Study On The Mechanism And Applications Of Responsive Luminescent Hybrid Metal Halides

Responsive materials can undergo structural and property changes under external stimuli,and have important application prospects in the fields of sensing,information storage,and drug delivery.At present,more researches on stimulus-responsive materials are concentrated in the field of organic materials such as conjugated organic molecules,polymers,gels,and inorganic materials represented by nanomaterials.In order to expand existing research,inorganic-organic metal hybrids（IOMHs）materials obtained by combining organic and inorganic materials have shown attractive prospects for the development of responsive materials in new application fields.Among them,IOMHs represented by perovskite are more attractive due to their simple synthesis method,easy purification,low cost,rich functions,and superior performance.However,related research is still in its infancy,and the understanding of the mechanism behind the stimulus response behavior of IOMHs is still limited,and most of the applied research is just a continuation of existing applications.Therefore,the research on the principle and new applications of responsive IOMHs is of great significance.In this thesis,the response behavior of IOMHs caused by the"insertion/extraction"of guest molecules or ionic compounds are studied,combined with the changes in the microstructure characteristics of the material before and after stimulation,the microscopic mechanism of the response behavior is in-depth explored.On this basis,new applications of hybrid metal halides in"information duration adjustable"fluorescent rewritable paper,fluorescent anti-counterfeiting materials with multiple thermal response,and time-resolved information encryption have been developed.In the field of information storage,the research on adjusting the duration of information is still blank.This thesis studies the controllable and selective insertion and extraction of small gas molecules in zero-dimensional IOMHs,and the resulting controllable fluorescence"on-off"rate,and uses this principle to study the rewritable paper with controllable information duration.By orderly changing the volume of the alkyl chain of the cationic part of IOMHs with zero dimensional structures,[TEMA]₂Sb Cl₅（1,TEMA⁺=methyltriethylammonium）,[TEA]₂Sb Cl₅（2,TEA⁺=tetraethylammonium）,[TEBA]₂Sb Cl₅（3,TEBA⁺=benzyltriethylammonium）,[Ph₄P]₂Sb Cl₅（4,Ph4P⁺=tetraphenylphosphonium）were synthesized.The relationship between‘free space’for the movement of atoms inside the compound and the structural parameters including the degree of disorder and bond length,and photoluminscentce performance parameters including Stokes shift and quantum efficiency are established.The"free space"in the compounds explain the selective adsorption and desorption behaviors of small guest gas molecules（H₂O,methanol and ethylene glycol）in the zero-dimensional hybrid metal halide structure.The absorption of the above-mentioned small molecules in the zero-dimensional hybrid metal halide can quench their photoluminscence,and the desorption process can restore the photoluminscence.Using PXRD,thermogravimetric and other characterization methods,the non-destructive structure of the absorption and desorption of small guest molecules in the zero-dimensional IOMHs was determined.Using the controllable photoluminscence"on"and"off"responses,the application of IOMHs in laser-writeable rewritable fluorescent paper was studied by combining the compound with a substrate such as filter paper or PMMA.The effects of the cation of the compound,the material of the substrate,the type of small guest gas molecules,and the laser power on the duration of the information on the rewritable paper were studied.Studies have found that increasing the cation of the compound can increase the difficulty of inserting and detaching small guest molecules into the structure,thereby increasing the duration of information;replacing the substrate material with a hydrophobic material will shorten the duration of information;The small gas molecules will increase the duration of information;the greater the laser power,the longer the duration of information.This thesis also studies the mechanism of a new"on-off-on"fluorescent thermal response mode and its application in information anti-counterfeiting.The reversible insertion and extraction of[Bzmim]Cl as an ionic compound in zero-dimensional IOMHs[Bzmim]₃Sb Cl₆（5,[Bzmim]⁺=1-benzyl-3-methylimidazolium）and[Bzmim]₂Sb Cl₅（6）,and the resulting structural and fluorescence transformations were studied.The extraction of[Bzmim]Cl from 5 is its response to humidity stimulus,and the insertion of[Bzmim]Cl in 6 is its response to heating or drying stimuli.Through the comparison of the microscopic crystal structures of 5 and 6 and the analysis of the weak interaction within the structure,the insertion and extraction sites of[Bzmim]Cl in 5 and6 were determined.The relationship between the"on-off","color transition"and"on-off-on"three thermal response modes of the composite material of[Bzmim]Cl and6 and temperature was studied.In addition,their application in laser-writeable rewritable fluorescent paper have also studied.Finally,this thesis also studies the mechanism and potential applications of zero-dimensional IOMHs in time-resolved information encryption and multiple information encryption.The reversible insertion and extraction of the ionic compound[Bzmim]Cl in 6 and[Bzmim]Sb Cl₄（7）,as well as the transformation of their structure and fluorescence were studied.Unlike the aforementioned[Bzmim]Cl extraction from 5under the stimulation of humidity,the extraction of[Bzmim]Cl from 6 needs to be completed in ethanol liquid,which was verified by PXRD.The influence of the concentration of[Bzmim]Cl at room temperature and the openness of the system on the rate of its insertion into 7 to produce 6 was studied.Using the controllable reaction rate and the resulting controllable fluorescence display,the time-resolved information encryption process based on the reaction rate is studied.Combining the control of the concentration of[Bzmim]Cl on the composition of the final product,and the"color transition"produced by the thermal response of the composite of[Bzmim]Cl and 6,the process of multiple information encryption based on IOMHs was studied.