High Yield Synthesis of single crystal FCC Silver Nanoparticles and their Size Control
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1056-HH03-11
High Yield Synthesis of single crystal FCC Silver Nanoparticles and their Size Control Hiroyuki Nakamura1, Toshiyuki Shimizu2, Masato Uehara1, Yoshiko Yamaguchi1, and Hideaki Maeda1,2 1 Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, 807-1 Shuku, Tosu, Saga, 841-0052, Japan 2 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka, 816-8580, Japan ABSTRACT Twin free face centered cubic (FCC) silver nanoparticles of nearly monodispersed particle size were prepared by simple ripening of multi-twined particles (MTP). The particle size was 12nm and the product yield was almost 100%. The growth mechanism was considered to be similar to Ostwald ripening except that it utilized chemical potential gap between MTP and FCC NPs. The kinetics of particle generation stage affected the final particle size and the possibility of controlling the final defectless particle size from 8-17 nm maintaining almost 100% product yield was achieved. The particle generation stage kinetics is considered to determine the ratio between FCC and MTPs before ripening, and consequently the final particle size. INTRODUCTION Recently, methods of nanoparticle syntheses have been rapidly developed and numerous reports have reported details on particle-size distributions and shape controls. Particle size control is mainly allowed by halting the reaction with appropriate timing, nucleation frequency control1 and/or surfactant selection2 to control nucleation and growth kinetics. However, growth halting brings low product yield for smaller particles, and nucleation control and surfactant selection is still in a black box and sometimes taming is difficult. Product yield can also be affected by particle growth kinetics. Ostwald ripening is a well-known process that can grow particles while maintaining its equilibrium yield. Smaller particles with a higher chemical potential (i.e. higher solubility) dissolve in the reaction solution, while larger particles with a lower chemical potential (lower solubility) grow by consuming the dissolved species.3 However, Ostwald ripening of narrow size distribution particles yields a wider size distribution4 because the free energy, which governs this process, varies continuously with particle size. Therefore, smaller particles dissolve and shrink, while larger particles grow, and this kind of ripening is usually avoided to obtain nanocrystals with narrow size distribution1. Here, if a clear energetic gap exists between the particles that dissolve and those that grow, that kind of ripening maybe applicable without broadening the size distribution, and this can be an effective method to control particle size while maintaining a high product yield. For FCC metal nanoparticles (e.g., Ag, Cu, Au, Pd, Pt, and Ni) it is often reported that multinary twin particles (MTPs) are dominant 5,6 , and this is explained based on free energy difference by the particle crystal structure, i.e., particles larger than the th
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