Application And Research Of Photoelectrochemical Sensor Based On Composites In Antioxidant Analysis

In the process of metabolism,organisms will produce many oxidation active substances in the mainly form of free radicals.When their concentration is too high,cells will be damaged,tissue balance will be destroyed,and then diseases will be induced.Natural antioxidants can effectively eliminate free radicals,so that organisms can delay aging and keep healthy.Therefore,it is of great significance to determine and evaluate the ability of antioxidants to eliminate oxidative active substances in food.In addition,as food additives,antioxidants can also prevent or delay food oxidation,improve the stability of food and extend the storage life.Oil oxidation is one of the main reasons for the deterioration of oil and oily food.Adding antioxidants can effectively prolong the shelf life.However,excessive use of several commonly used synthetic antioxidants will cause certain safety hazards.The country has strict limits on the content of antioxidants added in oil products.Therefore,it is very important to develop methods for the determination of antioxidants.At present,the conventional detection methods for antioxidants are chromatography,spectroscopy,and electrochemical method.More specifically,the cost of chromatographic instrument is quite expensive.The spectral method is easy to be interfered by the background color.As for the electrochemical method,the electrode is frequently be polluted by analytes,resulting in poor reproducibility.Therefore,it is urgent to develop a simple,fast,low cost,and effective method to overcome the above shortcomings.Photoelectrochemical technology has the advantages including low cost,high integration,high signal-to-noise ratio and high sensitivity.It has been applied in chemical biosensor and analysis fields.Hence,in this dissertation,we have designed several photoelectric semiconductor materials to construct the photoelectrochemical sensors and have applied them to the analysis and determination of antioxidants.The main research contents are highlighted as follows:1.Oxidized Titanium Carbide MXene-Enabled Photoelectrochemical Sensor for Quantifying Synergistic Interaction of Ascorbic Acid based Antioxidants SystemAntioxidants can protect organization from damage by scavenging of free radicals.When two kinds of antioxidants being consumed together,the total antioxidant capacity might be enhanced via synergistic interactions.Herein,we develop a simple,direct,and effective strategy to quantify the synergistic interaction between ascorbic acid(AA)and other different antioxidants by photoelectrochemical(PEC)technology.MXene Ti3C2-TiO2 composites fabricated via hydrogen peroxide oxidation were applied as sensing material for the antioxidant's interaction study.This PEC sensor exhibits a good linear range to AA concentrations from 12.48 ?M to 521.33 ?M with a detection limit of 1.2 ?M.And the results indicate obvious antioxidants capability synergism.In particular,the photocurrents of AA+gallic acid(GA)and AA+chlorogenic acid(CHA)mixtures at 476.19 ?M increase 1.95 and 2.35 times respectively comparing with the sum of photocurrents of AA and GA or CHA.Moreover,the synergistic effect mainly depends on that AA with the low redox potential(0.246 V vs NHE)can reduce other antioxidants radical to promote regeneration.Hence,the overall antioxidant performance is improved.And it is proved that the greater redox potential of antioxidants,the more obvious the synergistic effect.In addition,the sensor was used to real sample assay,which provides available information towards food nutrition analysis,health products design and quality inspection.2.Label-free and selective photoelectrochemical assay of synthetic antioxidant tertiary butylhydroquinone based on g-C3N4-TiO2/Ti3C2 MXene heterostructureAs an important synthetic phenolic antioxidant,tertiary butylhydroquinone(TBHQ)is usually added to food products to prevent oxidative degradation of fats and oils.The determination of TBHQ has been of great concern due to that its excessively adding may cause some negative effects to health.Herein,we have developed a label-free PEC sensor based on g-C3N4-TiO2/Ti3C2 MXene heterostructure.This sensor material was synthesized by oxidation in situ.There is a heterostructure constructed between g-C3N4 and TiO2 and a Schottky junction formed between TiO2 and Ti3C2 MXene,which can promote the separation of photo-generated holes-electrons and thus improve the photocurrent response.Under visible light excitation(470 nm)and zero potential(vs.Ag/AgCl),this PEC sensor exhibits high sensitivity,good stability,repeatability,and reproducibility.Moreover,it can selectively recognize TBHQ from its structural similar compounds due to its lower redox potential,and thus TBHQ can be more easily oxidized by photocatalyst.And this PEC sensor showed wide linear range from 2.49 ?M to 521.3 ?M with a detection limit as low as 15 nM.Furthermore,the PEC sensor was viably applied in the assay of TBHQ in edible oil,providing a simple,low cost but effective method for supervising the overuse of TBHQ to control food safety.3.MoS2/ZnO Heterostructures Based Label-free,Visible-Light-Excited Photoelectrochemical Sensor for Sensitive and Selective Determination of Synthetic Antioxidant Propyl GallateAs one of the important synthetic antioxidants,propyl gallate(PG)is widely used in prevention of oxidative deterioration of oils during processing and storage.The determination of PG has received extensive concerns because of its possible toxic effects on human health.Herein,we report a photoelectrochemical(PEC)sensor based on ZnO nanorods and MoS2 flakes with vertically constructed a heterojunction.In this system,the ZnO-MoS2 heterostructures exhibited much better optoelectronic behaviors than their individual materials.Under zero potential and visible light excitation(470 nm),the PEC sensor exhibited extraordinary response for PG determination,as well as excellent anti-inference properties and good reproducibility.The PEC sensor showed wide linear range from 0.125 ?M to 1.47 mM with a detection limit as low as 12 nM.MoS2/ZnO heterostructure with proper band level between MoS2 and ZnO could make the photo-generated electrons and holes separated more easily which eventually results in great improvement of sensitivity.On the other hand,formation of five membered chelating ring structure of Zn(II)with adjacent oxygen atoms of PG played significant roles for selective detection of PG.Moreover,the PEC sensor was successfully used for PG analysis in different samples of edible oils.It demonstrated the ability and reliability of the MoS2/ZnO-based PEC sensor for PG detection in real samples,which is beneficial for food quality monitoring and reducing the risk of overuse of PG in foods.