Studies On The Construction And Performance Of Graphene Based Biosensors

Graphene, a one atom thick material consisting of sp2bonded carbon with a honeycomb structure, has drawn a vast amount attention after its discovery in2004. As a supportive material, graphene can great impove the properties of biosensors. In this thesis, we scientifically studied the construction and performance of graphene and its derivatives based biosensors, such as enzymatic electrode sensor, non-enzymatic biosensor, functionalized HEMT DNA sensor, and metal-free surface enhanced Raman scattering (SERS) sensor. It demonstrated the structure of graphene affected on the biosensors and analysised the detecting mechanism specifically.We constructed reduced graphene oxide (rGO) modified enzyme electrode glucose sensor. How the structure of rGO affected the modified enzyme electrode was studied as well. It was found that rGO sheets help to induce the direct electron transfer (DET) on the rGO-modified electrode at a low oxygen concentration, and the reduction of H2O2occurred instead of DET on the surface of the rGO-modified electrode at a higher oxygen concentration. When rGO modified the enzyme electrode under the working model of H2O2reduction, an increase in the number of the oxygen functional groups could lead to the improvement of the affinity and sensitivity.Two non-enzymatic glucose sensors were constructed. One was produced by in-situ synthesized Ni/NiO-rGO nanocomposite which was adopted to screen printed electrode (SPE). The Ni/NiO-Nafion-rGO/SPE possessed strong electrocatalytic ability toward glucose in alkaline media, and can sensitive detect glucose from29.9μM to6.44mM (R=0.9937). It also exhibited goode selectivity and acceptable stability. To enlarge the detect limit that can meet the requirment of diabetics glucose monitoring, the other non-enzymatic glucose sensor was constructed by CVD systhesized graphene hydrothermal prepared CuNiO nanoparticals. The proposed nonenzymatic glucose sensor exhibited wide linear range up to16mM. Excellent selectivity and acceptable stability were also remained.We designed and constructed rGO functionalized high electron mobility transistor (HEMT) for rapid and ultra-sensitive detection of label-free DNA in real time. The real time monitor and detection of DNA hybridization by rGO functionalized HEMT presented interesting current responses:a "two steps" signal enhancement in the presence of target DNA; and a "one step" signaling with random DNA. The working principle of the rGO functionalized HEMT can be demonstrated as the variation of the ambience charge distribution. Furthermore, the as constructed DNA sensors showed excellent sensitivity of detect limit at0.07fM with linear detect range from0.1fM to0.1pM. Good reproducibility and repeatability also obtained in this kind of device.We exploratory investigated graphene oxide (GO) SERS substrate for glucose sensing. The SiO2/Si substrate spin-coated with GO sheets (GO-SiO2/Si), which was adapted to the SERS probe, showed high SERS activity towards glucose from1800to2000cm. Such a region generally demonstrates no vibration for most interference from any functional groups of glucose, so it can be employed to the high specific quantification of glucose. We attribute such a novel enhancement to the charge transfer between GO and glucose molecules, which results in chemical mechanism. The as proposed GO-SiO2/Si SERS sensor can linear respond to glucose from0.1to100mM. High sensitivity and specificity was also achieved.