| The characteristics of chemically modified electrode lies in that the electrode surface can be designed using molecular with different functional groups to achieve highly selective and high sensitive detection, making it have extensive applications in electrochemical area. Mercapto compounds could be adsorbed to Au electrode through forming Au-S bond, as a result, the surface structure or property could be controlled. The investigation on SAMs is of importance for the researches of electron transfer process, bioelectrocatalysis, molecular recognition and detection, development of chemicalsensor and so on. Owning to favorable photo- and electro-chemical activity, porphyrins and their metal chelates have been widely applied in catalysis, molecular recognition, photo-electron conversions, memorial material and medicinal fields. Porphyrin compounds widely distribute in nature, they are expected to play key roles in biological and biomimetic systems. In present paper, a novel bifunctional sensor for determination of porphyrin based on a self-assembled monolayer was demonstrated. Then thiol-porphyrin self-assembled gold electrode was fabricated, it was used to detect dopamine in the presence of ascorbic acid. Furthermore, an electrochemical sensor based on the molecular imprinted polymer has been reported for the detection of melamine.The detection of porphyrins is significant for porphyria and porphyrin-related disease diagnosis, monitor of environmental pollution. Traditional methods for determination of porphyrin are not fast and simple, meanwhile, the operation of apparatus is complicated and maintenance cost is extremely expensive. Herein, a feasible method of fabricating porphyrin sensor was developed by functionalizing gold electrode with phosphate groups. Porphyrin combing with phosphorus on surface of the electrode formed 1:1 cationic sitting-atop (SAT) type of P(V)-porphyrin complex, resulting in electron transfer resistance increase of the electrode surface within a certain range and accompanying by a dramatic color change of porphyrin solution which can be observed with the naked-eye. These phenomena provide two methods which can be used for detection of porphyrin, visual colorimetric and electrochemical impedance spectroscopy. Detailed mechanism of sensing porphyrin was proposed by applying phosphate-based self-assembled monolayer. Moreover, the designed sensor was successfully used for sample detection.Molecular imprinted PMBI modified gold electrode (2-MBI/Au) was prepared by electrochemical polymerization of 2-MBI with cyclic voltammetry in the presence of template molecule melamine. The modified electrode could successfully avoid the interference of arginine, histidine and glucose. A linear response curve was obtain from 1.0×10-8 M to 5.0×10-5 M,with the detection limit of 3.0×10-9 M. The main driving force for recognition isπ-πeffect.Porphyrins are effectively combined with self-assembled monolayer technique to construct functional ordered ultrathin monolayer films. The physical and chemical characteristics of porphyrin SAMs, the sensing of dopamine porphyrin assembled on gold electrode have been investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Water-soluble porphyrin was used to further validate that it can recognize dopamine by UV-vis spectroscopy. Porphyrin self-assembled monolayer sensor can selectively recognize dopamine. In addition, it will not produce interference in the presence of ascorbic acid and uric acid. EIS established a new method of determination of dopamine, has a good prospect in applying field. |
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