Novel optical NO2-selective sensor based on phthalocyaninato-iron(II) incorporated into a nanostructured matrix

A novel highly sensitive optical NO2-selective sensor was developed using phthalocyaninato-iron(II) as a selective complexing agent. In order to solubilize the ironII+phthalocyanine and to obtain the monomer species, a N-donor ligand was used as a solvent. The membrane solution was deposited onto a novel aluminum oxide/hydroxide nanoporous material by a spin-coating technique. The chemical reaction principle and the preparation of this new sensor are presented in detail. The effect of the type and concentration of the N-donor ligand, and the influence of the iron phthalocyanine concentration were investigated as well as the effect of the composition and the morphological characteristics of the nanostructured material. In addition, the influence of some relevant external parameters such as flow-rate and interfering compounds were investigated. The results show that the sensor responds to NO2 concentrations in the gas phase between 5 × 10−3 ppm and >0.5 ppm with a linear concentration range between 2 × 10−2 and 0.4 ppm, the detection limit being at 20 ppb. The dynamic range it is not influenced by the flow-rate, by humidity, NO, CO, CO2 and SO2, and the NO2-selective optical sensor shows good stability to ambient in view of a long lifetime as a gas and fire alarm detector. Generally 1 ppm NO2 gas corresponds to 2.0 mg m−3 and 44.5 × 10−6 mol m−3.