| Cucurbit[n]uril（also known as Q[n]or CB[n]）,also known as"pumpkin-shaped"macrocyclic molecules,is an important research subject in the field of supramolecular chemistry.Its name is derived from its resemblance to a pumpkin or a gourd.The structure of cucurbituril consists of glycouril units linked by methylene bridges to form a cyclic structure.The rigid structure and high symmetry of cucurbituril give it a unique cavity structure and selective molecular encapsulation capabilities.Cucurbituril can be utilized in various fields,primarily based on its molecular recognition and encapsulation properties.It can accommodate molecules of different sizes and shapes,making it widely used in drug delivery,purification,catalysis,molecular sensing,biological imaging,and material science.In chemical sensing,cucurbituril can be used to encapsulate fluorescent probe molecules for detecting target substances.Its molecular recognition properties can stabilize the complex between the fluorescent probe molecule and the target substance,resulting in changes in fluorescence signals,thereby achieving high sensitivity and selectivity in target substance detection.In biological imaging,cucurbituril has good biocompatibility and fluorescence imaging properties,and can be used for biological imaging and molecular imaging.It can act as a fluorescent probe molecule to specifically target molecules for imaging in the body.In this thesis,several cucurbiturils with different cavity sizes are selected to interact with guest molecules to construct fluorescent assemblies.The basic properties of the assemblies were studied.For the fluorescent assemblies constructed by cucurbituril-guest molecule interactions,their applications in material detection and biological imaging were investigated.The specific research methods and contents are as follows.Firstly,the encapsulation of palmatine（PAL）by a cucurbit[7]uril（Q[7]）as the host molecule and palmatine（PAL）as the guest molecule was investigated using a variety of modern analytical tools.Findings show that PAL can be contained in the cavity of Q[7]to form a 1:1 host-guest inclusion complex,and that this inclusion complex exhibits moderate fluorescence intensity in aqueous solution.Interestingly,a sharp decrease in fluorescence intensity of the inclusion complex was observed upon addition of the pesticide paraquat,in contrast to other insecticides,none of which caused any fluorescence change.Therefore,we have developed a fluorescent assembly based on Q[7]and PAL constructs capable of specific single identification of paraquat with a detection limit of 2.90×10-6mol/L.Secondly,the encapsulation of palmatine（PAL）by a cucurbit[8]uril（Q[8]）as the host molecule and palmatine（PAL）as the guest molecule was investigated using a variety of modern analytical tools.The experimental results show that PAL can be contained in the cavity of Q[8]to form a 1:2 host-guest inclusion complex,which exhibits moderate fluorescence in aqueous solution,and interestingly,a sharp increase in the fluorescence intensity of the inclusion complex is observed upon addition of phenylalanine.The addition of other amino acids did not cause any change in fluorescence.Therefore,we have developed a fluorescent assembly based on Q[8]and PAL constructs capable of recognising phenylalanine with a detection limit of 2.33×10-6mol/L.Thirdly,the encapsulation of 1,2-bis（4-pyridyl）ethylene（BPE）by a cucurbit[8]uril（Q[8]）as the host molecule and 1,2-bis（4-pyridyl）ethylene（BPE）as the guest molecule was investigated using a variety of modern analytical tools.The experimental results show that BPE can be contained in the cavity of Q[8]in either the solid or liquid state to form a 1:2 host-guest inclusion complex.This inclusion complex did not exhibit fluorescence in aqueous solution.Interestingly,a dramatic increase in the fluorescence intensity of the inclusion complex was observed upon addition of the pesticide pymetrozine.In contrast,the addition of any other insecticide did not cause any change in fluorescence.Therefore,we developed a fluorescent assembly based on the constructs of Q[8]and BPE which was able to recognize pymetrozine with a detection limit of3.69×10-6mol/L.Fourthly,the encapsulation of styryl derivatives（SPy）by a cucurbit[8]uril（Q[8]）as the host molecule and a styryl derivative（SPy）as the guest molecule was selected and investigated using a variety of modern analytical tools.The experimental results show that the main SPy can be contained in the cavity of Q[8]to form a 2:2 main-guest inclusion complex,which does not exhibit fluorescence in aqueous solution,and interestingly,a dramatic increase in the fluorescence intensity of the inclusion complex was observed upon addition of the pesticide difenzoquat.In contrast,the addition of other pesticides did not cause any change in fluorescence.Therefore,we developed a fluorescent assembly based on Q[8]and SPy constructs that was able to identify the pesticide difenzoquat with a detection limit of 2.27×10-7mol/L.Fifthly,the encapsulation of the styryl derivative（p-DSPBCH）by the cucurbit[8]uril（Q[8]）as the host molecule and the styryl derivative（p-DSPBCH）as the guest molecule was investigated using a variety of modern analytical tools.The experimental results show that p-DSPBCH can be contained in the cavity of Q[8]to form a 2:2 host-guest inclusion complex.This inclusion complex showed moderate intensity fluorescence.Interestingly,a sharp burst of fluorescence intensity of the inclusion complex was observed after the addition of the pesticide dodine.In contrast,the addition of none of the other insecticides caused any fluorescence changes.Therefore,we developed a fluorescent assembly based on the constructs of Q[8]and p-DSPBCH that was able to recognize the pesticide dodine with a detection limit of 2.56×10-6mol/L.Sixthly,cucurbit[8]uril（Q[8]）was chosen as the host molecule and a styrene derivative（p-DSPBA）was chosen as the guest molecule.Various modern analytical techniques were used to investigate the interaction mode between the host and guest molecules.A fluorescence assembly system was constructed to detect Fe3+and applied to cellular imaging.The inclusion complex exhibited a significant fluorescence intensity boost upon the introduction of Fe3+,while the addition of the other 19 metal ions to the assembly solution did not cause any notable changes in fluorescence.Therefore,we have developed a fluorescence assembly based on Q[8]and p-DSPBA.Through the analysis and research of this assembly system,we found that the assembly system has good selectivity and sensitivity for Fe3+metal ions,and can effectively identify and detect Fe3+in cells,with a detection limit of 3.45×10-6mol/L.This provides a possibility for the detection of metal ions in cells. |
