Issue 8, 2019

The role of polyvinylpyrrolidone (PVP) as a capping and structure-directing agent in the formation of Pt nanocubes

Abstract

In this work, we have investigated the specific role of PVP and Ag+ ions in the formation of platinum nanocubes (NCs) in polyol synthesis. Various characterization techniques such as transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to unravel the effects of PVP and Ag+ ion concentrations on the monodispersity and particle size of the obtained Pt NCs. Very interestingly, we have already fabricated Pt NCs with similar monodispersity and particle size using only 0.4 M PVP (absence of Ag+ ions). Furthermore, the dispersity of the Pt NCs strongly depends on the initial PVP concentration. This observation underscores the important role of PVP during the NC formation processes by controlling the relative growth rates along the <100> direction with respect to those of the <111>. Time-resolved experiments show that the formation and growth of Pt NCs are much faster in the absence of Ag+ ions than with Ag+ ions, which can be explained by the enhanced growth rate along the <100> direction or/and the suppression of the growth rate along the <111>. Electronic interactions between the chemisorbed pyrrolidone ring of the PVP and Pt surface are revealed from the XPS and FTIR data, showing a negative shift of the binding energy of N 1s and a red shift of the Pt–CO vibration band. From our experimental results, we propose extended formation and growth mechanisms based on PVP as the main structure-directing agent. Our model indicates that the aliphatic chains of PVP forming a multi-layer shell influence the mass transport of precursor ions to the initial Pt seed to control the growth rate of Pt NCs with exposed {100} planes. Altogether, we provide a simple, efficient and resource-friendly synthetic guideline for the preparation of nano-sized Pt NCs with high monodispersity and high purity.

Graphical abstract: The role of polyvinylpyrrolidone (PVP) as a capping and structure-directing agent in the formation of Pt nanocubes

Article information

Article type
Paper
Submitted
27 Mar 2019
Accepted
23 Jun 2019
First published
24 Jun 2019
This article is Open Access
Creative Commons BY-NC license

Nanoscale Adv., 2019,1, 3095-3106

The role of polyvinylpyrrolidone (PVP) as a capping and structure-directing agent in the formation of Pt nanocubes

I. A. Safo, M. Werheid, C. Dosche and M. Oezaslan, Nanoscale Adv., 2019, 1, 3095 DOI: 10.1039/C9NA00186G

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