| Objective:In this study,two glucose sensors with different sensing principles are constructed using single-layer graphene purchased directly and self-prepared graphene/gallium nitride samples.Since the detection environment of these two sensors is neutral,the structure,the preparation process and the detection method are simple.They can well avoid the shortcomings of the traditional graphene electrochemical glucose sensor and gallium nitride glucose sensor,providing a new method for glucose detection.Methods:In this study,two biosensors are constructed using directly purchased single-layer graphene and graphene/gallium nitride samples prepared by a graphene substrate transfer process,respectively.The current-voltage curves of a series of isoconcentration gradient glucose solutions on the surface of the two sensors are detected by the probe station.According to the different sensing principles of the two sensors,the required electrical parameters are obtained from the current-voltage curves:for single-layer graphite sensors,the electrical parameter obtained from the current-voltage curve is conductance,while the required electrical parameter for graphene/gallium nitride sensors is turn-on voltage.The relationship between the obtained electrical parameters and glucose concentration are fitted to a standard curve,and the sensing parameters such as the sensitivity,linear detection range and limit of detection of the sensor are calculated from the standard curve.On this basis,graphene and graphene/gallium nitride sensors are used to detect lead standard solution and glutamic acid solution.In subsequent experiments,the concanavalin A molecule is modified on the surface of graphene to improve the selectivity of graphene and graphene/gallium nitride glucose sensors.Results:In this study,two electrical parameters,conductance and turn-on voltage,of single-layer graphene and graphene/gallium nitride are used to detect the glucose concentration.The standard curve of the glucose sensor constructed with monolayer graphene is G=0.00132-6.62785×10-7C,the sensitivity is 662.785μS/M,the limit of detection is29.614μM,the linear detection range is 100μM-1000μM,the relative standard deviation of the seven repeated experiments is 1.41%,the relative standard deviation of the experiments before and after 15 days is 0.563%,and the influence of each interfering substance after the surface of the samples was modified by concanavalin A molecules are all lower than 1.94%.The standard curves of graphene sensors for lead and glutamic acid solutions are G=0.00159-1.11568×10-6C and G=0.00119-1.02331×10-6C,respectively.The standard curve of the glucose sensor constructed using the graphene/gallium nitride heterojunction interface is U=0.22363+1.89968×10-4C,the sensitivity is189.968 V/M,the limit of detection is 0.330μM,and the linear detection range is 1μM-1000μM,the relative standard deviation of the seven repeated experiments is2.89%,the relative standard deviation of the experiment before and after 15 days is0.03‰,and the influence of each interfering substance after the surface of the sample was modified by concanavalin A molecules are all less than 1.50%.The standard curves of graphene/gallium nitride sensors for lead and glutamate solutions are U=0.08984+4.28877×10-4C and U=0.232-2.44951×10-4C,respectively.Conclusion:Both the conductivity properties of single-layer graphene and the turn-on voltage properties of the graphene/gallium nitride contact interface can be used for the detection of glucose concentration.By comparing the detection parameters of the two glucose sensors,it is found that the sensing properties based on the graphene/gallium nitride heterojunction interface are better than that of single-layer graphene.Besides the graphene/gallium nitride samples are more wear-resistant than single-layer graphene,retaining initial electrical properties after repeated experiments. |
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