Oxidation of CuSn alloy nanotree and application for gas sensors

The CuSn alloy nanotree formed by DC electroplating is a true three-dimensional (3D) structure with many branches that separate the trunk perpendicularly. We carried out the oxidation of CuSn nanotrees in atmosphere in order to study the possibility of such nanotrees for application to sensors. It was confirmed that the oxygen concentration in the CuSn nanotree oxide increased with temperature and reached 40 at. % at 350 °C. The optical reflectance spectra of the CuSn nanotree oxide formed at 250 °C showed a 3–4% reflectance in the wavelength range between 400 and 900 nm, and its behavior differed from those of Cu and Sn oxides formed at 250 °C. The temperature dependence of electrical resistivity for the CuSn nanotree oxide showed a typical semiconductor behavior. By the introduction of H2, O2, N2, and CO gases into the chamber, the resistance of the CuSn nanotree oxide responded against H2 most sensitively, as well as against O2 and CO gases. From the resistance change tendency, it is strongly suggested that the CuSn nanotree oxide is a p-type semiconductor, because it shows an increase in conductivity caused by the adsorption of a negative charge such as O−. However, the conductivity decreases with the adsorption of a positive charge such as H+. The present study suggests the high potential of the CuSn nanotree oxide as a gas sensor, since it has a very high surface-to-volume ratio

Nano-honeycomb electrode based QCM sensor and its application for PPI detection

An anodic aluminon oxide (AAO)-based nano honeycomb electrode was coated on a quartz crystal for use as a sensing device in a quartz crystal microbalance (QCM) to monitor the protein-protein interactions (PPIs). As examples, we detected PPIs of anti-Bcl-2 and Bcl-2, and Bcl-2 and Bax in real time. A sensor with a flat Au electrode showed a tiny frequency shift upon sample injection. However, our fabricated device could detect 10 μg/mL of Bcl-2 and Bax in sequence.2016年度関西大学研究拠点形成支援経

Fabrication of nanocone arrays by two step metal assisted chemical etching method

This work develops a novel method for preparing a moth eye structure, which has a sub-wavelength periodical Si nanocone structure on Si (100) substrate, using two-step metal assisted chemical etching (MACE). The 1st and 2nd MACE were respectively performed with the intention to form perpendicular Si nanowire arrays on a Si substrate and sharpening the Si nanowire arrays. We found the inhomogeneous absorption and aggregation of Au particles used as a catalyst for 2nd MACE was important to obtain the nanocone shape. The obtained Si nanocone arrays showed superior anti-reflecting properties especially in wavelength below 600 nm compared to the Si nanowire arrays. A possible mechanism involved in the formation of the nanocone structure by the 2-step MACE is discussed in this paper.This work was supported by KAKENHI Grant Numbers 25790024, 25600048 and15K04602 from the Japan Society for the Promotion of Science (JSPS), Strategic Project to Support the Formation of Research Bases at Private Universities: Matching Fund Subsidy from the Ministry of Education, Culture, Sports, Science and Technology(MEXT), and Kansai University Subsidy for supporting Young Scholars 2013

ZnO Nanostructure Based QCM Sensor to Detect Ethanol at Room Temperature Fabricated by All Wet Process

QCM is one of major sensing methods for volatile organic compounds (VOC) at room temperature. Nanostructure is effective to increase the sensitivity because of its large surface area. We introduced ZnO nanostructure to detect ethanol gas. ZnO nanostructure was fabricated by all wet process such as electrodeposition and chemical bath deposition (CBD). In this case, seed layer was obtained by electrodeposition, and nanostructure was formed by the CBD. The thickness of seed layer was controllable by charge amount on the electrodeposition, and that of nanostructure was controllable by deposition time on the CBD. As the results, the sensitivity increased with the thickness of the seed layer when the deposition time on CBD was set as 30 min. These results indicate that we can obtain high sensitive VOC sensor by using all wet process which is fit to large scale production with cost-effective

Fabricating a Highly Sensitive QCM Sensor Using AAO Nanoholes and Its Application for Biosensing

A nanostructure composed of Anodic Aluminum Oxide (AAO) was obtained on an electrode of a quartz crystal microbalance (QCM) chip by anodizing Al thin film in an oxalic acid solution. The effective surface area was expanded by these nanostructures. Several morphologies were observed under various anodic conditions by using scanning electron microscopy (SEM). We demonstrated that a QCM chip with the AAO was effective in biosensing because of its large surface area. The frequency shift corresponding to an antigen-antibody reaction improved on the nanostructured electrode compared with a flat surface electrode