Single element differentiation of chemical vapors using an array
We present a heterosensor array that exploits the collective recognition ability of a set of different gas sensors to identify individual chemical vapors. In contrast to the conventional sensing approach based on the "lock-and-key" design, the heterosensor array rely on the response patterns produced over the collection of different sensors. Diverse sensors with different operating principles are employed to provide as much chemical diversity as possible. We demonstrate that this platform provides a highly discriminative tool with single element precision.
Detection of hazardous gases and vapors: pattern recognition analysis of data from an electrochemical sensor array
A portable device is being developed by Argonne National Laboratory to detect, identify, and warn US Coast Guard emergency response personnel of the presence of hazardous gases and vapors. The device operates in the situation of a spill or ship cargo hold where a puddle of the contaminant may be present. The prototype device uses an array of four different electrochemical sensors, which can be operated in four different modes. Thus, the array yields 16 channels of data for each chemical species detected. Pattern recognition is one way of determining the uniqueness of the information obtained and the capacity of each of the channels for classification. The matrices generated by detecting 22 gases and vapors with a prototype instrument are being examined by use of pattern recognition methods. Results to date indicate that approximately half of the channels provide unique information. 11 references, 9 figures, 3 tables.
Substituent effects on the redox reactions of tetraphenylporphyrins.
The effect of substituents on pi radical reactions of para-substituted tetraphenylporphyrins was investigated by cyclic voltammetry in methylene chloride. In all cases electron donating substituents produced a more difficult reduction and an easier oxidation. Plots of E1/2 vs. a yielded Hammett linear free energy relationships for cation radical and dication formation and anion radical and dianion formation. An average reaction constant of p=0.07+/-0.01 V was obtained. This was true for tetraphenylporphyrins containing the central metals VO, Mn, Fe, Co, Ni, Cu, and Zn, as well as the free base H2 (p-X)TPP. The value of p appears not to be directly affected by the central metal oxidation state or the overall charge on the complex.