Growth of arrays of oriented epitaxial platinum nanoparticles with controlled size and shape by natural colloidal lithography.

Vladimir Komanicky,Hoydoo You,Chenhui Zhu,Michael Pierce,Miroslava Lackova,Andi Barbour,Milena Zorko

doi:10.1186/1556-276x-9-336

Abstract

We developed a method for production of arrays of platinum nanocrystals of controlled size and shape using templates from ordered silica bead monolayers. Silica beads with nominal sizes of 150 and 450 nm were self-assembled into monolayers over strontium titanate single crystal substrates. The monolayers were used as shadow masks for platinum metal deposition on the substrate using the three-step evaporation technique. Produced arrays of epitaxial platinum islands were transformed into nanocrystals by annealing in a quartz tube in nitrogen flow. The shape of particles is determined by the substrate crystallography, while the size of the particles and their spacing are controlled by the size of the silica beads in the monolayer mask. As a proof of concept, arrays of platinum nanocrystals of cubooctahedral shape were prepared on (100) strontium titanate substrates. The nanocrystal arrays were characterized by atomic force microscopy, scanning electron microscopy, and synchrotron X-ray diffraction techniques.

Highlights

Supported transition metal nanoparticles are widely used as catalysts and electrocatalysts in many industrial applications
Microscopy characterization of silica monolayers and platinum nanoparticle arrays Ordered silica bead monolayers, which later served as templates for the platinum metal deposition, were made by depositing solutions containing either 450- or 150-nm silica beads
We have demonstrated a simple method for the preparation of platinum nanoparticle arrays with control of nanoparticle size, spacing, and shape

Summary

Introduction

Supported transition metal nanoparticles are widely used as catalysts and electrocatalysts in many industrial applications. In the case of nanoparticulate catalysts, the shape can be an important governing factor in overall catalyst activity [2] because the nanoparticle shape is dictated by the crystallography of facets with the lowest surface energy. Particle-substrate interface crystallography and with other techniques has been successfully used to produce metallic nanostructures and nanoparticle crystallites of random shape [9] and orientation [10]. The purpose of this report is to present a simple two-step process based on mask templates of a self-assembled silica colloidal sphere monolayer suitable for production of epitaxially oriented platinum nanoparticle arrays with precisely controlled shape. Shape and orientation of the particles are controlled via substrate crystallography, and particle size and spatial distribution are controlled via size of colloidal silica spheres used in monolayer template. Since the nanoparticles are supported on the annealable and electrically conducting Nb-doped strontium titanate (STO) substrates, the samples can be used both in electrocatalysis and gas phase catalysis

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