Wavelength-shift Based Fluorescence Sensing Of CsPbBr₃ Perovskite Nanocrystals

Compared with the traditional sensing methods,fluorescence sensing has attracted much attention because of its high sensitivity,high cost performance,and intuitive detection effect.In recent years,fluorescence visualization has gradually developed from the change of fluorescence intensity to the change of fluorescence hue,and the latter is more visible and easier to recognize by human eyes.The change of fluorescence hue is mainly realized by constructing ratio quantum dots or using wavelength shift.In this dissertation,we will use all inorganic lead halide perovskite nanocrystals(CsPbX3 NCs,X=I,Br,Cl)to construct wavelength-shift-based fluorescence sensing system.CsPbX3 NCs have excellent properties such as high quantum yield,narrow half peak width and ion exchange.They are not only widely used in solar panels,light-emitting diodes,photodetectors,lasers and other photoelectric fields,but also have excellent application prospects in the field of sensing.By adjusting the proportion of halogen ions in the structure,the fluorescence spectrum of CsPbX3 NCs can be adjusted,which will cover the whole visible spectrum region and produce a significant fluorescence change from blue to red.The above phenomenon is very beneficial for the establishment of wavelength-shift-based fluorescence sensing.The fluorescence visual sensing based on wavelength shift can achieve obvious change of fluorescence hue without any additional materials.Because of high visual sensitivity,obvious color gradient change,strong anti-interference,these methods can provide convenient determination approaches on site.Based on the ion exchange characteristics(halogen exchange)of CsPbX3 NCs,wavelength-shift-based fluorescence sensing approaches with high visual sensitivity have been constructed and applied to the rapid determination of substances.This dissertation is divided into five chapters:Chapter Ⅰ,in this introduction chapter,we briefly introduce the structure and characteristics of all inorganic lead halide perovskite nanocrystals.Meanwhile,the applications of CsPbX3 NCs in detection,light,temperature,humidity,anticounterfeiting and other fluorescence sensing fields are listed.Secondly,this chapter summarizes the reported fluorescence visual sensing methods,and lists the application examples of fluorescence intensity change and fluorescence hue change.Finally,based on the above research background,combining CsPbX3 NCs with fluorescence visual sensing,the study fields considered and focused to structure wavelength-shift-based fluorescence sensing approaches using CsPbX3 NCs.Chapter Ⅱ,wavelength-shift-based fluorescence sensing for peroxide number of edible oil using CsPbBr3 perovskite nanocrystals.In this chapter,based on the halogen exchange characteristics of CsPbX3 NCs and the redox reaction of 9-octadecylamine iodide with peroxides in edible oil,a wavelength-shift-based fluorescence sensing method using CsPbX3 NCs was developed.This research realizes the rapid visual detection of peroxide number in edible oil samples.The fluorescence sensing method has two processes:redox and halogen exchange.It has a good linear correlation in the range of peroxide value from 0 g/100g to 0.6 g/100g,and the detection limit is 0.139 mg/100g.Meanwhile,this method overcomes the shortcomings of the traditional determination method of peroxide number,such as complex analysis process,poor reproducibility,unable to carry out on-site rapid detection and so on.The detection process only takes 15 minutes,with high visual sensitivity,obvious color gradient change,small interference,no additional materials as luminescent reference materials,convenient and accurate.This study laid a foundation for the development of wavelength-shift-based fluorescence sensing using CsPbBr3 NCs.Chapter Ⅲ,wavelength-shift-based fluorescence sensing for peroxide number of powdered milk using CsPbBr3 perovskite nanocrystals.In this chapter,the application of CsPbBr3 NCs fluorescence sensing method extends from the determination of peroxide number of liquid substances to that of solid powder substances.Through the optimization and integration of powdered milk fat extraction,redox reaction and halogen exchange,a fluorescence sensing method was established to determine the peroxide number of powdered milk samples.The process of powder milk fat extraction integrates with the redox process,which greatly shortened the determination time.This fluorescence method has a good linear correlation in the range of peroxide value from Ommol/kg to 1.956 mmol/kg,and the detection limit is 0.0556 μ mol/kg.This study further deepens the application prospect of wavelength-shift-based fluorescence sensing using CsPbBr3 NCs.Chapter Ⅳ,wavelength-shift-based fluorescence sensing for oxide content in aqueous solution using CsPbBr3 perovskite nanocrystals.In this chapter,the fluorescence sensing method of CsPbBr3 NCs initially extended from the detection of organic phase materials in the previous two chapters to the determintion of aqueous phase materials.The halogen exchange reaction between iodine ion in aqueous phase and CsPbBr3 NCs in organic phase was used to detect the substance in aqueous phase。In this experiment,the effects of halogen exchange reaction between two kinds of water-soluble iodine containing materials and CsPbBr3 NCs on the two-phase interface were compared,which preliminarily confirmed the availability of CsPbBr3 NCs fluorescence sensor for oxides in aqueous.This study expands the application scope of wavelength-shift-based fluorescence sensing using CsPbBr3 NCs.Chapter Ⅴ,summary and outlook.In this dissertation,we successfully used CsPbBr3 perovskite nanocrystals to construct several fluorescence wavelength-shiftbased sensing approaches,and applied them to the rapid determination of different substances.The research results further promote the development of all inorganic lead halide perovskite nanocrystals in the field of analytical sensing,and develop a research strategy based on wavelength shift for high visual sensitivity fluorescence sensing methods.At the same time,with the development of mobile terminal technology,the research work in this dissertation expects to combine with smart phone.An efficient,convenient and intelligent online detection platform can develop,which fully meet the needs of environmental monitoring,food safety and other rapid determination fields.