Preparation and characterization of Ag/AgO nanoshells on carboxylated polystyrene latex particles
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Smooth and uniform Ag/AgO nanoshells (about 3–4 nm) on carboxylated polystyrene latex particles were prepared by electrostatic attraction between negatively charged –COO− on the surface of carboxylated polystyrene latex particles and positively charged Ag(NH3)2+ in the solution, and subsequent decomposition of the silver complex. The resultant nanoparticles were characterized with Fourier transform infrared, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. The effects of reducing agents, the amount of NaOH and temperature on the morphology of hybrid latex particles were discussed.
I. INTRODUCTION
Interest in the design and controlled fabrication of metal–polymer nanocomposites consisting of a polymer and metal particles on the surface or in the interior (core) of the polymer spheres continues to increase, due to their great potential in the areas of electronics, photonics, magnetics, and catalysis.1–7 It is well known that silver is superior to other nanostructured metal materials for many reasons such as electrical conductivity,8 antimicrobial effects,9 optical properties,2,10 and oxidative catalysis.11 Therefore, fabrication of silver-coated latex particles is of special interest, and several routes have been reported in the literature, including surface precipitation reaction12,13 thermal evaporation techniques or sputtering onto latex particles14 and self-assembly.1,6 However, in most cases, irregular thickness, a large number of non-coated particles, merely metal islands, and incomplete surface coverage were usually obtained by these methods. Particles coated with silver nanoshells are generally difficult to synthesize because the reduction reaction is too fast to be controlled. The uniform and complete coverage of each latex particle in a sample by a defined silver coating below 20 nm thickness thus still remains a challenge and is the basis for several fundamental investigations involving optical phenomena.2 The most successful reports are two-step strategies involving initial control of silver nucleation and subsequent control of particle growth,2 and the layer-by-layer technique.1 However, these protocols use various reducing agents, which may easily cause the reduction and formation of
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0065 J. Mater. Res., Vol. 21, No. 2, Feb 2006
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the silver particles before diffusion or attachment to the latex particle surface and rapid particle growth, thus making the procedures complex and difficult to operate. Here we report a simple and effective method for fabrication of ultrathin uniform Ag/AgO nanoshells on carboxylated polystyrene latex particles without reducing agents. The positively charged Ag(NH3)2+ was rapidly attracted by negatively charged –COO− on the latex particle surface through electrostatic attraction and subsequent decomposition of the silver complex leads to smooth and uniform Ag/AgO nanoshells that can be m
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