Fabrication, characterization, and application of boron-doped diamond microelectrodes for in vivo dopamine detection

Highly boron-doped diamond (BDD) was deposited on chemically etched micrometer-sized tungsten wires using microwave plasma assisted chemical vapor deposition (MPCVD), and these were used to fabricate BDD microelectrodes. BDD microelectrodes with very small diameter (about 5 microm) and 250 microm in length could be made successfully. In addition to the unique properties of BDD electrodes, such as a very low background current, high stability, and selective oxidation of dopamine (DA) in the presence of ascorbic acid (AA), other superior properties of the microelectrodes, including a constant current response, an increase in the mass transport, and the ability for use in high resistance media were also shown. An application study was conducted for in vivo detection of DA in mouse brain, where the BDD microelectrode was inserted into the corpus striatum of the mouse brain. A clear signal current response following medial forebrain bundle (MFB) stimulation could be obtained with high sensitivity. Excellent stability was achieved, indicating that the BDD microelectrodes are very promising for future in vivo electroanalysis.     

Hydrazine degradation by ultrasonic irradiation

The influence of pH on the degradation of hydrazine with a concentration of 0.1mmol/L was investigated under the stirring (300rpm) and ultrasonic irradiation conditions (200kHz, 200W) in the pH range of 1-9. It was found that the hydrazine degradation depended greatly upon pH under the ultrasonic irradiation condition, while it did not take place over the whole pH range under the stirring condition. Although it has been known that OH radicals and hydrogen peroxide are sonochemically formed from water, it was considered that the OH radicals played an important role of the hydrazine degradation, but not hydrogen peroxide. The pH dependence of the hydrazine degradation was discussed in terms of the relationship between the chemical structure and the basic dissociation constants of hydrazine.     

Micropattern Formation by Molecular Migration via UV‐induced Dehydration of Block Copolymers

A novel UV lithographic technique for the patterning of the block copolymer (Pluronic) thin films is developed. The present method is based on UV‐induced water affinity changes in block copolymer films. By water vapor post‐treatment of the film, a difference in water content is established between UV illuminated and unilluminated sections, which can induce an osmotic pressure at the interface. This osmotic pressure drives the migration of Pluronic molecules, resulting in formation of patterns on the block copolymer films. Remarkably, this patterning method requires neither initiators nor polymerizable moieties which are essential for a conventional photolithographic approach. Additionally, the etching process is bypassed, eliminating the use of destructive acids or organic solvents and making this an environmentally friendly patterning protocol. It is reported that Pluronic is photo‐responsive to UV exposure, which causes the dehydration of the PEO‐PPO‐PEO backbone.     

Temporal development of partial discharge and its application tobreakdown prediction in SF6 gas

The authors measured the temporal change of partial discharge (PD) characteristics leading to breakdown in SF₆ gas for AC voltage application. At the final stage close to the breakdown, positive PD pulses with relatively high magnitude began to take place in the phase region near the applied voltage peak. This event was interpreted in terms of the change of PD type in SF₆ gas from streamer to leader. Optical observation also revealed that PD type transition occurred. With the results considered, the mechanisms of PD were discussed. Moreover, they discussed the possibility of breakdown prediction in GIS. An attempt was made to find a breakdown prediction parameter which characterized the change of PD type: the ratio R_L of maximum charge to the average charge of PD pulses appearing in the phase region near the peak in positive half cycle. It was found that R_L allowed to predict the time to breakdown successfully within the error of 4~20%     

Removal of Interlayer Water of two Ti3C2Tx MXenes as a Versatile Tool for Controlling the Fermi-Level Pinning-Free Schottky Diodes with Nb:SrTiO3

Striving for the sixth-generation communication technology discovery, semiconductors beyond Si with wider bandgaps as well as non-conventional metals are actively being sought to achieve high speeds whilst maintaining devices miniaturization. 2D materials may provide the potential for downsizing, but their functional advantage over existing counterparts still longs to be discovered. Along that path, surface-adsorbed or bulk-intercalated water molecules remaining after wet-chemical synthesis of 2D materials are generally seen as obstacles to high-performance achievement. Herein, the control of such water within the interlayers of solution-processed metallic 2D titanium carbide (MXene) by vacuum annealing duration is demonstrated. Moreover, the impact of water removal on work function (WF) and functional terminations is unveiled for the first time. Furthermore, the usefulness of such water for controlling a novel Schottky diode in contact with an n-type oxide semiconductor, niobium-doped strontium titanate (Nb:SrTiO₃) is observed. The advantage of MXene compared to conventional gold as facile processing, WF tunability, and lower turn-on voltage in the Schottky anode application is highlighted. This fundamental study shows the way for a novel Schottky diode preparation in atmospheric conditions and provides implications for further research directions aiming at commercialization.     

Power factor control for inverters under high penetration of distributed generation

The paper proposes a method to select a power factor for an inverter of distributed power generation systems to keep appropriate voltage of a power system with the high penetration of inverter-interfaced generation. The increase of inverter-interfaced power sources, such as wind and photovoltaic power generation, arouses concerns on the voltage fluctuations in a power system. While constant power factor control of an inverter has been studied as a means to stabilize the voltage of a power system, there still remains room to improve the control. The proposed method in the paper selects the power factor based on the R/X ratio of the looking-back impedance into the interconnected power system. By normalizing the related variables, a general formula is derived for the power factor, and the resultant relationship between the apparent power and voltage of an inverter becomes identical irrespective of the R/X ratio with the control. Sample studies show that, by operating an inverter with the power factor, voltage fluctuations are effectively suppressed even for a power system with the high penetration of inverter-interfaced generation.