Synthesis Of Novel Aggregation-Induced-Emission Molecules And Their Application In Chemo-Sensor And Bioassay

The fluorescence-based techniques are extensively used methods for chemical analyses and bioassay,because they offer the advantages of high sensitivity,low background noises and wide dynamic ranges.However,for common fluorescence(FL) probes,some defects cut down their application range.For example,some of them show small Stokes shifts and nonlinear calibration curves with the change of concentration.Moreover,almost all of the available FL probes suffer the disadvantage of aggregation-induced FL quench,which is a thorny problem and limits the effective ranges of their application.Aggregation-induced emission(AIE),a unique photophysical phenomenon observed for some novel FL chromophores offers a new methodology to solve the above-mentioned problems.Firstly,the molecules with AIE effect avoid aggregation induced FL quenching in solid states.Secondly,the FL spectra of mostly AIE molecules do not shift as the concentration increases.Finally,FL techniques by using AIE molecules as probes are more effective because they apply a turn on mechanism.Therefore,to synthesize novel AIE molecules and explore them in the fields of chemo-sensors and bioassays are of great scientific significances and promising technical applications.Firstly,we forwarded a new method to detect the critical micelle concentration (CMC)of surfactants by using AIE molecules as FL probes.Based on HPS and A₂HPS,two AIE active molecules,the CMCs of cationic surfactants,anionic surfactants,an amphiphilic bio-molecule and an amphiphilic block copolymer were determined.The results are in good consistence with the data reported in literature, which confirmed the validity and the generality of the new method.Secondly,we introduced the protonated AIE-active molecules,([H₂A₂HPS]²⁺)as FL probes into the self-assembling process of polycations(PDDAC)and polyanions (PSS).It has been found that the[H₂A₂HPS]²⁺species can uniformly deposit in the PDDAC/PSS double layers,and the relationship between the FL intensity of the assembled films and the number of the double layers keeps in good linearity. Moreover,such kind of linearity has been recorded not only on the quartz but also on the ordinary glass substrates,which indicated that,taking the advantages of AIE characteristics,the FL technique can be extended to the monitoring of layer-by-layer self-assembling process on versatile substrates.Thirdly,the pyridinyl-functionalized TPE derivative(M2)was synthesized and it was found that M2 is highly sensitive to H⁺,Fe³⁺,Cr³⁺,and Al²⁺cations(in concentration of～10^-5mol/L),even in the co-existence of large amount(in concentration of～0.01 mol/L)of Zn²⁺,Ni²⁺,Cu²⁺,Cd²⁺,Pb²⁺,Ca²⁺,Mg²⁺,Co²⁺ cations.The responses of M2 to H⁺,Fe³⁺,Cr³⁺,and Al³⁺cations are characterized by the dramatically changed emission colors from green to red,the prominently batho-shifted absorption maximum and the large Stokes shift.A comparative research suggested that the fundamental mechanism of the FL sensitivity of M2 to Fe³⁺,Cr³⁺, and Al³⁺cations is associated with the interactions between the pyridinyl functionalities on M2 and naked H⁺.Finally,a tetraphenylethylene(TPE)derivative with cationic pyridinyl functionalities(M3)was designed and synthesized.The cationic pyridinyl functionalities rendered M3 with water solubility and it was used for the detection of ct DNA.The linear range of M3 is 0μg/mL-50μg/mL for ct DNA and the K_sv constant is as high as 1.4×10².