• Title/Summary/Keyword: organic template

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Roll-to-roll microcontact-printed microlens array for light extraction film of organic light-emitting diodes (유기발광다이오드의 외부 광추출층을 위한 롤투롤 마이크로컨택 방식으로 인쇄된 마이크로렌즈 어레이)

  • Hwa, Subin;Sung, Baeksang;Lee, Jae-Hyun;Lee, Jonghee;Kim, Min-Hoi
    • Journal of IKEEE
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    • v.26 no.2
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    • pp.205-210
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    • 2022
  • We demonstrated roll-to-roll microcontact printed (mCP) microlens array (MLA) to enhance the light extraction of organic light emitting diodes (OLEDs). The commercially provided microlens array is used as a template for polydimethylsiloxane (PDMS) roll stamp. The fluorinated film is formed on the PDMS roll stamp from fluorinated ink with low boiling point and printed onto the bottom side of the organic light emitting diode without high pressure and high thermal treatment. With optimized concentration of ink, the pattern which is almost identical to that of the template MLA was successfully printed. Due to the structure and low optical absorbance of microcontact printed MLA, the external quantum efficiency of OLED was improved by about 18%.

Synthesis and Characterization of Methyltriethoxysilyl-Mediated Mesoporous Silicalites

  • Rabbani, Mohammad Mahbub;Oh, Weon-Tae;Nam, Dae-Geun
    • Transactions on Electrical and Electronic Materials
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    • v.12 no.3
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    • pp.119-122
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    • 2011
  • A series of mesoporous silicalites was synthesized using different compositions of tetraethylorthosilicate and methyltriethoxysilane (MTES) as the silica source. Cetyltrimethylammonium bromide was used as the organic template. Their detailed pore structures were investigated by transmission electron microscopy, X-ray diffraction, and N2 adsorption method. The thermal properties of these silicalites were studied by thermogravimetric analysis. The increased amount of MTES destroyed mesoporous channels and reduced pore sizes from 3.4 nm to 2.8 nm in calcined silicalites. The calcined silicalite transformed completely into an amorphous state at 30% MTES loading. Methyl pending groups of MTES hindered the structural ordering of ≡Si-O- frameworks, resulting in an amorphous structure. This was caused by the insufficient formation of supramolecular assembly with the organic template. No capillary condensation step was found in MS 7/3 silicalite. The other capillary condensation steps shifted toward the lower relative pressure with increasing MTES content, indicating the reduction of pore sizes.

Effect of Activation Temperature on CO2 Capture Behaviors of Resorcinol-based Carbon Aerogels

  • Moon, Cheol-Whan;Kim, Youngjoo;Im, Seung-Soon;Park, Soo-Jin
    • Bulletin of the Korean Chemical Society
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    • v.35 no.1
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    • pp.57-61
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    • 2014
  • In this study, carbon aerogel (CA) was synthesized using a soft-template method, and the optimum conditions for the adsorption of carbon dioxide ($CO_2$) by the carbon aerogel were evaluated by controlling the activation temperature. KOH was used as the activation agent at a KOH/CA activation ratio of 4:1. Three types of activated CAs were synthesized at activation temperatures of $800^{\circ}C$(CA-K-800), $900^{\circ}C$(CA-K-900), and $1000^{\circ}C$(CA-K-1000), and their surface and pore characteristics along with the $CO_2$ adsorption characteristics were examined. The results showed that with the increase in activation temperature from 800 to $900^{\circ}C$, the total pore volume and specific surface area sharply increased from 1.2165 to $1.2500cm^3/g$ and 1281 to $1526m^2/g$, respectively. However, the values for both these parameters decreased at temperatures above $1000^{\circ}C$. The best $CO_2$ adsorption capacity of 10.9 wt % was obtained for the CA-K-900 sample at 298 K and 1 bar. This result highlights the importance of the structural and textural characteristics of the carbon aerogel, prepared at different activation temperatures on $CO_2$ adsorption behaviors.

