Utilizing Deep Eutectic Solvent in Microemulsion for Eco-Friendly Synthesis of Fluorescent Carbon Nanoparticles and their Highly Sensitive Sensing of Antibiotics and Nitroaromatic Compounds

Abstract

Microemulsions (MEs) comprising of cholinium dodecylbenzene sulphonate Cho[DBS], a bio-based ionic liquid surfactant as an emulsifier, hydrophobic deep eutectic solvent (HDES) as nonpolar phase, and water as a polar component are constructed. Negative value of ∆G estimated from isothermal titration calorimetry (ITC) plots indicate spontaneous aggregation of Cho[DBS] both in water and HDES. The aggregates of Cho[DBS] in HDES and water show the critical micellar concentration (cmc) of ≈4.26 and ≈2.4 mMm, respectively. Cho[DBS] shows a better emulsifying capacity with a high monophasic region in the ternary phase diagram. MEs are utilized as nanoreactors for the sustainable synthesis of nano-sized fluorescent carbon nanoparticles (FCNPs) with precise control over size and morphology. FCNPs are characterized using PXRD, Raman, XPS, HR-TEM, UV–vis, and Fluorescence spectroscopic techniques. FCNPs exhibited remarkable properties viz. adjustable luminescence, good solubility, and biocompatibility. FCNPs are applied for fluorometric sensing of nitroaromatic compounds (NACs) and antibiotics through a quenching response originating from the inner filter effect, with a fast response nanomolar detection, and are found highly selective toward TNP (NAC), NFT, and NZF (antibiotics).