Study On The Preparation Of Molybdenite Sensor And The Detection Of Ascorbic Acid And Phenolic Compounds

The electrochemical sensor can convert the concentration of substance to an electrical signal.It has the advantages of high sensitivity,good specificity,fast analysis speed and simple operation.Based on molydenite(MLN),two electrochemical sensors were prepared.These two sensors were prepared by electrochemical deposition and physical co-adsorption with organic dyes.The electrochemical sensors were used to detect ascorbic acid(AA)and phenolic compounds,respectively.After optimizing the preparation and operating conditions,two electrochemical sensors with high sensitivity,wide linear range,low detection limit,good stability and fast response were fabricated.This study not only provides novelty and cheap raw materials for electrochemical sensors,but also provides a new high value-added platform for sulfide minerals.1.A non-enzymatic ascorbic acid(AA)electrochemical sensor was prepared by electrochemical depositing methylene blue(MB)on a natural molybdenite(MLN)modified glassy carbon electrode(GCE).The morphology of the sensor electrode surface was studied using the advanced automatic mineral quantitative analysis system(AMICS)and laser confocal scanning microscope(LCSM).The prepared p(MB)/MLN/GCE electrochemical sensor exhibits good electrochemical behavior.The linear range of AA detection is 3-1000 μM,the lower detection limit is 0.083 μM(S/N=3),and the response time is less than 5 seconds.In addition,the sensor also has good stability,reproducibility and anti-interference ability.There is no significant current decrease was observed after the sensor was used for 20 days,which indicating a long life-time.Methylene blue film not only increases the electron transfer rate,but also prolongs the life-time of the sensor.2.A phenolic compound-based electrochemical biosensor(TYR/AO/MLN-GCE)was constructed by physical co-adsorption of molybdenite(MLN),tyrosinase(TYR)and acridine orange(AO)on the glassy carbon electrode(GCE).The electrochemical characteristics are as follows: linear range,0.1-80 μM;sensitivity,0.0315 μA/μM;detection limit(LOD),0.29 μM;and fast response time(< 4 s).In addition,the prepared biosensor also has good reproducibility,stability and long life-time.In order to investigate the unique property of molybdenite,other sulfide minerals were used for comparative tests.The selective sulfide minerals also exhibit good performance.Electrochemical impedance spectroscopy(EIS)and dissipative quartz crystal microbalance(QCMD)data show that AO has the following effects:(1)Effectively increases the adsorption of TYR on MLN-GCE;(2)Make TYR maintains a favorable configuration on the surface of MLN-GCE;(3)Provides a suitable biological microenvironment for the TYR adsorbed on the MLN-GCE surface.In order to investigate the influence of the structure of MLN,other sulfide minerals were used to prepare catechol based electrochemical sensors.And these sensors also exhibit good performance.