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Colloidal Synthesis and Characterisation of Asymmetrically Coated Plasmonic Particles

By Huixin Bao (14.03.2011)

This work describes the development of colloidal techniques to produce, for the first time in a single-phase solution, asymmetrical silver patches on core particles. The work describes an unexpected finding, namely that silica particles coated with alternating copolymers and treated with ammoniacal silver hydroxide could be coated by simple electroless plating with asymmetrical silver shells. Optimization of the various steps greatly improved the poor initial yield of the coatings. It was then shown that although a PEG-containing copolymer can contribute to the yield, it was not essential for the formation of asymmetrical silver coating. We also showed that the number of silver caps per particle can be tuned by using different maleic-anhydride containing alternating copolymers.

Figure 1: SEM image of silver patches on silica spheres.[Bildunterschrift / Subline]: Figure 1: SEM image of silver patches on silica spheres.

We further optimized the synthetic procedure and our work showed that in fact the asymmetrical coatings can be formed without pretreating the silica spheres with any polymer. The silver complex pretreatment was found to be a critical factor in the process. The effect of this step on the asymmetrical silver shell growth was studied by changing the parameters involved (silica surface properties, type and amount of silver complex, presence of silver ions, solvent pretreatment). We also considered the mechanism of the final silver shell growth. Our results indicated that the balance of silver diffusion from bulk solution and on the surface determined the unusual surface growth mode. It was found that the number and structure of the silver patches could be influenced by the silver-complex pretreatment, order of addition of the reactants and type of reducing agent and base. We also showed by comparison with new simulation results that the optical properties of the silver Janus particles are determined by the coverage and thickness of the silver caps.

Many techniques, including zeta potential measurement, thermogravimetric analysis, X-ray photoelectron spectroscopy, anodic stripping voltammetry, UV-VIS-NIR spectrophotometer, scanning electron microscopy, transmission Electron Microscopy and single particle optical spectroscopy, were utilized to analyze the structure and properties at various stages during and after fabrication of the silver patches.

Huixin Bao
Huixin Bao
* 1980, Nei Mongo
  • Since 4/2010
  • Institute of particle technology, FAU, Erlangen-Nuremberg (PhD student)
  • 10/2007 - 12/2009
  • Elite Graduate Program Advanced Materials and Processes, FAU, Erlangen-Nuremberg (Master of Science with Honors )
  • 09/2002 - 07/2005
  • Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (Master)
  • 09/1998 - 07/2002
  • Jilin University, China (Bachelor)

Berufliche Erfahrungen
  • 04-2009 - 05/2009
  • BASF SE, Ludwigshafen (internship)
  • 12/2005 - 07/2007
  • Fudan University, China, Technician

  • * Robin N. Klupp Taylor, Huixin Bao, Chenting Tian, Serhiy Vasylyev, Wolfgang Peukert. Facile route to morphologically tailored silver patches on colloidal particles. Langmuir, 2010, 26, 13564-13571.
  • * Bao Huixin, Wang Xiaohui, Yu Haijia, Fu Manliang, Qu Xiaogang, Zheng Yongchen, Ren Jinsong, Physical and spectral characterization of the human cyclin. A gene and its interactions with anthracycline anticancer drugs.
  • Chemical physics letters, vol.436 n.1-3 pp:252-257 (2007).