Preparation of Silica Monoliths with Macropores and Mesopores and of High Specific Surface Area with Low Shrinkage using a Template Induced Method

  • Guo, Jianyu;Lu, Yan;Whiting, Roger
    • Bulletin of the Korean Chemical Society
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    • v.34 no.2
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    • pp.447-452
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    • 2013
  • In this study we report a new method for the synthesis of a silica monolithic column bed with bimodal pores (throughpores and mesopores). The template induced synthesis method was used to direct bimodal pores simultaneously instead of the usual post base-treating method. Block polymer Pluronic F127 was chosen as a dual-function template to form hierarchically porous silica monolith with both macropores and mesopores. This is a simplification of the method of monolithic column preparation. Poly(ethylene glycol) was used as a partial substitute for F127 can effectively prevent shrinkage during the monolith aging process without losing much surface area (944 $m^2/g$ to 807 $m^2/g$). More importantly, the resultant material showed a much narrower mesopore size (centered at 6 nm) distribution than that made using only F127 as the template reagent, which helps the mass transfer process. The solvent washing method was used to remove the remaining organic template, and it was proved to be effective enough. The new synthesis method makes the fabrication of the silica monolithic column (especially capillary column) much easier. All the structure parameters indicate that monolith PFA05 prepared by the above method is a good material for separation, with the merits of much higher surface area than usual commercial HPLC silica particles, suitable mesopore volume, narrow mesopore size distribution, low shrinkage and it is easily prepared.

Invention of Ultralow - n SiO2 Thin Films

  • Dung, Mai Xuan;Lee, June-Key;Soun, Woo-Sik;Jeong, Hyun-Dam
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.281-281
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    • 2010
  • Very low refractive index (<1.4) materials have been proved to be the key factor improving the performance of various optical components, such as reflectors, filters, photonic crystals, LEDs, and solar cell. Highly porous SiO2 are logically designed for ultralow refractive index materials because of the direct relation between porosity and index of refraction. Among them, ordered macroporous SiO2 is of potential material since their theoretically low refractive index ~1.10. However, in the conventional synthesis of ordered macroporous SiO2, the time required for the crystallization of organic nanoparticles, such as polystyrene (PS), from colloidal solution into well ordered template is typical long (several days for 1 cm substrate) due to the low interaction between particles and particle - substrate. In this study, polystyrene - polyacrylic acid (PS-AA) nanoparticles synthesized by miniemulsion polymerization method have hydrophilic polyacrylic acid tails on the surface of particles which increase the interaction between particle and with substrate giving rise to the formation of PS-AA film by simply spin - coating method. Less ordered with controlled thickness films of PS-AA on silicon wafer were successfully fabricated by changing the spinning speed or concentration of colloidal solution, as confirmed by FE-SEM. Based on these template films, a series of macroporous SiO2 films whose thicknesses varied from 300nm to ~1000nm were fabricated either by conventional sol - gel infiltration or gas phase deposition followed by thermal removal of organic template. Formations of SiO2 films consist of interconnected air balls with size ~100 nm were confirmed by FE-SEM and TEM. These highly porous SiO2 show very low refractive indices (<1.18) over a wide range of wavelength (from 200 to 1000nm) as shown by SE measurement. Refraction indices of SiO2 films at 633nm reported here are of ~1.10 which, to our best knowledge, are among the lowest values having been announced.

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Synthesis and Biological Evaluation of 4-Heteroaryl-2-amino-5-methylimidazole Analogs as NHE-1 Inhibitors

  • Lee, Sun-Kyung;Yi, Kyu-Yang;Lee, Byung-Ho;Yoon, Boo-Soon
    • Bulletin of the Korean Chemical Society
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    • v.30 no.11
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    • pp.2621-2625
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    • 2009
  • To identify a non-acylguanidine NHE-1 inhibitor, an acylguanidne group was replaced with an imidazole group in the potent NHE-1 inhibitors with furan or benzothiphene core template, found from our previous studies. We synthesized and biologically evaluated 4-heteroaryl-2-amino-5-methylimidazole derivatives. All those imidazole compounds (16-18) represented the potent NHE-1 inhibitory activities, similar to the corresponding acylguanidine compounds.

