Synthesis,Analysis And Applications Of Gold And Copper Nanoparticles With Chiroptical Activities

Since the first discovery and raising of natural optical activity in the early nineteenth century,scientists have devoted themselves to the researches of chirality.Even today,it has promoted the development of science and technology in different fields,nanoscience being a prime example.Since 2000 Schaaff and Whetten first observed strong optical activities in the synthesis of AuNCs,preparation MNCs with optical activities imported from drugs has become a hot topic.Chiral MNCs not only have large surface area and fluorescence emission,but also have optical activities.Therefore,researches about chiral MNCs provide some reference values for life science such as recognition and sensing of biological macromolecules,asymmetric catalysis for drugs,and targeting therapy of living tissues.Although the work for chiral MNCs is relatively mature,most of them focus on AuNCs or AgNCs,mainly because of easy oxidation of Cu.As a result,this paper intends to simply and rapidly synthesize stable red-emitting CuNCs with excellent optical activities based on functionalized technologies and chiral synthesis results,chiral ligand molecules being stabilizers and reducing agents.In order to further improve the stability of CuNCs,the Au was added to prepare AuCu NCs with more excellent optical activities.As a result,the main researches about CuNCs and AuCu NCs include the following two aspects:1 Synthesis of chiral red-emitting CuNCs and applications to p H sensor and cellular imaging Despite a significant surge in the number of investigations into both optically active gold and silver nanostructures,there is currently only limited knowledge about optically active copper nanoclusters and their potential applications.Here,we have succeeded in preparing a pair of optically active red-emitting CuNCs on the basis of complexation and redox reaction between Cu(II)and Pen enantiomers,in which Pen serves as both a reducing agent and a stabilizing ligand.Significantly,the CuNCs with excellent optical activities show the maximum g factors(8.3 x 10 – 4),and also have a unique AIE feature being sensitive to pH.Impressively,the chirality of ligands plays a dramatic role for the creation of brightly emissive CuNCs,attributed to the conformation of racemic Pen being unfavorable for the electrostatic interaction,and thus suppressing the formation of cluster aggregates.This suggests that CuNCs with chirality and fluorescence are successful prepared.In addition,the clusters display potential toward cytoplasmic staining and labelling due to the high photoluminescence QY and remarkable cellular uptake,in spite that no chirality-dependent effects in autophagy and subcellular localization are observed in the application of chiral cluster enantiomer-based cell imaging.It is of great value to regard the combination of drug chirality and cluster fluorescence as a signal probe for the exploration of life.2 Synthesis of chiral AuCu NCs and analysis of optically active Although small mixed-metal clusters have been synthesized by adulterating heteroatoms into atomically precise Au NCs to obtain enhanced chemical,catalytic and optical activities,the optical behaviour of bimetallic NCs protected by chiral ligands are barely studied.Thus,chiral AuCu NCs were synthesized via reduction of varying mole fractions of HAuCl4 and CuCl2 by NaBH4 in the presence Pen enantiomers.AuCu NCs not only show unique cotton effects,but also gain maximum g factors while the ratio of Au/Cu is 1:1,suggesting that the incorporation of Cu heteroatoms plays a dramatic role for the creation of the strong optical activities.Although CuNCs are unstable,but AuCu NCs are stable which is similar to AuNCs.These remarkable results bring some reference values for the alloy effect especially on chiral catalysis and recognition in the future.