• Applied Chemistry for Engineering
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• v.20 no.3
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• pp.329-334
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• 2009

Yttrium ions doped $TiO_2$ particles have been prepared using a low temperature combustion method. The physical properties were investigated, together with the activity of $TiO_2$ particles as a photocatalyst for the decomposition of methylene blue. From XRD results, the major phase of all the $TiO_2$ particles prepared under basic condition was an anatase structure but a rutile peak was observed when they are prepared under acidic condition. The crystallite size of $TiO_2$ particles was decreased as the molar ratio of CA/TTIP increased. The photocatalytic activity increased with an increase of CA/TTIP molar ratio and pH in the solution. In addition, the doping of 1.0 mole% yttrium ion on the $TiO_2$ enhanced the photocatalytic activity and showed the higher activity than commercial P-25 catalyst.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.306-310
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• 2015

In this research, hematite nanoparticles were synthesized by DC thermal plasma process to increase the overall surface area. The effect of binders on hematite electrodes was investigated by changing the type and composition of binders when preparing electrodes. Nitrogen gas was also added to the DC thermal plasma process in order to dope the hematite with N for enhancing photoelectrochemical properties of hematite nanoparticles. The efficiency of water splitting reaction was measured by linear sweep voltammetry (LSV) under solar simulator. In LSV measurements, the onset potential and maximum current density at a fixed voltage were measured. The durability of electrodes was checked by repeating LSV measurements. CMC (carboxymethyl cellulose) binder with 50 : 1 composition exhibits the highest current density of $12mA/cm^2$ and CMC binder with 20 : 1 composition, showing the initial current density of $3mA/cm^2$, endures 20 times of repetitive LSV measurements. Effects of nitrogen doping on hematite nanoparticles were proven to be insignificant.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.143-147
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• 2012

Photocatalytic properties of $TiO_2$ nanopowders has been received much attention due to their high potentials for environmental applications such as remediation of polluted environments. The $TiO_2$ nanopowders doped with metal or non-metal elements have been synthesized by variety methods such as flame method, chemical vapor synthesis, sol-gel, ion implantation, which affect a doping behavior in different ways resulting in different surface characteristics, leading to different photocatalytic activity. In addition to an effect of synthesis methods, the photocatalytic activity of $TiO_2$ nanopowders can be improved by subsequent heat-treatments. In this study, to obtain a highly efficient photocatalyst, we synthesized $TiO_2$ nanopowders doped with tungsten by the chemical vapor synthesis method (CVS) and determined their physical properties and photocatalytic activity, together with subsequent post-treatment in the range of $300^{\circ}C$ to $700^{\circ}C$.

• Polymer(Korea)
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• v.33 no.5
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• pp.407-412
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• 2009

Vacuum deposited N,N-di-1-naphthyl-N,N-diphenyl-1,1'-biphenyl-4,4'-diamine (NPD) as a hole transporting (HTL) materials in OLEDs was placed on PEDOT-PSS, a hole injection layer (HIL). PEDOT-PSS was spin-coated on to the ITO glass. $C_{60}$-doped NPD-$C_{60}$(10 wt%) film was formed via co-evaporation process and the morphology of NPD-$C_{60}$ films was investigated using XRD and AFM. The J - V, L - V and current efficiency of multi -layered devices were characterized. According to XRD results, the deposited $C_{60}$ thin film was partially crystalline, but NPD-$C_{60}$ film was observed not to be crystalline, which indicates that $C_{60}$ molecules are uniformly dispersed in the NPD film. By using $C_{60}$-doped NPD-$C_{60}$ film as a HTL, the current density and luminance of multi-layered ITO/PEDOT-PSS/NPD-$C_{60}/Alq_3$/LiF/Al device were significantly increased by about 80% and its efficiency was improved by about 25% in this study.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.418-423
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• 2009

MWCNT(multi-wall carbon nanotube)-doped PEDOT:PSS(poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)), used as a HIL(hole injection layer) material in OLEDs(organic light emitting diodes), was spin-coated on to the ITO glass to form PEDOT:PSS-MWCNT nano composite thin film. Morphology and transparency characteristics of nano composite thin films with respect to the loading percent of MWCNT have been investigated using FT-IR, UV-Vis and SEM. Furthermore, ITO/PEDOT:PSS-MWCNT/NPD/$Alq_3$/Al devices were fabricated, and then J-V and L-V characteristics were investigated. Functional group-incorporated MWCNT was prepared by acid treatment and showed good dispersion property in PEDOT:PSS solution. PEDOT:PSS-MWCNT thin films possessed good transparency property. For multi-layered devices, it was shown that as the loading percent of MWCNT increased, the current density increased but the luminance dramatically decreased. It might be conclusively suggested that the enhanced charge mobility by MWCNT could increase the current density but the hole trapping property of MWCNT could dramatically decrease the hole mobility in the current devices.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.495-499
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• 2010

