Aggregate structure and crystallite size of platinum nanoparticles synthesized by ethanol reduction |
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Authors: | Shin-Ru Wang Wenjea J Tseng |
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Institution: | (1) Department of Materials Science and Engineering, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 402, Taiwan |
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Abstract: | Monodispersed platinum (Pt) nanoparticles were synthesized from reducing hydrated hydrogen hexachloroplatinic acid (H2PtCl6·nH2O) with ethanol in the presence of polyvinylpyrrolidone (PVP) as a steric stabilizer. Concentration of both PVP and ethanol
influenced the aggregate structure and crystallite size of the nanoparticles. When the molar ratio of monomeric unit of PVP
to Pt, i.e., PVP]/Pt], was one, the synthesized Pt particles coagulated pronouncedly into an inter-connected particulate
network or self-organized into spherical superstructures with an apparent diameter ranging from 60 to 80 nm, depending on
the ethanol concentration. The geometry and structure of these complex aggregates were characterized by fractal analysis.
Fractal dimensions of 2.13–2.23 in three dimensions were determined from the Richardson’s plot, which suggests that a reaction-limited
cluster–cluster aggregation model (RCLA) was operative. The Pt colloids became apparently more stable when the PVP]/Pt]
ratio was increased greater than 20. Crystallite size of the Pt nanoparticles was found to increase linearly with the ethanol concentration as the PVP]/Pt] was held at one. This suggests that the reduction rate of PtCl6
2− ions in solution is critically important to the synthesized crystallite size. |
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Keywords: | Pt nanoparticles Aggregation Fractal Synthesis |
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