We report on the fabrication of self-organized titanium oxide nanotube arrays of enhanced surface area prepared by anodic oxidation of a pure titanium sheet in electrolyte solutions containing potassium fluoride (KF) or sodium fluoride (NaF). The effects of electrolyte composition and concentration, solution pH, and the anodic potential on the formation of nanotubes and dimensions of the resulting nanotubes are detailed. Although nanotube arrays of length greater than 500 nm are not possible with hydrofluoric acid containing electrolytes [G.K. Mor, O.K. Varghese, M. Paulose,N. Mukherjee, C.A. Grimes, J. Mater. Res. 18, 2588 (2003)], by adjusting the pH of a KF containing electrolyte to 4.5 using additives such as sulfuric acid, sodium hydroxide, sodium hydrogen sulfate, and/or citric acid, we could increase the length of the nanotube-array to approximately 4.4 μm, an order of magnitude increase in length. The as-prepared nanotubes are composed of amorphous titanium oxide. Independent of the electrolyte composition, crystallization of the nanotubes to anatase phase occurred at temperatures ⩾280 °C. Rutile formation occurred at the nanotube-Ti substrate interface at temperatures near 480 °C. It appears geometry constraints imposed by the nanotube walls inhibit anatase to rutile transformation. No disintegration of the nanotube array structure is observed at temperatures as high as 580 °C. The excellent structural and crystal phase stability of these nanotubes make them promising for both low- and high-temperature applications.
The synthesis and testing of two gold-thiolate monolayer-protected (nano)clusters as interfacial layers on a dual-chemiresistor vapor sensor array are described. Responses (changes in dc resistance) to each of 11 organic solvent vapors are rapid, reversible, and linear with concentration at low vapor concentrations, becoming sublinear at higher concentrations. Limits of detection (LODs) range from 0.1 to 24 parts per million and vary inversely with solvent vapor pressure. When configured as a GC detector and used to analyze 0.5-L preconcentrated samples of the 11-vapor mixture, the array provides LODs of < or = 700 parts per trillion for most vapors, comparing favorably with those from an integrated array of polymer-coated surface acoustic wave sensors configured and tested similarly. This first report on the use of such an array as a GC detector shows that the combination of response patterns and GC retention times improves capabilities for vapor recognition compared to the sensor array alone or to single-detector GC systems. Spray-coated nanocluster thin films can be deposited reproducibly and exhibit response stability in air that ranges from fair to excellent for up to several months. Scaling the active device area down by a factor of 16 has no significant effect on sensitivity. Implications of these results for portable vapor sensing systems are discussed.
Driven by the urgent demand of detecting trace amounts of pentachlorophenol (PCP) in contaminative water, a label-free immunosensor with ultra sensitivity and high selectivity was constructed based on a hybrid CdSe(x)Te(1-x) (0 ≤ x ≤ 1) nanocrystal (NCs)-modified TiO(2) nanotube (NT) arrays for the first time. The CdSe(x)Te(1-x) NCs were photoelectrodeposited on inner and outer space of the TiO(2) NTs, leading to high photoelectrical conversion efficiency in the visible region. PCP antibodies are covalently conjugated on the TiO(2) NTs due to the large surface area and good biocompatibility. Since the photocurrent is highly dependent on the TiO(2) surface properties, the specific interaction between PCP and the antibodies results in a sensitive change in the photocurrent, with a limit of detection (LOD) of 1 pM. High sensor-to-sensor reproducibility is achieved. The sensor was applied for the direct analysis of river water samples.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.