Graphene and Graphene Quantum Dots for Glucose Sensing

• Main Author: Filimon Hadish
• Other Authors: Shyankay Jou
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/2yk9u4

博士 === 國立臺灣科技大學 === 材料科學與工程系 === 106 === Diabetic patients were concerned in most developed countries and stimulate the advancement of glucose biosensors. Accurate and rapid detection of glucose, based on enzymatic glucose oxidase (GOx) electrode sensors can be developed with graphene as electron mediator. Pristine graphene (PG) attracted researchers for its extraordinary properties. The remarkably high electron mobility in graphene at room temperature, which exceeds 2000 cm2/Vs, highest thermal conductivity (3000 W/mK), combined with the excellent optical characteristic of graphene-based materials holds promises in electronic, optoelectronics and biosensor application. However, development of graphene-based devices requires control over the functionalization and modification of the graphene surface. Thus, in the first work modification of monolayer graphene surface with downstream oxygen plasma treatment to form graphene oxide (GO) for use in glucose biosensors was studied. Raman spectrum and XPS characterization techniques were involved to confirm the functionalization of graphene. Amperometric and voltammetric methods were engaged to ensure the simultaneous reduction of GO with fast immobilization of glucose oxidase (GOx) enzyme modified graphene surface. Cyclic voltammetry investigation indicated that fabricated glucose sensor shows a high surface resistance as a resultant sensitivity of 0.118 µA mM-1cm-2 and a detection limit of 0.0526 mM towards glucose confirmed by amperometric measurments. This method provides fast and simultaneous immobilization of GOx and reduction of GO, and can be used in the fabrication of other electrochemical biosensors. Considering success and limitations of the first work, we projected the glucose sensor to use graphene quantum dots as substitute of reduced graphene oxide. Graphene quantum dots (GQDs) have fascinating photoluminescence (PL) properties with promising applications in fluorescent sensing. In this work, PL properties of GQDs obtained from precursors of glucose and spent coffee ground (SCG) were synthesized via a simple hydrothermal reduction. In the second work we developed a hydrothermal approach for synthesis of GQDs and boro-graphene quantum dots (BGQDs) with glucose precursor for application of simple and sensitive PL probe glucose sensing, which provides an alternative to the commonly used potentiometric detection method. Boron free and doped GQD based sensor was used for detection of glucose in the range of 5–50 mM after 5 months of preparation. Thus, this fluorescent based sensor was easily synthesized and can be stored for a period of long time. In general, GQDs PL probe showed a satisfactory detection of glucose, however up on doping with boron the BGQDs based sensor provided a linear response to glucose with a correlation coefficient of 0.98985 and a low detection limit of 4.8 mM. Third work was similar in all aspect except SCG was utilized as precursor. Thus, we have prepared BGQDs employing glucose in second work and SCG where less amount of boric acid was mixed as boron dopant to realize fluorescent glucose sensor. Various characterizations reveal that the boron atoms have been successfully doped into graphene structures with the atomic percentage of 19 and 70.8% for both BGQDs made from glucose and SGC. The photoluminescence of developed BGQDs showed a linear response to glucose over a concentration range of 5–45 mM. The BGQDs biosensor exhibited a sensitivity of 0.00772 mM-1 and a limit of detection of 3.23 mM for glucose sensing. These results demonstrate that the synthesized BGQD, has a promising potential in electro catalytic and efficient to the PL enhancement mechanism determination of glucose. Keywords: Graphene, downstream oxygen plasma, glucose sensor, graphene quantum dots, spent coffee ground, photoluminescence.