Preparation Of Au NF@SiO₂-rbitc Composite Particles And Their Response To Copper???

Fluorescent nanoparticles?NPs?possess high brightness and improved photostability as compared to conventional fluorescent dyes,they have attracted considerable interest over the past decade as valuable alternative to conventional organic fluorophores in a diversity of applications.Owing to the growing demand for selective chemo-sensors in biology and environmental monitoring,the design of sensing devices based on fluorescent nanoparticles,usable in aqueous medium,is a topic of sustained interest.However,the applications are often limited due to the low fluorescence intensity.Therefore,it is highly needed to enhance the fluorescence intensity of the dyes to improve the sensitivity.Noble metals have been demonstrated to enhance fluorescence of rare-earth ions,organic dyes,and quantum dots using the resonant coupling between the surface plasmon resonance bands of metals and absorption or emission band of fluorescent materials,which is known as metal enhanced fluorescence.However,up until now,there has been no study on the fluorescence enhancement of gold nanoflowers.Core-shell structures have been reported as an effective mean to improve the stability of gold nanoflowers,as well as to provide a spacer to control the distance between metal enhancer and fluorophore for optimized fluorescence efficiency.Inspired by metal enhanced fluorescence,we prepared core-shell?gold nanoflower core-silica shell?composite particles doped with RBITC based on the metal-spacer fluorophore approach,and investigated the fluorescence enhancement property and copper ions detection of Rhodamine B isothiocyanate?RBITC?with the assistance of gold nanoflowers.The article includes two parts:1.Study on the controllable preparation and the fluorescence properties of Au NF@SiO₂-RBITC composite particles.In St?ber system,a series of Au NF@ SiO₂ composite particles were prepared by adjusting the amount of ammonia.As a result,thicknesses of the silica shell were regulated between 7 nm and 22 nm.Then,RBITC were doped into silica shell by covalent coupling with?3-aminopropyl?-triethoxylsilane?APS?.The effect of Au core,the concentrations of RBITC and the thicknesses of silica shell on the fluorescent properties of the composite particles were investigated by steady-state and time-resolved fluorescence measurement.It was found that the Au NF@SiO₂-RBITC composite particles achieved optimized metal-enhanced fluorescence effect when the actual doping concentration of RBITC was 7.25×10-4 mg / m L and the thickness of the silica shell was 15 nm.Compared with SiO₂@SiO₂-RBITC composite particles under the same conditions,the fluorescence intensity of Au NF@SiO₂-RBITC composite particles was enhanced by 4 times and the fluorescence lifetime of the dye was significantly decreased.2.Study on the fluorescence response ability of Au NF@SiO₂-RBITC composite particles to copper ions.The Au NF@SiO₂-RBITC composite particles with silica shell thickness of 15 nm were chosen to study their fluorescence response to copper ions.Ammoniacal copper complex ions?[Cu?NH3?4]2+?were formed by the coordination of copper ions and ammonia.The absorption peak of the complex ions was about 600 nm,which can be overlapped with the emission spectra of Au NF@SiO₂-RBITC composite particles.Since that,the fluorescence of the composite particles were quenched due to energy transfer between the [Cu?NH3?4]2+ and the composite particles.It was found that the ratio of fluorescence intensity decreased linearly when the concentration of copper ions was between 8×10-8⁸×10-6 mol / L.Compared with SiO₂-RBITC particles,the Au NF@SiO₂-RBITC composite particles significantly improved the detection linear range and sensitivity.