Construction Of Graphene Nitride Composite Electrode And Its Electrochemical Detection Of Food Pigment

Synthetic pigments are produced by separation and extraction from coal tar using chemical techniques.Synthetic synthesis has many unsafe factors compared to natural pigments.Excessive consumption of synthetic pigments increases the metabolic burden of the human body and increases the risk of various serious diseases.Therefore,a rapid and efficient method for detecting synthetic pigments is very necessary.Nowadays,there are many methods for the detection of food additives,but the electrochemical-based sensor technology has been researched for its rapid response speed,low equipment cost,easy operation,good selectivity and high electrode sensitivity.A lot of attention and research.All the work of this thesis is based on the comprehensive literature report,using graphene nitride(NG)as a basis for its large specific surface area,rich electrochemical active sites,strong electrocatalytic ability and unique spatial structure.Materials were prepared from graphene nitride composites and three-dimensional graphene nitride.A series of electrochemical sensors for detecting food pigments were constructed by using graphene nitride composites and three-dimensional graphene nitride as modified electrode materials.The specific experimental contents are as follows:(1)β-CD / NG is obtained by calcination using graphene oxide(GO)and melamine as raw materials,and β-cyclodextrin(β-CD)is bound to the NG surface by physical action.An electrochemical sensor was constructed using β-CD/NG as the electrode material for the detection of food color patent blue V.Under the same conditions,the peak current ofβ-CD/NG/GCE was higher than that of the sensor constructed with NG and β-CD alone.This is mainly due to the synergy of β-CD and NG,β-CD aggregates and accommodates more patented blue V,and the high electrochemical activity of NG makes the sensor have better sensitivity and better electrochemical performance.The experiment optimized the pH,sweep speed,enrichment time and potential.Under the optimal conditions,the detection range of β-CD/NG for Patent Blue V is: 3nM-1μM,and the lower limit of detection is 0.8nM(S/N=3).The β-CD/NG sensor was first used for the patented blue V electrochemical detection and performed well in actual sample detection.(2)In the experiment,graphene nitride(NG)was prepared by hydrothermal method using GO and melamine as raw materials,and fine gold nanoparticles(Au)were fixed on the surface of NG.An electrochemical sensor was constructed using Au/NG as electrode material for electrochemical detection of quinoline yellow.Compared with different modified materials,the Au/NG composites under the synergistic effect showed more obvious electrochemical response curves than the Au or NG electrodes alone.This is mainly attributed to the fact that Au nanomaterials provide more contact sites and catalytic properties.Combined with the excellent electrochemical catalytic activity of NG,theperformance of Au/NG composites is higher than that of other materials.Under optimized conditions,in the detection of quinoline yellow,the linear range of Au/NG composites was0.005 μmol/L to 8 μmol/L,and the lower limit of detection was 0.0016 μmol/L(1.6 nmol/L)(S/N = 3).It shows a wide detection range and high sensitivity.In the effective surface area comparison,Au/NG/GCE is about 10 times that of Bare/GCE,which is about 5 times that of NG/GCE.The saturated adsorption capacity of Au/NG/GCE is as high as5.14468×10-10 mol/cm2.Au/NG performed well in actual sample analysis.(3)A three-dimensional graphene oxide aerogel(NGA)having a three-dimensional structure was prepared by a hydrothermal method.An NGA/GCE electrochemical sensor was constructed using NGA materials and used for electrochemical detection of Sudan I.Compared with the bare glassy carbon electrode,NGA/GCE produced a stronger oxidation peak current for Sudan I,indicating that NGA has a good catalytic oxidation effect on Sudan I.The concentration of Sudan I was detected by differential pulse voltammetry using an NGA electrode with a linear range of 1 nM to 20 μmol/L and a lower limit of detection of 0.3 nmol/L(S/N = 3).The sensor performs excellently in terms of reproducibility and selectivity.The recovery rate of the experiment was also determined,and the recovery rate was 97.8 % ~ 101.5 %,and it was successfully applied to the actual sample detection.