Photo-electric chemical sensors (PECS) represent a new platform sensing technology based on photo-induced charge movements (PICM) and molecular recognition at sensor electrode surfaces (US patent # 7,354,770). The sensors must be immersed in water, in our apparatus in a photo-spectrometer cuvette. The electrical signals generated by PICM are also identified as interfacial photo-voltages. The general idea is that selected materials which function as photo-voltage active materials (or PAMs) on electrode surfaces immersed in aqueous test solutions generate robust electrical signals (photo-voltages or PVs) upon flash illumination. The ideal PAMs, of which hundreds are known, have the ability to: 1) recognize and bond (complex, chelate, etc.) with target chemical analytes, 2) generate interfacial PVs, and 3) alter their PVs in response to bonding with the target analytes, allowing the presence and concentrations of those analytes to be determined.

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The PAM-analyte interactions are quantitized, meaning that at the molecular level they are either bonded or not, and that these bonds result between individual (or small numbers of) PAMs and analyte atoms, ions or molecules. The PVs result from the manifold of PAM molecules and PAM-analyte complexes on the illuminated electrode surface, so each analyte bonding event incrementally (and nearly infinitesimally) alters the net PV observed with a standard flash. Consequently the PVs are systematically altered by variations in the analyte concentration in the solution bathing the electrode. Observing changes in the PVs provides information on the type, presence and concentration of the analyte. So these PECS are light-flash activated chemical contact sensors.

Many (though not all) non-water soluble colorimetric agents function as PAMs. Some analytes, for example Ni++ chelates with dimethyl glyoxime (the PAM in this case), and that reduces the PV amplitude monotonically from 17 mV to ~ 2 mV as the NiCl2 concentration is increased from zero to 0.3 mM. Other analytes, for example Zn++ increase the PV amplitudes from 2, 2’-biquinoline (the PAM) from 7 mV to 40 mV as the ZnCl2 concentration is increased from zero to ~ 1 mM. Analytes which have been successfully detected using this sensor technology include many anion, cations and neutral species of many elements and compounds, such as environmental pollutants, macro-nutrients, metals, pesticides, polyaromatic-hydrocarbons, toxic industrial chemicals, toxins, volatile organic chemicals, and more.

Thus PECS is argued to be a new chemical sensing platform technology as new analytes can be added to the list of those that are detectable by simply discovering appropriate PAMs for recognizing the new analytes.