Research On Applications Of Porphyrins In Electrochemical Sensors For Detecting Nitroaromatics

Porphyrin derivatives continue to attract a great deal of attention for a variety offunctions because of their versatile molecular framework and catalytic properties, andstrong light absorptivity. Due to the strong electron-withdrawing ability of the nitrogroup, nitroaromatics(NACs) are electron-deficient groups. While, porphyrinderivatives are π electron-rich groups, which can be acted as good π electron donors.Take the advantage of the opportunity, porphyrin derivatives and NACs are vulnerableto form π electron donor–acceptor（EDA）complexes. The properties of nanometermaterials, for instance, large surface area, surface-effect, small-size effect, the goodability to promote electro-transfer reactions and remarkable catalytic ability, whichcan be used as good catalyst in electrochemical sensing.On the basis of the above, weconstructed nanometer materials and porphyrin composites modified electrodesmainly used in NB detection.In the first chapter, An electrocatalytic platform and electrochemical sensor fornitrobenzene using tetra(4-methoxy-phenyl) porphyrin functionalized N-dopedordered mesoporous carbon（TMPP/N-OMC）as sensitive material is reported. Glassycarbon electrode modified with TMPP/N-OMC was characterized by scanningelectron microscope（SEM）, cyclic voltammetry（CV）and electrochemical impedancespectroscopy（EIS）. The electrode has shown high electrocatalytic activity towardsthe reduction of nitrobenzene in a sodium chloride solution （pH=7.0）.Electrocatalytic reduction currents of nitrobenzene were found linearly related toconcentration over the range0.528to132.00μM with a correlation coefficient of0.9971using differential pulse voltammogram（DPV）method. The detection limit wasdetermined as0.2162μM （S/N=3） at a signal-to-noise ratio of3. The results showthat the TMPP/N-OMC/GCE reveals high selectivity, reusability, and stability.In the second chapter, two type of poly-tetrakis（3-amino-phenyl）porphyrin（TAPP） film modified glassy carbon electrodes （CP-TAPP/GCE andUNCP-TAPP/GCE） were prepared from electro-polymerization and diazotizationseparately. Electrochemical and surface characterization by scanning electronmicroscope（SEM）, cyclic voltammetry（CV）and electrochemical impedance spectroscopy （EIS） confirmed the presence of TAPP films on GCE. The twoelectrodes have shown high electrocatalytic activity toward the reduction ofnitrobenzene in a sodium chloride solution （pH=7.0）.Furthermore, a orderedmesoporous carbon（OMC）together with diazotizating TAPP and deposited AgNPsmodified glassy carbon electrode was fabricated for the electrochemical detection ofNB by differential pulse voltammetry（DPV）, During various combinations tested, themost synergistic signal effect was observed for the nanocomposite modified glassycarbon electrode（GCE）containing OMC tied up with diazotizating TAPP and Agnanoparticles（AgNPs/TAPP/OMC/GCE）. This combinating provides best sensitivityfor detecting NB. Differential pulse voltametry（DPV）resulted in a detection limit of20nM, with linearity up to4orders of magnitude.In the third chapter, herein, single-wall carbon nanotube （SWCNTs） andtetraphenyl porphyrin（TPP）/tetra（4-methoxy-phenyl）porphyrin（TMPP）modifiedglassy carbon electrodes were constructed and characterized by cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）, glassy carbon electrodemodified with SWCNTs/TMPP nanocomposite showed higher sensitivity forathodic voltammetric detection of trinitrophenol （TNP）,when compared toSWCNTs or SWCNTs/TPP modified electrode. The higher sensitivity is attributed tothe stronger interaction between TMPP and TNP, which is called π electrondonor-acceptor interaction. In addition, we characterized the π-π interactionsbetween TPP/TMPP and graphene oxide（GO） by ultraviolet-visible （UV）absorption spectrum and fluorescence. The electrochemical and optical experimentsturned out that electron-donating group enhanced the interaction between theelectron-rich porphyrins and the electron-deficient NACs/GO, and therefore lead tothe higher sensitivity of TMPP toward TNP than TPP.