Design And Synthesis Of Non-planar Fluorescence Sensing Units And Their Applications In VOC Sensing

Analysis and monitoring of volatile organic compounds(VOCs)are of great significance in disease diagnosis,precision agriculture,environmental pollution,drug diagnosis,food safety,and other fields.VOC sensing technology enables the detection and monitoring of VOC levels in the surrounding environment to protect human health and the environment,as well as ensure the safety of product production processes and product quality.Recently,sensor technology based on VOC detection has developed rapidly,including gas chromatography(GC),mass spec-trometry(MS),electrochemical sensors,and photochemical sensors.Among them,thin-film flu-orescence sensors have the advantages of high sensitivity,high specificity,visualization,and rich output signals,making them powerful tools for detecting and measuring various substances.Common fluorescent probes,such as perylene imide(PBI),triphenylamine-based metal cage,and their respective derivatives,usually exhibit strong aggregation in concentrated solutions or solids leading to quenching(ACQ)and photobleaching effects,resulting in low luminous effi-ciency or even fluorescence quenching and poor photochemical stability.Therefore,designing and synthesizing fluorescent compounds that can exhibit excellent luminescence in both solu-tion and solid state is still a huge challenge.In addition,non-planar fluorescence sensing units offer several advantages over planar systems,such as lower sensitivity to solvent polarity,higher photostability,and better spectral characteristics.These advantages make it ideal for a variety of applications,including environmental monitoring,medical diagnostics,and drug discovery.This paper introduces fluorescent small molecules through molecular design to obtain organic molecular channel materials with excellent fluorescence performance and applies these materi-als to the fields of optical limiting and sensing.The specific research contents are as follows:In the first part of the thesis,a metal cage was successfully synthesized by synergistic self-assembly of triphenylamine ligand,90°Pt,and 1,4-benzenedicarboxylic acid ligand.The com-position and structure of the metal cage were verified by characterization methods such as ~1H NMR and UV-vis absorption spectroscopy.Photophysical property studies showed that the metal cage had an absorption center wavelength of 440 nm.Compared with the triphenylamine ligand,the metal cage showed obvious red-shifted luminescence with a central wavelength of600 nm,which could increase penetration depth.This phenomenon can be attributed to the co-ordination of Pt(II)metal nodes with pyridine nitrogen,which prevented the photoinduced elec-tron transfer(PET)process from pyridine to fluorescent groups.Moreover,the formation of Pt-N also weakened the intramolecular charge transfer(ICT)effect inside the triphenylamine lig-and,resulting in a significantly weaker solvatochromic effect of the metal cage than that of the constituent ligand.When applied to diethyl chlorophosphate(DCP)sensing,metal cages show great DCP sensing potential due to their high surface area and selective adsorption capacity.With further research and development,these materials may lead to more reliable and sensitive DCP sensing technologies.In addition,the decrease in transmittance of the metal cage was lin-early related to the square of laser intensity,making it promising for future device construction.In the second part of the thesis,a perylene bisimide derivative modified with long-chain alkanes was designed and prepared to improve the solubility of perylene bisimide derivatives.The photophysical properties of perylene bisimide derivatives were characterized by UV-visible absorption and fluorescence emission spectroscopy.It was found that when the concentration of perylene bisimide derivatives decreased,the typical absorption peak would shift toward the short-wave direction.Moreover,as the concentration decreased,the intensity ratio between two typical emission peaks would change,indicating that the aggregation state had changed.Subse-quent studies plan to apply this perylene bisimide derivative to detect aniline vapor.