Young-You Kim

Identification of luminous region in porous silicon layers

Photoluminescence spectra were measured experimentally and compared with the results of the optical model calculations in oder to identify the region of photoluminescence in a porous silicon layer. It is found that the upper surface region in the porous silicon layer contributes most of the luminescence, by analyzing the interference patterns of the photoluminescence spectra and those of reflectances. It is confirmed by comparing the results of a detailed computer simulation with the experiments, and by analyzing the photoluminescence characteristics of a free-standing porous silicon film. Analyses of the photoluminescence spectra measured using several different excitation wavelengths also support our conclusion.

Synthesis and characterization of nickel(II) and copper(II) complexes with a tetramethyltetraaza macrocycle containing 2-pyridylmethyl pendant arms

Abstract The complexes [Ni(L2)](ClO4)2·H2O (1) and [Cu(L2)]Cl2·4H2O (2) have been synthesized and characterized by X-ray crystallography, electronic absorption and cyclic voltammetry. The crystal structure of 1 reveals a distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendant pyridylmethyl groups. The structure of 2 shows that the complex is centrosymmetric and the metal center has a tetragonally distorted octahedral environment. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.

Observation of convection phenomenon by high-performance transparent heater based on Pt-decorated Ni micromesh

In this study, we report for the first time on the convection phenomenon for the consistent and sensitive detection of target materials (particulate matter (PM) or gases) with a high-performance transparent heater. The high-performance transparent heater, based on Pt-decorated Ni micromesh, was fabricated by a combination of transfer printing process and Pt sputtering. The resulting transparent heater exhibited excellent mechanical durability, adhesion with substrates, flexibility, and heat-generating performance. We monitored the changes in the PM concentration and temperature in an airtight chamber while operating the heater. The temperature in the chamber was increased slightly, and the PM2.5 concentration was increased by approximately 50 times relative to the initial state which PM is deposed in the chamber. We anticipate that our experimental findings will aid in the development and application of heaters for sensors and actuators as well as transparent electrodes and heating devices.

Self-assembly of copper(II) tetraaza macrocyclic complex with cyclohexane-1,3-dicarboxylic acid-5-monocarboxylate linked by hydrogen bond

A novel complex with the composition {[Cu(L)]⋅(Cl)⋅(H,H-cdc)⋅(H2O)}n (1) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane; H,H-cdc = cyclohexane-1,3-dicarboxylic acid-5-monocarboxylate) has been synthesized and structurally characterized by X-ray diffraction method. It crystallizes in the monoclinic system P21/n with a = 9.507(9), b = 12.624(3), c = 26.922(4) Å, β = 96.79(1)°, V = 3208(3) Å3, Z = 4. The complex contains a 1D hydrogen-bonded polymeric chain with copper(II) macrocycle and bridging H,H-cdc ligand. The copper(II) coordination geometry is best described as a square-plane with four Cu–N bonds. The weak interaction between copper(II) ion and the chloride ion is also found.

Droplet evaporation characteristics on transparent heaters with different wettabilities

To develop more effective defogging/deicing (or anti-fogging/anti-icing) devices based on transparent heaters, it is necessary to investigate droplet evaporation on the heater surfaces. However, the characteristics of this evaporation process have not yet been reported. Here, we present the evaporation characteristics of water droplets and their evaporation rates on various transparent heaters (based on metal mesh, indium tin oxide thin film, and Ag nanowires) with various surface wettabilities. We determined that the evaporation characteristics of a droplet on the surface of a transparent heater depend on the surface wettability and that the evaporation rate can be controlled by modifying the surface wettability.

The sensing characteristics of MOPS structure based on porous silicon for ethanol gas

To use the porous silicon as gas sensors, we made the MOPS structure from the porous silicon with Al evaporation and investigated the sensing characteristic of ethanol. When the MOPS structure is in contact with ethanol gas, the maximum peak of PL changes and it return to original intensity without contact. The MOPS structure had response time 0.78s and recovery time 4.13s when it is in contact with ethanol, which satisfied the required sensor standards. Further complimentary researches, however, are required to investigate the contact mechanism between MOPS structure and ethanol and to solve the surface contamination problem.