Boric acid-treated acid-modified graphene doped sodium carboxymethyl cellulose nanocomposites

Low-cost and easily prepared graphene-based "green" nanocomposite films were synthesized by the solvent evaporation method using commercial nanographene (reinforcement) and sodium carboxymethyl cellulose (Na-CMC) (matrix). The key novelty of this work lies in the unique approach of first acid-modifying graphene with HCl and HNO₃ to enhance its compatibility with the cellulose matrix, followed by heteroatom doping with H₃BO₃. This dual modification leads to synergistic properties within the Na-CMC matrix, significantly improving graphene's dispersion and interaction with the polymer. Na-CMC/H₃BO₃-treated acid-modified graphene nanocomposite films were obtained by incorporating the modified graphene nano-sheets. The synthesized Na-CMC/modified graphene nanocomposite films were characterized using FT-IR, XRD, SEM-EDX, Raman Spectroscopy, TGA/DTG, DSC and AFM techniques. The results reveal that the original structure of graphene is preserved after modification with HCl and HNO₃. Functional end groups (hydroxyl group, -OH) were generated at the interface of the graphene layer upon acid modification according to FT-IR, XRD and Raman Spectroscopy findings, thereby overcoming the immiscibility barrier, one of the largest challenges of graphene in composite development. Morphological analysis carried out through SEM and AFM techniques also confirmed the acid modification of graphene. Thermal gravimetric analysis (TGA/DTG, and DSC) results demonstrated signficantly affected thermal stability for Na-CMC/H₃BO₃-doped acid-modified graphene nanocomposite films containing 1 % (m/m) graphene, showing an average decrease of 10 °C in thermal decomposition temperatures compared to pristine Na-CMC. Furthermore, the boric acid doping was found to increase the electrical conductivity of the nanocomposites by up to 10⁵-fold compared to pristine Na-CMC. These advancements indicate successful interactions between graphene and boric acid, as well as an optimized nanocomposite structure. The improved properties suggest potential applications for these nanocomposite films in various fields, including biodegradable materials, sensors, and electronic devices.