Construction Of Electrochemical Sensors Modified With Copper Nanoparticles And Its Application In Nitrite Detection

Nitrite is an inorganic nitrogen-containing salt with strong toxicity and carcinogenicity.It is one of the important indicators in food safety detection.Accurate and rapid detection of nitrite content in food is of great significance to ensure food safety and human health.Compared with traditional instrumental analysis methods,electrochemical sensing methods have the advantages of low cost,high sensitivity,and on-site detection.They are the most potential analysis methods in the field of rapid detection.Copper nanoparticles have the advantages of low cost,high catalysis,and large specific surface area.They can combine with carbon nanomaterials,conductive polymers,and other materials to produce a synergistic effect and increase the electrocatalytic capacity of electrochemical sensors for nitrite.In this paper,copper nanoparticles were used as modified materials to prepare a new type of nitrite electrochemical sensor that could be adapted to a portable rapid detector.The main research contents were as follows:（1）Three-dimensional copper nanodendrites（Cu NDs）were synthesized by an electrodeposition method.Based on reduced graphene oxide（RGO）,a new type of nitrite electrochemical sensor with high sensitivity was constructed.In the experiment,Poly dimethyl diallyl ammonium chloride（PDDA）was used to functionalize RGO,which effectively reduced the aggregation of RGO.Two-dimensional lamellar RGO could provide a supporting framework for the growth of Cu NDs and promote the formation of Cu NDs with high specific surface area.The synergistic effect of the two nanomaterials could greatly improve the conductivity and specific surface area of the composite material,thereby improving the sensor’s catalytic performance for NO₂^-.Under the optimal conditions,the limit of detection（LOD）of this sensor for nitrite was 0.06μM（S/N=3）,the sensitivity was 0.763μA·μM^-1·cm^-2,and the sensor had a good linear relationship in the range of 1～15,000μM.（2）In order to reduce the oxidation rate of copper nanoparticles in air,carboxy-methylcellulose sodium@copper nanoparticles（CMC@Cu NPs）nanomaterial was prepared by chemical synthesis and modified on the surface of glassy carbon electrode（GCE）containing reduced graphene oxide-sodium carboxymethyl cellulose（RGO-CMC）.A novel anti-oxidation nitrite electrochemical sensor was successfully prepared.Utilizing the characteristics of CMC’s high hydrophilia,high chemical stability and excellent film-forming ability,an anti-oxidation film with thickness of 2.5 nm was coated onto the surface of Cu NPs.At the same time,CMC was used to modify RGO,which effectively increased the dispersion ability of RGO in aqueous solution,and could be firmly fixed on the surface of GCE without other binders.The linear detection ranges of the sensor were 1～15,000μM and 15,000～41,000μM respectively with LOD of 0.05μM（S/N=3）.And sensitivities were 0.171μA·μM^-1·cm^-2 and 0.108μA·μM^-1·cm^-2,respectively.In the stability test,the sensor was able to retain 91.1%of its initial sensitivity after25 days of exposure to air（4℃）,which was better than the stability of PDDA-RGO/Cu NDs/GCE.（3）A novel low-cost polyaniline-sodium carboxymethyl cellulose@copper nanoparticles（PANI-CMC@Cu NPs）nitrite electrochemical sensor was prepared.PANI had excellent electrochemical performance with low cost,which was used as the substrate and combined with CMC@Cu NPs with low synthesis cost.The prepared sensor was not only low in cost but also satisfactory in sensitivity and linearity detection range.The linear detection ranges of the sensor were 3～15,000μM and 15,000～29,000μM with LOD 0.170μM（S/N=3）,and the sensitivities were 0.113μA·μM^-1·cm^-2 and 0.049μA·μM^-1·cm^-2,respectively.The above research provided a new idea for the rapid detection of nitrite in food by the electrochemical sensing technology,and at the same time laid a foundation for the development of rapid nitrite detection instruments.