Utilizing VO2 as a Hole Injection Layer for Efficient Charge Injection in Quantum Dot Light-Emitting Diodes Enables High Device Performance.

Quantum dot light-emitting diodes (QLEDs) are promising devices for display applications. Polyethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) is a common hole injection layer (HIL) material in optoelectronic devices because of its high conductivity and high work function. Nevertheless, PEDOT:PSS-based QLEDs have a high energy barrier for hole injection, which results in low device efficiency. Therefore, a new strategy is needed to improve the device efficiency. Herein, we have demonstrated a bilayer-HIL using VO2 and a PEDOT:PSS-based QLED that exhibits an 18% external quantum efficiency (EQE), 78 cd/A current efficiency (CE), and 25,771 cd/m2 maximum luminance. In contrast, the PEDOT:PSS-based QLED exhibits an EQE of 13%, CE of 54 cd/A, and maximum luminance of 14,817 cd/m2. An increase in EQE was attributed to a reduction in the energy barrier between indium tin oxide (ITO) and PEDOT:PSS, caused by the insertion of a VO2 HIL. Therefore, our results could demonstrate that using a bilayer-HIL is effective in increasing the EQE in QLEDs.

A technique for a nano-textured gapless microlens array using self-formation characteristics of anodic alumina.

This paper presents a method to utilize the growth properties of anodic alumina possessing self-formation characteristics to fabricate a nano-textured microstructure and also introduces an application technique of the proposed method. The growth rate of anodic alumina, fabricated on aluminum surfaces, has a strong dependence on the intensity of the applied current density or electric field. The uniformity of the thickness of anodic alumina is determined by its electrical distribution characteristics. Accordingly, microscale structures can be fabricated using the growth rate deviation of anodic alumina. A patterned insulative layer is an important factor that determines the current density distribution property of a local region. A computational analysis and a verification experiment can verify this characteristic through the correlation between structural dimensional conditions and a cross-section of the fabricated anodic alumina. The anodic alumina fabricated by the verification experiment in this study had a swollen shape and a nano & micro complex structure, in which a nanoscale base pattern was formed on all bottom surface due to the process characteristics. Based on the advantages of the proposed process, evidenced by the reliability evaluation results, gapless microlens array (MLA) replication molds with nanostructured surfaces were fabricated to verify the applicability of the proposed technique to other fields. A patterned insulative layer with a cylindrical cavity and dimensional conditions was designed to induce the fabrication of lens-shaped anodic alumina. The anodic alumina fabricated by the long process was selectively etched out, and an additional process was conducted to fabricate a nanoporous structure having controlled dimensional conditions on the engraved gapless MLA surface. The textured aluminum surface was used as a replication mold for the imprinting process. The analysis of the fabrication results showed that the gapless MLA surface had a nanopillar structure. In addition, we investigated the reflection characteristics of the fabricated gapless N-MLA structure according to the incident light and verified the low reflectance of the gapless microlens. The results of this study affirmed that the proposed technique is applicable to various fields including those concerning optical devices.

Psoas compartment block for treatment of motor weakness and pain following herpes zoster.

Reactivation of the latent varicella zoster virus in the sensory ganglion causes herpes zoster (HZ). Its characteristic symptom is a painful rash in the involved dermatome. HZ-induced motor weakness is rare and is usually resolved within one year of the onset, but some patients permanently experience motor dysfunction. Epidural steroid administration, with antiviral therapy, can be effective in treating pain from HZ and preventing postherpetic neuralgia. But an epidural block is contraindicated in patients receiving thromboprophylaxis. A psoas compartment block (PCB) provides equivalent analgesic efficacy with significantly low incidence of complication, compared to an epidural block. A 68 year old male patient recieving thromboprophylaxis presented with motor weakness following painful rash in his left L4 dermatome. Ten days before presentation, herpetic rash occurred on his left leg. We performed PCB with a steroid and local anesthetic, which successfully and safely alleviated the pain and motor weakness from HZ.

Reduction of nitrate by resin-supported nanoscale zero-valent iron.

For environmental remediation of a contaminated groundwater, the use of nanosized zero-valent iron (nZVI) represents one of the latest innovative technologies. However, nZVI gets easily agglomerated due to its colloidal characteristics and has limited applications. To overcome this drawback, nZVI was immobilized on a supporting material. In this study, nZVI was formed and bound to ion-exchange resin spheres at the same time through the borohydride reduction of an iron salt. The pore structures and physical characteristics of the supported nZVI were investigated and its reactivity was measured using nitrate. The degradation of nitrate appeared to be a pseudo first-order reaction with the observed reaction rate constant of 0.425 h(-1) without pH control. The reduction process continued but at a much lower rate with a rate constant of 0.044 h(-1). When the simulated groundwater was used to assess the effects of coexisting ions, the rate constant was 0.078 h(-1) and it also reduced to 0.0021 h(-1) in later phase. The major limitation of ZVI use for nitrate reduction is ammonium production. By using a support material with ion-exchange capacity, this problem can be solved. The ammonium was not detected in our batch tests.

Enhanced reduction of nitrate by supported nanoscale zero-valent iron prepared in ethanol-water solution.

Nanoscale zero-valent iron is famous for its high reactivity originating from its high surface area, and has emerged as an extension of granular zero-valent iron technology. Due to its extremely small size, nanosized iron cannot be used as a medium in a permeable reactive barrier system, which is the most popular application of granular iron. To overcome this shortcoming, supported nanoscale zero-valent iron was created. In addition to this, the preparation solution was modified to enhance the reactivity. An ethanol/water solvent containing a dispersant of polyethylene glycol was used to synthesize nanoscale iron. This preparation was done in the presence of an ion-exchange resin as a supporting material. Nanoscale zero-valent iron was formed and bound to the granular resin at the same time through the borohydride reduction of an iron salt, and the resulting product was compared with that prepared in a conventional way of using water only. Switching the preparation solution increased the supported nanoscale iron's BET surface area and Fe content from 31.63 m2 g(-1) and 18.19 mg Fe g(-1) to 38.10 m2 g(-1) and 22.44 mg Fe g(-1), respectively. Kinetic analysis from batch tests revealed that a higher denitrification rate was achieved by the supported nanoscale zero-valent iron prepared in the modified way. The pseudo-first-order reaction constant of 0.462 h(-1) suggested that the reactivity of the supported iron, prepared in ethanol/water, increased by 61% compared with the one prepared in water. The higher rates of reaction, based on higher specific area and iron content, suggest that this new supported nanoscale iron can be used successfully for permeable reactive barriers.