Synthesis And Sensing Application Of Dual Ligand Functionalized Fluorescent Gold Nanoclusters

As a burgeoning and promising kind of fluorophores,gold nanoclusters(Au NCs)with the diameter below 2 nm have gained much attention in biosensing and bioimaging due to their unique photophysical properties,excellent biocompatibility ultrasmall size,high sensitivity and good selectivity.Prompted by their potential applications,near infrared fluorescent Au NCs have been synthesized utilizing various protected ligands,including protein,polymers,alkanethiol or peptide,etc.Plasmon-enhanced fluorescence(PEF)becomes an emerging technology by virtue of its capability to largely amplify fluorescence signals and significantly improve the detection sensitivity.A novel PEF-based core-shell gold nanorod as a near-infrared fluorescent turn-on sensor can be used for highly sensitive and selective detection.The main contents of this thesis are summarized as follows:(1)A facile one-step strategy for rapidly preparing dual ligand co-functionalized fluorescent gold nanoclusters(Au NCs)and establish a “turn on” approach for selective sensing of glutathione(GSH)in aqueous solution and living cells was developed.The prepared Au NCs exhibited orange red fluorescence(?em=608 nm),a long lifetime(5.62 ?s),a large stokes shift(>300 nm),considerable stability and were systematic characterized by using fluorescence spectra,high-resolution transmission electron microscopy(HRTEM),dynamic light scattering(DLS),X-ray photoelectron spectroscopy(XPS),fluorescence lifetimes,infrared spectra(IR)and ultraviolet absorption spectrum.Based on the fluorescence recovery induced by competitive coordination with Cu2+ between Au NCs and GSH,the present “turn on” approach offers a high sensitivity and excellent selectivity toward GSH detection with a detection limit of 9.7 nM.More importantly,this “turn on” approach could also be successfully applied for visualizing and monitoring change of the intracellular GSH level in Hep G2 cells,providing available potential for diagnostic applications.(2)Optical cross-reactive sensor arrays have recently been recognized as a powerful technique for high-throughput protein detecting and analysis.Here,a multidimensional sensor array capable of analyzing various proteins and discriminating between serums from different stages of breast cancer patients were developed based on six kinds of near infrared fluorescent dual ligand functionalized Au NCs(functionalized with different amino acids)as sensing receptors.Ten proteins could be simultaneously and effectively discriminated by this “chemical nose/tongue” sensor array.Linear discrimination analysis(LDA)of the response patterns showed successful differentiation of the analytes at concentrations as low as 10 nM with high identification accuracy.Isothermal titration calorimetry(ITC)experiment illustrates that Au NCs interacted with proteins mainly by hydrogen bonding and van der Waals forces.Furthermore,the greatest highlight of this sensor array is demonstrated by successfully discriminating between serums from different stages of breast cancer patients(early,middle and late)and healthy people,suggesting great potential for auxiliary diagnosis.(3)In this work,gold nanorods were synthesized and characterized by high resolution transmission electron microscopy and ultraviolet absorption spectroscopy.The experimental results show that the synthesized gold nanorods possess good uniformity,and the uniform silica coating of gold nanorods,was successively achieved.High resolution transmission electron microscopy showed uniformity of coating.The silica coated gold nanorods may be used for the development of plasmon-enhanced fluorescence based sensing system.