The Study Of Trace Heavy Metals Detection Based On Electrochemical Modified Electrodes

High-performance working electrodes are crucial for electrochemical detection of heavy metal ions.Its detection sensitivity,however,is always limited by the large background noise,especially when large-size electrodes are used.To change this situation,microelectrodes with the adavantages of low backgournd noise and ultra-high mass transmission efficiency are employed as working electrodes here.More specifically,carbon fiber microelectrodes were built and modified with r GO/AuNPs composite materials.Their performances on low concentration heavy metal ions detection(Cu²⁺,Pb²⁺and Cd²⁺)were evaluated and compared with glass carbon electrodes.The glass carbon electrodes were modified by reduced graphene oxide and Gold nanoparticles（r GO/AuNPs GCE）.The performance of modified GCE was tested by CV,EIS and SWASV.It was shown that rGo/AuNPs improved the electrochemical properties of GCE.The modified electrodes were used for Cu²⁺detection using SWASV method.The operational conditions,such as p H value,deposition time and potential,were optimized.Under the optimized conditions（p H=4,deposition time=180s and deposition potential=-1.2V）,the linear rage of Cu²⁺was from 0.01 to 4.00μM,with the detection limit concentration of 13.40n M（S/N=3）.Besides,the microsensors’excellent repeatability,long term stability and selectivity were verified by our experiments.Similar method was introduced to modify the carbon fibers with reduced graphene oxide and Gold nanoparticles（r GO/AuNPs CFMEs）.The modified microelectrodes were observed with SEM.The r GO/AuNPs CFMEs had significantly high specific surface area,strong adsorption capacity and high catalytic activity.Thus,they were utilized as novel electrochemical microsensors for Cu²⁺detection using square wave anodic stripping voltammetry（SWASV）method.The operational conditions,such as p H value,conductivity deposition time and potential,were optimized.Under the optimized conditions（p H=4,conductivity=36.1 S/m,deposition time=360s and deposition potential=-1.2V）,the linear rage of Cu²⁺was from 0.005 to 1.00μM,with the detection limit concentration of 2.40n M（S/N=3）.The sensors’excellent repeatability,long term stability and selectivity were also verified by our experiments.In addition,the detection limit of Cu²⁺、Pb²⁺and Cd²⁺with r GO/AuNPs GCE and r GO/AuNPs CFMEs was evaluated and compared.It was showed that rGo/AuNPs CFMEs have lower LOD than rGo/AuNPs GCE,which were suitable for trace heavy metal ions detection.