Carrier transport mechanisms of hybrid ZnO nanorod-polymer LEDs

A hybrid polymer-nanorod (NR) light-emitting diode (LED), consisting of a hole-conducting polymer poly (9-vinyl carbazole) (PVK) and ZnO nanorod (NR) composite, with the device structure of glass/indium-tin-oxide (ITO)/PEDOT:PSS/(PVK + ZnO nanorods)/Al is fabricated through a simple spin coating technique. TEM images shows inhomogeneous deposition and the agglomeration of ZnO NRs, which is explained through their low probability of adsorption on PVK due to two-dimensional structural property. In the current-voltage characteristics, negative differential resistance (NDR) phenomenon is observed corresponding to device structure without ZnO NRs. The carrier transport behavior in the LED device is well described by both ohmic and space-chargelimited-current (SCLC) mechanisms. Broad blue electroluminescence (EL) consisting of two sub peaks, are centered at 441 nm and the other at 495 nm, is observed, which indicates that the ZnO nanorod play a role as a recombination center for excitons. The red shift in the position of the EL compared to that photoluminescence is well explained through band offsets at the heterojunction between the PVK and ZnO NRs

Capacitance of MnO2 Micro-Flowers Decorated CNFs in Alkaline Electrolyte and Its Bi-Functional Electrocatalytic Activity toward Hydrazine Oxidation

Well-dispersed MnO2 micro-flowers were grown directly on carbon nanofibers via a simple hydrothermal technique without any template. Structure and morphology were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) equipped with rapid energy dispersive analysis X-ray (EDX). The appealed characterization techniques specified that the obtained material is carbon nanofibers decorated by MnO2 micro-flowers. Super capacitive performance of the MnO2 micro-flowers decorated CNFs as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium and yield a reasonable specific capacitance of 120 Fg−1 at 5 mV s−1. As an electrocatalyst for hydrazine oxidation, the MnO2 micro-flowers decorated CNFs showed high current density. The impressive bi-functional electrochemical activity of MnO2 micro-flowers decorated CNFs is mainly attributed to its unique architectural structure.This Research was financially supported by National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. 2014R1A4A1008140

Photoinduced charge separation in ZnO quantum dots and carbon nanomaterial composites

We report the successful conjugation of carbon nanomaterials on the surface of ZnO quantum dots (QDs) and vice versa. The synthesis of ZnO QDs and carbon nanomaterial composites was achieved using a mild solution-process method, which resulted in fast photoinduced charge separation. The conjugation of the ZnO QDs to the multi-walled carbon nanotubes (MWCNTs), the graphene to the ZnO QDs and the fullerene (C60) to the ZnO QDs led to PL quenching of about 80%, 65% and 98%, respectively, which can be attributed to the efficient transfer of photoinduced electrons from the ZnO QDs to the MWCNT, from the ZnO QDs to the C60 or from the ZnO QDs to the graphene through Zn–O–C chemical bonding.status: publishe

Carrier transport of inverted quantum dot LED with PEIE polymer

An inverted-type quantum-dot light-emitting-diode (QD LED), employing low-work function organic material polyethylenimine ethoxylated (PEIE) as electron injection layer, was fabricated by all solution processing method, excluding anode electrode. From transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies, it was confirmed that CdSe@ZnS QDs with 7 nm size were uniformly distributed as a monolayer on PEIE layer. In this inverted QD LED, two kinds of hybrid organic materials, [poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo)(F8BT) + poly(N,N′-bis(4- butylphenyl)-N,N′-bis(phenyl)benzidine (poly-TPD)] and [4,4′-N,N′-dicarbazole-biphenyl (CBP) + poly-TPD], were adopted as hole transport layer having high highest occupied molecular orbital (HOMO) level for improving hole transport ability. At a low-operating voltage of 8 V, the device emits orange and red spectral radiation with high brightness up to 2450 and 1420 cd/m2, and luminance efficacy of 1.4 cd/A and 0.89 cd/A, respectively, at 7 V applied bias. Also, the carrier transport mechanisms for the QD LEDs are described by using several models to fit the experimental I-V data.status: publishe

