CO 2 -Responsive Hydrophobic Deep Eutectic Solvent Based on Surfactant-Free Microemulsion-Mediated Synthesis of BaF 2 Nanoparticles.

A new form of surfactant-free microemulsion (SFME) including hydrophobic deep eutectic solvent (HDES)/ethanol/water was constructed based on its CO 2 response, and three regions, that is, HDES-in-water (HDES/W), bicontinuous (B.C.), and water-in-HDES (W/HDES) regions, were recognized. It is anticipated that SFMEs with tunable microstructures have outstanding applications as nanoreactors in reaction processes. The feasibility of preparing nanoparticles from HDES/ethanol/water SFME using barium fluoride (BaF 2 ) as a model nanoparticle was investigated. HDES-based microemulsions benefit from HDES's excellent properties (novel, low toxicity, CO 2 -responsive, easy availability) and have potential in universal reactions, drug delivery, advanced material fabrication, etc. In this research, HDES-based microemulsions were prepared using HDES as the oil phase. Phase equilibria and microstructure were investigated using a ternary phase diagram, UV spectrophotometry, and the conductivity method. The CO 2 switchable characteristics of the HDES-based microemulsions were investigated. HDES-based microemulsions were proposed as nanoreactors for the synthesis of barium fluoride nanomaterials. The microemulsion structure can modulate the size, morphology, and physicochemical properties of the nanoparticles through the CO 2 switchable properties. It is argued that nanoreactors constructed with versatile HDES will offer a new direction for creation of cutting-edge scientific applications.