EAGER: Collaborative Research: Defined Band Gap Materials by Fractionation of Graphene Oxide

石墨烯及其衍生物是电子和光子应用的重要材料。 虽然这些材料的物理和应用正在世界范围内快速探索，但由于用于分离石墨烯和氧化石墨烯（GO）片的控制不良的化学程序，材料性质的再现性非常困难。 最近已经显示GO具有取决于表面氧化程度的不同的光致发光性质。 这个EAGER项目由固态和材料化学以及电子和光子材料计划资助，旨在利用这种表面功能并根据氧化水平分离GO的部分，并以更可控的方式将氧化水平与电子和光子特性相关联。 将采用标准氧化方法，但采用系统和受控的方式。 表面化学将与适当的表面活性剂相匹配，以优化纸张分离。将使用AFM技术分析样品，该AFM技术允许可视化GO表面上的表面活性剂的排列。 这将提供关于如何设计更好的表面活性剂用于分离的反馈。 这项工作是重要的，因为它不仅将提供有关化学氧化石墨的重要信息，但它也将提供一个程序，用于隔离更好的化学定义的GO材料的物理性能（特别是光子）application.NON-TECHNICAL摘要：这项工作的目标是一个新的光电材料的发展与可调的电子带隙。光电材料用于将光转换为电流，反之亦然。典型的应用是太阳能电池、光电探测器、数码相机、发光二极管或固态激光器。带隙的大小在很大程度上决定了哪些波长的光参与这些过程。现有的问题是，只有有限数量的光电材料可用，并且它们的带隙是固定的。例如，这决定了可用于发光二极管的颜色，或者可以使用太阳能电池有效转换为电力的太阳光的比例。在该项目中，氧化石墨烯（GO）被研究为具有可调带隙的新材料;这项工作的更广泛影响将包括开发能够设计具有更高转换效率的太阳能电池或许多不同颜色的节能光源的材料。虽然GO可以经济地由石墨制成，但所获得的材料不是非常纯，因此具有多种不同的带隙。在这个项目中，将探索新的分离方法来纯化这种材料，以达到电子应用所需的水平。

TECHNICAL SUMMARY:Graphene and its derivatives are very important materials for electronic and photonic applications. While the physics and applications of these materials is being explored world-wide at a rapid pace, the reproducibility of materials properties is very difficult because of the poorly controlled chemical procedures used to isolate graphene and graphene oxide (GO) sheets. GO has been recently shown to have different photoluminescent properties depending on the extent of surface oxidation. This EAGER project, funded by both the Solid State and Materials Chemistry and Electronic and Photonic Materials Programs, aims to exploit this surface functionality and separate fractions of GO according to oxidation level and correlate that oxidation level in a more controlled manner with the electronic and photonic properties. Standard oxidation methodologies will be applied but in a systematic and controlled way. Surface chemistries will be matched with appropriate surfactants for optimizing the sheet separations. Samples will be analyzed using an AFM technique that allows visualization of the arrangements of surfactants on the surface of GO. This will provide feedback about how to design better surfactants for the separation. This work is important because it will not only provide important information about the chemical oxidation graphite , but it will also provide a procedure for isolating better chemical defined GO materials for physical property (especially photonic) applications.NON-TECHNICAL SUMMARY:The goal of this work is the development of a new optoelectronic material with an adjustable electronic band gap. Optoelectronic materials are used to convert light into electric currents or vice versa. Typical applications are solar cells, photo detectors, digital cameras, light emitting diodes or solid state lasers. The size of the band gap largely determines which wavelengths of light are involved in these processes. An existing problem is that there are only a limited number of optoelectronic materials available, and their band gaps are fixed. For instance, this determines the colors that are available for light emitting diodes, or the fraction of sunlight which can be efficiently converted to electricity using solar cells. In this project graphene oxide (GO) is investigated as a new material with adjustable band gap; broader impacts of this work will include developing materials that will enable the design of solar cells with higher conversion efficiency, or energy-efficient light sources of many different colors. While GO can be made from graphite economically, the obtained material is not very pure and thus has a great variety of many different band gaps. In this project new separation approaches will be explored to purify this material to the level needed for electronic applications.