Silver Nanoparticles Enhanced Terbium Luminescence For Catecholamines Determination

Catecholamines(CAs)are important neurotransmitters which can regulate the nervous system in the human body.Common CAs include dopamine(DA),adrenaline(EP),and norepinephrine(NE).The study found that abnormal DA content in the human body can cause central nervous system disorders,such as Parkinson's disease,Huntington disease.The contents of EP and NE were correlated to hypertension and thyroid diseases.Therefore,the high sensitive detection of CAs is very important for medical research and biological diagnosis.Rare earth down-conversion luninescence analysis method can be used for the determination of CAs,but the selectivity and sensitivity of traditional rare earth luninescence analysis methods should be further improved.Rare earth up-conversion luminescence need near infrared laser as excitation light source.980 nm laser was commonly used,but the heat effect of water molecule at 980 nm could cause biological tissue thermal damage.The aim of this study is to establish high sensitive and selective rare earth down-conversion luminescence method for CAs determination by metal-enhanced fluorescence(MEF)of anisotropic silver nanoparticles,rare earth co-luminescence effects and synergistic ligand.Finally,with the synergistic enhancement of surfactants and silver nanoparticles,the up-conversion luminescence method of Tb(III)for the determination of DA in aqueous solution was established.This paper concludes four parts.In the first part of the paper,the determination of CAs,the down-conversion and up-conversion luminescence of rare earth analysis method and their development were discussed.The sensitizing effects for rare earth luminescence:metal enhanced fluorescence,rare earth co-luminescence,synergistic agents and surfactants were reviewed.In the second part of the paper,we synthesized silver nanoflowers(AgNFs)to act as MEF matrix.The co-luminescence enhancement of rare earth was realized by the coupling of electric field between the sharp tips and edges of AgNFs.The effects of 4f orbital electron distribution of co-luminescence ion on the system were studied.We found that La3+,Gd3+ and Y3+,which has inert 4f orbital electron distribution,were more likely to result in co-luminescence effects in this system.The Tb(III)-La(III)co-luminescence system with the best fluorescence enhancement effect was selected to realize the sensitivity measurement of DA and EP.The interaction mechanism of AgNFs enhanced rare earth co-luminescence was also discussed.In the third part of the paper,the silver nanoprisms(AgNPrs)with suitable local surface plasmon resonance(LSPR)absorption peak were obtained by regulating the amount of sodium citrate,PVP,hydrogen peroxide and sodium borohydride.The tip effect and large spectral overlap make it a good fluorescence enhancement substrate.The acetate ligand was fiurther added as the spacer between Tb3+-DA complex and AgNPrs,and also the recognition group of DA.The study found:16 kinds of biological small molecules(amino acids,neurotransmitters,EP,etc.),as well as common anions,cations did not interfere with the determination of DA.The interference of NE with the same concentration of DA on the fluorescent signal of the system is also within ±5%error range.This method achieved the selective determination of DA.The fluorescence enhancement mechanism and the selective identification mechanism of Ac" to DA were studied by Fourier transform infrared spectra,Raman spectroscopy,resonance light scattering spectra and TEM images.In the fourth part of the paper,the up-conversion luminescence of Tb(III)for DA determination in aqueous solution was developed by synergistic enhancement effect of surfactant and spherical AgNPs.The effects of alkylphenol polyoxyethylene ether(OP),sodium dodecyl benzene sulfonate(SDBS),sodium dodecyl sulfonate(SDS),cetylpyridinium bromide(CPB)and cetyltrimethylammonium bromide(CTAB)on the fluorescence enhancement of rare earth were studied.The result showed that,SDS has a better sensitizing effect on the rare earth luminescence.With the excitation wavelength at 300 nm and 610 nm the Tb3+-DA complex can emit characteristic fluorescence at 547 nm,which corresponds to the down-conversion and up-conversion luminescence type,respectively.The experimental conditions were optimized by the upconversion luminescence of the system.The down-conversion and up-conversion luminescence method for DA determination was established under the optimal conditions.The up-conversion luminescence analysis method had higher sensitivity and selectivity.The interaction mechanism of the system was also discussed by resonance light scattering spectra,UV-vis spectra and TEM imagesThe main features of this paper:1.The effects of anisotropic silver nanoparticle morphology(flower-liked,triangular prims)on the enhancement effect of rare earth luminescence were studied.The effects of different LSPR distributions of AgNPrs on the MEF effect were investigated.2.The introduction of AgNFs improved the intermolecular energy transfer efficiency and promoted the co-luminescence of Tb(III)-La(III)rare earth co-luminescence.The simultaneous determination of DA and EP were realized3.The synergistic effect of AgNPrs and second ligand improved the sensitivity and selectivity of DA,and the fluorescence enhancement mechanism and selective mechanism of Ac-coligand towards DA was studied.4.The upconversion luminescence method of Tb(III)enhanced by surfactant and AgNPs for the analysis of DA in aqueous solution was established.Compared with the down-conversion luminescence analysis method,the up-conversion luminescence has higher selectivity and sensitivity.The method does not require laser excitation and can be mearsured with ordinary fluorescence instrument.The method is simple and could realize upconversion luminescence in aqueous solution.This method has important theoretical value and practical significance for the research of rare earth upconversion luminescence analysis.