Construction And Applications Of Fluorescent Probes Based On Aggregation-induced Emission Of Noble Metal Nanoclusters

Metal nanoclusters(NCs)as a new kind of luminescent material have fascinated scientists for decades owing to their unique molecule-like optical properties and outstanding physicochemical properties.The ultrasmall size,low toxicity,good photostability and large Stokes shift of metal NCs have endowed them with great attentions in various applications.However,the luminescence of NCs,which is their most attractive feature,is still not sufficiently good in the practical applications.Under most circumstances,the luminescence quantum yields from metal NCs are still low when compared to those of quantum dots and organic dyes,posing a major hurdle for the development of their applications.Recently,the aggregation-induced emission(AIE)behavior of NCs opens a door to resolve the above problem due to its abilities of optimizing and adjusting the emission properties of NCs.The origin of NCs emission relates to the capping ligands on the surface of NCs.The aggregation of NCs is capable to restrain the intramolecular vibration and rotation of ligands,thus suppress ligand-related nonradiative relaxation of excited states and enhance the emission of metal NCs.For thiol-containing ligands-stabilized Au NCs and Cu NCs,the AIE property has been found and widely applied in the past years.Nevertheless,little is known about this characteristic of Ag NCs and Au/Ag NCs and their applications in chemo/biosensing.In this paper,the different fluorescent probes were constructed based on the AIE property of Ag NCs and Au/Ag NCs for the detection of biothiols,pyrophosphate and pyrophosphatase.It has certain significance to study and apply the AIE property of noble metal nanoclusters.The main research contents of this thesis include the following two aspects:(1)Preparation and analytical application of ratiometric fluorescent probe based on aggregation-induced emission of silver nanoclusters.In this work,glutathione-stabilized silver nanoclusters and g-C₃N₄ nanosheets were first synthesized.Then,a novel ratiometric fluorescence nanoprobe based on Au³⁺-triggered aggregation-induced emission behavior of silver nanoclusters was designed for the label-free detection of biothiols.We employed Au³⁺as linking bridge.The probe was constructed by loading of Au³⁺on g-C₃N₄ nanosheets surface and subsequently aggregating Ag NCs via ion binding.As Au³⁺could conversely regulate the emission of g-C₃N₄ nanosheets and Ag NCs and has stronger coordination with biothiols,the remove of Au³⁺from nanoprobe by coordination with biothiols would change the emission ratio of nanoprobe that could be used for biothiols detection.The probe provided high sensitivity for glutathione(GSH)determination with the limit of detection as low as 0.8?M and showed satisfying performance in human serum samples.In addition,the probe showed positive responses to thiol-containing molecules,but no response to other thiol-free species,which exhibits that the nanoprobe has excellent selectivity toward thiols.This report may offer a new sight for the construction of ratiometric probe based on the AIE behavior of Ag NCs and broaden its applications in biosensing.(2)Preparation and analytical applications of fluorescent probe based on aggregation-induced emission of gold-silver alloy nanoclusters.Based on the above work,we studied the AIE property of glutathione-stabilized Au/Ag NCs.First,glutathione-stabilized Au/Ag NCs was synthesized by a new synthesis method.Then,the nanoprobe was constructed based on the AIE property of Au/Ag NCs.The reliable and sensitive determination of pyrophosphate(PPi)and pyrophosphatase(PPase)was achieved by zinc ion regulation.Zn²⁺can interact with Au/Ag NCs to adjust the aggregation-induced emission behavior of Au/Ag NCs and there is stronger coordination between Zn²⁺and PPi.When PPi were present in the system,the remove of Zn²⁺from Au/Ag NCs by coordination with PPi would change the emission of Au/Ag NCs that could be used for PPi detection.When Au/Ag NCs,Zn²⁺,PPi and PPase were present in the system,PPase would cause the PPi-Zn²⁺complex to rapidly decompose into free zinc ions and phosphate ions.Then,the free zinc ions interacted with Au/Ag NCs to trigger the aggregation of Au/Ag NCs and the fluorescence emission of Au/Ag NCs was enhanced.According to the relationship between fluorescence intensity and PPase level,the purpose of detecting PPase was achieved.The nanoprobe has high sensitivity and selectivity for PPi and PPase and has satisfactory results in human serum samples.This work may provide a basis for further research on the AIE property of noble metal clusters and expand its applications in bioanalysis.