Sensing Characteristics to Acid Vapors of a TPPS Coated Fiber Optic: A Preliminary Analysis
In this work we report on preliminary analysis of a novel optoelectronic gas sensor based on an optical fiber integrated with a tetrakis(4-sulfonatophenyl)porphyrin (TPPS) thin film. The sensitive materials are selectively deposited on the core region of a fiber tip by UV light induced deposition technique. A simple and cheap process which can be easily extended to different porphyrin derivatives. When the TPPS film on the fiber tip is exposed to acid and/or base vapors, dramatic changes occur in the aggregation structure of the dye molecules in the film, from Jto H-type, resulting in a profound modification of their corresponding reflectance spectra. From the achieved experimental results it is evident that the presence of intense and narrow band peaks in the reflected spectra could be monitored to detect hazardous vapors. Keywords—Optical fiber sensor, Porphyrins, Thin films UVinduced deposition, TPPS.
Syndiotactic polystyrene thin film as sensitive layer for an optoelectronic chemical sensing device
Abstract In this work the performance of an optoelectronic sensor system able to measure the concentration of organic analytes, in aqueous environment was analyzed. Syndiotactic polystyrene (sPS) in the nanoporous crystalline δ form was here used as sensitive polymeric layer due to its high sorption properties towards chlorinated and aromatic compounds. In particular, a thin semi-crystalline sPS film with crystalline nanoporous δ form was cast on the cleaved end of a standard fiber optic and measurements of reflectivity as the analyte was sorbed by the polymer were carried out allowing on-line detection of even very low concentrations (in the range of few ppm) of chloroform and toluene in water. The refractometer performance was compared with that of a classical resonant quartz-crystal microbalance sensor (QCM), using the same polymer as sensing element.
Photoelectrochemical properties of metalloporphyrins
The photovoltaic responses of meso tetraphenyl-, meso tetra-propyl- and octaethyl-porphyrins, porphines, chlorins, cofacial diporphyrins and mesoporphyrin IX diesters were investigated using two cell configurations: Al| Porphyrin |Ag, and Al| Porphyrin | Fe(CN)6−3, Fe(CN)6−4 |Pt. We found (1) that the Al–porphyrin interface is photoactive: the action spectra closely follow the absorption spectra of the porphyrins, and this interface is best described as a semiconductor–insulator–metal diode consisting of porphyrin |A12O3 |Al; (2) that within a homologous series, in which the porphyrin skeleton is fixed but the metal is varied, the quantum yields parallel the ease of oxidation of the porphyrin in nonaqueous solvents. The more easily oxidised compounds exhibit the higher quantum yields; (3) no obvious correlations are found with the luminescent properties of the porphyrins in solution; (4) the morphology of the films influences the quantum yields: amorphous films are better than microcrystalline ones; and (5) the most efficient cells reach quantum yields of ∼0.2 and energy efficiencies of ∼1% for monochromatic light at the peak of the action spectrum in the region of 400–450 nm.