Abstract
A liquid-phase reducing method of synthesizing Pt nanocrystals was demonstrated, and dendrite-, cube-, and cuboctahedron-shaped Pt nanocrystals (NCs) with well-defined monomorphic were successfully synthesized through iodine ions mediated with the CTAB agent. When the KI concentration was increased to thirty times of K2PtCl4 at the nucleation stage, the high-quality Pt nanodendrites could be obtained. However, no matter how many KI were added at the growth age, only cube- and cuboctahedron-shaped Pt nanocrystals formed. The results of high-resolution TEM, EDX, and XRD indicated that the size and shape of Pt NCs could be turned by changing the concentration and time of KI. In the nucleation stage, it might be due to that some iodine ions adsorb on the surfaces of Pt NCs, which probably cause the rapid growth process resulting in the formation of Pt nanodendrites. In the growth stage, although high concentrations of I− ions could contribute to the shape control and generate bigger particles of Pt NCs, small Pt particles do not grow into dendrites. The insight into the role of I− ions in synthesis of Pt NCs reported here provided a viewpoint for clearly understanding the formation mechanism of anisotropic platinum nanostructures.
Highlights
The remarkable progress of nanotechnology has attracted great attention [1,2,3,4,5,6], mainly due to the ability to finely control the shape and size of metal nanocrystals (NCs) in order to manipulate their electronic [7, 8], optical [9], and catalytic properties [10, 11]
Some reports demonstrated that the catalytic performance of Pt NCs strongly depends on their size, shape, composition, and surface structure [12, 19]; for these reasons, Pt NCs have gained consideration in the development of high-activity Pt-based catalysts characterized by low amounts of Pt
We propose a facile and simple synthesis of Pt nanodendrites, octahedra, and cubes, achieved by only changing the timing and the amount of I− ions
Summary
The remarkable progress of nanotechnology has attracted great attention [1,2,3,4,5,6], mainly due to the ability to finely control the shape and size of metal nanocrystals (NCs) in order to manipulate their electronic [7, 8], optical [9], and catalytic properties [10, 11]. Among the viable Pt NC synthesis methods, the solutionphase chemical reaction process is the more appropriate and cost-effective way to obtain Pt NCs with well-defined shapes [21, 22]; the most common is the polyol process [23, 24] This method consists essentially in the reduction of a metal salt by a polyol and always occurs at elevated temperatures [25]. It has been reported that by adding aqueous NaBH4 to a solution of K2PtCl4, KBr, and Na2H2P2O7 with slow dripping speed, Pt concave nanocubes enclosed by high-index facets can be obtained [33] In this growth process, the selective overgrowth of Pt seeds at the edges and corners and the capping activity of Br− ions block the growth of the axis. The effect of I− ions on the shape of Pt NCs synthesized using the CTAB agent has been reported
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