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Piao, Longhai,Lee, Kyung-Hoon,Min, Byoung-Koun,Kim, Woong,Do, Young-Rag,Yoon, Sung-Ho Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.1
Size-controlled Ag nanoparticles (NPs) were prepared from the decomposition of Ag(I) carboxylates using ethanolamine derivatives as a reducing agent without an additional stabilizing agent. The size of the Ag NPs with a narrow size distribution (sub-10 nm to ca. 40 nm) was controlled precisely by varying the processing parameters, such as the type of reducing agent and the chain length of the carboxylate in the Ag(I) carboxylate. The optical properties, surface composition and crystallinity of the Ag NPs were characterized by ultraviolet-visible spectroscopy, gas chromatography-mass spectrometry, thermal gravimetric analysis, transmission electron microscopy and X-ray diffraction.
폴리실라잔 가교제를 이용한 LED 에폭시 봉지재의 경화와 열 안정성 연구
박용해(Longhai Piao),김진권(Jin Kwon Kim) 한국고분자학회 2015 폴리머 Vol.39 No.5
본 연구에서는 에폭시 그룹과 가교반응하는 폴리실라잔 가교제를 이용하여 LED용 비스페놀 A 에폭시 봉지재와 실리콘-에폭시 봉지재를 경화시키고 열 안정성을 연구하였다. 비스페놀 A 에폭시 봉지재는 열 안정성이 높은 실리콘 기반의 반응성 폴리실라잔 가교제를 사용함으로써 기존의 저분자 유기 가교제를 사용할 때에 비해 월등히 높은 열 안정성을 보였고, 실리콘-에폭시 봉지재는 실리콘 함량의 저하 없이 경화시킴으로써 높은 열 안정성을 유지하는데 도움이 되었다. 또한 실리콘 봉지재의 굴절률이 낮은 단점을 보완하기 위해 굴절률이 높은 TiO₂ 나노입자와 실리콘-에폭시, 폴리실라잔 복합체를 형성하여 입자함량이 굴절률에 미치는 영향을 연구하였다. Bisphenol A epoxy and silicone-epoxy LED encapsulants were cured by using polysilazane cross-linking agents, which could be used to initiate the ring-opening polymerization of epoxy group, and the heat stabilities of the encapsulants were examined. Bisphenol A epoxy encapsulants cured by polysilazane showed better heat stability than that with conventional organic cross-linking agents due to the superior heat stability of silicon-based polysilazane cross-linking agent. Silicone-epoxy encapsulants also presented excellent heat stability owing to the high silicon content of polysilazane cross-linking agent. In order to increase the refractive index of the silicone-epoxy encapsulants, TiO₂ nanoparticles were dispersed in the silicone-epoxy and cured by polysilazane. The relationship between the refractive index and the TiO₂ content was investigated.
Euyjin Lee,Longhai Piao,Jinkwon Kim 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.1
Silver(I) [bis(alkylthio)methylene]malonates were synthesized from the reaction of silver nitrate and potassium [bis(alkylthio)methylene]malonates. The structures of the Ag complexes were characterized with nuclear magnetic resonance (NMR), inductively coupled plasma atomic emission spectrometry (ICP-AES) and elemental analysis. Ag nanoparticles (NPs) were obtained from the decomposition of the Ag complexes in 1,2-dichlorobenzene at 110 oC without an additional surfactant. The average sizes of the Ag NPs are in the range of 5.1-6.3 nm and could be controlled by varying the length of the alkyl chain. The optical properties, crystalline structure and surface composition of Ag NPs were characterized with ultraviolet-visible (UV-visible)spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), gas chromatography-mass spectrometry (GC-MS), X-ray Photoelectron Spectroscopy (XPS) and thermal gravimetric analysis (TGA).
Mechanism of Organogel Formation from Mixed-Ligand Silver (I) Carboxylates
Jiyeon Kim,윤성호,Longhai Piao,Cheol-Hee Park,김상호 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.9
Ag(I) carboxylate gelators with mixed-ligands were systemically investigated to understand the mechanism of the organic gel formation. The gelators constructed 3-D networks of nanometer-sized thin fibers which facilitated gel formation in various aromatic organic solvents, even at very low concentrations. The loss of reflection peaks in the X-ray diffraction data indicated the reduction of strong interactions between the long alkyl chains as the Ag(I) carboxylates formed gels by maximizing their interactions with the organic solvents. The gelation temperature (T^gel) was measured to explore the interaction between the gelator molecules and solvents depending on their composition and concentration. Based on the gelation phenomena, a dissociation/re-association mechanism was proposed.
