Exploring the Structure–Property Relationship in Montmorillonite–Carbon Quantum Hybrid Nanomaterials

Combining montmorillonite (MMT), a layered silicate clay, with carbon quantum dots (CQD) is a promising strategy to develop hybrid nanomaterials with enhanced and tunable properties. In this work, we explore the structure–property relationships in montmorillonite–carbon quantum dot (MCQD) hybrid nanomaterials synthesized through two distinct routes. In Route 1, pre-synthesized CQDs using citric acid and urea as precursors were physically mixed with MMT, giving rise to MCQD-R1 hybrid nanomaterials. In Route 2, MMT was added in situ in the CQD reaction medium before thermal treatment, with contact times from 1 to 16 h, generating MCQD-R2-1 and MCQD-R2-16, respectively. Structural and spectroscopy techniques were employed to investigate the resulting hybrids. PXRD analysis revealed that the synthesis conditions preserved the crystalline structures of both CQD and MMT clay. The FT-IR indicated that in the MCQD-R1, the interactions with CQD occur primarily via the interlayer water molecules in MMT, whereas in the MCQD-R2-16 samples, the establishment of new chemical bonds involving the carbonyl group of CQD takes place. UV-Vis spectroscopy shows improved colloidal stability of MCQD-R2 hybrids compared to pristine CQDs. Finally, hemolysis assays demonstrated hemolytic activity below 5%, indicating good biocompatibility of the synthesized hybrid nanomaterials.