Nanoplataformas híbridas a base de pontos quânticos de carbono e suportes inorgânicos naturais e sintéticos

Abstract

Clays are widely combined with other nanomaterials to improve their properties and to obtain multifunctional hybrid systems. These materials offer advantages such as enhanced mechanical and rheological performance, reduced toxicity, and compatibility with green chemistry principles, making them suitable platforms for incorporating functional nanostructured materials. In this work, hybrid nanomaterials based on carbon quantum dots (CQDs) and inorganic supports with different morphologies were developed, including fibrous sepiolite (SEP), layered montmorillonite (MMT), and ZIF-8. CQDs were synthesized by a solvothermal route using citric acid and urea in dimethylformamide and subsequently associated with the supports either using preformed CQDs or through in situ synthesis. Spectroscopic analyses indicate that CQDs interact with SEP mainly through surface silanol groups and hydroxyl groups associated with zeolitic water, as evidenced by FT-IR spectroscopy. Photoluminescence (PL) spectroscopy demonstrates that the association between CQDs and clay minerals does not compromise the PL properties of the CQDs. The hybrid nanomaterials exhibit shifts in the maximum emission wavelength, indicating modification of the emissive states induced by the clay environment. In addition, most hybrid systems display dual-emission behavior. Raman analysis shows an increase in the sp² carbon network for sepiolite–CQD hybrids synthesized in situ, accompanied by a decrease in the ID/IG ratio, indicating higher structural ordering as a function of synthesis time. For the MMT-based hybrid nanomaterials, X-ray diffraction (XRD) analysis reveals both the presence of diffraction features associated with CQDs and an increase in the basal spacing of MMT. Drug intercalation studies demonstrate that 5-fluorouracil is incorporated into MMT as a monolayer with planar orientation, producing an increase in basal spacing from approximately 1.21 nm to values close to 1.27 nm, depending on drug loading. The resulting clay–CQD–drug systems exhibit stable structural organization without collapse of the layered framework. The ZIF-8/CQD hybrid nanomaterial preserves the crystalline structure and porosity of ZIF-8, as confirmed by XRD and nitrogen adsorption–desorption analyses, although a reduction in specific surface area is observed due to the incorporation of CQDs. Hemolysis assays performed over a concentration range from 5000 to 36 µg mL⁻¹ show hemolysis percentages below 5%, indicating good hemocompatibility. Overall, the results demonstrate that the association of CQDs with clays and metal–organic frameworks leads to structurally stable hybrid nanoplatforms with tunable optical properties, preserved porosity, and low toxicity.