Abstract

In this work, we explore the electrical, optical and spectroscopic properties of different Graphene Oxide (GO) samples focusing on new oxidative strategies to tune their physicochemical properties. Three types of GO samples were prepared by changing the oxidative conditions resulting in carbonyl-, epoxy- or hydroxyl-rich GO. These materials were characterized by UV-VIS absorption, Raman spectroscopy and X-ray diffraction. The experimental results indicate that all samples exhibit oxidation and exfoliation degrees typical of graphene oxides obtained by using the modified Hummers’ method. The optical bandgap values were measured using the Tauc’s plot from UV-VIS data and showed that the stoichiometry of GO impacts the width of the bandgap. The carbonyl-rich sample presented the lowest gap around 3.20 ± 0.02 eV, while epoxy- and hydroxyl-rich GOs showed out gaps of about 3.48 ± 0.07 and 3.72 ± 0.05 eV, respectively. These experimental results are consistent with theoretical calculations of bandgaps obtained with coronene and circumcoronene GO models. The calculations were obtained using different theoretical approaches, such as: Huckel, PM3, AM1 and DFT. The present work suggests that a precise tuning of the optical bandgap of GOs can be achieved by only changing their stoichiometry thus allowing their use in a large range of electronic applications.

Graphical abstract

中文翻译：

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氧化石墨烯的光学带隙波动起因

摘要

在这项工作中，我们探索了不同氧化石墨烯（GO）样品的电学，光学和光谱性质，重点研究了新的氧化策略以调节其理化性质。通过改变氧化条件来制备三种类型的GO样品，从而生成富含羰基，环氧或羟基的GO。这些材料通过UV-VIS吸收，拉曼光谱和X射线衍射表征。实验结果表明，所有样品均表现出使用改良的Hummers方法获得的典型氧化石墨烯的氧化和剥落度。使用Tauc曲线从UV-VIS数据测量光学带隙值，结果表明GO的化学计量会影响带隙的宽度。富含羰基的样品在3.20±0.02 eV附近呈现出最小的间隙，而富含环氧和羟基的GO的间隙分别约为3.48±0.07和3.72±0.05 eV。这些实验结果与使用可乐烯和环戊烯GO模型获得的带隙的理论计算结果一致。计算是使用不同的理论方法获得的，例如：Huckel，PM3，AM1和DFT。当前的工作表明，仅通过改变它们的化学计量就可以实现对GOs的光学带隙的精确调节，从而允许它们在广泛的电子应用中使用。

图形概要