Electrochemical Detection Of Several Environmental Pollutants Using Electrodes Modified With Carbon-gold Nanocomposites

With the development of society and the improvement of people’s living standards,more and more people were beginning to pay attention to food safety and environmental pollution.The use of a large number of chemical products and food additives resulted in the direct or indirect uptake of organic pollutants into the environment and the human body,which threatens seriously the human health and the ecological environment stability.Sulfite and nitrite ions are two typical inorganic pollutants.They have been widely used as additives,antioxidants and preservatives in the food industry.But when their usage exceeds the scope of safety regulations,they would cause gastrointestinal disorder,high blood pressure,and so on,as well as environmental pollution problems.Bisphenol A,catechol and hydroquinone are common phenolic pollutants.Excessive exposure to them can lead to birth defects,obesity and even neurological damage to human being.Therefore,it is very important to develop some simple and rapid methods for the detection of the above-mentioned pollutants.Among the developed analytical methods,electrochemical technology have received extensive attention from researchers due to their fast response and high sensitivity.Electrochemical sensors usually use the chemically modified electrodes for the different analytes to improve the detection sensitivity.Based on the excellent electrical and catalytic properties of carbon-based materials,this article focused on the detection of several environmental pollutants including sulfite,nitrite,bisphenol A,catecarcinol and hydroquinone.Three kinds of electrochemical sensors were constructed by using carbon-gold nanocomposites as the modification films.Cyclic voltammetry（CV）and differential pulsed voltammetry（DPV）were used to realize the sensitive,fast and stable detection of the above analytes.The specific research content was listed as follows:1.Graphene oxide nanoribbons（GONRs）were prepared and they were immobilized on the surface of glassy carbon electrodes（GCE）by drip-drying method.Gold nanoparticles（GNPs）were synthetized on the GONRs modified GCE via cyclic voltammetry and GCE/GONPs-GNPs electrodes was prepared.The modification coating was characterized by scanning electron microscope-energy spectrum analysis（SEM-EDS）、transmission electron microscope（TEM）and infrared spectroscopy（IR）.The electrochemical response of SO₃^2-and NO₂^-on different electrodes,GCE,GCE/GONRs and GCE/GONRs-GNPs were investigated,respectively.Under the optimal experimental conditions,the individual and simultaneous detection of SO₃^2-and NO₂^-were realized using GCE/GONRs-GNPs.The anodic peak current on the cyclic voltammetric curve exerted a linear relationship with the analyte concentration in the range of 0.010-10.0 m M,and the limit of detection（LOD）values were1.1μM and 1.3μM（S/N=3）,respectively.The developed electrochemical sensor displayed a good anti-interference performance.It was successfully used for the detection of SO₃^2-and NO₂^-in two water samples and a good recovery was obtained.2.3D nitrogen-doped carbon nanotubes（3DNCNTs）were synthesized by hydrothermal method,Gold nanoparticles（GNPs）were prepared on their surfaces based on the reduction of chloroauric acid in the presence of ethylene glycol and 3DNCNTs@GNPs nanocomposites were generated.The nanomaterial was characterized by SEM,IR,X-ray electron spectroscopy（XPS）.The electrochemical responses of bisphenol A（BPA）on GCE,GCE/3DNCNTs and GCE/3DNCNTs@GNPs electrodes were compared.Under the optional experimental conditions,the DPV anodic peak current on GCE/3DNCNTs@GNPs was found to be in propotion to the BPA concentration in the range of 0.25-50μM and 50-200μM,and the LOD value was 42 n M（S/N=3）.The electrochemical sensor had a good selectivity and it could be used for the detection of BPA in actual samples.3.Nitrogen-doped graphene quantum dots@nitrogen-doped carbon nanotubes（NGNs@NCNTs）nanocomposites were synthesized by hydrothermal method,and GCE/NGNs@NCNTs was prepared by drip-drying method.Polycaffeic acid（PCA）and gold nanoparticles（GNPs）were produced in turn via chronoamperometry.As a result,the new nanomaterial-modified electrode,GCE/NGNs@NCNTs/PCA-GNPs was constructed.The modification coating was characterized by TEM and SEM-EDS.The electrochemical behaviors of catechol（CT）and hydroquinone（HQ）on several chemically modified electrodes were investigated.Under the optimal experimental conditions,the simultaneous detection of CT and HQ was realized using GCE/NGNs@NCNTs/PCA-GNPs.The anodic peak current on the CV curve varied directly with the concentration of the two analytes in the range of 0.50-50μM and 50-400μM.The LOD values were calculated to be 0.076μM and 0.061μM,respectively.The modified electrode exhibited a good selectivity,reproducibility and stability.It was employed successfully for the detection of CT and HQ in three water samples.