Muthurasu A, Ganesh V
Electrodics and Electrocatalysis (EEC) Division, CSIR-Central Electrochemical Research Institute (CSIR-CECRI), Karaikudi, 630006, Tamilnadu, India.
Appl Biochem Biotechnol. 2014 Oct;174(3):945-59. doi: 10.1007/s12010-014-1019-7. Epub 2014 Jul 2.
Green colour emitting graphene quantum dots (GQDs) are prepared by a simple acid reflux reaction of graphene oxide (GO) produced using a modified Hummer's method. Structural and morphological characterizations of such GQDs are performed using spectroscopic (FTIR, UV-vis and photoluminescence) and microscopic (transmission electron microscopy) techniques. These studies reveal the formation of stable, uniform spherical particles of GQDs which emit a green colour and possess surface functional moieties such as epoxide, hydroxyl (-OH) and carboxyl (-COOH) groups. Further, the possibility of immobilizing biomolecules on GQDs using these surface active functional groups is explored. As an example, an enzyme namely horseradish peroxidase (HRP) is shown to be anchored on these GQDs using a coupling reaction between an acid and amine leading to the formation of a peptide amide bond. Enzymatic activity of HRP is investigated by simply drop-casting HRP-immobilized GQDs onto a glassy carbon electrode. Electrochemical studies clearly reveal the formation of a well-defined redox peak and the dependence of redox peak current on scan rate suggests that the HRP enzyme is anchored onto the electrode, surface confined and exhibits a direct electron transfer process that is predominantly controlled by a diffusion process. These HRP-functionalized GQDs are used as a sensing platform for hydrogen peroxide detection. This particular electrochemical biosensor shows the sensitivity values of 0.905 and 7.057 μA/mM and detection limits of ~530 nM and 2.16 μM along with a fast response time of ~2-3 s.
通过对采用改进的Hummer法制备的氧化石墨烯（GO）进行简单的酸回流反应，制备出发射绿色光的石墨烯量子点（GQD）。使用光谱技术（傅里叶变换红外光谱、紫外可见光谱和光致发光光谱）和显微镜技术（透射电子显微镜）对这些GQD进行结构和形态表征。这些研究揭示了形成了稳定、均匀的球形GQD颗粒，其发射绿色光并具有表面官能团，如环氧基、羟基（-OH）和羧基（-COOH）基团。此外，还探索了利用这些表面活性官能团将生物分子固定在GQD上的可能性。例如，通过酸与胺之间的偶联反应，使辣根过氧化物酶（HRP）这种酶锚定在这些GQD上，从而形成肽酰胺键。通过将固定有HRP的GQD简单滴铸到玻碳电极上，研究了HRP的酶活性。电化学研究清楚地揭示了形成了明确的氧化还原峰，氧化还原峰电流对扫描速率的依赖性表明，HRP酶锚定在电极上，表面受限，并表现出主要由扩散过程控制的直接电子转移过程。这些功能化的HRP-GQD用作过氧化氢检测的传感平台。这种特定的电化学生物传感器的灵敏度值分别为0.905和7.057 μA/mM，检测限分别约为530 nM和2.16 μM，响应时间约为2-3秒，响应速度快。
