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

技术概述：石墨烯及其衍生物是电子和光子领域非常重要的材料。虽然这些材料的物理和应用正在世界范围内快速探索，但由于分离石墨烯和氧化石墨烯（GO）片的化学过程控制不善，材料性质的再现性非常困难。氧化石墨烯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EAGER项目由固态和材料化学以及电子和光子材料项目共同资助，旨在利用这种表面功能，根据氧化水平分离氧化石墨烯的组分，并以更可控的方式将氧化水平与电子和光子特性联系起来。将采用标准的氧化方法，但要以系统和控制的方式进行。表面化学反应将与适当的表面活性剂相匹配，以优化薄片分离。样品将使用AFM技术进行分析，该技术可以可视化氧化石墨烯表面活性剂的排列。这将为如何设计更好的分离表面活性剂提供反馈。这项工作很重要，因为它不仅提供了关于石墨化学氧化的重要信息，而且还提供了一种方法，可以分离出更好的化学定义的氧化石墨烯材料，用于物理性质（特别是光子）的应用。非技术总结：这项工作的目标是开发一种具有可调节电子带隙的新型光电材料。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参与这些过程的光的波长。目前存在的一个问题是，可用的光电材料数量有限，而且它们的带隙是固定的。例如，这决定了可用于发光二极管的颜色，或者可以使用太阳能电池有效地转换为电能的阳光的比例。在这个项目中，氧化石墨烯（GO）作为一种具有可调带隙的新材料进行了研究；这项工作的广泛影响将包括开发材料，使太阳能电池的设计具有更高的转换效率，或多种不同颜色的节能光源。虽然石墨可以经济地制成氧化石墨烯，但所获得的材料不是很纯净，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，使其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.