Lee, Euy-Jin,Piao, Longhai,Kim, Jin-Kwon Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.1
Silver(I) [bis(alkylthio)methylene]malonates were synthesized from the reaction of silver nitrate and potassium [bis(alkylthio)methylene]malonates. The structures of the Ag complexes were characterized with nuclear magnetic resonance (NMR), inductively coupled plasma atomic emission spectrometry (ICP-AES) and elemental analysis. Ag nanoparticles (NPs) were obtained from the decomposition of the Ag complexes in 1,2-dichlorobenzene at $110^{\circ}C$ without an additional surfactant. The average sizes of the Ag NPs are in the range of 5.1-6.3 nm and could be controlled by varying the length of the alkyl chain. The optical properties, crystalline structure and surface composition of Ag NPs were characterized with ultraviolet-visible (UV-visible) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), gas chromatography-mass spectrometry (GC-MS), X-ray Photoelectron Spectroscopy (XPS) and thermal gravimetric analysis (TGA).
Photocatalytic degradation of 4‐nitrophenol by using multicomponent Cu 2 O‐Cu@TiO 2 nanoparticl
Jiang Jianwei,문석영,윤성호,Piao Longhai 대한화학회 2024 Bulletin of the Korean Chemical Society Vol.45 No.4
Multicomponent nanomaterials with synergistic effect were typically used to enhance the photocatalytic performance. Herein, three‐component nanomaterials composed of Cu 2 O, Cu, and TiO 2 were prepared using a facile method, and applied in the photocatalytic degradation reactions. The synthetic procedure involves the formation of Cu 2 O nanoparticle aggregates (NPAs) followed by Cu nanoparticles growth on the surface of Cu 2 O NPAs in one pot, and TiO 2 encapsulation (Cu 2 O‐Cu@TiO 2 ). The catalyst structure was characterized by x‐ray diffraction, field emission‐scanning electron microscopy, transmission electron microscopy, and energy‐dispersed x‐ray. The catalytic performance of Cu 2 O‐Cu@TiO 2 NPAs was evaluated through the photocatalytic degradation of 4‐nitrophenol under the simulated solar light. We found that it exhibited greater activity than the Cu 2 O‐Cu NPAs, commercial TiO 2 , and Cu 2 O@TiO 2 NPAs, probably due to their synergistic interactions resulting in the effective photogenerated carrier transfer in the multicomponent nanomaterials. Multicomponent nanomaterials with synergistic effect were typically used to enhance the photocatalytic performance. Herein, three-component nanomaterials composed of Cu2O, Cu, and TiO2 were prepared using a facile method, and applied in the photocatalytic degradation reactions. The synthetic procedure involves the formation of Cu2O nanoparticle aggregates (NPAs) followed by Cu nanoparticles growth on the surface of Cu2O NPAs in one pot, and TiO2 encapsulation (Cu2O-Cu@TiO2). The catalyst structure was characterized by x-ray diffraction, field emission-scanning electron microscopy, transmission electron microscopy, and energy-dispersed x-ray. The catalytic performance of Cu2OCu@ TiO2 NPAs was evaluated through the photocatalytic degradation of 4-nitrophenol under the simulated solar light. We found that it exhibited greater activity than the Cu2O-Cu NPAs, commercial TiO2, and Cu2O@TiO2 NPAs, probably due to their synergistic interactions resulting in the effective photogenerated carrier transfer in the multicomponent nanomaterials.
Preparation and Characterization of PEG/PLA Multiblock and Triblock Copolymer
Hesong Zhao,Zhun Liu,박상혁,김상호,김정현,Longhai Piao 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.5
A series of poly (lactic acid) (PLA) and poly (ethylene glycol) (PEG) tri and multiblock copolymers with relatively high molecular weights were synthesized through the coupling reaction between the bis(acyl chloride) of carboxylated PLA and mono or dihydroxy PEG. The coupling reaction and the copolymer structures were monitored by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The melting temperature (Tm) of PEG blocks decreased with the presence of PLA sequences attaching to PEG blocks. The CMC values were determined to be 10-145 mg/L depending on the length of PLA and PEG blocks and the structure of the block copolymers.