Optical fibre sensor for NO2 based on metal-phthalocyanines of
This project has been developed in collaboration with the IFAC-CNR and with the PRODOTEC srl in the PF MSTA II
Introduction
Material chemistry and particularly the synthesis and characterisation of new materials is allowing the design and the development of many new chemical sensors which are opening highly exciting perspectives in the area of chemical sensing. The optical fibre sensor for NO2 consists on the utilisation of an organic material, a phthalocyanine-based compound, that can detect very low concentrations of strong electron acceptor gases such as NO2. This class of materials gives rapid and reversible detection of ppb levels of NO2 at room temperature. The compound utilised is a new metal phthalocyanine Ti(Pc)2, a sandwich-type molecule used as an optical transducer capable of changing its optical spectrum during the interaction with NO2. The chemical transducer Ti(Pc)2, is immobilised on alumina membrane, which is embedded with saturated solution of the compound or covered by a thin film. An optoelectronic device, which makes use of simple light emitting diodes as optical sources, is connected to a laptop and is capable to interrogate the optical probe and to process the collected signals. Either solid-state photodetectors or a diode array capable of discriminating different wavelengths are used as optical detector.
Innovative Features Studies on sensor system for detecting environmental gaseous pollutants, such as nitrogen dioxide, have been constantly expanding during the recent years. On the other hand, many limitations of the most commonly used active materials (metal oxides) have been described, such as poor selectivity for the lack of specificity, interference from foreign species, poor durability and reversibility.
The innovation of this new approach is represented mainly by the choose of a new sensitive material used join to a simple and effective technological frame. This material working at room temperature has a good sensitivity , good detection limited accuracy absence of interference from other species as NO, CO, SO2, NH3 and excellent stability .
Reversibility can be also obtained by treating the chemical transducer with suitable UV light (Italian Patent N° RM2000A000028).
Application Field
The developed sensor could be employed to monitor air quality in very different environments, thanks to its large working range from ppb levels to hundreds of ppm: from the factory chimney to the urban polluted air to the indoor environment. Furthermore the possibility to make it as a miniature device allows its use in any place such as museums or invaluable monuments.
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