Surface Enhanced Terbium Luminescence Of Gold/Gold-Silver Alloy Nanoparticles For Dopamine Detection

Dopamine(DA),a crucial catecholamine neurotransmitter in biology,plays an important role in the function regulation of central nervous,hormonal,cardiovascular,and renal systems.The abnormal content of DA can cause some neurological diseases,such as Parkinsonism,schizophrenia,Huntington's and Alzheimer's diseases,etc.Hence,developing a new method to facilely,sensitively and selectively determine DA is of great significance for related pharmacological studies and clinical diagnosis.Rare earth(RE)luminescent ions-Tb3+,is an excellent fluorescent probe candidate.Because it possesses many advantages,such as sharp emission profiles,long photoluminescence lifetime with large Stokes shifts,and favorable coordination ability.Tb(?)can coordinate with DA,and realize DA determination by fluorescence signal changes.Co-ligands,RE co-luminescence ions,surfactants,and noble metal nanoparticles can be adopted to improve detection sensitivity and selectivity directed at the poor absorption and low quantum yield of Tb(?).Present studies concentrate on silver nanoparticles(AgNPs)enhanced Tb(?)luminescence,gold nanoparticles(AuNPs)induced fluorescence quenching,and photocatalysis and SERS effect of gold-silver nanoparticles(Au-Ag alloy NPs).AgNPs possess active plasmonic property,while the chemical stabilty is poor.Gold nanopartiles(AuNPs)possess good chemical stabilty and coordination ability.The paper aimed at comparative study of the plasmonic properties and surface enhanced Tb(?)fluorescence effects of AuNPs,AgNPs,and Au-Ag alloy NPs for highly sensitive determination of DA.This dissertation is divided into three chapters.In chapter one,we summarized the significance and existing methods of DA detection,introduced sensitization methods of RE probes,and analyzed the influence of nanomaterial composition on SEF effect.In chapter two,a fluorescent method with improved selectivity and sensitivity was developed based on the synergistic action of citrate and AuNPs.There is a large spectral overlap between the localized surface plasmon resonance(LSPR)peak(at 523 nm)of AuNPs and the emission spectrum(547 nm)of Tb(?).Besides the co-ligand effect,citrate can adjust the SEF distance and enlarge the spectral overlapping efficiency for enhanced SEF effect of AuNPs.The specific recognization of citrate for the primary amine group of DA significantly improved the method selectivity among many metal ions and biological molecules.The assay was successfully applied to the determination of DA in real samples.The action mechanism of the system was investigated by ultraviolet absorption spectra,Fourier transform infrared spectra,Raman spectra and TEM images.In chapter three,a facile and highly sensitive new fluorescent probe was developed for DA detection with Au-Ag alloy NPs as SEF substrates.We synthesized Au-Ag alloy NPs and AuNPs with different sizes,and contrasted their plasmonic properties.The study found that Au-Ag alloy NPs integrated good plasmonic property of Ag and good chemical stability of Au.Au-Ag alloy NPs exhibit superior SEF property than single AuNPs.Compared with AuNPs,Au-Ag alloy NPs possess stronger ultraviolet absorption and electric field,and thus more active plasmonic property.The protective agent in Au-Ag alloy NPs solution-citrate,provided suitable SEF distance and immobilization to Tb3+-DA.The enhancement mechanism was studied by the fluorescence decay curves,ultraviolet absorption spectra,TEM and Raman spectroscopy.The creative method realized sensitive determination of DA,with the LOD as low as 0.19 nM(S/N = 3).