Study On Supramolecular Assembly And Properties Of Silver Nanoclusters Induced By Biomolecules

Supramolecular self-assembly is to build different functional supramolecular materials from bottom to up by using the non-covalent interactions between building elements.It refers to the ordered supramolecular materials obtained by precise control of the non-covalent interactions between molecules.The properties of this material are superior to the sum of building elements,and show some new properties that building elements do not have.Metal nanoclusters(NCs)is a kind of organic-inorganic hybrid material,which is composed of several to hundreds of metal atoms and whose surface is modified by organic ligands.Because of their like-molecular characteristics,they have excellent properties in optical,electrical and magnetic fields.However,the metal NCs in aqueous solution have poor stability and weak fluorescence,which greatly limit their applications.Based on the supramolecular self-assembly strategy and the Aggregation-Induced Emission(AIE)proposed by academician Benzhong Tang in 2001,it can not only improve the stability of metal NCs,but also significantly improve its fluorescence performance,and also promote the cooperation between various functions to achieve multi-field applications.As regulators of important physiological activities in organisms,biological small molecules have been widely studied by researchers in recent years,and have been widely used in biological imaging,tumor therapy,catalysis and sensing etc fields.In addition,using biological small molecules as building blocks of supramolecular materials can obtain some attractive new characteristics.To sum up,multi-component self-assembly between silver clusters and biological small molecules has great application value and important academic research significance.The main contents of this paper are divided into the following four parts:Part Ⅰ,study on hydrophilic peptide induce the supramolecular assembly of Ag9NCs.The supramolecular co-assembly of hydrophilic peptide DD-5 and Ag9-NCs originates from the interactiongs of H-bond,π-π stacking and argentophilic.The chirality of DD-5 was successfully transferred to supramolecular aggregates to obtain supramolecular chirality.The kinetics of gel formation was studied,in the process of gel formation Ag9-NCs were induced to orderly arrangement,triggering Ag9-NCs AIE effect,and finally better fluorescence emission was obtained to achieve circularly polarized luminescence(CPL).The gel has sensitivity and specificity for the detection of biological small molecule arginine,thereby constructing an arginine sensor;The freeze-dried powder of gel has good response in both low temperature and high temperature regions,and can be used for temperature sensing.This study shows that the supramolecular materials of metal NCs have potential applications not only in the field of temperature sensing,but also in the field of biological detection.Part Ⅱ,study on multi-components self-assembly system composed of hydrophobic peptides and Ag9-NCs.The solvent engineering strategy to induce the selfsorting of water-soluble Ag9-NCs and hydrophobic(D,D)to build more complex supramolecular system.Under the synergistic effect of hydrophobic and H-bond,(D,D)can form gel in very short time,forming an effective phase separation with Ag9-NCs,constructing self-sorting assembly system.In addition,the presence of gel matrix increases the crystallinity of Ag9-NCs assembly,enhances the order of Ag9-NCs aggregates,and the AIE effect of clusters is induced to enhance the luminescence of the system.In this work,metal NCs are used for the first time to build self-sorting assembly system,which deepens the assembly mechanism of metal nanoclusters,provides multiple schemes for the assembly and performance control of metal NCs,and takes a solid step towards simulating the multi-components self-sorting system in nature.Part Ⅲ,study on fmoc-amino acid salt induced supramolecular chirality of onedimensional ultra-long ultra-flexible silver cluster nanowire in high viscosity system.High concentration of surfactant C12E4 was studied by slowing the aggregation,nucleation and growth of Ag9-NCs to obtain one-dimensional ultra-long ultra-flexible silver cluster nanowire in a long time scale,and triggering AIE of Ag9-NCs to obtain better fluorescence emission.By adding water-soluble Fmoc-amino acid salt in the high viscosity system,the chiral uncontrollable nanowire constructed by breaking the symmetry of pseudochiral Ag9-NCs are transformed into controllable chiral nanowire induced by amino acid salt,thus obtaining better circularly polarized luminescence(CPL)signal.This research opens up a new path for the supramolecular assembly of metal NCs and deepens researchers’ understanding supramolecular assembly of metal NCs.