Time filter

Source Type

Endicott, NY, United States

Zhang Q.,Kyushu University | Tsang D.,i3 Electronics | Kuwabara H.,Kyushu University | Hatae Y.,Kyushu University | And 5 more authors.
Advanced Materials | Year: 2015

The design of efficient and concentration-insensitive metal-free thermally activateddelayed fluorescence (TADF) materials is reported. Blue and green organic light-emitting diodes (OLEDs) containing a hole-transport layer, an undoped TADF emissive layer, and an electron-transport layer achieve maximum external quantum efficiencies of 19%, which is comparable to the best doped OLEDs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cain S.R.,Binghamton University State University of New York | Tasillo E.,i3 Electronics | Infantolino W.,Binghamton University State University of New York | Wolfgramm P.,Binghamton Center for Emerging Technologies
Journal of Power Sources | Year: 2014

It has been demonstrated experimentally that a capacitor bank when connected in parallel with a battery increases the energy output by mitigating the effects of high current spikes in the load. High current draws are taken from the capacitor bank which can furnish a small amount of energy quickly. The battery which can furnish substantial energy over a period of time then recharges the capacitor bank during times of decreased load. With a current square wave (P-P of 1.5 to 2× the average), capacitors afforded an increase in the retrievable energy of approximately 8% for a lead acid battery, 40% for a rechargeable lithium ion battery, and 46% for a non-rechargeable lithium ion battery. © 2014 Elsevier B.V. All rights reserved.

Cheng H.-W.,Shanghai Institute of Technology | Cheng H.-W.,Binghamton University State University of New York | Schadt M.J.,Binghamton University State University of New York | Schadt M.J.,i3 Electronics | And 4 more authors.
Analyst | Year: 2015

As nanoparticles with different capping structures in solution phases have found widespread applications of wide interest, understanding how the capping structure change influences their presence in phases or solutions is important for gaining full control over both the intended nanoactivity and the unintended nanotoxicity. This report describes a simple and effective phase extraction method for analyzing the degree of ion pairing in the capping molecular structure of nanoparticles. Gold nanoparticles of a few nanometers diameter with a mixed monolayer capping structure consisting of both hydrophobic and hydrophilic and reactive groups were studied as a model system, and a quantitative model was derived based on chemical equilibria in a two-phase system, and used to assess the experimental data for phase extraction by cationic species. In contrast to the traditional perception of 100% ion pairing, only a small fraction (∼20%) of the negatively-charged groups was found to be responsible for the phase extraction. The viability of using this phase extraction method for analyzing the degree of ion-pairing in the capping molecular structure of different nanoparticles is also discussed, which has implications for the control of the nanoactivity and nanotoxicity of molecularly-capped or bio-conjugated nanoparticles. © 2015 The Royal Society of Chemistry.

Cheng H.-W.,Shanghai Institute of Technology | Schadt M.J.,Binghamton University State University of New York | Schadt M.J.,i3 Electronics | Zhong C.-J.,Binghamton University State University of New York
Chemistry - An Asian Journal | Year: 2016

This report describes findings of an investigation of the role of capping molecules in the size growth in the aggregative growth of pre-formed small-sized gold nanoparticles capped with alkanethiolate monolayers toward monodispersed larger sizes. The size controllability depends on the thiolate chain length and concentration in the thermal solution. The size evolution in solution at different concentrations of alkanethiols is analyzed in relation to adsorption isotherms and cohesive energy. The size dependence on thiolate chain length is also analyzed by considering the cohesive energy of the capping molecules, revealing the importance of cohesive energy in the capping structure. Theoretical and experimental comparisons of the surface plasmonic resonance optical properties have also provided new insights into the mechanism, thus enabling the exploitation of size-dependent nanoscale properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fujimoto H.,Kyushu University | Fujimoto H.,i3 Electronics | Edura T.,Kyushu University | Miyayama T.,ULVAC PHI Inc. | And 3 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2014

The authors report the use of high-performance liquid chromatography (HPLC) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) utilizing a gas cluster ion beam to accurately measure the dopant concentration and its depth profile in organic thin films used for organic light-emitting diodes. The total dopant concentrations estimated by HPLC for films of 4,4'-bis(carbazol-9-yl)biphenyl (CBP) doped with tris(2-phenylpyridinato)iridium(III) (Ir(ppy)3) are consistent with those measured by quartz crystal microbalances (QCMs) during the deposition. Concentrations measured for Ir(ppy)3:CBP films by HPLC and TOF-SIMS show a nearly linear relationship in the range of 1-8 wt. %. At concentrations higher than 8 wt. %, TOF-SIMS values significantly deviate because of the matrix effect. The depth profile of the dopant concentration measured by TOF-SIMS was in good agreement with that measured by QCMs during film deposition for concentrations below 8 wt. %. These methods are especially useful for comparing the dopant concentration of films deposited in different batches and equipment. © 2014 American Vacuum Society.

Discover hidden collaborations