The Brookhaven National Laboratory, a multipurpose research institution funded by the U.S. Department of Energy, recently reported that exposure to air transforms gold alloys into catalytic nanostructures. According to the Brookhaven researchers, these uniquely-structured gold-indium nanoparticles have high stability, great catalytic potential, and a simple synthesis process. This material has potential applications in many commercial and industrial processes, particularly the automotive industry where these new nanostructures may prove to be a suitable material for catalytic converters. The team will conduct further investigations to characterize the gold-indium oxide particles in different catalytic reactions and to apply the same oxidation process to other metal alloys to create new functional materials.
Due to the fact that these nanostructures are only a few nanometers in size, analyzing gold-indium alloy particles requires instrumentation that is sufficiently sensitive to the morphology and chemistry of the gold-indium core sample and its amporphous and catalytic oxide shell. Several technologies were used, including transmission electron microscopy to characterize the structures and their composition, x-ray photoelectron spectroscopy to determine the chemical bonding at the surface, and ion-scattering spectroscopy to identify the outermost atoms of the nanoparticle shell.
Transmission electron microscopy (TEM) is an imaging technique for obtaining structural information about solid materials. TEMs use electrons as a light source, which enables much higher resolution than light microscopes, down to atomic levels. Adding to the capabilities of the TEM, x-ray microanalysis systems detect the characteristic x-ray created by the interaction of the sample and the electron beam, providing a picture of the elemental composition (phases) in the material. In materials science studies, TEMs are used to determine the morphology, structure, and chemical composition of metals, ceramics, and minerals.
X-ray photoelectron spectroscopy (XPS) is a technique for analyzing the surface chemistry of a material. XPS can measure the elemental composition, empirical formula, chemical state and electronic state of the elements within a material. Many of the problems associated with modern materials can be solved only by understanding the physical and chemical interactions that occur at the surface or at the interfaces of a material’s layers. The surface chemistry influences such factors as corrosion rates, catalytic activity, adhesive properties, wettability, contact potential and failure mechanisms. Because a material’s surface is the point of interaction with the external environment and other materials, surface modification can be used to alter or improve the performance and behavior of a material in a wide variety of applications.
Ion-scattering spectroscopy (ISS), a spectroscopic technique used in conjunction with XPS instrumentation. The kinetic energy of scattered ions is measured; peaks are observed corresponding to elastic scattering of ions from atoms at the surface of the sample. A technique that is highly sensitive to surface chemistry, ISS is used to study semiconductors, thin films, coatings, microelectronics, magnetic storage devices, bioreactive surfaces, catalytic surfaces, and electrochemical surfaces. ISS capability can be incorporated into multi-technique XPS (or ESCA) instrumentation, for example, XPS Microprobe systems designed to provide high resolution surface imaging.
To learn more, view these on-demand webinars addressing topics in x-ray microanalysis.