MOD-processed YBCO coated conductors on the $CeO_2$-buffered IBAD-MgO template

  • Shin, G.M.;Ko, R.K.;Oh, S.S.;Moon, S.H.;Yoo, S.I.
    • Progress in Superconductivity and Cryogenics
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    • v.11 no.4
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    • pp.20-24
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    • 2009
  • YBCO coated conductors (CC) on the $CeO_2$-buffered IBAD-MgO template were fabricated by metal-organic deposition (MOD) Process with Ba-trifluoroacetate and fluorine-free Y and Cu precursor materials. The precursor solution was coated on $CeO_2$-buffered IBAD MgO templates using the multiple dip-coating method, decomposed into inorganic precursors by pyrolysis up to $400^{\circ}C$ within 3 h, and finally fired at $740{\sim}800^{\circ}C$ in a reduced oxygen atmosphere. Microstructure, texture, and superconducting properties of YBCO films were found highly sensitive to both the firing temperature and time. The high critical current density ($J_C$) of $1.15\;MA/cm^2$ at 77.3K in the self-field could be obtained from $1\;{\mu}m$ thick YBCO CC, fired at $740^{\circ}C$ for 3.5 h, implying that high performance YBCO CC is producible on IBAD MgO template. Further enhancement of $J_C$ values is expected by improving the in-plane texture of $CeO_2$-buffer layer and avoiding the metal substrate contamination.

Influencing Factors on the Crystallizations of ZSM-5 in the Absence of Organic Template (유기 템플레이트 배제하의 ZSM-5 결정화에 따른 영향인자)

  • Kim, Wha-Jung;Lim, Chang-Whan;Lee, Seung-Ae;Lee, Myung-Chul;Jeong, Chan-Yee
    • Applied Chemistry for Engineering
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    • v.4 no.4
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    • pp.776-784
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    • 1993
  • A pentasil zeolite, ZSM-5 was synthesized in the absence of organic template, $TPA^+$ ion at $210^{\circ}C$. It was realized that a conventional method can not be applied to the synthesis system where organic templates are not used. The results indicated that the compositional range for the crystallization of ZSM-5 is very narrow, requiring very careful controls in the $Na_2O/SiO_2$and $SiO_2/Al_2O_3$ratios. In addition, the results showed that the effects of mixing method, aging and reaction time on the crystallization of ZSM-5 were extraordinarily significant.

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Template-free preparation of TiO2 microspheres for the photocatalytic degradation of organic dyes

  • Al Ruqaishy, Mouza;Al Marzouqi, Faisal;Qi, Kezhen;Liu, Shu-yuan;Karthikeyan, Sreejith;Kim, Younghun;Al-Kindy, Salma Mohamed Zahran;Kuvarega, Alex Tawanda;Selvaraj, Rengaraj
    • Korean Journal of Chemical Engineering
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    • v.35 no.11
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    • pp.2283-2289
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    • 2018
  • $TiO_2$ microspheres were successfully synthesised by simple solution phase method by using various amount of titanium butoxide as precursor. The prepared $TiO_2$ were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance absorption spectra (UV-DRS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XRD analysis revealed that the as-synthesized $TiO_2$ microsphere poses an anatase phase. The photocatalytic degradation experiments were carried out with three different dyes, such as methylene blue, brilliant black, reactive red-120 for four hours under UV light irradiation. The results show that $TiO_2$ morphology had great influence on photocatalytic degradation of organic dyes. The experimental results of dye mineralization indicated the concentration was reduced by a high portion of up to 99% within 4 hours. On the basis of various characterization of the photocatalysts, the reactions involved to explain the photocatalytic activity enhancement due to the concentration of titanium butoxide and morphology include a better separation of photogenerated charge carriers and improved oxygen reduction inducing a higher extent of degradation of aromatics.

Hydrophobic Organic/Inorganic Composite Films with 3D Hierarchical Nanostructured Surfaces (3D 계층적 나노구조화된 표면을 갖는 소수성 유/무기 복합 필름)

  • Seo, Huijin;Ahn, Jinseong;Park, Junyong
    • Composites Research
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    • v.34 no.4
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    • pp.264-268
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    • 2021
  • In this study, we propose a method for fabricating hydrophobic coatings/films with three-dimensional (3D) hierarchical nanostructured organic/inorganic composite surfaces. An epoxy-based, large-area 3D ordered nanoporous template is first prepared through an advanced photolithography technique called Proximity-field nanoPatterning (PnP). Then, a hierarchically structured surface is generated by densely impregnating the template with silica nanoparticles with an average diameter of 22 nm through dip coating. Due to the coexisting micro- and nano-scale roughness on the surface, the fabricated composite film exhibits a higher contact angle (>137 degrees) for water droplets compared to the reference samples. Therefore, it is expected that the materials and processes developed through this study can be used in various ways in the traditional coating/film field.