Research On Graphene Based Biosensor

Biosensor is an analytical device that can convert biological signals into electrical signals.It has the advantages of low cost and high specificity compared with traditional sensors.Therefore,it is regarded as an important technology in the field of detection and analysis.Graphene,as a novel two-dimensional material,has attracted researchers' attention because of its excellent performance in electrical,optical and mechanical properties.The combination of graphene and biosensors provides the possibility of high sensitivity and selectivity for the detection and analysis of biomolecules.In this paper,an acetylcholinesterase(ACh E)-reduced graphene oxide(RGO)hybrid films based biosensor has been developed for the detection of DMMP in gas phase.Quartz crystal microbalance(QCM)was used as transducer.The responses of the sensor and the effect of external factors on its performance were explored.The main contents are as follows:(1)Firstly,the adsorption method was used as the immobilization method of acetylcholinesterase.The effect of graphene substrate on the performance of the sensor was studied.And the repeatability and stability of the sensors made by that method were explored.The experimental results showed that the surface of the electrode modified by graphene was more favorable for the attachment of the enzyme.The sensor prepared by the adsorption method displayed a linear response to different concentrations of DMMP ranging from 10mg/m3 to 25mg/m3(R2 = 0.9965).It also showed good reproducibility to25mg/m3 DMMP,but its stability was poor.In order to explore the influence of external factors on the performance of the sensor,the effects of p H,graphene amount and immobilization time on the response of the sensor were carried out.The results showed that each enzyme had its optimum p H,and the optimum value for sensor made by the adsorption method was p H 6.8.The surface area of the graphene increased the amount of the enzyme,the optimal amount of RGO for the sensor was 0.04 ml in this experiment.And the enzyme had reached the maximum adsorption capacity after 12 h.(2)The cross-linking method was also used as the immobilization method of acetylcholinesterase.The repeatability and stability of the sensor were carried out.The sensor prepared by the cross-linking method displayed a high sensitivity to different concentrations of DMMP ranging from 10mg/m3 to 50mg/m3.It held a good repeatability to 40mg/m3 DMMP,and enzyme on the surface of the device remains high(3)activity after 7 days.The influence of external factors including p H,graphene amount,immobilization time and crosslinker's concentration on the performance of the sensor were explored.The results showed that the optimum value for sensor made by the cross-linking method was p H 6.8.Good antibacterial and biocompatibility of graphene is conducive to the preservation of ACh E membrane.The response of the sensor made by cross-linking method only fell by 21% after 7 days with the 0.03 ml amount of RGO and the cross-linking reaction was finished within 4h.When the concentration of the glutaraldehyde is too low,the cross-linking reaction will not complete.And while the concentration is too high,the excess glutaraldehyde will close the active site of the enzyme and affect the contact and diffusion of the enzyme with DMMP.The sensor prepared by cross-linking method showed the best performance when the concentration of glutaraldehyde is 5wt%.