (=C=C=CR R )(C0)5] (M = Cr, Mo, W) containing non-donnor substituents at Cy are in general thermally unstable [11-15]. For this reason, most of the reported examples are substituted derivatives bearing heteroatomic Ti-donor groups [9]. In this sense, the first stable Group 6 allenylidenes reported in the literature were the amino-allenylidene complexes 2, prepared by E. O. Fischer and coworkers by a Lewis-acid induced elimination of ethanol from the 3-dimethylamino-l-ethoxy-3-... 

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