Construction And Application Of Optical Probes Based On Carbon Quantum Dots And Copper Nanoclusters

Nanomaterial possesses unique properties,such as volume effect,surface effect,quantum size effect,tunnel effect and dielectric confinement effect.These unique properties provide several special properties of nanomaterial in optical property,mechanical property,electrical property and magnetic property.In the research of optical probe,nanomaterial is one of the most important optical material for the special optical property.Nanomaterial as an ideal optical material is a promising probe for biological analysis,cell imaging and protein labeling.In this thesis,we developed two probes for protamine and ascorbic acid,respectively.The dual-mode probe for protamine was based on fluorescence resonance energy transfer(FRET)between carbon quantum dots(CQDs)and gold nanoparticles(AuNPs).An "on-off-on" probe for ascorbic acid was based on electron—transfer between copper nanoclusters(CuNCs)and Fe(III)ions.The properties of the probe,mechanism and the linear range were investigated by various characterizations and experiments.The main contents in this thesis are listed in the following:1.An optical biological probe with dual signals was designed for decting protamine.The probe consists of a mixture of CQDs and AuNPs,and combines the advantages of colorimetric and fluorometric.In this probe,CQDs serve as a fluorometric reporter and AuNPs function as colorimetric reporter and fluorescence quencher.The probe was characterized by high-resolution transmission electron microscopy(HRTEM),X-ray photoelectron spectroscopy(XPS),time correlated single photon counting(TCSPC),UV-VIS spectroscopy,fluorescence spectroscopy,dynamic lights cattering(DLS)and Zeta potential.The fluorescence of CQDs is quenched significantly by AuNPs through FRET.Protamine is rich in basic arginine residues with a positive charge at physiological conditions.Consequently,protamine can induce the AuNPs to aggregate and the fluorescence of CQDs is recovered due to the competitive adsorption of protamine and CQDs on AuNPs.Linear fluorometric and colorimetric responses are obtained over the range 10-220 ng/mL and 20-160 ng/mL with the low detection limit 1.2 ng/mL and 2 ng/mL for protamine,respectively.Moreover,this dual-signal probe also shows excellent selectivity toward protamine,and has great potential for applications in determining of protamine in a real analysis.2.We reported that CuNCs represent a viable fluorescent probe for ascorbic acid.The CuNCs were stabilized by tannic acid and characterized by HRTEM,XPS,UV-VIS,TCSPC and fluorescence spectroscopy.It is found that the fluorescence of CuNCs(at excitation/emission peaks of 355/430 nm)is quenched by Fe(Ⅲ)due to electron-transfer between CuNCs and Fe(Ⅲ).If ascorbic acid is added,Fe(Ⅲ)is reduced to Fe(Ⅱ)and quenching is suppressed.Under optimal conditions,a linear relation exists between fluorescence recovery and the concentration of AA in the 0.5 μmoL/L to 10 μmoL/L concentration range.The detection limit is 0.11 μmoL/L.The method was applied to determine AA in(spiked)fruit and vegetables and gave recoveries ranging from 89 to 110%.