Synthesis And Application Of Gold Nanoclusters And Their Composite Fluorescent Probes

In recent years,Au NCs with ultra-small size become the research focus in materials science and biology.Au NCs are attractive for not only their small size,good photostability,large Stokes shift,facile preparation and innoxious,but also Au NCs can be used to monitor the metal ions in real-time by fluorescence imaging technology.Au NCs have a promising application in the fields of analytical detection,biomarker,fluorescence imaging and so on.Au NCs are widely used as monochromatic fluorescence sensors,but the monochromatic fluorescence sensors are susceptible to environmental interference and it's color changes cannot be oberseved by eyes.The ratiometric fluorescence sensors developed on the basis of the monochromatic fluorescence sensors overcome these shortcomings and have played an increasingly important role in the field of fluorescence detection.Ratiometric fluorescence sensors typically have two or more fluorescent probes with different emission wavelengths.When the target detector is added,it tends to cause a strong response of one of the fluorescence probes and make its fluorescence intensity quench or enhance.But it has no obvious effect on another fluorescence probes.So achieving the detection of the target according to the ratio of the two fluorescence intensity not only enhance the selectivity and sensitivity,but also be beneficial to eliminate the interference of other factors and improve the accuracy of detection.Metal ions are physiologically essential,but excessive metal ions may cause severe risk to plants and animals.Here,we prepared gold nanoclusters(Au NCs)protected by 11-mercaptoundecanoic acid(11-MUA),which have excellent fluorescence performance for the detection of metal ions.The study results showed that the copper ions(Cu2+)and iron ions(Fe3+)in the solution have obvious quenching effect on the fluorescence intensity of Au NCs.The detection range of Fe3+ was 0.8 ?M-4.5?M(R2=0.992)and 4.5 ?M-11.0 ?M(R2=0.997).And Cu2+ has a lower linear range(0.1 ?M-1.0 ?M,R2=0.993).When ethylenediaminetetraacetic acid(EDTA)was added into the reaction system,it was observed that the quenching effect of Cu2+ and Fe3+ on Au NCs showed different phenomenon.Then,the effect of metal ions on the fluorescence of Au NCs was investigated.The selective detection of Cu2+ was achieved by EDTA masking of Fe3+.In addition,we realized the metal ions detection application of Au NCs in the serum.The composite spheres covered by CDs@SiO2 was made by reverse micellar method and successfully modified amino on the surface of SiO2 microspheres.Then use EDC and NHS to active the carboxyl groups on the surface of the gold nanoclusters.And by coupling the carboxyl groups on the surface of the SiO2 microspheres and the carboxyl groups on the surface of the gold nanoclusters,the CDs@SiO2@GSH-Au NCs and CDs@SiO2@MUA-Au NCs were successfully prepared.The fluorescence spectra of CDs@SiO2@GSH-Au NCs produced at 350 nm and 620 nm wavelengths when they are excited at 350 nm wavelength,and a dual-luminous ratio fluorescent probe was successfully prepared.Based on the CDs insensitivity to hydrogen peroxide and gold nanoclusters' sensitivity to hydrogen peroxide,the carbon spot covered in SiO2 was used as the reference light source and the gold nanoclusters were used as the detection light source.And we successfully quantified the hydrogen peroxide.The results showed that when the concentration of H2O2 was in the range of 5 ?mol/L-100 ?mol/L,the linear regression equation was y =-7.1590x + 0.3340(R2= 0.9960),and the detection limit was 2 ?mol/L.