Electrochemical Sensors Based On Nanocomposites For The Selective Determination Of Ascorbic Acid And Dopamine

Electrochemical analysis is an important analytical method in Analytical Chemistry,however,the construction of electrochemical sensor is a key for the electroanalysis.Non-enzymatic electrochemical sensors are widely used in clinical diagnosis,environmental analysis,food inspection,and other fields due to their simple preparation,convenient operation,low price,stable performance,and sensitive detection of the target substance.The content of ascorbic acid?AA?,dopamine?DA?,uric acid?UA?and other biological small molecules in the human body is closely related to the production of a variety of diseases.Therefore,it is of great significance for human health to construct a sensitive method for detecting these biomolecules.Herein,three novel non-enzymatic electrochemical sensors were constructed based on the synergistic effect of nanocomposites,which were applied to the selective detection of AA and DA.The thesis was introduced in the following four parts:1.The research progresses of electrochemical sensors were reviewed.The construction methods of electrochemical sensors are described respectively.The classification of electrochemical sensors and the research status of interface materials for non-enzymatic electrochemical sensors,and the electrochemical methods used in this paper were described in the first chapter.2.A zinc porphyrin dye?YD₂-o-C₈,abbreviated YD?noncovalently functionalized graphene oxide?GO?nanohybrid?GO@YD?was facilely synthesized through hydrogen bonding and?-?stacking interaction.The nanohybrid?GO@YD?was then modified on the surface of glassy carbon electrode by using the surfactant four octyl ammonium bromide?TOAB?to obtain an novel non-enzymatic electrochemical sensor?TOAB/ERGO@YD/GCE?after being electrochemical reduced.The interaction between YD and GO and the catalytic mechanism of the sensor on ascorbic acid?AA?were characterized by spectroscopic techniques,electrochemistry,and density functional theory?DFT?.Under the optimal conditions,the sensor was employed to sense ascorbic acid?AA?and it showed a high sensitivity of 13.58?A/mM,a wide linear concentration from 1.33 mM to 1.46 mM?R=0.998?,and a limit of detection?LOD?as low as 0.28?M.Furthermore,the sensor not only showed high selectivity but also exhibited excellent operational and storage stability due to the hydrophobicity of TOAB.This study not only broadens the application of YD molecule in analytical chemistry,but also proposes a new constructing method for the determination of biological molecule AA.3.Ptlatinum nanoparticles?Pt NPs?was in-situ electrodeposit on the surface of mesoporous carbon?MC?to form MC/Pt composite nanomaterial,which was then modified on the surface of GCE by using Nafion film to obtain a novel electrochemical sensor?Nafion/Pt/MC/GCE?.Due to the synergistic effect of Nafion film,Pt NPs,and MC,the as-prepared sensor?Nafion/Pt/MC/GCE?exhibited excellent electrocatalytic activity towards the oxidation of dopamine?DA?.Moreover,the oxidation potential of DA on the sensor was perfectly distinguished from those of uric acid?UA?and ascorbic acid?AA?on the sensor.The differences in oxidation peak potential for UA-DA and DA-AA were 123 and 204 mV,respectively.The proposed sensor can selectively determine DA in the linear concentration range of 0.1-193?M with a detection limit as low as 0.034 uM,good reproducibility,and excellent stability.4.Foliate cobalt selenide(Co_0.85Se)was synthesized by the hydrothermal method and was combined with trace platinum?Pt?to form a Pt/Co_0.85Se material,which was modified on the surface of a glassy carbon electrode?GCE?to fabricate a novel non-enzymatic electrochemical sensor?Pt/Co0.85Se/GCE?for the selective determination of dopamine?DA?.On the Pt/Co0.85Se interface,well-separated oxidation peaks of DA,ascorbic acid?AA?,and uric acid?UA?were observed due to the superior conductivity of Co_0.85Se and the excellent catalytic activity of Pt.With the synergistic effect of Pt and Co_0.85Se,the sensor showed high detecting ability and great selectivity for sensing DA.This study not only reduce the amount of noble Pt but also realize the application of Co_0.85Se in Analytical Chemistry.In summary,three kinds of metal nanocomposites were prepared and their synergistic effects were used to construct three novel non-enzymatic electrochemical sensors,which were applied to determine biological molecules of AA and DA.The researches not only provide new methods for preparing composite materials,but also supply new research ideas and technical supports for the construction of non-enzymatic electrochemical sensor.