In order to select the best materials based on metalloporphyrins to develop colorimetric microsensors for detection of high level of CO2 in space habitation areas, we have focused on three main actions:
• Selection of an optical/colorimetric responsive metalloporphyrin
• The study of the surface phenomena produced in gas absorption
• The improving of the response by using complex host–guest molecules or by using additives (indicators or silver colloids)
A novel structure of Fe(III)-metalloporphyrin symmetrically substituted, namely Fe (III)-5,10,15,20-tetra(3,4-di-methoxi-phenyl)-porphyrin (FeTDMeOPP) was sensitive to gas adding by increasing the Soret band intensity in agreement with a linear dependence, but also by changing the color from green to red (Figure 1). Adding of small amounts of silver colloids to this system significantly increased the sensitivity.
This work represent our first approach to select the best porphyrinic derivatives for obtaining a matrix made from colorimetric microsensors for a friendly detection of the air quality (i.e. detection of CO, NOx and high level of CO2 and low level of O2) easy to be operated, free hands and detachable for monitoring a healthy atmosphere in space habitation areas.
One of the most important technological challenges will be the CO2 detection (state of the art studies show that only few research teams can detect CO2 using colorimetric microsensors) and for it, we will come with a new innovative technological solution based on a microfluidic device. The design, synthesis and optical response of new sensing materials (porphyrin derivatives and nanostructured hybrid materials) represent the first step to develop these gas sensors.
A novel A3B porphyrin asymmetrically mixed substituted, namely 5-pyridyl-10,15,20-tris(3,4-di-methoxi-phenyl)-porphyrin (PyTDMeOPP) responded to gas adding by increasing the Soret band intensity in agreement with a linear dependence with a good correlation coefficient (Figure 1). The AFM images reveal that porphyrin was initially structured in ring aggregates (after 15 minutes) and that the most part of rings looks filled after CO2 absorption (80 minutes).
Figure 1. The increase and widening of the Soret band of (PyTDMeOPP) porphyrin function of increasing amounts of CO2. AFM ring aggregates after 15 minutes (left side) and filled after CO2 absorption (80 minutes).
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Figure 1. The increase and widening of the Soret band of (PyTDMeOPP) porphyrin function of increasing amounts of CO2. AFM ring aggregates after 15 minute. |
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