通过由层的层的方法制备二氧化硅核金壳结构材料

2011 International Conference on Advanced Materials Engineering

IPCSIT vol.15 (2011) ? (2011) IACSIT Press, Singapore Preparation of Silica Core-Gold Shell Structural Materials via Layer

by Layer Method

Wenjiang li and Minfang Chen

School of Materials Science and Engineering, Key Laboratory of Display Materials & Photoelectric Devices , Tianjin Key Lab for Photoelectric Materials & Devices, Tianjin University of Technology Tianjin

300384, China

Abstract. The silica core-gold shell structural material was prepared using mono-dispersed silica microsphere as template and gold nanoparticles from HAuCl4 solution. Gold nanopartilces were assemblied

on the silica surface modified by aminopropyl triethoxysilane (APTES) via a convenient layer-by-layer method. The evolution of gold - coverage over the surface of silica microspheres are demonstrated via transmission electron microscopy (TEM) and scanning electron microscopy (SEM). TEM and SEM images

show that the gold nano-particles could be deopisted on the surface of silica spheres, and the total gold

nanoparticle got increase with the deposited layer number. And ultraviolet-visible adsorption spectrum was

introduced to characterize the successful incorporation of gold nanoparticles on the microspheres. The layer-

by-layer method could provide a simple way to controll the ratio of gold on the silica surface.

Keywords: gold, silica microspheres,core-shell, step-by-step

1.Introduction

The design and controlled fabrication of core-shell nanomaterials and nanostructure are important in many research areas, including the developments of novel catalysis, the potential applications as chemical sensors, and some advanced photonic researches such as surface-enhance Raman scattering (SERS), photonic crystal, and nanoengineering of optical resonance. In particular, the fabrication and study of metallic nanoshells with dielectric cores have attracted wide interests because of their good optical and chemical properties for biomedical imaging and therapeutic applications.[1-3] Several strategies have been reported to prepare metallic nanoshells, including layer-by-layer (LBL) self-assembly of nano-particles on suitable colloid particles,[4] precipitation/chemical conversion,[5] and electroless deposition.[6] Interestingly, some novel functions can be realized after coating with metals, such as the photonic band gap, which can be tuned as desired by controlling some parameters.[7]

Recently, nano-scale silica complexes such as magnetic silica microspheres, fluorescent particles with quantum dots and metal-silica core-shell compounds gradually become the focus of biochemical researches due to their special optical properties and promising potentials for wide applications.[8-10] Silica-gold core-shell compounds (Au@SiO2) have got rapid development in biomedical fields such as the drug releasing, the cancer treating, biological sensoring and imaging.[11,12] Among all the methods that can synthesize a contiguous gold shell over silica microspheres, the deposition-precipitation (DP) approach is an inexpensive and easy method to prepare the core-shell materials. [13] Phonthammachai et al.[14] have reported that the homogeneous gold shells could be obtained by optimizing these key parameters including pH value, reaction time and reaction temperature. Here, we develop a multideposition method to prepare the silica core-gold shell materials using mono-dispersed silica microsphere as template and gold nanoparticles from the reduction of the HAuCl4 solution. In this work, Our main idea is to use the mono-dispersed silica microsphere as a template to prepare a metallo-dielectric silica-gold core-shell structural particles. The original pure silica spheres as the supporting core to improve the mechanics stability of silica-gold core-shell materials. Moreover, transparent silica sphere and very fine gold particles layer can allow the partial light to

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propagate through the silica core – gold shell. Using the multideposition method, the gold nanoparticles could be directly deposited on the surface of silica spheres.

2.Experimental Sections

2.1.Preparation of Monodispersed Silica Microspheres

Monodipsered SiO2 microspheres with an average diameter of approximate 200 nm were prepared by hydrolysis of tetraethylortho silicate (TEOS) in ethanol medium with the presence of deionized water and ammonium hydroxide, a reformation of the method reported by St?ber et al. (1968). In general, we added TEOS:EtOH ( 1:3 volume rate) to one beaker with vigorously stirring for 5 minutes. Then the mixture was added into a flask with EtOH: deionized water: ammonium hydrxide (9: 4: 0.5 volume rate) already under stirring. About 2 minutes later, white particles began to emerge, making the solution change from transparent to a little turbid. Under vigorously stirring for 2 hours, the solution was then totally a white turbid suspension. We took away a little suspension, wash three times using centrifugation and ultrasonical re-dispersion with deionized water.

2.2.Gold Nanoparticles Growing Over Sio2 Microspheres as Seeds

After natural precipitation of the SiO2 suspension, we removed the upper liquid. Then, 5ml of a pre-prepared solution of 60 mM aminopropyl triethoxysilane (APTES) in an EtOH: deionized water (3:1 volume ratio) was added into the solution under vigorously stirring at 95℃ for 1 hour. Then, 10 ml of 50 mM HAuCl4 solution and 5ml of 0.1M NaOH solution was added to the APTES grafted silica spheres to adjust the pH value to 7.2, and the solution was under stirring for 15 minutes to incorporate gold seed into the spheres. After that, we could see the white SiO2 particles show a golden color, demonstrating the gold nanopartilces were successfully incorporated on the silica spheres. The solution was centrifugated and washed for 3 t …… 此处隐藏：12054字，全部文档内容请下载后查看。喜欢就下载吧 ……