| Nitrite is widely used and even abused in food processing.Nitrite is a carcinogen and causes serious harm to human health and the environment.According to GB2760-2014,the National Food Safety Standard for Food Additives,the residual amount of nitrite in stewed meat products should be controlled within 30 mg·kg-1.Therefore,sensitive and rapid detection of nitrite becomes very important.In recent years,many methods for nitrite detection have been proposed,among which the electrochemical method is very popular because of its fast analysis speed,simple operation process,and strong selectivity.Carbon materials are widely used in the field of electrocatalysis due to their excellent charge conduction efficiency,structural adjustability,pollution-free,and high-temperature resistance.In this study,a series of electrochemical sensors modified by porous carbon materials were successfully prepared by using a variety of experimental methods and technical means,and their performances were optimized and compared.The main contents of this study are as follows:(1)A novel nitrite sensor based on microporous molybdenum carbide(Mo2C@NPC)was prepared using the activation method The microporous structure can greatly increase the specific surface area,thereby dramatically increasing the contact area when the catalyst interacts with the reactants.At the same time,the shape and size of the microporous structure facilitate the uniform dispersion of catalyst active sites,thus improving the activity and stability of the catalyst.Mo2C can convert nitrite into nitrogen oxide through the electrons adsorbed on the surface of the catalyst,thereby realizing the catalytic degradation of nitrite.The linear range of the Mo2C@NPC/GCE modified electrode for nitrite detection was 1-2600μM,with a detection limit of 0.35 μM(S/N=3).The sensitivity was 23.20 μA·μM-1·cm-2.In the actual sample detection,the average recovery rate was 97.93%-104.26%and RSD was 1.12%-4.34%,indicating that this method presents excellent accuracy.Therefore,the electrochemical sensor has a good application prospect in nitrite detection.(2)A silver particle-loaded hydroxyl-functionalized hollow mesoporous carbon nanospheres(HMCS-COOH/Ag)were designed by the hard template method.The mesoporous structure is a porous material that contains a large number of pore structures with very regular pore size and distribution,which can be used as storage and transport channels for molecules.HMCS-COOH has hydrophilic functional groups,which can effectively avoid the aggregation of AgNPs.The linear range of the HMCS-COOH/Ag/GCE modified electrode for nitrite detection was 0.20-1750 μM,with a detection limit of 0.15 μM(S/N=3).The sensitivity was 11.62 μA μM-1·cm-2.In the actual sample detection,the average recovery rate was 96.16%-102.80%and the RSD was 1.24%-4.21%,which indicated that the HMCSCOOH/Ag/GCE sensor has excellent accuracy in nitrite detection for food samples.(3)Graded porous carbon doped with electrochemically active nitrogen(HNPC700)was synthesized using precursor carbonization.HNPC700 possesses pore structures of different sizes.Mesopores can provide sufficient storage space or effective transport channels for the nitrite,while microporous structures with a high specific surface area can provide enough contact area for interaction with the nitrite.These materials have excellent adsorption and catalytic properties.The nitrogen atom-doped carbon material can provide electrons through the nitrogen atoms adsorbed on the catalyst surface,thus enabling the reduction and degradation of nitrite.The linear range of the HNPC700/GCE modified electrode for nitrite detection was 2-3410μM,with a detection limit of 0.11 μM(S/N=3).The sensitivity was 11.32 μA·μM-1·cm-2.In the actual sample detection,the average recovery rate was 97.63%103.75%and the RSD was 1.35%-4.32%.The results indicated that this electrochemical sensor has excellent performance and strong practicability in actual sample analysis. |
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