Biological Analysis And Imaging Study Of High Quantum Yield Fluorescent Gold Clusters

Fluorescent Au NCs,as new emerging nanomaterials,imaging and electro-optic display fields because of diverse merits including ultrasmall size,outstanding photoluminescence（PL）,high stability,large Stokes shift,low cytotoxicity and excellent biocompatibility.And Au NCs has a broad application prospect in biomedical fields such as biosensors,biological imaging,photothermal treatment and antimicrobial agents.This paper intends to carry out work from the following three aspects:（1）A method for the synthesis of Au-PAMAM NCs by a one pot etching approach was proposed.Interestingly,Au-PAMAM NCs display sensitive and selective fluorescence responsiveness toward temperature and Cr₂O₇^2-ions,respectively.Au-PAMAM NCs has the advantages of small size,good water solubility,low cytotoxicity and strong cell penetration.This study paves the way for synthesizing high emission and high biocompatible Au NCs and promising their great potentials for biosensing and imaging in the future.（2）A novel fluorescent d-Au NCs nanoprobe with two unique emission peaks at 420 and 630 nm was prepared by a simple in situ reaction method.In this paper,the formation and emission mechanism of dual emission nanoprobe are studied.Two-stage formation mechanism evidences its sensitive responses to valine and trivalent chromium ions(Cr³⁺)in completely different spectral ratiometric modes in living cells with high contrast to well avoid signal fluctuations.Moreover,this d-Au NCs nanoprobe exhibit good water solubility,low cytotoxicity and favorable biocompatibility.They can be applied for sensitive imaging of valine and Cr³⁺fluctuations in living cells with high contrast,respectively.This work provides experimental and theoretical basis for further design of synthesizing ratiometric fluorescent Au NCs nanosensors.（3）We successfully synthesize various Au NCs with continuously tunable emission colors from deep red to blue under a single wavelength excitation by a convenient one-step growth approach.The synthesized products have different but independent emission centers and exhibit excellent optical properties,e.g.high quantum yields（QYs）of up to 26.77%,long excited-state lifetimes,month-long high stability,excitation-independent luminescence,which have been successfully applied to multicolor cell imaging.To the best of our knowledge,this is the first time to synthesize full color emissive nanomaterials by a one-step method.This work promises huge application potentials of multicolor emissive Au NCs in various fields such as multicolor display,light-emitting diodes and biomedical science.