A Ratiometric Fluorescence Analysis Method Based On Lead Halide Perovskite Nanocrystals

Lead halide perovskite nanocrystals have attracted extensive attention because of their excellent optical properties such as high fluorescence quantum yield,narrow emission spectrum and tunable emission spectrum.Based on the properties of lead halide perovskite nanocrystals,some fluorescence methods have been established and successfully used in the detection of ions,gases,organics.These fluorescence methods use the fluorescence intensity of a single emission wavelength to perform quantitative analysis,which is known to be susceptible to the detection environment.The ratiometric fluorescent probe can be self-calibrated via two or more transmitted signals,which reduces the influence of the detection environment and the concentration of the fluorescent probe on the detection results and improves the accuracy of detection.In order to establish an accurate and sensitive fluorescence method for sulfide ions and acetylcholinesterase.In this thesis,tetraphenylporphyrin tetrasulfonic acid and lead halide perovskite nanocrystals were used to construct a double-emission ratiometric fluorescent probe by self-assembly strategy.The ratiometric fluorescent probe can be applied in the detection of sulfide ions and acetylcholinesterase.The detailed contents are as follows:Part one.Ratiometric fluorometric method detection of sulfide ions based on its quenching effect on tetraphenylporphyrin tetrasulfonic acid modified perovskite nanocrystalsIn this thesis,a ratiometric fluorescence method for the determination of sulfide ions is reported.CsPbBr3/TPPS nanocomposites were synthesized through a self-assembly strategy.The nanocomposites have dual emission wavelengths centering at 520 nm and 650 nm,respectively,under single excitation wavelength at 365 nm.It is found that sulfide ions can quench the green fluorescence at 520 nm,but have no such effect on the red fluorescence at 650 nm.Therefore,TPPS as a reference fluorescent probe and CsPbBr3 NCs as a sulfide-responsive fluorescent probe.The nanoprobe has the characteristics of fast response time and high sensitivity to sulfide ions detection.The decrease amplitude of the relative fluorescence intensities（ΔF520/650）is linearly dependent on the concentration of sulfide ions in the range of 0.2-15.0 nmol·L-1 with a detection limit of 0.05 nmol·L-1.The relative standard deviation was 3.3%at 10.0 nmol·L-1 sulfide ions concentration level（n=11）.This method has been successfully applied to the detection of sulfide ions content in water samples.Part two.Ratiometric fluorometric method detection of acetylcholinesterase based on its quenching effect on tetraphenylporphyrin tetrasulfonic acid modified perovskite nanocrystalsAcetylcholinesterase（AChE）is a hydrolytic enzyme that catalyzes the hydrolysis of the neurotransmitter acetylcholine.It plays a crucial role in maintaining the normal function of the cholinergic nerve.Therefore,it is of great significance to establish a simple,fast and sensitive AChE analysis method.It is found that when AChE and CsPbBr3/TPPS nanocomposites were present in the system,AChE reduces the fluorescence signal of CsPbBr3 NCs at 520 nm,but has no significant effect on the fluorescence signal of TPPS at 650 nm.As the concentration of AChE increases,the fluorescence intensity of CsPbBr3 NCs in the system gradually decreases.Based on this,a ratiometric fluorescence method was constructed for AChE.Compared with other analytical methods,this method dispense with the application of zymolytes.It simplifies the experimental process and improves the detection efficiency.The nanometer probe was used to quantitatively detect AChE in the range of 0.01-1.0 mU·mL-1.The detection limit is 0.0042 mU·mL-1.Successive determination of 0.2 mU·mL-1 AChE gave the relative standard deviation of 3.6%（n=11）.This method was first applied to the determination of AChE in serum,and it will certainly provide a certain reference value for future medical diagnosis and research.In summary,a ratiometric fluorometric methods was constructed for the determination of sulfide ions and acetylcholinesterase.The method has the advantages of simple operation,short reaction time and high sensitivity.It has been successfully applied to the determination of sulfide ion in water samples and acetylcholinesterase in serum.