Issue 48, 2014

Influence of gold additives on the stability and phase transformation of titanate nanostructures

Abstract

Gold nanoparticles were prepared and characterized on protonated (H-form) titanate nanotubes (TiONTs) and nanowires (TiONWs). The chemical nature and morphology of gold particles were monitored by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD) and high resolution electron microscopy (HRTEM). The optical properties of Au-containing titanate nanowires were explored by means of ultraviolet-visible diffuse reflectance spectroscopy. The size distribution and homogeneity of gold particles depend on the reduction mode from the corresponding gold salt to metal particles. Smaller clusters (3–8 nm) were obtained with the NaBH4 reactant at 293 K than with molecular hydrogen reduction. An unexpectedly high binding energy gold state was found by XPS in gold-loaded titanate nanostructures. This state was absent from the spectra of gold-loaded TiO2(110). A likely explanation for this phenomenon, supported also by the characteristic decrease of band gap energy from 3.10 eV to 2.74 eV with increasing Au content, is that depending on the metal loading and titanate structure, Au is stabilized on titanate nanowires partially in positively charged gold form by ion exchange and also as Au clusters. Our important new finding is that the thermal annealing behavior of Au-loaded titanate nanotubes and nanowires is different. The former lose their tubular morphology and are readily transformed into anatase even at a very low temperature of 473 K. On the other hand, gold stabilizes the layered structure of titanate nanowires up to 873 K.

Graphical abstract: Influence of gold additives on the stability and phase transformation of titanate nanostructures

Supplementary files

Article information

Article type
Paper
Submitted
11 Sep 2014
Accepted
29 Oct 2014
First published
31 Oct 2014

Phys. Chem. Chem. Phys., 2014,16, 26786-26797

Author version available

Influence of gold additives on the stability and phase transformation of titanate nanostructures

P. Pusztai, R. Puskás, E. Varga, A. Erdőhelyi, Á. Kukovecz, Z. Kónya and J. Kiss, Phys. Chem. Chem. Phys., 2014, 16, 26786 DOI: 10.1039/C4CP04084H

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