Self-Assembly Regulation Of Copper Nanoclusters In Polar Mixed Solvents

Supramolecular chemistry is the study of the formation of molecular aggregates by non-covalent interactions between molecules.Supramolecular self-assembly is an assembly method based on non-covalent bonding to construct complex ordered aggregates with specific functions.In recent years,metal nanoclusters have become a hot topic in the field of nanomaterials.Metal nanoclusters have rich composition and various molecular structures,and their sizes are generally less than 2 nm.They are characterized by long life span,large Stokes shift and good biocompatibility,and can be used in biomedicine,electrochemistry and other fields.Among all luminous metals,copper-based nanomaterials have attracted wide attention due to their abundant earth resources and relatively low cost.However,since copper is prone to surface oxidation when exposed to air,most methods of preparing copper nanoclusters usually form unstable or large copper particles,and it is difficult to directly obtain stable and luminous copper nanoclusters.Moreover,compared with current organic phosphors and semiconductor nanocrystals,the emission intensity of copper clusters is lower and the quantum yield rarely exceeds 0.1%.In recent years,aggregation-induced emmision(AIE)proposed by Tang Benzhong’s group has been found to significantly improve the luminescence intensity and quantum yield of metal nanoclusters.For example,AIE can be realized by adjusting the ratio of good solvent to bad solvent,metal doping and other methods to make copper cluster self-assembly.At present,it is still a challenge to fabricate unstable copper nanoclusters into uniform copper nanoclusters with good stability,controllability and high luminosity.The preparation of copper nanoclusters by hydrophilic or hydrophobic stable preparation is a common method to prepare stable copper nanoclusters.Among them,hydrophilic copper nanoclusters have the advantages of ultra-small size,non-toxic,strong light stability,good biocompatibility and potential anticancer activity.However,their imprecise structures hinder the directional tracking in cells or organisms.However,the structure and composition of hydrophobic copper nanoclusters are more accurate,because his hydrophobic nanoclusters are unlikely to be directly applied to water.In conclusion,the successful dispersion of hydrophobic copper nanoclusters into aqueous mixed solvents and the realization of AIE behavior has great application value and important academic research significance.Based on this,the main content of this paper is divided into the following four parts:The first part is introduction.The concept and force of supramolecular selfassembly are introduced,with emphasis on solvent-phobic interaction and π-π stacking.The concept of metal nanoclusters and the self-assembly behavior of metal nanoclusters are introduced,and the properties and assembly behavior of hydrophilic copper nanoclusters and hydrophobic copper nanoclusters are emphasized.The concept of aggregation-induced emission and the research progress of aggregation-induced emission of metal clusters were summarized.The present technical means of dispersing hydrophobic substances are introduced.Finally,the research content and significance of this thesis are presented.In the second part,self-assembly of copper nanoclusters regulated by surfactants is studied.In this work,we first synthesized atomically precise triphenylphosphine terminated(PPh3)copper nanoclusters(Cu4I4).We then used a solvent engineering strategy to induce self-assembly of Cu4I4 into hexagonal slices,thus achieving aggregate induced emission(AIE)with an absolute quantum yield of up to 22.6%.In addition,we performed structural characterization and optical analysis,revealing that the high density of the assembly enhances the copper-philic interaction and inhibits the intramolecular vibration and rotation of the Cu4I4 ligand,protecting the copper core from the quenching of singlet oxygen.By using the solubilization of surfactant,the hydrophobic Cu4I4 was successfully dispersed into aqueous solution,and its stability was greatly improved,which provided the basis for the complete properties of hydrophobic copper clusters.In addition,the dispersion can be used for Fe3+ sensing.The results show that the dispersion has good recognition ability and high selectivity for Fe3+.The third part is the study of polyoxomethylene dispersed stable hydrophobic copper nanoclusters.In this work,the atomically precise Cu4I4(ligand triphenylphosphine(PPh3))was successfully introduced into water to form a stable dispersion with the help of polyoxometallic acid(EuW10)in the presence of a co-solvent(dimethyl sulfoxide,DMSO).This strategy enables the dispersion to achieve aggregate induced luminescence(AIE),and its absolute quantum yield is as high as 19.34%.It also greatly improves the stability of hydrophobic Cu4I4 in water system.One of the reasons is that Cu4I4 clusters are highly compact due to the Cu4I4 clusters’ Cu4I4 interaction,which inhibits the intramolecular vibration and rotation of Cu4I4 ligands,resulting in the AIE phenomenon.Another reason is that the hydrophobic interaction between EuW10 and the peripheral ligand of Cu4I4 and the solvation of EuW10 with the mixed solvent make Cu4I4 disperse stably in the mixed system.In addition,Cu4I4/EuW10 stabilized dispersions can be used for Fe3+ sensing.The results show that the dispersion has good recognition ability and high selectivity for Fe3+.Our strategy of combining polyoxomethoxylate with hydrophobic Cu4I4 to construct AIE systems in mixed solvents is expected to provide new insights into the development of bioprobes,bioimaging,catalysis and sensitive sensors for environmental applications such as metal ion detection.In the fourth part,the self-assembly behavior of hydrophilic/hydrophobic nanoclusters in mixed solvents is studied.In this work,a chiral hydrophilic copper nanocluster Cu5-NCs has been synthesized.The results show that the mixing of hydrophilic copper nanoclusters with hydrophobic copper nanoclusters not only greatly improves the stability of Cu4I4 in aqueous solution,but also makes Cu4I4 self-assembly behavior,and greatly improves the luminescence intensity,and the fluorescence color can change obviously with the change of the addition amount of Cu5-NCs and Cu4I4.With the addition of Cu5-NCs,the assembly of hydrophilic/hydrophobic copper clusters gradually showed good chiral signals.The idea of a new type of dispersed hydrophobic copper cluster is provided,and a kind of color-adjustable,stable and chiral assembly solution is obtained.