单分散纳米金尺寸的分步晶种生长控制

以聚乙烯吡咯烷酮(poly(vinylpyrrolidone), PVP)为保护剂, 硼氢化钠为还原剂, 合成了尺寸为(1.9±0.4) nm的单分散金胶体, 再以其作为一级晶种, 并分别用抗坏血酸和PVP为还原剂和保护剂, 通过改变各步晶种尺寸和氯金酸与晶种的摩尔比分步逐级合成了尺寸为3.2、4.7、6.3、8.0、10.3、14.0 nm的系列金纳米颗粒. 以LaMer模型为基础, 对分步晶种生长过程中影响金胶体产物尺寸分布(单分散性)的主要因素进行了讨论. 缓慢加入抗坏血酸并降低氯金酸对晶种的相对量对于单分散金纳米颗粒的控制合成有决定性作用. 快速加入抗坏血酸会因二次成核而导致金颗粒尺寸分布范围变宽.

Size-Control of Monodispersing Gold Nanoparticles via Stepwise Seed-Mediated Growth

A stepwise seed-mediated growth approach is practiced to synthesize monodispersing Au particles in diameters of 3.2-14.0 nm using poly(vinylpyrrolidone) (PVP) and D-ascorbic acid as the capping agent and reductant,respectively. The starting Au seeds are in diameters of (1.9±0.4) nm and are obtained by reduction of aqueous HauCl_4 with NaBH4 in the presence of PVP. By control of the ratio of seeds to metal precursor (HAuCl4), nearly dispersing Au particles with average diameters of 3.2, 4.7, 6.3, 8.0, 10.3, and 14.0 nm are obtained in sequential growth steps without the need of using alternative reductant and capping agent. Key factors affecting the size distribution or monodispersity of Au particles are discussed on the basis of LaMer growth model. The use of higher seeds-to-HauCl_4 ratios in coupling with slow ascorbic acid addition is crucial for the control of monodispersity of product Au nanoparticles. Fast ascorbic acid addition would lead to secondary nucleation which results in Au particles with broadly dispersed sizes.