Large-area vertically aligned 2D MoS2layers on TEMPO-cellulose nanofibers for biodegradable transient gas sensors.

Crystallographically anisotropic two-dimensional (2D) molybdenum disulfide (MoS2) with vertically aligned (VA) layers is attractive for electrochemical sensing owing to its surface-enriched dangling bonds coupled with extremely large mechanical deformability. In this study, we explored VA-2D MoS2layers integrated on cellulose nanofibers (CNFs) for detecting various volatile organic compound gases. Sensor devices employing VA-2D MoS2/CNFs exhibited excellent sensitivities for the tested gases of ethanol, methanol, ammonia, and acetone; e.g. a high response rate up to 83.39% for 100 ppm ethanol, significantly outperforming previously reported sensors employing horizontally aligned 2D MoS2layers. Furthermore, VA-2D MoS2/CNFs were identified to be completely dissolvable in buffer solutions such as phosphate-buffered saline solution and baking soda buffer solution without releasing toxic chemicals. This unusual combination of high sensitivity and excellent biodegradability inherent to VA-2D MoS2/CNFs offers unprecedented opportunities for exploring mechanically reconfigurable sensor technologies with bio-compatible transient characteristics.

Enhanced Gas-Sensing Performance of GO/TiO2 Composite by Photocatalysis.

Few studies have investigated the gas-sensing properties of graphene oxide/titanium dioxide (GO/TiO2) composite combined with photocatalytic effect. Room temperature gas-sensing properties of the GO/TiO2 composite were investigated towards various reducing gases. The composite sensor showed an enhanced gas response and a faster recovery time than a pure GO sensor due to the synergistic effect of the hybridization, such as creation of a hetero-junction at the interface and modulation of charge carrier density. However, the issue of long-term stability at room temperature still remains unsolved even after construction of a composite structure. To address this issue, the surface and hetero-junction of the GO/TiO2 composite were engineered via a UV process. A photocatalytic effect of TiO2 induced the reduction of the GO phase in the composite solution. The comparison of gas-sensing properties before and after the UV process clearly showed the transition from n-type to p-type gas-sensing behavior toward reducing gases. This transition revealed that the dominant sensing material is GO, and TiO2 enhanced the gas reaction by providing more reactive sites. With a UV-treated composite sensor, the function of identifying target gas was maintained over a one-month period, showing strong resistance to humidity.

Newly designed minimally invasive plating of a humerus shaft fracture; a different introduction of the plate.

PURPOSE: Open reductions and internal fixations are currently being used the most in surgeries of humeral shaft fractures. However, there are some limitations such as invasive techniques and formation of many operation scars. To overcome these limitations, a minimally invasive plate osteosynthesis has been recently introduced. However, this has technical limitations such as deep dissections of the distal portion and narrowness of the fixation space. To address these problems, we designed another introductory technique of a minimally invasive osteosynthesis and we have examined the clinical usefulness of that. METHODS: The results were retrospectively analyzed with 83 patients who visited INHA hospital due to a humeral shaft fractures and who had undergone the above said surgery from the beginning of 2010 to the end of 2012. The patients were divided into two groups: patients treated by the MIPO technique using the newly designed dual approaches (group A) and patients treated by open reduction and plating internal fixation (group B). RESULTS: There was no significant difference in mean duration of injury, the mean fracture union time, range of motion and MEPI for group A and B. There was no statistical significance between the two groups. However, the occurrence of iatrogenic radial nerve palsy in group B, was significantly higher than in group A. CONCLUSIONS: MIPOs using the dual approaches on the adult humerus shaft fracture show an excellent bony union without nerve injury which is clinically useful.

Crystallographic Wet Chemical Etching of Semipolar GaN (11-22) Grown on m-Plane Sapphire Substrates.

This paper reports the etch rates and etched surface morphology of semipolar GaN using a potassium hydroxide (KOH) solution. Semipolar (11-22) GaN could be etched easily using a KOH solution and the etch rate was higher than that of Ga-polar c-plane GaN (0001). The etch rate was anisotropic and the highest etch rate was measured to be approximately 116 nm/min for the (1011) plane and 62 nm/min for the (11-20) plane GaN using a 4 M KOH solution at 100 °C, resulting in specific surface features, such as inclined trigonal cells.

