Chemochromes

Seibert, M., Flynn, T., and Benson, D. 2001a. Method and apparatus for rapid biohydrogen phenotypic screening of microorganisms using a chemochromic sensor, U.S. Patent 6,277,589. 

However, it quickly became apparent that the selective pressures were not specific enough and yielded a mixed population of survivors. A chemochromic sensor was then developed in collaboration with D. Benson at NREL to allow us to quickly screen the survivors of the selective pressures for H2-producing clones. The screening was based on the ability of a multilayer, thin film device containing W03 and Pd to change color (from transparent to blue) upon exposure to nanomoles of H2. The usefulness of the film in... 

Figure 1 Chemochromic sensor system for identifying H2-producing algal colonies plated put on a petri dish. After the cells were induced, they were illuminated from below to initiate Hj-production activity. Specific areas on the sensor film in closest contact to Hrproducing colonies turne from transparent to a blue color when H2 was detected.

Characterized strains that were identified by chemochromic screening... 

Seibert, M., Fl mn, T, and Benson, D. Method for Rapid Biohydrogen Phenotypic Screening of Microorganisms Using a Chemochromic Sensor, ... 

Fundamental studies have yielded new chemochromic materials produced from electrochemical deposition techniques with controlled morphologies. 

The National Renewable Energy laboratory (NREL) fiber-optic sensor consists of chemochromic (a color change produced as a result of a chemical reaction) coatings at the end of an optical fiber that... 

In addition to innovative coatings for the protection of the hydrogen dissociation catalyst, mesoporous metal oxide layers for enhanced performance of the sensor elements were investigated. The results demonstrated the suitability of an electrodeposited tungsten oxide (WO3) as a chemochromic layer for hydrogen detection, providing a valuable alternative to vacuum deposition. 

Electrodeposited mesoporous metal oxides were investigated as chemochromic hydrogen sensor films. 

Chemochromism Induced by specific chemical agents, i.e. toxic gases, detergents, etc. 

The basic requirements for synthetic heme models are, therefore, a five-coordinate iron(II) porphyrin in a high-spin state, with a proximal nitrogen base and a vacant site for dioxygen. Futhermore, the formation of chemochromes by axial coordinaton of two N-bases to the iron(II) pro-phyrin should be prevented.Several approaches were put forward. It is found that a sterically hindered axial base, such as C2-dimethylimidazole, favors formation of a five-coordinate high-spin complex. Furthermore, covalent attachment of the axial ligand or steric hindrance of one of the two faces of the heme can also be used to prevent axial... 

Table 2.22 Hydrogen sensors designed on the basis of chemochromic materials...

Benson DK, Tracy CE, Lee S-H, Hishmeh GA, Haberman DP, Ciszek PA (1998) Low-cost, fiber-optic hydrogen gas detector using guided-wave, surface-plasmon resonance in chemochromic thin films. NREL/CP-590-25611, pp 1-18... 

Litzelman SJ, Rothschild A, TuUer HL (2005) The electrical properties and stability of SrTi, jFe, jjOj 5 thin films for automotive oxygen sensor applications. Sens Actuators B 108 231-237 Liu P, Lee S-H, Tracy CE, Turner JA, Pitts JR, Deb SK (2003) Electrochromic and chemochromic performance of mesoporous thin-film vanadium oxide. Solid State Ionics 165 223-228 Liu RQ, Xie YH, Wang JD, Li ZJ, Wang BH (2006) Synthesis of ammonia at atmospheric pressure with Ce M Oj-delta (M=La, Y, Gd, Sm) and their proton conduction at intermediate temperature. Solid State Ionics 177 73-76 Logothetis EM (1980) Resistive-type exhaust gas sensors. Ceram Eng Sd Proc 2 281-301... 

Pitts JR (2002) Detecting hydrogen with chemochromic thin films. Ind Physicist (AIP) Forum June/July 31 Polla DL, White RM, Muller RS (1985) Integrated chemical-reaction sensor. In Digest of technical papers of TRANSDUCERS 85. 1985 International conference on solid-state sensors and actuators, 11-14 June 1985, Philadelphia, pp 33-36... 

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