Chemical And Biological Sensing Based On Carbon Quantum Dot-Functionalized Solution-Gated Graphene Transistors

Graphene,a carbon nanomaterial with a honeycomb 2D single atomic layer structure,has attracted great attention from scientific researchers since 2004.Due to its unique physical,chemical and electrical properties,graphene has been viewed as a potential candidate for chemical and biological sensors.Among various graphene-based sensors,solution-gated graphene transistor,which can operate in electrolyte,has been widely studied as a promising platform for high-performance sensors.It has several advantages over conventional methods.First,the transistor-based structure has both the sensing and the amplification functions,which implies higher sensitivity.Second,it can work in aqueous environment with relatively low operating voltages,which is important for detection of many chemical and biological analytes.Third,miniaturization and integration is feasible because the device performance depends on the ratio of the channel width to length rather than device size.In this paper,carbon quantum dot-functionalized solution-gated graphene transistors are fabricated successfully.Single layer graphene prepared by chemical vapor deposition(CVD)is used as channel material.Since the surface of carbon quantum dots is easy to be modified by various functional groups,high sensitive and high selective sensors can be reasonably designed according to the affinity differences between different analytes and different functional groups.They could realize the detection of various analytes such as ions,small molecules,DNA and so on.The technology,which does not require the complex procedures and expensive large-scale equipment required,shows great potential for on-the site analysis,real-time monitoring of body fluids,and wearable electronics.Based on the high affinity of amino on carbon quantum dots to Cu²⁺ions,the sodium alginate-based carbon quantum dot is prepared and the Cu²⁺ion sensor is fabricated.The minimum detection limit of the sensor for Cu²⁺ions is 10 f M,far lower than traditional methods.In addition,the sensor has many advantages,such as high selectivity,short detection time and low cost.The sensing principle can be attributed to the coordination reaction between the carbon quantum dots on the gate and the Cu²⁺ions in the solution,which changes the capacitance of the electric double layer near the gate.Based on the similar principle,we prepared lignose-based carbon quantum dots rich in hydroxyl and carboxyl groups and then fabricated ultra-sensitive and highly selective Fe³⁺ion sensor,which could detect the concentration of Fe³⁺ions as low as 0.1 f M.These works indicate that it is feasible to use carbon quantum dot-functionalized solution-gated graphene transistors as chemical sensors,which can be used to detect various ions.We also explore the applications of the transistors for biosensors.According to the specific binding ability of boric acid group and glucose,the phenylboric acid-based carbon quantum dot was designed and prepared.The functional device realizes highly sensitive and rapid detection of glucose,and the detection limit is 10 f M.The sensor can realize real-time monitoring of glucose in the body fluid,which is of great significance for prevention,monitoring and treatment of diabetes.This work validates the feasibility of carbon quantum dot-functionalized solution-gated graphene transistors for biosensors.To sum up,we have designed and manufactured chemical and biological sensors based on functionalized solution-gated graphene transistors with specific functions.The solution-gated graphene transistors functionalized by carbon quantum dots still have a lot of room for further exploration to develop into a high-throughput and multi-functional real-time sensing platform.It is expected that the sensing platform will provide a new strategy for the development of novel health and environment real-time monitoring sensors with high performance,low cost and convenient operation.