Vol.:(0123456789) 1 3 Graphene Technology https://doi.org/10.1007/s41127-019-00028-7 ORIGINAL ARTICLE Graphene oxide in water: a systematic computational experimental study Valdemir Ludwig 1  · João Paulo Almeida de Mendonça 1  · Alessandro Henrique de Lima 1  · Zélia Maria Da Costa Ludwig 1  · Geórgia Maria Amaral Junqueira 1  · Welber Gianini Quirino 1  · Fernando Sato 1 Received: 18 April 2019 / Revised: 20 October 2019 / Accepted: 27 November 2019 © Springer Nature Switzerland AG 2019 Abstract In this work, solvent effects on graphene oxide (GO) in liquid water were analyzed in terms of hydrogen bonds and electronic properties. The sequential Monte Carlo/quantum mechanics simulation was used to generate the molecular structures of the GO sheet structure in aqueous solution. It was observed a large increase of approximately 130% in the dipole moments of the GO sheets in water solvent and hydrogen bonding statistics were obtained. In addition, INDO/CIS quantum mechanics calculations were performed in the super-molecular generated structures in order to obtain the ultraviolet–visible spectra for GO in liquid water. These theoretical results were supported by our experimental data. Keywords Graphene oxide · UV–Vis · Simulation 1 Introduction In recent years, graphene oxide (GO) has been subject to intense research, mainly due to the successfully tested potential applications [1, 2]. Its remarkable mechanical and thermal capacity and its ability to form stable solutions in several solvents open an unlimited path for liquid phase pro- cessing and applications such as supercapacitors [3], biosen- sors [4], and photovoltaics [5]. GO is the oxidized form of a monolayer graphene sheet and can be synthesized by using different methodologies through oxidation and exfoliation of natural powder and/or flake graphite in the presence of strong oxidants [6–8]. The basal plane of GO sheet was attached with epoxy (–O–), hydroxy (–OH), and carboxy (–COOH) groups, allowing for monolayer exfoliation and dispersion in polar solvents including water [9]. The solution processability of the GO offers a practical route to carbon-based composites. The reactivity of the groups with graphene sheet is determined by the chemical environment and the functional group itself [10]. The nature of hydrogen bonds in the liquid environ- ment and the sites of these interactions have a severe impact on the electronic properties of the solute. Thereby, the vibra- tional and UV–Vis spectroscopies play a very important role in elucidating the structure and optoelectronic properties of GO materials. In recent experiments, GO materials were examined by Raman spectroscopy, and the positions and width of the G and D bands were analyzed with defects produced by the oxidation processes [11]. Besides, the results of the UV–Vis spectroscopy have also been used to investigate the elec- tronic properties of GO in different solvents [10, 12–14]. However, there is a lack of understanding about the interac- tions between GO sheets and solvents frequently used to disperse them. In addition, the existence of data is scarce, and the results are not well-systematized and sometimes they appear to be controversial [15, 16]. Therefore, detailed research is needed to provide insight into atomic-scale inter- actions between GO and solvents. An important step now is understanding hydrogen bonds in an explicit solvent model. Whereas in the hydrogen-bonded complex, a minimum energy structure was used for the model, in the liquid one, there are several structures governed by the temperature to represent the statistical nature of the liquid. In this sense, molecular modeling techniques combined with quantum Electronic supplementary material The online version of this article (https://doi.org/10.1007/s41127-019-00028-7) contains supplementary material, which is available to authorized users. * Valdemir Ludwig ludwig.valdemir@gmail.com 1 Departamento de Física, Universidade Federal de Juiz de Fora, Juiz de Fora, MG CP 36036-330, Brazil