Abstract
The present report deals with the tailoring, preparation and characterization of novel nanomaterials sensitive to CO2 for use in detection of this gas during space habitation missions. A new nanostructured material based on mixed substituted asymmetrical A3B porphyrin: 5-(4-pyridyl)-10,15,20-tris(3,4-dimethoxyphenyl)-porphyrin (PyTDMeOPP) was synthesized and characterized by 1H-NMR, FT-IR, UV-vis, fluorescence, MS, HPLC and AFM. Introducing one pyridyl substituent in the 5-meso-position of porphyrin macrocycle confers some degree of hydrophilicity, which may cause self-assembly properties and a better response to increased acidity. The influence of pH and nature of the solvent upon H and J aggregates of the porphyrin are discussed. Porphyrin aggregation at the air–THF interface gave a triangular type morphology, randomly distributed but uniformly oriented. When deposition was made by multiple drop-casting operations, a network of triangles of uniform size was created and a porous structure was obtained, being reorganized finally in rings. When the deposition was made from CHCl3, ring structures ranging in internal diameter from 300 nm to 1 µm, but with the same width of the corona circular of approx. 200 nm were obtained. This porphyrin-based material, capable of generating ring aggregates in both THF and CHCl3, has been proven to be sensitive to CO2 detection. The dependence between the intensity of porphyrin UV-vis absorption and the concentration of CO2 has a good correlation of 98.4%.
Highlights
IntroductionSpectrophotometric and colorimetric microsensors for an easy and friendly detection of the air quality (i.e., detection of carbon monoxide (CO), NOx and high level of CO2 and low level of O2) have attracted much interest in the last decade
Spectrophotometric and colorimetric microsensors for an easy and friendly detection of the air quality have attracted much interest in the last decade
Optical CO2 sensors based on color changes of the pH indicator dye α-naphthol-phthalein coupled with the fluorescence of tetraphenylporphyrin attached to a polystyrene layer have been intensively studied on different substrates, but especially on ethyl cellulose layers [1,2,3,4,5]
Summary
Spectrophotometric and colorimetric microsensors for an easy and friendly detection of the air quality (i.e., detection of CO, NOx and high level of CO2 and low level of O2) have attracted much interest in the last decade. The detection of CO2 in water was attempted using the same combination [6] Another reported porphyrin derivative used in combination with α-naphtholphthalein as colorimetric pH indicator in order to detect CO2 is a platinum porphyrin dye (Pt-tetrakispentafluorophenylporphyrin) incorporated in a plastic matrix together with a phase transfer agent tetraoctyl- or cetyltrimethyl-ammonium hydroxide [7]. CO2 sensors which use an inner filter quenching effect were described. One such system consisted of a phosphorescent platinum octaetylporphyrin and a pH-sensitive dye in poly(vinylidene chloride-co-vinyl chloride-ethyl cellulose) thin films or microparticles with low permeability to oxygen [8]
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