Self-Assembled Vesicles from Carbon Quantum Dots Induced by a Gemini Surfactant for Selective Detection of Picric Acid

In this work, we investigated the self-assembly of a binary system composed of a cationic gemini surfactant and oppositely charged carbon quantum dots (CQDs), forming vesicles. The main driving force behind their self-assembly is the electrostatic attraction between the positively charged gemini surfactant and the negatively charged CQDs. The morphological structures of the self-assembled vesicles were examined by using field-emission scanning electron microscopy and transmission electron microscopy. The photoluminescence quantum yields of CQDs and the CQDs@gemini surfactant assembly were found to be 42.77 and 31.18%, respectively. Further, it was discovered that the fluorescence of the vesicles was selectively reduced by picric acid (PA) because of the combined effects such as the inner-filter effect and static quenching from ground-state charge-transfer complexation. The limit of detection for PA using this system is 27.5 nM, considerably lower than that of most similar systems reported earlier. The sensor showed excellent sensitivity toward PA, displaying a strong linear response across the 0-800 nM concentration range. The study indicates that CQDs and the gemini surfactant could present functional structural components for supramolecular assemblies and several aggregate morphologies, leading to various prospective uses.