Electrically-Tunable Surface Energy and Reactivity of Graphene

非技术描述：通常，在不干扰材料固有特性的情况下，传统材料的表面特性是无法改变的。例如，化学处理被用来改变半导体的表面特性，连续的电流被用来改变金属的表面特性。相比之下，石墨烯（由六方键合碳原子组成的单原子层）的表面特性可以动态调整，同时保持石墨烯的优异性能。这是由于石墨烯的原子薄性质和独特的性能。本项目研究石墨烯的可调表面特性，以实现一种新型多功能涂层材料。动态调整石墨烯表面特性的能力可用于推进抗腐蚀和抗氧化涂层、传感、冷凝传热、电池和超级电容器效率以及微流体。这些改进提高了能源、制造业和卫生部门的生产率并降低了成本。此外，在这个项目中获得的新知识和更广泛的影响提供了一个很好的教育机会，以加强社区参与和推广令人兴奋和不断发展的纳米技术领域。具体的传播途径包括在线学习平台、学生暑期研究体验、高中生实地考察和暑期科学营。技术描述：石墨烯由完全饱和和化学惰性的sp2杂化碳原子组成，通过离域π电子感知附近的外部分子并与之相互作用。与传统的块状材料不同，外部分子可以通过与这些离域的、无质量的狄拉克费米子相互作用来调节石墨烯的掺杂水平。同样，掺杂水平的调节反过来会影响石墨烯与外部分子的反应方式。该项目的目标是建立对电掺杂诱导的石墨烯可调表面能和反应性的基本理解，以解决石墨烯电子态与其表面能/反应性之间耦合的知识空白。主要研究人员的假设是，通过掺杂对石墨烯电子状态的调制有助于石墨烯对外部分子施加可调静电力，从而影响石墨烯的可调表面能和反应性。该研究将原位实验研究与量子和原子理论建模相结合。通过原位显微镜（如原子力显微镜和电子显微镜）以及光谱表征（包括拉曼光谱和x射线光电子能谱）来实验研究掺杂如何影响石墨烯的表面能和反应性。此外，还进行了理论研究，包括详细的量子、原子和反应分子动力学计算，以补充和解释掺杂诱导的表面能/反应性的实验发现，而实验获得的参数用于发展预测和发展新的表面现象的综合理论。该项目推进了掺杂水平调节如何影响石墨烯与外部分子反应的科学知识，并提高了石墨烯可调表面特性的技术能力。

Non-technical Description: Typically the surface characteristics of conventional materials cannot be changed without disturbing materials' intrinsic properties. For example, chemical treatments are used to alter the surface characteristics of semiconductors, and a continuous flow of electrical currents is used to change the surface characteristics of metals. In contrast, the surface characteristics of graphene, a material which consists of a single atomic layer of hexagonally bonded carbon atoms, can be dynamically tuned while preserving the superb properties of graphene. This is due to the atomically-thin nature and unique properties of graphene. This project studies tunable surface characteristics of graphene to enable a novel and multi-functional coating material. The capacity to dynamically tune the surface characteristics of graphene can be used to advance corrosion and oxidation resistant coating, sensing, condensation heat transfer, battery and supercapacitator efficiency, and microfluidics. These improvements increase productivity and reduce costs in the energy, manufacturing, and health sectors. In addition, the new knowledge and broader implications realized in this project offer an excellent educational opportunity to enhance community engagement and outreach in the exciting and growing field of nanotechnology. Specific avenues for dissemination include online learning platforms, summer research experiences for students, and field trips and summer science camps for high-school students.Technical Description: Graphene, which consists of fully saturated and chemically inert sp2-hybridized carbon atoms, senses and interacts with external molecules in close vicinity via delocalized pi electrons. Unlike conventional bulk materials, external molecules can modulate the doping levels of graphene by interacting with these delocalized, massless Dirac fermions. Likewise, the modulation of doping levels can in turn affect the way graphene reacts with external molecules. The objective of this project is to establish a fundamental understanding of electrical doping-induced tunable surface energy and reactivity of graphene to address the knowledge gap concerning the coupling between graphene's electronic states and its surface energy/reactivity. The principal investigators' hypothesis is that the modulation of graphene's electron state by doping contributes to the tunable electrostatic force which graphene exerts on external molecules, and in turn impacts the tunable surface energy and reactivity of graphene. The research combines in situ experimental investigations with quantum and atomistic theoretical modeling. In situ microscopy, such as atomic force microscopy and electron microscopy, as well as spectroscopic characterizations, including Raman spectroscopy and X-ray photoelectron spectroscopy, are performed to experimentally investigate how doping influences the surface energy and reactivity of graphene. Furthermore, theoretical investigations, including detailed quantum, atomistic and reactive molecular dynamics calculations, are performed to complement and explain experimental finding of doping-induced surface energy/reactivity, while the experimentally obtained parameters are used to develop a comprehensive theory for the prediction and development of new surface phenomena. This project advances the scientific knowledge of how modulation of doping levels affect graphene's reaction to external molecules as well as improves the technical capability of tunable surface characteristics of graphene.