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7. Bipyridine-based iridium( ) triplet emitters for organic light-emitting diodes (OLEDs): application and impact of phenyl substitution at the 5′-position of the -coordinating pyridine ring

Author

Zaen, Rena, Kim, Myeongbee, Park, Ki-Min, Lee, Kyung Hyung, Lee, Jun Yeob, and Kang, Youngjin

Subjects
Materials science, Dopant, 010405 organic chemistry, chemistry.chemical_element, 010402 general chemistry, Photochemistry, 01 natural sciences, 0104 chemical sciences, Inorganic Chemistry, chemistry.chemical_compound, Bipyridine, chemistry, Pyridine, OLED, Quantum efficiency, Iridium, Homoleptic, Phosphorescence
Abstract

Three blue phosphorescent homoleptic iridium( ) complexes based on a bipyridine ligand were synthesized., Three blue phosphorescent homoleptic iridium( ) complexes based on a bipyridine ligand were synthesized. The structures of these Ir( ^ ) analogues were determined by single-crystal X-ray diffraction analysis. Two geometrical isomers, and , formed as the major products, and the ratio of the products depended on the substituents. The photophysical and electrochemical properties of the complexes were analyzed, and they were used as dopants for the fabrication of phosphorescent organic light-emitting diodes (PHOLEDs). The dependence of current density on dopant concentration in the devices, as well as their external quantum efficiencies and current efficiencies, were evaluated. All complexes exhibited intense, sky-blue phosphorescent emission at = 479, 484 and 488 nm, and the absolute quantum efficiencies in the thin films were high at 0.72, 0.75 and 0.81. A maximum current efficiency of 39.8 cd A and an external quantum efficiency (EQE) of 14.9% were obtained, which signified superior performance among blue phosphorescent organic light-emitting diodes. High efficiencies of 39.2 cd A and 14.0% EQE were still achieved at a luminance of 1000 cd m .

Published
2019
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13. Evaluation of Ball-Milling Process for the Production of Carbon Particles from Rice Straw Waste.

Author

Nandiyanto, Asep Bayu Dani, Oktiani, Rosi, Zaen, Rena, Danuwijaya, Ari Arifin, Abdullah, Ade Gafar, and Haristiani, Nuria

Subjects
ACTIVATED carbon, RICE straw, BALL mills, HEAT treatment, SIZE reduction of materials
Abstract

The purpose of this study is to evaluate the ball-milling process for the production of carbon particles from rice straw waste. In the experimental method, carbon particles are prepared by adding heat treatment to the rice straw waste at the temperature of 250ºC. The heated rice straw waste is grinded using a conventional grinding method and put into the ball-milling process. Physicochemical properties of carbon particles are evaluated before and after the ball-milling process. The results indicate that sizes of carbon particles decrease significantly from micro (after the conventional grinding process) to submicron range (after additional ball milling process). Almost no changes in the chemical properties of carbon particles are observed. This result implies that the ball-milling process is effective to decrease the size of the prepared carbon particles. The collision phenomenon combined with shear stress among the stainless steel balls is the main reason for breaking carbon particles, making the particle sizes smaller. [ABSTRACT FROM AUTHOR]

Published
2018

14. Monodispersed and Size-controllable Potassium Silicate Nanoparticles from Rice Straw Waste Produced Using a Flame-assisted Spray Pyrolysis.

Author

Nandiyanto, Asep Bayu Dani, Zaen, Rena, Oktiani, Rosi, Abdullah, Ade Gafar, and Danuwijaya, Ari Arifin

Subjects
POTASSIUM silicate, WASTE management, RICE straw, PYROLYSIS, NANOPARTICLES, MONODISPERSE colloids
Abstract

The purpose of this study was to demonstrate a facile method to produce monodispersed and sizecontrollable potassium silicate nanoparticles from rice straw waste. Different from other methods that use expensive raw chemicals, our method utilises rice straw waste as a source of silica that is cost-free and largely available. In the experimental procedure, rice straw waste was burned. Then, the burned rice straw waste was put into the alkaline extraction process (using potassium solution) and flame-assisted spray-pyrolysis apparatus system. To support the flame-assisted spray-pyrolysis, we utilised commercially available liquid petroleum gas as a fuel source for the flame combustion process. Experimental results showed that the prepared particles are monodispersed, spherical, and having sizes in the range of nanometer (from 20 to 80 nm). The fuel flow rate plays important role in controlling particle size in the final product. Increases in the fuel lead to the formation of larger particles. Since the present method can convert rice straw into useful and valuable potassium silica particles, further development of this study would give a positive impact for the reduction of rice straw waste emission. [ABSTRACT FROM AUTHOR]

Published
2018

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