DOI: 10.5061/dryad.7sqv9s52k
title: Reduction and modification of graphene derivatives with bioactive compounds

description: Green routes based on non-covalent functionalization approaches have been
 developed to prepare surface-functionalized graphene oxide (GO) nanosheets
 with bioactive compounds such as polyphenols. Amongst them, gallic acid
 (GA) and tannic acid (TA) are known to have strong antioxidant activity
 and can act as reducing and stabilizing agents of GO, resulting in reduced
 graphene oxide (rGO) derivatives with improved properties such as
 solubility in organic solvents, thermal stability and mechanical
 performance. Polyphenols act as crosslinkers between the GO 
 nanosheets, leading to higher thermal resistance and improved stiffness,
 strength and toughness. A synergistic effect of both GO and polyphenols on
 inhibiting bacterial growth has also been found. The Π-Π and H-bonding
 interactions are believed to be the reason for the improved properties.
 The combination of bioactive molecules and carbon nanomaterials is a
 useful method towards the development of green, low-cost, biodegradable
 nanocomposites to be used in biomedicine, energy storage devices or other
 enviromentally friendly applications. 
description: Scanning electron microscopy (SEM) analysis was performed with a
 Digital Scanning Microscope DSM-950 (Carl Zeiss, Germany) equipped with a
 tugnsten filament as electron source, working under vacuum at 20 kV. Prior
 to observation, samples were dried out and sputtered with a thin gold
 layer to avoid charging during electron irradiation. Examination of the
 micrographs was accomplished with the ImageJ software. Fourier-transformed
 infrared (FT-IR) spectra were acquired at 25 °C in the MIR region
 (500–4000 cm<sup>−1</sup>) with a resolution of
 4 cm<sup>−1</sup> using a Frontier infrared spectrophotometer
 (Spectrum Two, Waltham, MA, USA) working in ATR mode.
 Raman spectra were acquired at RT using a high performance
 inVia confocal Raman instrument (Renishaw, Gloucestershire, UK) fitted
 with a Nd:YAG 532 nm laser. Five scans were at least recorded for each
 compound at a power of 500 mW. The acquisition of data was controlled with
 Windows®-based Raman Environment software v.2.3. Baseline correction
 method was applied to remove the baseline drift caused by fluorescence.
 Mechanical properties were tested using a Universal Testing Machine with a
 100 N load cell at 1 mm/min loading rate and processed using Origing
 software version 8.5, Oringin Lab Corporation. 
description: # Reduction and modification of graphene derivatives with bioactive
 compounds
 [https://doi.org/10.5061/dryad.7sqv9s52k](https://doi.org/10.5061/dryad.7sqv9s52k) ## Description of the data and file structure Synthesis GA-rGO: Scheme for the synthesis procedure of reduced graphene oxide (rGO) surface functionalized with gallic acid (GA). A few mg of GO were added to a phosphate buffer solution (pH = 8.0), and the resulting dispersion was ultrasonicated at RT for 60 min. Subsequently, GA  was added to the GO dispersion and the resulting product was dried for 24 h at RT. Blue lines indicate π-π stacking interactions among aromatic rings and red dashed lines indicate the formation of H-bonding interactions between hydroxyl and carboxylic acid groups of GO and hydroxyl groups of GA SEM_GA-rGO: Raw scanning electron microscopy (SEM) and energy dispersive X-ray diffraction (EDX) data in word files of GO non-covalently modified with GA. TEM_GA-rGO: Raw transmission electron microscopy (TEM) data in word files of GO non-covalently modified with GA. FT-IR_GA-rGO: Fourier transformed Infrared Spectrum of GO (black line), GA (red line) and GA_rGO (blue line). FT-IR spectrum of GO showed typical peaks at 3480 cm−1 due to the O-H stretching, 1730 cm−1 from C=O stretching, 1630 cm−1 from aromatic C=C stretching, 1400 cm−1 from O-H bending, 1220 cm−1 from C-O-C stretching, and 1050 cm−1 from C-O stretching [1]. The characteristic peaks of GA were observed at 3380 cm−1 from O-H stretching, 1600, 1500 and 1450 cm−1 from aromatic C=C stretching, 1340 cm−1 from O-H bending and 1030 from C-O stretching [2]. In the FT-IR spectrum of GA-rGO, most of the characteristic peaks from oxygen containing moieties can still be observed, indicative that GA has successfully functionalized the surface of GO nanosheets. Raman_GA-rGO: Raman spectrum of GO also showed representative D- and G-peaks at 1340 and 1585 cm−1 which are derived from the disordered band and intact sp2 carbon structures, respectively. The relative intensity ratio of D- and G-peaks (*ID/IG*) from GO was determined to be 0.89 but this value increased to 1.3 for GA-rGO. The increase of *ID/IG* via chemical reduction has been frequently observed in former studies [3,4] since it leads to the formation of atomic vacancies during removal of oxygen functional groups and small sized sp2 carbon domain. Those results clearly indicated that GO was successfully reduced and functionalized with GA. Tensile-GA-rGO: mechanical properties of GO and cross-linked GA-rGO were characterized via tensile experiments by using UTM. As a result of TA reduction and functionalization, the tensile strength and modulus of GO significantly increased, by about 20 fold and 9-fold, respectively, while the strain was significantly reduced, by around 65%. This is the typical behaviour found in GO nanocomposites [5,6]. The enhanced modulus and decreased elongation are typically observed in cross-linked GO-based nanocomposites and thus those changes of mechanical properties implied the interaction between GO sheets were strengthened by the surface-adsorbed GA moieties via π-π stacking interactions among aromatic rings and the formation of H-bonding interactions. Overall, polyphenols like GA and TA can be applied as multifunctional agents for the reduction, functionalization, and cross-linking of GO sheets. A synergistic effect on the mechanical properties of GA-rGO nanocomposites has been obtained, which is useful for the development of green low cost nanocomposites for enviromentally friendly uses. ## Code/software The files can be open freely in word and jpg. ## References \[1] D. Lin-Ven, N.B. Colthup, W.G. Fateley, J.G. Grasselli. The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules, (1st ed.), Academic Press (1991), pp. 155-225. \[2] A.A. Kamal (2021). Extraction of Gallic Acid from Chromolaena sp. Using Ultrasound-assisted Extraction. Engineering Journal 25(2):269-276. DOI:[10.4186/ej.2021.25.2.269](http://dx.doi.org/10.4186/ej.2021.25.2.269) \[3] A.C. Ferrari, D.M. Basko (2013). Raman spectroscopy as a versatile tool for studying the properties of graphene. Nat. Nanotechnol., 8, 235-246. [10.1038/nnano.2013.46](https://doi.org/10.1038/nnano.2013.46) \[4] Y.K. Kim, M.H. Kim, D.H. Min. (2011). Biocompatible reduced graphene oxide prepared by using dextran as a multifunctional reducing agent. Chem. Commun., 47, 3195-3197,DOI: [10.1039/c0cc05005a](https://doi.org/10.1039/c0cc05005a) \[5] Kwon, YB., Lee, SR., Seo, T.H. *et al. (2022). * Fabrication of a Strong Artificial Nacre Based on Tannic Acid-Functionalized Graphene Oxide and Poly(vinyl alcohol) Through Their Multidentate Hydrogen Bonding. Macromol. Res. 30, 279–284. DOI: 10.1007/s13233-022-0031-y \[6] S, Yaoting et al. (2024). A chitosan-based conductive double network hydrogel doped by tannic acid-reduced graphene oxide with excellent stretchability and high sensitivity for wearable strain sensors. International Journal of biological macromolecules 258, 28861.