Exploring nitrogen-doped graphene quantum dot—layered double hydroxide hybrid coatings for corrosion resistance and biocompatibility of WE43

This study developed nitrogen-doped graphene quantum dot (NGQD)–layered double hydroxide (LDH) hybrid coatings in a layer-by-layer architecture to enhance the corrosion resistance and biocompatibility of the WE43 magnesium alloy. NGQDs synthesised at 120–200 °C showed temperature-dependent size and surface chemistry, with NGQD synthesised at 160 °C exhibiting a distinct optical bandgap (3.68 eV), improved dispersion stability, and higher nitrogen incorporation (N/C = 0.073). Morphological and cross-sectional analyses revealed varied morphologies within each functional layer and a bilayer architecture approximately 213 nm thick. Electrochemical testing studies demonstrated that NGQD-LDH exhibited increased intermediate impedance and reduced corrosion kinetics from PDP. Hydrogen evolution tests show a reduction in the corrosion rate of WE43 from 11.9 mm·y⁻¹ to 5.27 mm·y⁻¹. MTT assay performed on HEK293 cells using coating extracts, and a direct cell-adhesion study confirmed high cell viability (84.94% at 100% extract over 72 h) and cell attachment with comparative improved spreading to the NGQD-LDH NGQD system. The DPPH assay showed concentration-dependent free radical-scavenging activity with NGQD at 10 µM (43.14%), which decreased with decreasing concentration, potentially establishing NGQD-engineered multilayers as effective, corrosion-resistant, and cytocompatible coatings for biodegradable Mg alloys, as supported by comprehensive characterisation.