Construction And Applications Of Multiple Stimuli-Responsive Fluorescent And Carbon Dots-Based Persistent Room Temperature Phosphorescent Materials

Stress response behavior,the basis of various complex life activities,is ubiquitous in nature.Inspired by this,scientists have designed and synthesized a variety of stimuli（force,light,electricity,temperature,polarity,viscosity,molecular/ion）responsive"intelligent"organic fluorescence/phosphorescent molecules to meet the needs of chemical sensing,optoelectronics,advanced anti-counterfeiting encryption,biological imaging and many other high-tech fields.However,for a long time,organic luminescent molecules have been faced with many problems,such as aggregation-caused quenching（ACQ）,difficult generation and instability of triplet excitons,and only single mode luminescence.Moreover,most of the reported luminescent materials so far only respond to a single stimuli,which is hard to meet the needs of diversified applications.However,the construction of multiple stimuli-responsive luminescent materials is a considerable challenge.In this thesis,several novel luminescent molecules with excellent performance were designed and synthesized,their luminescence mechanism and potential applications in chemical sensing and advanced anti-counterfeiting encryption were investigated.The specific research contents are as follows:（1）A class of D-A type cyanostilbene derivative BP-1 and BP-2 were designed and synthesized.They not only showed obvious solvatochromic and aggregation-induced emission（AIE）properties.Moreover,the presence of multiple phenyl rotors and twisted intramolecular charge transfer（TICT）effect endowed it with sensitive viscosity response behavior,which could be utilized as a potential viscosity probe.On this basis,it successfully realized the quantitative monitoring of total polar materials（TPM）in frying oil.Their crystals exhibited multiple mechanofluorochromic（MFC）,which was suitable for recognition of alien force stimuli（smash,ground,compress）.The relationship between molecular conformation,stacking pattern and fluorescent behavior was established at molecular level by DSC,PXRD and SC-XRD.（2）A multi-stimuli responsive fluorescent probe TPI were designed and constructed.The stronger TICT effect gave it good polarity sensing performance,and further used for the quantitative detection of trace water in various commodities.Moreover,in a wide range of temperature,its solution state had good linearity,reversibility,visual and“turn on”fluorescence response to temperature.What was more,the primary amine group enabled it with high sensitive to acid gases with a limit of detection as low as ppb levels.The unique response mechanism originated from the change of molecular stacking pattern induced by electrostatic force.For ease of use,a simple paper sensor was developed for rapid and quantitative determination of acid gases.（3）A simple strategy for the in-situ preparation of excitation-and time-dependent multicolor CDs-based persistent RTP materials based on the melt reaction of boric acid（BA）with various organic precursors was proposed.Among them,7HOCA_0.01%/BA achieved both high photoluminescence quantum yield（66.13%）and long phosphorescence lifetime（1.74 s）,and the afterglow lasted more than 26 s.The unique phosphorescent properties were attributed to the fact that the multi-confinement effects efficiently inhibited non-radiative deactivation of the triplet excitons.Moreover,the structure of the precursor can effectively and precisely control the phosphorescence properties of the composites.In a word,the reasonable combination of precursors and BA was considerable flexibility,which would greatly promot the design and preparation of highly efficient,economical and color tunable matel-free RTP materials.