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

技术综述：石墨烯及其衍生物是重要的电子和光子应用材料。虽然这些材料的物理和应用正在世界范围内得到快速探索，但由于用于分离石墨烯和氧化石墨烯(GO)的化学过程控制不善，材料性能的重现性非常困难。GO最近被证明具有不同的光致发光性质，这取决于表面氧化的程度。这个由固态和材料化学以及电子和光子材料计划资助的项目旨在开发这种表面功能，并根据氧化水平分离GO的不同部分，并以更可控的方式将该氧化水平与电子和光子特性关联起来。将采用标准的氧化方法，但要以系统和受控的方式进行。表面化学成分将与适当的表面活性剂相匹配，以优化片材分离。样品将使用AFM技术进行分析，该技术允许可视化表面活性剂在GO表面的排列。这将为如何为分离设计更好的表面活性剂提供反馈。这项工作非常重要，因为它不仅将提供有关化学氧化石墨的重要信息，而且还将为分离物理性能(特别是光子)应用的更好的化学定义GO材料提供一种方法。非技术概述：这项工作的目标是开发一种具有可调电子带隙的新的光电材料。光电子材料被用来将光转化为电流，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了这些过程。存在的一个问题是，现有的光电材料数量有限，而且它们的带隙是固定的。例如，这决定了发光二极管可用的颜色，或者可以利用太阳能电池有效地将阳光转化为电能的部分。在这个项目中，氧化石墨烯(GO)被作为一种带隙可调的新材料进行研究；这项工作的更广泛影响将包括开发能够设计出转换效率更高的太阳能电池的材料，或者许多不同颜色的节能光源。虽然GO可以经济地由石墨制成，但所获得的材料不是很纯，因此具有各种各样的许多不同的带隙。在这个项目中，将探索新的分离方法，将这种材料提纯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.