Study On The Interaction Of Aggregation-induced Emission Probe And Cationic Surfactants

Cationic surfactants（CS）are widely used in daily life and industry because of their strong surface activity and good bactericidal performance.However,there were some problems such as slow biodegradation rate and harm to aquatic environment.Therefore,it is of great significance to develop a convenient method for detecting CS in water for environmental monitoring and governance.Traditional detection methods have some limitations,such as low sensitivity of two-phase titration,involving obvious toxic solvents such as chloroform;the instrument used in chromatographic method is expensive,the analysis cost is high,and the requirement of sample pretreatment is high.Therefore,a simple and quick detection method is needed.Aggregation induced emission（AIE）probe has been widely used in chemical and biosensors in recent years.AIE phenomenon is a new and fast method to analyze and detect surfactants.Therefore,in this paper,a water-soluble molecule 1,1,2,2-tetrakis[4-（3-sulfonatopropoxyl）phenyl]ethylene salt（TSTPE）was synthesized with tetrastyrene（TPE）group as the parent molecule.The photophysical properties of TSTPE and the fluorescence emission response of TSTPE to different kinds of CS were studied to explore the interaction between TSTPE and CS.Within the research scope of this paper,the main research contents and conclusions are summarized as follows:（1）Synthesis and photophysical properties of sodium tetrastyrene sulfonate（TSTPE）TSTPE was synthesized in two steps by Mc Murry Coupling reaction and transesterification reaction.The product was characterized by nuclear magnetic resonance spectroscopy(¹H NMR,¹³C NMR)and electrospray soft ionization mass spectrometry（ESI-MS,negative ion mode）,and the molecular structure of TSTPE was verified.The luminescence properties of TSTPE were studied by fluorescence spectra and UV-Vis absorption spectra.When the concentration of TSTPE was 4.5×10^-5 mol/L,the fluorescence intensity of TSTPE in the ethanol/water（Et OH/H₂O）mixed solution increased as the volume fraction of Et OH（f_e,v%）increased.When f_e=95%,the fluorescence intensity of TSTPE was about 3.8 times higher than that in pure water,which verified that TSTPE exhibited a typical AIE character.（2）Study on the interaction between TSTPE and dodecyltrimethylammonium bromide（DTAB）TSTPE and DTAB combined to form TSTPE-DTAB complex through electrostatic interaction,and TSTPE-DTAB complex aggregated with each other to produce obvious fluorescence emission.Based on this,the quantitative analysis and detection of DTAB in aqueous phase is realized.When the concentration of TSTPE was 4.5×10^-5 mol/L,the concentration of DTAB was in the range of 1.05～1.7×10^-4 mol/L.There was a good linear relationship between the fluorescence intensity F of TSTPE-DTAB mixture system and the concentration c of DTAB,and the detection limit of DTAB was about 5.7×10^-7 mol/L.The fluorescence emission of TSTPE-DTAB mixture system had good stability in the p H range of 3～10,three inorganic salts of Na Cl,KCl and Na NO₃ had little interference with the fluorescence emission of the TSTPE-DTAB mixture system,and the recovery rate of DTAB in simulated water samples was not less than 95%.（3）Study on the interaction between TSTPE and different kinds of cationic surfactantsTwo perspectives:1.The interaction between TSTPE and CS（DTAB,tetradecyltrimethylammonium bromide TTAB and cetyltrimethylammonium bromide CTAB）of different hydrophobic chain lengths and the same hydrophilic head group.TSTPE and CS combined to form complex through electrostatic interaction,and the complexes aggregated with each other to produce obvious fluorescence emission.When the CS/TSTPE molar ratio in the system was the same,the longer the hydrophobic chain of CS(C₁₂,C₁₄ and C₁₆),the greater the fluorescence intensity F of the TSTPE-CS system,and the greater the fluorescence enhancement factor F/F₀.2.The interaction between TSTPE and CS（DTAB,dodecylpyridinium chloride DPC and dodecyldimethylbenzylammonium chloride DDBAC）with different hydrophilic head groups and the same hydrophobic chain length.CS and TSTPE with different hydrophilic head groups combined through electrostatic interaction,and the TSTPE-CS complex formed showed different fluorescence emission.When the CS/TSTPE molar ratio was 4:1,the TSTPE-DDBAC system was a white turbid liquid,and it had obvious blue emission under365 nm excitation,and had the AIE effect;the fluorescence intensity of the TSTPE-DTAB system was increased by about 4.6 compared to the original.The fluorescence intensity of the TSTPE-DPC system was about 0.5 times lower than the original,and it had an Aggregation-caused quenching（ACQ）effect.