No abstract

Novel deep eutectic solvents (DES) based on three different hydrogen-bond donors (HBD), namely phenol, o-cresol, and 2,3-xylenol, and choline chloride (ChCl) were successfully synthesized with different mole ratios of HBD to ChCl. Melting temperature of these DES were measured. Compared with an ideal mixture of the two components, the freezing temperature of the DES depresses greatly from (120 to 127) K. The physical properties, such as density, viscosity, and conductivity of phenol-based and o-cresol-based DES were determined at atmospheric pressure and temperatures from (293.2 to 318.2) K at an interval of 5 K. The results show that the type of HBD, the mole ratio of HBD to ChCl, and temperature have great influences on the physical properties of DES. Densities and viscosities of DES formed by phenol and ChCl decrease with increases of temperature and phenol content. The conductivities of the DES are from (1.40 to 7.06) mS·cm–1, similar to that of room temperature ionic liquids. The conductivities of the DES increase with an increase of temperature, and reach the highest values at phenol to ChCl mole ratios of 4.00 to 5.00. The temperature dependence of densities and conductivities for these DES were correlated by an empirical second-order polynomial with relative deviations less than 0.91 %, and the viscosities were fitted to the VTF equation with relative deviations less than 0.52 %.

Ammonium salts have been used to efficiently separate phenols from oils (where hexane, toluene and p-xylene were used as model oils) by forming a deep eutectic solvent, which is a nonaqueous process and avoids the use of mineral alkalis and acids that produces phenol containing waste water.

Pure organic room temperature phosphorescence (RTP) is highly preferable because of its long lifetime and potential applications. However, these kinds of materials are still very scarce due to the weak spin-orbit coupling between singlet and triplet states and easily nonradiative decay of the excited states. Achieving room temperature phosphorescence under visible light excitation is particularly challenging in aqueous solution. Herein, a micelle-assisted assembling strategy has been developed to realize pure organic RTP in water by using donor-acceptor molecules. A visible-light responsive long-lived RTP in water with a lifetime more than 3 ms is obtained by the prepared nanocrystals. However, the same molecules show no RTP as rigid bulk crystals. Spectroscopic studies, single-crystal structure analysis, X-ray diffraction patterns, and density functional theory calculations reveal that the intermolecular interactions, heavy atom effect, and the molecular packing way play critical role to the long-lived RTP character for the assembled nanocrystals in water and thermally activated delayed fluorescence for crystals in solid.