SiO2介导的5 nm金颗粒的高效富集及其催化活性研究

SiO2-Mediated High-efficiency Enrichment of 5 nm Gold Nanoparticles and Their Catalytic Activity

粒径小于10nm的金纳米颗粒(AuNPs)具有高的表面积与体积比,因此具有极强的催化活性,在催化领域应用广泛.传统湿法合成的金纳米颗粒浓度过低,需要进一步富集才能满足实验要求.然而,小粒径AuNPs在浓缩过程中容易聚集,失去催化活性.在保持催化活性的同时,浓缩小粒径的Au NPs是一个挑战.本工作用500 nm硅烷化修饰的Si O2颗粒,通过静电相互作用吸附5 nm Au NPs,在室温下自组装形成Au NPs@SiO2复合物. Au NPs的负载效率可达99.5%,每个Si O2上负载的Au NPs高达800~1000个,大大提高了Au NPs有效浓度,并且富集到Si O2表面的Au NPs不会团聚.催化活性研究结果显示,制备得到的Au NPs@SiO2的催化活性是同浓度Au NPs的3倍.该复合物颗粒重复使用5次后,催化转换效率仍能保持在80%左右.该复合物颗粒能稳定保存一个月,结构和催化活性不变.并且,通过调节AuNPs在Si O2表面的组装密度,可精确调控AuNPs@SiO2催化活性.本工作提供了一种制备高浓度小粒径Au NPs的简单方法,并大大提高了Au NPs催化活性,该方法在富集其它小粒径纳米颗粒中具有广泛应用.

Gold nanoparticles(Au NPs), smaller than 10 nm, have a high ratio of surface area to volume, and therefore have excellent catalytic activity. They are widely used in the field of catalysis. The concentration of small particle sized Au NPs synthesized by traditional wet chemical method is too low, and further enrichment is needed in order to meet the experimental requirements. However, small particle sized Au NPs are prone to aggregate during the concentration process and lose the catalytic activity. It is a challenge to concentrate the small Au NPs while keeping their catalytic activities. In this work, 500 nm silanized SiO2 particles which are covered by positive charges were used to adsorb 5 nm Au NPs through electrostatic interaction, and self-assemble to form Au NPs@SiO2 composite at room temperature. The loaded efficiency of Au NPs can reach 99.5% and the amount of Au NPs particles loaded on each SiO2 particle reached 800~1000, which greatly increased the effective concentration of Au NPs in the local area. Moreover, Au NPs enriched on the surface of SiO2 were bound by electrostatic action and uniformly distributed on the surface of SiO2 without agglomeration. The results showed that the catalytic activity of AuNPs@SiO2 was greatly enhanced by increasing the local concentration of AuNPs, and the catalytic activity was 3 times higher than that of AuNPs at the same concentration. After 5 times of reuse, the catalytic conversion efficiency remained at about 80%. The Au NPs@SiO2 composite could be preserved for one month with the same structure and catalytic activity. Moreover, by adjusting the molar ratio of SiO2 and Au NPs, the assembly density of Au NPs at SiO2 can be precisely regulated, and the catalytic activity of Au NPs@SiO2 can also be changed precisely. This work provides a simple method for preparing small sized Au NPs with high concentration and greatly improves the catalytic activity of Au NPs. The method has wide application in enriching other small sized nanoparticles.