STRUCTURAL AND OPTICAL PROPERTIES OF ZnO THIN FILMS GROWN ON FLEXIBLE POLYIMIDE SUBSTRATES

Nominally undoped ZnO thin films were grown on polyimide (PI) substrates at various temperatures by using radio-frequency magnetron sputtering. Atomic force microscopy images showed that the root mean squares of the average surface roughnesses for the ZnO thin films grown on the PI substrates at 27°C, 100°C, 200°C, and 300°C were 4.08, 4.50, 4.18, and 3.89 nm, respectively. X-ray diffraction patterns showed that the crystallinity of the ZnO films had a preferential (0001) direction and that the full width at half-maxima for the (0002) ZnO diffraction peak for the ZnO thin films grown on the PI substrates at 27°C, 100°C, 200°C, and 300°C were 0.22, 0.22, 0.22, and 0.23, respectively. The average optical transmittances in the visible ranges between 550 and 750 nm for the ZnO/PI heterostructures grown at 27°C, 100°C, 200°C, and 300°C were 87%, 83%, 87%, and 78%, respectively.ZnO thin film, polyimide, structural properties, optical properties

Li1·5Al0·3Si0·2Ti1·7P2·8O12 inorganic solid electrolyte for high-performance all-solid-state Li-ion batteries

Commercial Li-ion batteries are vital to our daily lives, powering everything from portable devices to high-powered electric vehicles. The current usage of flammable liquid electrolytes in conventional Li-ion batteries creates risks, necessitating the development of solid electrolytes that are secure and reliable. However, the ionic conductivity of solid electrolytes cannot compete with liquid electrolytes. Herein, we report the synthesis of Li1·5Al0·3Si0·2Ti1·7P2·8O12 (LASTP) powder with improved ionic conductivity and evaluate its performance as a solid electrolyte in an all-solid-state battery (ASSB). A facile solution-based method is used for the LASTP synthesis with optimized sintering and calcination temperatures. As a result, the LASTP sintered at 1050 °C has the highest relative density (96.84%) and ionic conductivity (9.455 × 10−4 S/cm) with the lowest activation energy (Ea, 0.226 eV). A coin cell is assembled with Li/LASTP/Li(Ni0·65Co0·15Mn0.20)O2 all-solid-state configuration to evaluate the electrochemical performance. In addition, an electrospun polymer conductor film (PVDF-HFP) is added between the electrodes and the solid electrolyte to reduce the interfacial resistance. The ASSB has shown a stable and high performance with remarkable discharge capacity (205.3 mAh/g) at 0.1C and could be operated even after 100 cycles with 85.3% of retention at 0.2C. Therefore, the present work suggests that the LASTP solid electrolyte is a promising material for next-generation safe ASSBs

Deep tissue penetration of nanoparticles using pulsed-high intensity focused ultrasound

Abstract Recently, ultrasound (US)-based drug delivery strategies have received attention to improve enhanced permeation and retention (EPR) effect-based passive targeting efficiency of nanoparticles in vitro and in vivo conditions. Among the US treatment techniques, pulsed-high intensity focused ultrasound (pHIFU) have specialized for improving tissue penetration of various macromolecules and nanoparticles without irreversible tissue damages. In this study, we have demonstrated that pHIFU could be utilized to improve tissue penetration of fluorescent dye-labeled glycol chitosan nanoparticles (FCNPs) in femoral tissue of mice. pHIFU could improve blood flow of the targeted-blood vessel in femoral tissue. In addition, tissue penetration of FCNPs was specifically increased 5.7-, 8- and 9.3-folds than that of non-treated (0 W pHIFU) femoral tissue, when the femoral tissue was treated with 10, 20 and 50 W of pHIFU, respectively. However, tissue penetration of FCNPs was significantly reduced after 3 h post-pHIFU treatment (50 W). Because overdose (50 W) of pHIFU led to irreversible tissue damages, including the edema and chapped red blood cells. These overall results support that pHIFU treatment can enhance the extravasation and tissue penetration of FCNPs as well as induce irreversible tissue damages. We expect that our results can provide advantages to optimize pHIFU-mediated delivery strategy of nanoparticles for further clinical applications

Multilayered graphene grafted copper wires

© 2018 Elsevier Ltd Multilayered graphene is grown on copper (Cu) wires by chemical vapor deposition. Mechanical, chemical, thermal and electrical performances are investigated as a function of growth conditions. The graphene layer which makes a volume of approximately 0.02% of the Cu wire enables a 28–37% improvement on tensile strength and strain-to-failure. The chemical resistance of graphene grafted Cu wires increases by 1.5–3 times in nitric acid, aqua regia, and 1M ammonium persulfate etchants. The electrical resistivity of graphene grafted Cu wires remains almost constant with increasing temperature up to 175 °C, while the resistivity degradation of Cu wires without graphene starts to increase from 70 °C. We demonstrate that graphene can protect the Cu wire from thermal oxidation and chemical etchants and can effectively enhance the mechanical and electrical properties of the Cu wire.status: publishe