Formation of Self-Organized Nanoporous Anodic Oxide from Metallic Gallium

Abstract

This paper reports the formation of self-organized nanoporous gallium oxide by anodization of solid gallium metal. Because of its low melting point (ca. 30 °C), metallic gallium can be shaped into flexible structures, permitting the fabrication of nanoporous anodic oxide monoliths within confined spaces like the inside of a microchannel. Here, solid gallium films prepared on planar substrates were employed to investigate the effects of anodization voltage (1, 5, 10, 15 V) and H(2)SO(4) concentration (1, 2, 4, 6 M) on anodic oxide morphology. Self-organized nanopores aligned perpendicular to the film surface were obtained upon anodization of gallium films in ice-cooled 4 and 6 M aqueous H(2)SO(4) at 10 and 15 V. Nanopore formation could be recognized by an increase in anodic current after a current decrease reflecting barrier oxide formation. The average pore diameter was in the range of 18-40 nm with a narrow diameter distribution (relative standard deviation ca. 10-20%), and was larger at lower H(2)SO(4) concentration and higher applied voltage. The maximum thickness of nanoporous anodic oxide was ca. 2 μm. In addition, anodic formation of self-organized nanopores was demonstrated for a solid gallium monolith incorporated at the end of a glass capillary. Nanoporous anodic oxide monoliths formed from a fusible metal will lead to future development of unique devices for chemical sensing and catalysis.

Adsorption of Primary Substituted Hydrocarbons onto Solid Gallium Substrates

“…Very similar surface features were also measured by us with scanning electron microscopy. 7 Importantly, there is no significant change in surface morphology upon UV/ozone treatment, as indicated by the similar RMS roughness (0.74 ± 0.17 nm; Figure 6b). …”

“…as reported previously. 7 All the CV data were obtained in 0.1 M TBAPF6 acetonitrile solution cooled by ice (ca. 0 °C) using a CH instruments model 618B electrochemical analyzer.…”

“…These monoliths pore diameters are ranging from 18-40 nm and can be used for future chemical sensors and catalyst applications. 7 In these applications, it is important to understand the surface chemistry of these metals.…”

Electrochemical and Morphological Investigations of Ga Addition to Pt Electrocatalyst Supported on Carbon

“…Recently, gallium and its alloys have attracted considerable interest as electrode materials because of their low toxicity and melting point (29.8°C) [21, 22]. Metallic gallium can be easily incorporated into microscale channels [23].…”

“…The element is suited to readily form alloys (e.g., eutectic alloys) with most metals in conjunction with being a component in low-melting alloys [24]. It is well known that metallic gallium is in self-passivation by an ultrathin gallium oxide layer upon exposure to air, behavior similar to aluminum [22]. …”