Methanol sensors

Zhang J etal., 2001, Fuel Cell (Methanol) Sensor with Small Load Resistance and High Oxidant Supply. WO 01/35478. 

L. Jiang, H.-K. Jun, Y.-S. Hoh, J.-O. Lrm, Sensing characteristics of polypyrrole-poly(vinyl alcohol) methanol sensors prepared by in situ vapor state polymerization. Sens. Actuators, B, Chem 105, 132-137(2005). 

Aston et al. (1984) devised a methanol sensor for use in drinking water treated by methylotrophic bacteria for nitrate removal. Methanol oxidase from Methylosimus trichosporium was immobilized on a carbon paste electrode containing l,l -dimethylferrocene. The measured signal was linearly dependent on methanol concentration in the range of 1 to 5 mg/1. The intermediate product of methanol oxidation to formate (formaldehyde) was indicated with half the sensitivity. The sensor was stable for only 3 h. 

Lin, C.W., B.J. Hwang, and C.R. Lee. 1998. Methanol sensors based evanescent wave sensor to monitor the deposition rate of thin films. Thin Solid Films 325 (1-2) 139. 

Athawale AA, Bhagwat SV, Katre PP (2006) Nanocomposite of Pd-polyaniline as a selective methanol sensor. Sens Actuators B 114 263-267... 

Janata J, Josowicz M (2003) Conducting polymers in electronic chemical sensors. Nat Mater 2 19-24 Jesenius H, Thaysen J, Rasmussen AA, Veje LH, Hansen O, Boisen A (2000) A microcantilever-based alcohol vapor sensor-application and response model. Appl Phys Lett 76 2615-2617 Jiang L, Jun H-K, Hoh Y-S, Lim J-O, Lee D-D, Huh J-S (2005) Sensing characteristics of polypyrrole-poly(vinyl alcohol) methanol sensors prepared by in situ vapor state polymerization. Sens Actuators B 105 132-137 Jin Z, Su YX, Duan YX (2001) Development of a polyanUine-based optical ammonia sensor. Sens Actuators B 72 75-79... 

The concentration of the methanol has to be around 1 molar (= 3% by weight), according to most published work (Shukla et al., 1998, Scott et al., 1999b, and Dohle et al., 2002). This is to prevent the crossover of methanol to the cathode. It will usually be necessary to have a methanol sensor in the fuel feed system to ensure that correct concentration is maintained, though the concentration might be deduced by a circuit monitoring the cell s output. (See Barton et al., 1998, for a description of a methanol sensor design.)... 

Barton S.C., Murach B.L., Fuller T.F., and West A.C. (1998) A methanol sensor for portable direct methanol fuel cells , Journal of the Electrochemical Society, 145, 3783-3788. 

The liquid DMFC generally uses diluted methanol in water mixture (typically 12 M) and only a fraction of the methanol is used at the anode. It is, therefore, important to recycle the effluent and replenish it to keep the concentration in the fuel feed constant. To be able to achieve this, methanol sensors play a very important part in the fuel cell system. Methanol sensors are usually based on an electrochemical system that measures the current from the electrooxidation of methanol [47,48]. Gaseous feed of the methanol—water mixture is also possible. 

At LANL (Los Alamos National Laboratories) a DMFC stack was produced that attained a 90% fuel utilization and produced 2.25 kW/kg. The stack temperature was 60 °C and the air pressure was the atmospheric pressure at the LANL site. The width of each ceU was 1.8 mm and the pressure drop across the ceUs was minimized. A stoichiometric airflow was achieved and a maximum power density of 1 kW/1 (0.3 W/ cm ) was reached. It was found, however, that the concentration of methanol in the fuel flow must be kept as constant as possible for which a methanol sensor was essential. 

Optical fuel sensor to determine percent methanol... 

Engines are also designed to use either gasoline or methanol and any mixture thereof (132—136). Such a system utilizes the same fuel storage system, and is called a flexible fueled vehicle (EEV). The closed loop oxygen sensor and TWC catalyst system is perfect for the flexible fueled vehicle. Optimal emissions control requires a fuel sensor to detect the ratio of each fuel being metered at any time and to correct total fuel flow. 

Small but environrrientallyjnendly. The Chemical Engineer, March 1993 Huge increases in technology in the past distributed manufacturing in small-scale plants miniaturization of processes domestic methanol plant point-of-sale chlorine simpler and cheaper plants economy of plant manufacture process control and automation start-up and shut-down sensor demand [145],... 

With the complex where L = pyridine an optical nanosensor was developed [135-137], the method used to fix the vapochromic material to the optical fiber was the electrostatic self assembling method (ESA) and the light source used was an 850 nm LED. The sensor was tested for two different alcohols (ethanol and methanol) and it was possible to distinguish between different concentrations. It was also possible to discriminate between the two different alcohols. 

Rousseau, R., Dietrich, G., Kruckeberg, S., Lutzenkirchen, K., Marx, D., Schweikhard, L. and Walther, C. (1998) Probing cluster structures with sensor molecules methanol adsorbed onto gold clusters. Chemical Physics Letters, 295, 41-46. 

A continuous potentiometric determination of sulphate in a differential flow system160 consisted of a flow cell with two Pb2+-selective electrodes in series. All solutions contained 75% of methanol and were adjusted to pH 4 a standard solution of Pb(II) passes the first sensor and, after being mixed with the sulphate sample stream, yielding a PbS04 precipitate in addition to excess of Pb(II), it passes the second sensor from the potential difference between the sensors the sulphate content of the sample can then be derived. 

Smooth and uniform polymer surface after vacuum plays a key role to ensure good OFRR sensing performance. We have observed in experiments that toluene after vacuum is prone to leave a number of cavities of a few micrometers in diameter on the surface. These cavities will induce additional scattering loss for the WGMs in the OFRR, which greatly degrade the g-factor, and hence the detection limit of the OFRR vapor sensor. Moreover, these small cavities have different adsorption characteristics compared to smooth polymer surface. Vapor molecules may be retained for a longer time at the cavity, which increases the response time and recovery time. Acetone and methanol are found to be better candidates for solvents because they usually leave uniform and smooth surface after vacuum. 

Fig. 7.16 Sensor response to the methanol, 2 propanol, and toluene concentrations in DI water. Reprinted from Ref. 22 with permission. 2008 Molecular Diversity Preservation International...

The sensors were exposed to the following VOC n-pentane, methanol, benzene, triethylamine and acetic acid. 

Zuppa et al.60 have used SOMs in the assessment of data from an electronic nose. Six chemicals—water, propanol, acetone, acetonitrile, butanol, and methanol—were presented at varying concentrations to a 32-element conducting polymer gas sensor array. The output was used to train a group of SOMs, rather than a single SOM, to avoid the problems of parameter drift. One SOM was associated with each vapor, and with suitable use of smoothing filters, the SOM array was found to perform effectively. 

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