To develop chemical and biosensors, this paper studies sensing characteristics of bulk carbon nanotube (CNT) electrodes by means of their electrical impedance properties due to their large surface area and excellence chemical absorptivity. The sensors were fabricated in the form of film and nano web style by using composite process for mass production. The bulk composite electrodes were fabricated with singlewall and multi-wall carbon nanotubes based on host polymers such as Nafion and PAN, using a solution-casting and an electrospinning technique. The resistance and the capacitance of electrodes were measured with LCR meter under the various amounts of buffer solution to study the electrical impedance change properties of them. On the experimental of sensor electrode, impedance characteristics of the composite electrode are affected by its host polymer and nanofiller and its sensing response showed saturated result after applying some amounts of buffer solution for test chemical. Especially, the capacitance values showed drastic changes while the resistance values only changed within few percent range. It is deduced that the ions in the solution penetrated and diffused into the electrodes surface changed the electrical properties of the electrodes much like a doping effect.

• Membrane Journal
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• v.19 no.3
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• pp.228-236
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• 2009

ABA type triblock copolymer of poly(hydroxyl ethyl acrylate )-b-polystyrene-b-poly(hydroxyl ethyl acrylate), i.e. PHEA-b-PS-b-PHEA, was synthesized throughatom transfer radical polymerization (ATRP). This block copolymer was thermally crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via the esterification between the -OH groups of PHEA in block copolymer and the -COOH groups of IDA. Upon doping with ${H_3}{PO_4}$ to form imidazole-${H_3}{PO_4}$ complexes, the proton conductivity of membranes continuously increased with increasing ${H_3}{PO_4}$ content. The PHEA-b-PS-b-PHEA/IDA/${H_3}{PO_4}$ polymer membrane with [HEA]:[IDA]:[${H_3}{PO_4}$]=3:4:4 exhibited a maximum proton conductivity of 0.01 S/cm at $100^{\circ}C$ under anhydrous conditions. Thermal gravimetric analysis (TGA) shows that the PHEA-b-PS-b-PHEA/IDA/${H_3}{PO_4}$ complex membranes were thermally stable up to $350^{\circ}C$, indicating their applicability in fuel cells.

• Polymer(Korea)
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• v.33 no.3
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• pp.191-197
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• 2009

We have investigated the effect of strong p-type organic semiconductor $F_4$-TCNQ-doped CuPc hole transport layer on the performance of p-i-n type bulk heterojunction photovoltaic device with ITO/PEDOT:PSS/CuPc: $F_4$-TCNQ(5 wt%)/CuPc:C60(blending ratio l:l)/C60/BCP/LiF/Al, architecture fabricated via vacuum deposition process, and have evaluated the J-V characteristics, short-circuit current ($J_{sc}$), open-circuit voltage($V_{oc}$), fill factor(FF), and power conversion efficiency(${\eta}_e$) of the device. By doping $F_4$-TCNQ into CuPc hole transport layer, increased absorption intensity in absorption spectra, uniform dispersion of organic molecules in the layer, surface uniformity of the layer, and enhanced injection currents improved the current photovoltaic device with power conversion efficiency(${\eta}_e$) of 0.16%, which is still low value compared to silicone solar cell indicating that many efforts should be made to improve organic photovoltaic devices.

• Membrane Journal
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• v.19 no.4
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• pp.302-309
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• 2009

A block copolymer of polystyrene-b-poly (hydroxyl ethyl methacrylate), PS-b-PHEMA, was synthesized via atom transfer radical polymerization (ATRP) and crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via esterification of the -OH groups of PHEMA in the block copolymer and the -COOH groups of IDA. Upon doping with $H_3PO_4$ to form imidazole-$H_3PO_4$ complexes, the proton conductivity of the membranes continuously increased as the content of $H_3PO_4$ increased. In addition, both the tensile strength and the elongation at break increased with IDA content. A proton conductivity of 0.01 S/cm at $100^{\circ}C$ was obtained for the PS-b-PHEMA/IDA/$H_3PO_4$ membrane with [HEMA]:[IDA]:[$H_3PO_4$] = 3:4:4 under anhydrous conditions. All of the PS-b-PHEMA/IDA/$H_3PO_4$ membranes were thermally stable up to $350^{\circ}C$, as revealed by thermal gravimetric analysis (TGA).

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.832-840
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• 2019

To improve the electrochemical performances of the cathode materials, boron-doped $LiNi_{0.90}Co_{0.05}Ti_{0.05}O_2$ were synthesized by using concentration gradient precursor. The characteristics of the prepared cathode materials were analyzed by XRD, SEM, EDS, PSA, ICP-OES and electrical conductivity measurement. The electrochemical performances were investigated by initial charge/discharge capacity, cycle stability, C-rate, cyclic voltammetry and electrochemical impedance spectroscopy. The cathode material with 0.5 mol% boron exhibited a capacity of 187 mAh/g (0.5 C) in a voltage range of 2.7~4.3 V(vs. $Li/Li^+$), and an capacity retention of 94.7% after 50 cycles. In the relatively high voltage range of 2.7~4.5 V(vs. $Li/Li^+$), it showed a high capacity of 200 mAh/g and capacity retention of 80.5% after 50 cycles.