Synthesis and Characterization of Graphene Quantum Dots/Trititanate Nanotube Composites for Enhanced Fluorescence and...

Graphene quantum dots (GQDs)/trititanate nanotube (TiNT) composites were synthesized via a hydrothermal method to enhance fluorescence intensity and photostability for bioimaging applications. In contrast to most reported GQD-TiO₂ or titanate-based systems that primarily focus on photocatalytic applications, this work develops GQDs/TiNT composites specifically designed to improve fluorescence stability for optical imaging. The optical and stability properties of the GQDs/TiNT composites were systematically compared with those of pristine GQDs and TiNT. The composites were characterized using fluorescence (FL) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (Raman), ultraviolet-visible absorption spectroscopy (UV-vis), and zeta potential measurements. The results demonstrate that the successful integration of GQDs with TiNT results in GQDs/TiNT composites that exhibit significantly enhanced fluorescence intensity and improved stability. Specifically, the composites achieved a photoluminescence (PL) intensity of approximately 90,504.47 au, corresponding to an ∼86% increase relative to GQDs alone. In addition, fluorescence intensity decay under UV irradiation was reduced to 27%, compared to 47% for GQDs and 40% for TiNT, indicating improved photostability. Furthermore, photoluminescence quantum yield (QY) measurements reveal that the GQDs/TiNT composites exhibit a significantly enhanced QY (18-24%) compared to pristine GQDs (8-10%), indicating improved radiative recombination efficiency after composite formation. Fluorescence confocal microscopy further demonstrated effective cellular uptake and low cytotoxicity in mouse brain microvascular endothelial cells, with predominant localization in the perinuclear region. These results highlight the potential of GQDs/TiNT composites as stable fluorescent probes for bioimaging applications.