Dissipative Particle Dynamics Simulation And Application Of BmimPF₆/DMF/H₂O Microemulsion

In the absence of surfactants,immiscible oil and water can also form microemulsions with the help of“amphi-solvent”,which can be called"Surfactant-Free Microemulsion"（SFME）.Studies show that the phase behavior and microstructure of SFME are similar to traditional microemulsions and SFME has significant application advantages in nanomaterial preparation,chemical reactions and medical extraction.In this paper,dissipative particle dynamics（DPD）computational simulation technology was utilized to study the phase behavior and stability of 1-butyl-3-methylimidazolehexafluorophosphate（bmim PF₆）/N,N-dimethylformamide（DMF）/water（H₂O）.Results show that the simulated phase diagram shares a similar tendency to the experimental results.It proved the DPD simulation method is convenient,fast,time-saving and efficient,and is an useful tool for analyzing and predicting the phase behavior of other functional IL-SFME and new unknown SFME systems.Futhermore,La（BTC）（H₂O）₆ was synthesized in the“BmimPF₆/DMF/H₂O”microemulsion,and then La（BTC）（H₂O）₆ as a parent framework was soaked in mixed Tb³⁺solutions to obtain Tb@La（BTC）.The fluorescence sensing detection of 2,6-pyridinedicarboxylic acid（DPA）by synthetic Ln-MOFs was sdudied.The main research contents are as follows:1.DPD simulation of the phase behavior of BmimPF₆/DMF/H₂OThe dissipative particle dynamics（DPD）method was used to simulate the BmimPF₆/DMF/H₂O surfactant-free microemulsion system for the first time.The phase behavior of the ternary system was investigated,showing that there were a single-phase microemulsion region and a multiphase region in the ternary phase diagram.Furthermore,in the single-phase microemulsion region,three different microregions,that is water-in-ionic liquid（W/IL）,a bicontinuous（BC）region and ionic liquid-in-water（IL/W）were identified.This simulated result is in agreement with experimental phase diagram to a certain extent.The further simulation of DPD found that there were microstructures of upper phase microemulsion,lower phase microemulsion and lamellar liquid crystal in the multiphase region.2.DPD simulation study on the stability of BmimPF₆/DMF/H₂O systemEffects of the shear rate,inorganic salt and temperature on the stability of SFME were precicted.Results show that both IL/W and W/IL microemulsions have good salt resistance stability,and the temperature resistance of W/IL microemulsions is better than that of IL/W microemulsions,but both of them are easily affected by external forces.3.Lanthanum-based metal-organic frameworks（Ln-MOFs）for fluorescence sensing of biomarkersThe rod-shaped lanthanum-based metal organic framework—La（BTC）（H₂O）₆ was successfully controlled and synthesized in BmimPF₆/DMF/H₂O SFME at room temperature,and then La（BTC）（H₂O）₆ as a parent framework was soaked in mixed Tb³⁺solutions to obtain Tb@La（BTC）.Ttransmission electron microscopy,scanning electron microscopy,X-ray diffraction,infrared spectroscopy and fluorescence spectroscopy and other techniques have been used to study the morphology and structure of the two Ln-MOFs.The synthesized Ln-MOFs were tested for photoluminescence quenching-based sensing of DPA across a wide concentration range for the rapid detection of an anthrax biomarker.The detection limit and the linear range of La（BTC）（H₂O）₆ are 0.996μM and0.15-150μM,respectively.And Tb@La（BTC）showed more lower detection limit（13.4n M）,and its linear range is 0.05-25μM,which indicated the Tb@La（BTC）sensor is more sensitive to DPA due to the addition of Tb³⁺.Compared with the synthesis method of Ln-MOF reported in the literature,microemulsion method and immersion method are simple and gentle for avoiding use of surfactants,high temperature and other conditions.