Establishment Of The Novel Optical Sensing Systems And Their Applications In Metal Ions And Enzyme-linked Immunoassay

As a simple and powerful analytical tool,optical sensing can be combined with specific recognized units for the capture of target molecules,and has been widely used in the assays of metal ions,biological small molecules,enzyme activity,and disease markers.Meanwhile,the rapid development of booming micro and nano materials also bring new opportunity for the construction of optical sensing analysis.This dissertation focuses on the establishment of new optical sensing systems,the preparation of high-performance and multi-functional all-inorganic halide perovskite and the study for their applications,in order to obtain a fast,accurate and flexible response system.The main achievement obtained are as follows:1.The new ratiometric fluorescent sensor constructed via copper ion catalysis:The specific internal reference and ratio signal of the ratio fluorescence sensor can be used to accurately determine the trace amount of the target substance.Integrating two kinds of fluorescent probes in one system to develop a ratiometric sensing platform is of prime importance for achieving an accurate assay.Inspired by the efficient overlapped spectrum of 2-aminoterephthalic acid(PTA-NH2)and 2,3-diaminophenazine(DAP),a new sensitive ratiometric fluorescent sensor has been developed for the determination of Cu2+on the basis of in situ converting o-phenylenediamine(OPD)into DAP through the catalysis of Cu2+.Here,the presence of Cu2+induced the emission of DAP,which acted as an energy acceptor to inhibit the emission of PTA-NH2.This dual-emission reverse change ratiometric profile based on the inner-filter effect improved sensitivity and accuracy,and the highly sensitive determination of Cu2+ with a detection limit of 1.7 nmol·L-1 was obtained.Moreover,based on the specific interaction between GSH and Cu2+,this ratiometric fluorescent sensor showed high response toward GSH owing to the inhibition of GSH.The proposed sensing strategy eliminated the tedious synthesizing process of new fluorescent nanomaterials,and the introduction of enzymes,with holding great potential for facile assays.2.New fluorescence system in situ induced by ascorbic acid for enzyme-linked immunosensor:A highly fluorescent emission reaction between terephthalic acid(PTA)and ascorbic acid(AA)via simple control of the reaction temperature was first revealed with the detailed formation mechanism and various characterizations including electron paramagnetic resonance and mass spectrometry.electron paramagnetic resonance and mass spectrometry.Based on the AA-responsive emission,the alkaline phosphatase(ALP)triggered the transformation of L-ascorbic acid 2-phosphate trisodium salt to AA was integrated with the present system for developing a sensitive,selective,and universal platform.The monitoring of the activity of ALP and the fabrication of ALP-based enzyme-linked immunoassay(ELISA)with carcinoembryonic antigen(CEA)as the model target was performed.Such a facile protocol based on the fluorescent reaction between PTA and AA without the assistance of catalysis of nanomaterials avoided the laborious synthesis procedure and provided a direct strategy for the early clinical diagnosis coupled with ALP-related catalysis.3.Chemiluminescence(CL)of CsPbBr3 nanocrystals at the hexane/water two-phase interface:All-inorganic halide perovskite CsPbBr3 nanocrystals(NCs)have attracted more attention in recent years due to the unique optical feature.To date,most of the research was mainly focused on the photoluminescence(PL)and electrochemiluminescence(ECL)of the perovskite NCs.The strong CL emission of CsPbBr3 NCs was observed for the first time on the hexane/water interface with the assistance of ammonium persulfate-(NH4)2S2O8 as coreactant.Different coreactants were investigated to demonstrate the efect on the CL behavior and it was found that CL intensity achieved the maximum in the presence of(NH4)2S2O8.The CL spectrum of CsPbBr3 NCs was also collected and was consistent with their PL and ECL spectra,indicating that CsPbBr3 NCs played a role of luminophor during the CL process.The discovery of monochromatic CL of highly crystallized CsPbBr3 NCs not only extends the applications of halide perovskite materials in the analytical field but also provides a new route for the exploration of the physical chemistry properties.4.High-stable CsPbBr3 NCs@PAN nanofibers for the design of fluorescent switch:CsPbBr3 NCs@PAN nanofiber membranes with strong fluorescence,narrow half-peak width(FWHM=24 nm),high photoluminescence quantum yield(PLQY?48%)and high stability in the presence of water and oxygen were synthesized in situ by one-step electrospinning.After soaking in water for 120 hours,the fluorescence intensity of the nanofiber membrane decreased only 5%.After stored in water for 30 days,its PLQY remained at about 42%.The electrochemical controlled fluorescent switch CsPbBr3 NCs@PAN was successfully constructed in water using water-stabilized CsPbBr3 NCs@PAN nanofiber membrane and electrochromic ruthenium violet(RP)material.This kind of lead halide perovskite fluorescent switch has good fatigue resistance,which provides a new direction for the design of electric stimulation response fluorescent switch,especially with pure color and diversified switch.