Faculty of Science and Engineering, School of Science and the Environment, Division of Chemistry and Environmental Science, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, Lancs, UK.
Nanoscale. 2012 Oct 21;4(20):6470-80. doi: 10.1039/c2nr31823g.
A newly synthesised type of graphene, Q-Graphene, has been physically and electrochemically characterised with Scanning and Transmission Electron Microscopy (SEM, TEM), X-ray Photoelectron Spectroscopy (XPS) and Cyclic Voltammetry (CV). Interpretation of SEM, TEM and XPS data reveal the material to consist of hollow carbon nanospheres of multi-layer graphene (viz. graphite), which exhibit a total oxygen content of ca. 36.0% (atomic weight via XPS). In addition to the carbon structures present, spherical magnesium oxide particles of ≤50 nm in diameter are abundantly present in the sample (ca. 16.2%). Interestingly, although the TEM/SEM images show macroporous carbon structures, Raman spectroscopy shows peaks typically characteristic of graphene, which suggests the material is highly heterogeneous and consists of many types of carbon allotropes. Q-Graphene is electrochemically characterised using both inner-sphere and outer-sphere electrochemical redox probes, namely potassium ferrocyanide(II), hexaammine-ruthenium(III) chloride and hexachloroiridate(III), in addition to the biologically relevant and electroactive analytes, norepinephrine, β-nicotinamide adenine dinucleotide (NADH) and l-ascorbic acid. The electrochemical response of Q-Graphene is benchmarked against edge plane- and basal plane-pyrolytic graphite (EPPG and BPPG respectively), pristine graphene and graphite alternatives. Q-Graphene is found to exhibit fast electron transfer kinetics, likely due to its high proportion of folded edges and surface defects, exhibiting a response similar to that of EPPG - which exhibits fast electron transfer rates due to the high proportion of edge plane sites it possesses. Furthermore, we demonstrate that the specific oxygen content plays a pivotal role in dictating the observed electrochemical response, which is analyte dependant. Consequently there is potential for this new member of the graphene family to be beneficially utilised in various electrochemical applications.
一种新合成的石墨烯类型，Q-Graphene，已通过扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X 射线光电子能谱（XPS）和循环伏安法（CV）进行了物理和电化学表征。SEM、TEM 和 XPS 数据分析表明，该材料由多层石墨烯（即石墨）的中空碳纳米球组成，其总氧含量约为 36.0%（通过 XPS 原子重量）。除了存在的碳结构外，样品中还大量存在直径≤50nm 的球形氧化镁颗粒（约 16.2%）。有趣的是，尽管 TEM/SEM 图像显示出大孔碳结构，但拉曼光谱显示出典型的石墨烯特征峰，这表明该材料高度不均匀，由多种类型的碳同素异形体组成。使用内球和外球电化学氧化还原探针，即亚铁氰化钾（II）、六氨合钌（III）氯化物和六氯高铼（III），以及生物相关和电化学活性分析物去甲肾上腺素、β-烟酰胺腺嘌呤二核苷酸（NADH）和 L-抗坏血酸，对 Q-Graphene 进行了电化学表征。将 Q-Graphene 的电化学响应与边缘平面和基面热解石墨（分别为 EPPG 和 BPPG）、原始石墨烯和石墨替代品进行了基准比较。发现 Q-Graphene 具有快速的电子转移动力学，这可能是由于其高比例的折叠边缘和表面缺陷，表现出类似于 EPPG 的响应 - EPPG 由于其具有高比例的边缘平面位点，因此具有快速的电子转移速率。此外，我们证明了特定的氧含量在决定观察到的电化学响应方面起着关键作用，这取决于分析物。因此，这种新的石墨烯家族成员有可能在各种电化学应用中得到有益的利用。
