Abstract: Ag@SiO2 core-shell nanoparticles were fabricated via water-in-oil (W/O) reverse microemulsion process. Using sodium borohydride (NaBH4) as reducing agent，the silver core was formed in water droplets and packed with amorphous silicon dioxide (SiO2 shell) formed by the hydrolysis of tetraethyl orthosilicate (TEOS) at the water/oil interface. The obtained nanoparticles were characterized by TEM，UV-Vis and XRD measurements respectively. The diameter of the obtained nanoparticles is approximately from 50 to 100 nm. The size of inner silver core varies by altering the R value (the molar ratio of water to surfactant). The formation of core-shell nanoparticles is affected by the order of ammonia addition. UV-Vis spectra indicated that the plasma resonance absorption of silver core wrapped with SiO2 has a red shift. XRD pattern proved that the nanoparticles have a structure with a crystalline silver core and an amorphous SiO2 shell.

摘要： 以NaBH4作还原剂，TEOS为前体，采用反相微乳液法制得粒径50～100 nm的Ag@SiO2核壳纳米粒子，其中Ag核为面心立方结构，壳层为无定形SiO2。考察催化剂加入的先后和微乳液R值（R＝n水/n表面活性剂）对Ag@SiO2核壳纳米粒子形成的影响。用TEM、UV-Vis、XRD对纳米粒子的形貌及性质进行表征。结果表明：催化剂若先于TEOS加入，易得到Ag@SiO2核壳纳米粒子，随着R值的增加，Ag核的粒径变大，纳米粒子逐渐由单核变成多核。催化剂若后于TEOS加入，则形成负载型Ag/SiO2复合物。Ag核被SiO2壳包覆后的等离子共振吸收峰发生了微弱红移。而当壳厚＞80 nm时，由于SiO2的散射作用，吸收峰会发生蓝移。