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Published on: October 4, 2012
Phytosynthesis of Au and Au/ZrO₂ bi-Phasic System Nanoparticles with Evaluation of Their Colloidal Stability
Veronika Holišová1, Zuzana Konvičcková1, Gabriela Kratošová1
1Nanotechnology Centre, VŠB - Technical University of Ostrava, 17. listopadu 15/2172, Ostrava 70833, Czech Republic.
Abstract:
Due to its easy availability, preparation, handling and non-toxic nature, Equisetum arvense horsetail extract was chosen as a reducing, stabilizing and functionalizing agent for Au and bi-phasic Au/ZrO₂ nanoparticle phytosynthesis-inorganic nanoparticle synthesis mediated by plant extract. We studied Au and bi-phasic Au/ZrO₂ nanoparticles in colloids by various physical-chemical and analytical methods over 5 weeks. Dynamic Light Scattering and Scanning Transmission Electron Microscopy compared core and hydrodynamic diameters of nanoparticles. ζ-potential measurement indirectly determined nanoparticles stability in liquid medium. Ultraviolet-Visible Spectroscopy characterized basic absorbance maxima for both Au and the bi-phasic Au/ZrO₂ system. Finally, total metal concentration was determined using Inductively Coupled Plasma Mass Spectrometry. ζ-potential measurements proved satisfactory stability of both Au (-13.4 to -17 mV) and Au/ZrO₂ nanoparticles (-14.1 to -17.5 mV) over the experimental period. Scanning Transmission Electron Microscopy with Selected Area Diffraction analysis confirmed nanoparticles crystalline nature, and we determined 24 nm and 40 nm core nanogold diameters in Au and Au/ZrO₂ nanoparticle colloids. Dynamic light scattering analysis confirmed the dichotomy between particle sizes in liquid medium in the hundreds of nanometers measured, and long-term measurements confirmed reasonable colloid stability-a paramount parameter for potential nanoparticles applications; especially in heterogeneous catalysis.
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