Low-ppm-Level colorimetric acid detection using gold nanoparticles with electro-steric stabilization.

Electro-sterically stabilized gold suspensions were employed in a colorimetric system for the detection of strong acid in water. Using oleyamine and oleic acid as steric stabilizer in 1,2-dichlorobenzene, hydrophobic gold nanoparticles were first synthesized by a reduction reaction of gold salts and were then transferred into water with a cationic surfactant. When the hydrochlo- ric acid solution higher than critical concentration was injected, particles were quickly aggregated and precipitated, creating a clear solution from the colored suspension. The particles were stable against chemical etching by corrosive ion such as chloride. Critical concentration was dependent of the size and concentration of the particles. The minimum concentration of dramatic color change was at 5 ppm level of hydrochloric acid, in which the largest colloidal gold nanoparticles (54 nm) were used. Furthermore, because of their steric repulsive soft layer on particles, particles could be reused for further detection experiments after regeneration by the simple pH-neutralization and washing process.

Room temperature deposition of silicon nanodot clusters by plasma-enhanced chemical vapor deposition.

The formation of nanometer-scale (ns)-Si dots and clusters on p-GaN layers has been studied by controlling the early stage of growth during plasma-enhanced chemical vapor deposition (PECVD) at room temperature. We found that ns-Si dots and clusters formed on the p-GaN surface, indicating that growth was the Volmer-Weber mode. The deposition parameters such as radio frequency (RF) power and processing time mainly influenced the size of the ns-Si dots (40 nm-160 nm) and the density of the ns-Si dot clusters.

Characteristics of the Ni-B film in printed circuit board for high-power light-emitting diodes.

To develop metal printed circuit boards for a high-power light-emitting diode package using electroless plated Ni-B films on an all-in-one Al2O3-Al substrate with a 10 nm pore size, the growth mode of an electroless Ni-B film on a screen-printed Ag pattern/Al2O3-Al substrate was studied. So as not to damage the Al2O3-AI substrate, a nearly neutral Ni plating solution bath (pH 6.5) included dimethylamine borane was used. It was confirmed that the Ni-B film was selectively grown on the printed Ag paste layer, without growth on the Al2O3. The structure of the electroless plated Ni-B film was amorphous, and the deposition rate of the film was 1.64 +/- 0.078 nm/sec. According to the increase in plating time, the grain sizes of the electroless plated Ni-B film became bigger, and the surface morphology gradually became flatter. In addition, both the mass difference and the film thickness were changed linearly. From these results, it can be concluded that the electroless Ni-B film on printed Ag paste grows immediately from the beginning, and then grows linearly with increasing plating time.

Ohmic contacts to N-face p-GaN using Ni/Au for the fabrication of polarization inverted light-emitting diodes.

The electrical properties of Ni-based ohmic contacts to N-face p-type GaN were investigated. The specific contact resistance of N-face p-GaN exhibits a linear decrease from 1.01 omega cm2 to 9.05 x 10(-3) omega cm2 for the as-deposited and the annealed Ni/Au contacts, respectively, with increasing annealing temperature. However, the specific contact resistance could be decreased down to 1.03 x 10(-4) omega cm2 by means of surface treatment using an alcohol-based (NH4)2S solution. The depth profile data measured from the intensity of O1s peak in the X-ray photoemission spectra showed that the alcohol-based (NH4)2S treatment was effective in removing the surface oxide layer of GaN.

An electrically modifiable synapse array of resistive switching memory.

This paper describes the resistive switching of a cross-point cell array device, with a junction area of 100 nm x 100 nm, fabricated using ultraviolet nanoimprinting. A GdO(x) and Cu-doped MoO(x) stack with platinum top and bottom electrodes served as the resistive switching layer, which shows analog memory characteristics with a resistance ratio greater than 10. To demonstrate a neural network circuit, we operated the cell array device as an electrically modifiable synapse array circuit and carried out a weighted sum operation. This demonstration of cross-point arrays, based on resistive switching memory, opens the way for feasible ultra-high density synapse circuits for future large-scale neural network systems.