title: Synthesis of contiguous silica-gold core-shell structures: critical parameters and processes.
abstract: A direct process for preparing contiguous gold shells (15-25 nm thick) over amorphous silica spheres (200 nm) is described. In this method, gold seeds are synthesized from HAuCl(4) in a dilute NaOH solution using deposition-precipitation with subsequent metallization by sodium borohydride (NaBH(4)). The ease of dispersing gold nanocrystals on spheres of bare silica and spheres after grafting with ammonia was studied as a function of pH (4-8), reaction temperature (65-96 degrees C), and time (5-30 min). Additional parameters requiring optimization included the quantity of NaBH4 and the HAuCl(4) in K(2)CO(3) solution to silica volume ratio. The evolution of gold nanocrystal growth was monitored by transmission electron microscopy, and the bathochromic shift of ultraviolet-visible absorption was correlated with shell perfection and thickness.
authors: School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798. nopphawan@ntu.edu.sg
authors: Nopphawan
authors: N
authors: Phonthammachai
authors: James C Y
authors: JC
authors: Kah
authors: Guo
authors: G
authors: Jun
authors: Colin J R
authors: CJ
authors: Sheppard
authors: Malini C
authors: MC
authors: Olivo
authors: Subodh G
authors: SG
authors: Mhaisalkar
authors: Timothy J
authors: TJ
authors: White
mesh_terms: D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D012822:Silicon Dioxide / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D006046:Gold; D012822:Silicon Dioxide