The Properties Of Porphyrin Derivatives And Their Applications In Chemical Sensors

The environmental pollution has become the global focus due to the increasing use of chemicals. Therefore, it is indispensible to develop low-cost chemical sensors to accurately detect toxic substances with low concentration. This paper mainly concentrates on the development of chemical sensors based on porphyrin derivatives from experimental and theoretical aspects. This dissertation includes the aggregation mode of porphyrin derivatives on solid substrate, the electronic transition behavior of free-base porphyins and corresponding metalloporphyrins, the interaction performance between metalloporphyrins and ammonia, the applications of mass and hyphenated sensors based on several porphyrin derivatives in the detection of toxic gases and the hyphenated optical chemical sensors (fluorescent and CSPT chemical sensors) based on coumarine macrocycle molecules utilized in mercury ion detection in real water samples. The more details are as follows:1.’Picket-Fence’porphyrin derivative (meso-tetra(aaaa-pivalamidophenyl) porphyrin, abbreviated as αααα-PivPP) and its three isomers (αβαβ-PivPP, aaBB-PivPP, αααβ-PivPP) were synthesized and separated. Langmuir-Blodgett technology, UV-vis spectroscopy and atomic force microscopy (AFM) were applied to study the self-assembly behavior of four molecules on solid substrate. The results indicate the porphyrin rings of four atropisomers lie almost vertically with respect to the solid substrate in the form of edge-to-edge mode (J-aggregation) with four substituted pivalamido groups interdigitated at lower surface pressure. On the other hand, at higher surface pressure, the aggregation mode of αβαβ-PivPP, αααβ-PivPP and αααα-PivPP is almost unchanged apart from more compact monolayer, while aaBB-PivPP forms double layer due to smaller steric hindrance between its peripheral groups.2. Density functional theory (DFT) and time-dependent DFT approach (TD-DFT) were employed to investigate absorption spectra of meso-tetra(o-nitrophenyl/o-aminophenyl) porphyrins (NO2PP, NH2PP) and their corresponding zinc derivatives (NO2ZnPP, NH2ZnPP). The excitation energies and oscillation strengths were also obtained from TD-DFT calculations with two different functionals PBE and B3LYP. Calculations show that the optical absorptions are associated with numerous electronic transitions. In addition, the PBE-predicted wavelengths of the B and Q bands are more consistent with experimental results than those predicted by B3LYP. Moreover, the B band of NO2-substituted derivative exhibits a bathochromic shift with respect to that of NH2-containing material, also in line with experimental results.3. The binding performances of eight bivalent metalloporphyrins (MPs)(M=Zn, Mg, Cu, Mn, Fe, Co, Ni, and Cd) with NH3were investigated by density functional theory. The atomic charge distribution and charge transfer of all MPs-NH3systems were calculated by natural population and frontier orbital analysis. As a consequence of the charge transfer and the hybridization of molecular energy levels, striking disparities of electronic properties of MPs-NH3are observed. The much greater Fukui functions of CoP, together with its larger binding strength, suggests that CoP is more favorable to form complexation with NH3, which might be a promising sensing material to response NH3.4. The mass sensors based on several porphyrin derivatives were applied to measure their response to toxic and volatile gases. In addition, the response performances of free-base porphyrins and corresponding metalloporphyrins to toxic gases were also evaluated. The results show that the porphyrin with regular supramolecular structure exhibits higher response to analytes, and it is also true for metalloporphyrins with respect to free-base porphyrin in term of gas detection. On the other hand, the effect of transducer type was also taken into account. The optical chemical sensor has shorter response-recovery time and better selectivity than that of mass chemical sensor based on the same materials, indicating the importance of the compatibility between sensing materials and transducers.5. The polymerized sensing materials based on coumarine structures were prepared to detect the mercury ion in real water samples. Moreover, the impacts of solution pH value, component ratio in polymer film and exposure time on the response were also investigated. Partial least squares regression (PLS) method was applied to interpret the optical output of optodes based on coumarine chromophore and implied for analysis of Hg2+content. The validation was performed using a leave-one-out cross-validation procedure. The detection results obtained by hyphenated optical sensor are in good agreement with the data from atomic absorption spectrophotometry, which indicates that coumarine-based molecules are excellent materials for mercury ion detection.