H. Tiznado

On the High Sensitivity of the Electronic States of 1 nm Gold Particles to Pretreatments and Modifiers

In this paper, the effect of modifiers and pretreatments on the electronic states of 1 nm gold nanoparticles (AuNPs) supported on silica was systematically studied. AuNPs deposited on silica (particle size of 2–4 nm) modified with Ce, La and Fe oxides, were studied by FTIR of adsorbed CO after different redox treatments at 100, 300 and 500 °C. This study was conducted at room temperature to allow detecting the electronic states of gold, which is more likely involved in CO oxidation at the same temperature. AuNP size distribution was measured by HRTEM. It is shown that the electronic state of gold species (Aunδ−, Au0, Aunδ+, Au+) in 1 nm AuNPs is sensitive to the modifier as well as to the temperatures of redox pretreatments. Supports modified with the same additives but containing larger AuNPs (~3, 4, 5, and 7 nm) were also studied. They showed that Au0 remains stable irrespective of additives and redox pretreatments, indicating no significant effect of such treatments on the electronic properties of larger AuNPs. Samples with a predominant AuNP size of 2 nm are an intermediate case between these two groups of materials.

Use of AES in corrosion of copper connectors of electronic devices and equipments in arid and marine environments

Purpose – The electronics industry has grown over the past 50 years, mostly in developed countries, contributing to their economic progress. Particularly in the Baja California State located in the northwest of Mexico, these companies have prospered in the industrial parks of Mexicali considered as an arid zone and Ensenada, a port and city on the Pacific Ocean considered as a marine region. In both environments, during winter and summer, the climate impacts on indoor conditions, affecting humidity and temperature, and generating corrosion which decreases the yields of the electronic devices and industrial machines. The purpose of this paper is to investigate the effects of corrosion on electronic devices in these arid and marine environments.Design/methodology/approach – The paper determines the corrosivity levels inside industrial plants of desertic and coast regions in Mexico, to evaluate the deterioration of electronic metals.Findings – Relative humidity, temperature, time of wetness, are recorded and...

Optimal sidewall functionalization for the growth of ultrathin TiO2 nanotubes via atomic layer deposition

One of the most suitable approaches for the production of inorganic nanotubes is by means of carbon nanotube (CNT) templates coated by atomic layer deposition (ALD). This approach is attractive because it has the potential of controlling the wall thickness down to the Angstroms level. However, it is a recognized fact that the chemistry of the substrate surface can delay the full coverage at the initial stages of the ALD coating process, mainly due to nucleation issues. This is an important issue that might restrict laying down homogeneous coatings within the ultrathin range, which is the foundation for producing self-supported inorganic nanotubes. Here, we explore the early stage of the TiO2 nucleation on CNT templates systematically functionalized with different chemical groups (COOH, OH) or N-doped. The effects of the functionalization on the nucleation process from tetrakis (dimethylamino) titanium and water were meticulously studied by means of transmission electron microscopy. Observations revealed grain-like growth of TiO2 over pristine, purified and –OH-functionalized CNTs. In contrast, COOH functionalization yielded good conformality, which was improved on N-doped CNTs. Results were confirmed by X-rays photoelectron spectroscopy analysis. We recommend either COOH or N-doped CNTs for the production of ultrathin TiO2 nanotubes.

Physical and electrical characterization of yttrium-stabilized zirconia (YSZ) thin films deposited by sputtering and atomic-layer deposition

The physical, chemical, and electrical characteristics of intercalated nano-layers of Y2O3 and ZrO2, sequentially deposited by sputtering and thermal atomic-layer deposition (ALD), are reported in order to assess their use as electronic and/or ionic conductor. In general, the physical and chemical properties of sputtered and ALD-YSZ show good characteristics while a relatively high dielectric constant of about 30, along with a large capacitance–voltage hysteresis, are obtained for ALD-YSZ. Additionally, using inert or reactive metals as gate electrodes on YSZ/n-Si structures, promotes a change in the conduction of electronic and ionic species of YSZ and their influence is also reported.

Study of electronic state of supported gold nanospecies by IR spectroscopy

The nature of different Au species supported on hexagonal mesoporous silica has been studied by infrared spectroscopy of adsorbed CO. Experiments revealed existence of the following states of supported gold: neutral metal particles Au°, ions Au⁺ and a number of partly charged states Au^δ+ with different effective charge. Redox pretreatments (vacuum, O₂ and H₂) of Au/SiO₂ at the different temperatures (100, 300 and 500°C) exert a significant effect on the electronic state of supported Au species. The experiments showed high stability of Au^δ+ states under all treatments; that may prove their active role in catalytic properties of gold.