title: Effect of hydrophobicity inside PEO-PPO-PEO block copolymer micelles on the stabilization of gold nanoparticles: experiments.
abstract: In this paper we present the effect of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer micelles and their hydrophobicity on the stabilization of gold nanoparticles. Gold nanoparticles were prepared by a method developed by Sakai et al. (Sakai, T.; Alexandridis, P. Langmuir 2004, 20, 8426). An absorption centered at 300-400 nm in time-dependent UV spectra provided evidence that the very first step of the synthesis was to form primary gold clusters. Then the gold clusters grew in size and were stabilized by block copolymer micelles. The stabilization capacities of the micelles were modulated by tuning the block copolymer concentration and composition and by adding salts. With good stabilization, gold particles were spherical and uniform in size with a diameter of 5-10 nm. Otherwise they were aggregates with irregular shapes such as triangular, hexagonal, and rodlike. The presence of a small amount of NaF significantly increased the stabilization capacity of the micelles and consequently modified the quality of the gold particles. Using FTIR and 1H NMR spectroscopy, micellization of the block copolymers and hydrophobicity of the micelles were proven very important for the stabilization. A higher hydrophobicity of the micelle cores was expected to favor the entrapment of primary gold clusters and the stabilization of gold nanoparticles.
authors.affiliation: Laboratory of Separation Science and Engineering, State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
authors.forename: Shu
authors.initials: S
authors.lastname: Chen
authors.forename: Chen
authors.initials: C
authors.lastname: Guo
authors.forename: Guo-Hua
authors.initials: GH
authors.lastname: Hu
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Jun-He
authors.initials: JH
authors.lastname: Ma
authors.forename: Xiang-Feng
authors.initials: XF
authors.lastname: Liang
authors.forename: Lily
authors.initials: L
authors.lastname: Zheng
authors.forename: Hui-Zhou
authors.initials: HZ
authors.lastname: Liu
mesh_terms: D003102:Colloids; D003116:Color; D006046:Gold / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D011092:Polyethylene Glycols / Q000737:chemistry*; D011409:Propylene Glycols / Q000737:chemistry*; D012996:Solutions; D013053:Spectrophotometry; D013696:Temperature
chemical_list: D003102:Colloids; D008823:Micelles; C116176:PEO-PPO-PEO; D011409:Propylene Glycols; D012996:Solutions; D011092:Polyethylene Glycols; D006046:Gold