Selective captivation of DOX via topotactic surface enrichment with hydrated sodium ions on engineered MXene nanosheets

Abstract

Effective adsorption of the doxorubicin drug from an aqueous system was achieved by utilizing a surface-functionalized, two-dimensional transition metal carbide (MXene). Synthesis of the impurity-free parent phase, followed by subsequent etching and alkalization produced the surface-functionalized MXene (Na⁺–MXene). The powder X-ray diffraction patterns and electron microscopy analysis results suggested that the Na⁺ ion was successfully intercalated into the two-dimensional MXene with high crystallinity. X-ray photoelectron spectroscopy results indicated that an O-rich surface was achieved in the Na⁺–MXene compared with the conventional MXene, suggesting an enhanced drug adsorption through the O-rich groups. According to the kinetics and isotherm studies, doxorubicin molecules were found to adsorb on Na⁺–MXene through the pseudo-second-order kinetics, forming a single layer with a maximum adsorption of ∼250 mg g⁻¹. The X-ray photoelectron spectrum after drug adsorption suggested that doxorubicin was either adsorbed by cation exchange- or nucleophilic addition-driven covalent bond formation. Monte Carlo simulation and comparative adsorption studies revealed that the strong affinity of doxorubicin toward Na⁺–MXene was mainly mediated by the interaction between the primary amino group and the MXene layer, resulting in both cation exchange and covalent bond formation.