Efficient Photon Extraction in Top-Emission Organic Light-Emitting Devices Based on Ampicillin Microstructures.

The desire to enhance the efficiency of organic light-emitting devices (OLEDs) has driven to the investigation of advanced materials with fascinating properties. In this work, the efficiency of top-emission OLEDs (TEOLEDs) is enhanced by introducing ampicillin microstructures (Amp-MSs) with dual phases (α-/ß-phase) that induce photoluminescence (PL) and electroluminescence (EL). Moreover, Amp-MSs can adjust the charge balance by Fermi level (EF ) alignment, thereby decreasing the leakage current. The decrease in the wave-guided modes can enhance the light outcoupling through optical scattering. The resulting TEOLED demonstrates a record-high external quantum efficiency (EQE) (maximum: 68.7% and average: 63.4% at spectroradiometer; maximum: 44.8% and average: 42.6% at integrating sphere) with a wider color gamut (118%) owing to the redshift of the spectrum by J-aggregation. Deconvolution of the EL intensities is performed to clarify the contribution of Amp-MSs to the device EQE enhancement (optical scattering by Amp-MSs: 17.0%, PL by radiative energy transfer: 9.1%, and EL by J-aggregated excitons: 4.6%). The proposed TEOLED outperforms the existing frameworks in terms of device efficiency.

Improved device efficiency and lifetime of perovskite light-emitting diodes by size-controlled polyvinylpyrrolidone-capped gold nanoparticles with dipole formation.

Herein, an unprecedented report is presented on the incorporation of size-dependent gold nanoparticles (AuNPs) with polyvinylpyrrolidone (PVP) capping into a conventional hole transport layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The hole transport layer blocks ion-diffusion/migration in methylammonium-lead-bromide (MAPbBr3)-based perovskite light-emitting diodes (PeLEDs) as a modified interlayer. The PVP-capped 90 nm AuNP device exhibited a seven-fold increase in efficiency (1.5%) as compared to the device without AuNPs (0.22%), where the device lifetime was also improved by 17-fold. This advancement is ascribed to the far-field scattering of AuNPs, modified work function and carrier trapping/detrapping. The improvement in device lifetime is attributed to PVP-capping of AuNPs which prevents indium diffusion into the perovskite layer and surface ion migration into PEDOT:PSS through the formation of induced electric dipole. The results also indicate that using large AuNPs (> 90 nm) reduces exciton recombination because of the trapping of excess charge carriers due to the large surface area.

Development of a Digital Healthcare Management System for Lower-Extremity Amputees: A Pilot Study.

The research, which was designed as a "pre- and post-single group" study, included patients with lower-limb amputation and aimed to evaluate the effectiveness of self-directed physical-strength training and cardiovascular exercise using a novel digital healthcare management service three times a week for 12 weeks. Muscle strength, thigh circumference, lipid profile and glycated hemoglobin levels, pulmonary function, quality of life, and physical activity level were evaluated before and after the intervention, while satisfaction was measured after the study. Among the 14 included patients, the proportion of adherence to the physical-strength training and physical-strengthening activity were 85.2% and 75.8%, respectively. The level of satisfaction with the digital healthcare management system was high. Significant changes were observed in the muscle-strength tests (dominant grip power and muscle strength of knee flexion and extension of the intact side), thigh circumference, and glycated hemoglobin levels. Further, the quality-of-life score showed improvement, although without significant differences. Individualized exercise management using the novel digital healthcare management system for lower-limb amputees could induce interest in self-care and promote physical activity and healthy behavior. Through this effect, we can expect a reduction in the incidence of cardiovascular diseases, diabetes mellitus, dyslipidemia, and severe injuries from falling.

Highly efficient, heat dissipating, stretchable organic light-emitting diodes based on a MoO3/Au/MoO3 electrode with encapsulation.

Stretchable organic light-emitting diodes are ubiquitous in the rapidly developing wearable display technology. However, low efficiency and poor mechanical stability inhibit their commercial applications owing to the restrictions generated by strain. Here, we demonstrate the exceptional performance of a transparent (molybdenum-trioxide/gold/molybdenum-trioxide) electrode for buckled, twistable, and geometrically stretchable organic light-emitting diodes under 2-dimensional random area strain with invariant color coordinates. The devices are fabricated on a thin optical-adhesive/elastomer with a small mechanical bending strain and water-proofed by optical-adhesive encapsulation in a sandwiched structure. The heat dissipation mechanism of the thin optical-adhesive substrate, thin elastomer-based devices or silicon dioxide nanoparticles reduces triplet-triplet annihilation, providing consistent performance at high exciton density, compared with thick elastomer and a glass substrate. The performance is enhanced by the nanoparticles in the optical-adhesive for light out-coupling and improved heat dissipation. A high current efficiency of ~82.4 cd/A and an external quantum efficiency of ~22.3% are achieved with minimum efficiency roll-off.

A molecular design towards sulfonyl aza-BODIPY based NIR fluorescent and colorimetric probe for selective cysteine detection.

Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) are essential biothiols for cellular growth, metabolism, and maintenance of a biological system. Thus, the detection of biothiols is highly important for early diagnosis and evaluation of disease progression. In this article, a series of sulfonyl aza-BODIPYs was synthesized, characterized, and examined by 1H-NMR, 13C-NMR, crystallization, photophysical properties and DFT calculation. Among these structures, a fluorescent probe, BDP-1, exhibited selective detection of Cys among various biothiols via nucleophilic aromatic substitution and typical size of Cys molecules. BDP-1 showed color change and near-infrared (NIR) fluorescence enhancement after reaction with Cys to generate BDP-OH, confirmed by HRMS. The red shift of absorption wavelength showed a similar tendency resulting in time-dependent density functional theory (TD-DFT). Furthermore, the calculated detection limit of BDP-1 toward Cys was 5.23 µM. This probe facilitates the colorimetric and fluorescent detection of Cys over other biothiols.

Fractional structured molybdenum oxide catalyst as counter electrodes of all-solid-state fiber dye-sensitized solar cells.

A novel hierarchical solution-processed fractional structured molybdenum oxide (MoO3) catalyst is fabricated from tricarbonyltris (propionitrile) molybdenum and used as the counter electrode of all-solid-state fiber-shaped dye-sensitized solar cells (S-FDSSC). The Tafel plot results and electrical impedance spectroscopy suggest that the use of the fractional structured MoO3 catalyst enhances the efficiency of the reduction of I3- to 3I- at the counter electrode/electrolyte interface. Because of the improvements of the short-current circuit and fill factor, the power conversion efficiency of the MoO3-modified S-FDSSC improves by 60% compared with that of the reference S-FDSSC. In addition, because of the robust fractional structure of MoO3, the MoO3-modified S-FDSSC maintains 90% and 95% of efficiency after 350-fold bending and the incident light angle dependency test, respectively. At 65% humidity and at 65 °C, the power conversion efficiency of the MoO3-modified device decreases by <20% after 350 h of storage, while that of the reference device drops by more than 70%.

Improvement of High Affinity and Selectivity on Biosensors Using Genetically Engineered Phage by Binding Isotherm Screening.

The genetically engineered M13 bacteriophage (M13 phage), developed via directed evolutionary screening process, can improve the sensitivity of sensors because of its selective binding to a target material. Herein, we propose a screening method to develop a selective and sensitive bioreporter for toxic material based on genetically engineered M13 phage. The paraquat (PQ)-binding M13 phage, developed by directed evolution, was used. The binding affinities of the PQ-binding M13 phage to PQ and similar molecules were analyzed using isothermal titration calorimetry (ITC). Based on the isotherms measured by ITC, binding affinities were calculated using the one-site binding model. The binding affinity was 5.161 × 10-7 for PQ, and 3.043 × 10-7 for diquat (DQ). The isotherm and raw ITC data show that the PQ-binding M13 phage does not selectively bind to difenzoquat (DIF). The phage biofilter experiment confirmed the ability of PQ-binding M13 bacteriophage to bind PQ. The surface-enhanced Raman scattering (SERS) platform based on the bioreporter, PQ-binding M13 phage, exhibited 3.7 times the signal intensity as compared with the wild-type-M13-phage-coated platform.

Self-Assembled Nanoporous Biofilms from Functionalized Nanofibrous M13 Bacteriophage.

Highly periodic and uniform nanostructures, based on a genetically engineered M13 bacteriophage, displayed unique properties at the nanoscale that have the potential for a variety of applications. In this work, we report a multilayer biofilm with self-assembled nanoporous surfaces involving a nanofiber-like genetically engineered 4E-type M13 bacteriophage, which was fabricated using a simple pulling method. The nanoporous surfaces were effectively formed by using the networking-like structural layers of the M13 bacteriophage during self-assembly. Therefore, an external template was not required. The actual M13 bacteriophage-based fabricated multilayered biofilm with porous nanostructures agreed well with experimental and simulation results. Pores formed in the final layer had a diameter of about 150⁻500 nm and a depth of about 15⁻30 nm. We outline a filter application for this multilayered biofilm that enables selected ions to be extracted from a sodium chloride solution. Here, we describe a simple, environmentally friendly, and inexpensive fabrication approach with large-scale production potential. The technique and the multi-layered biofilms produced may be applied to sensor, filter, plasmonics, and bio-mimetic fields.

A Simple Approach to Fabricate an Efficient Inverted Polymer Solar Cell with a Novel Small Molecular Electrolyte as the Cathode Buffer Layer.

A novel small-molecule electrolyte, 1,1'-bis(4-hydroxypropyl)-[4,4'-bipyridine]-1,1'-diium bromide (V-OH), containing a mixture of PTB7:PC71BM has been designed and synthesized as a cathode buffer layer for inverted polymer solar cells (iPSCs). The molecular structure of this new compound comprises a viologen skeleton with hydroxyl group terminals. While the viologen unit is responsible for generating a favorable interface dipole, the two terminal hydroxyl groups of V-OH may generate a synergy effect in the magnitude of the interface dipole. Consequently, the devices containing the V-OH interlayer exhibited a power conversion efficiency (PCE) of 9.13% (short circuit current = 17.13 mA/cm2, open circuit voltage = 0.75 V, fill factor = 71.1%). The PCE of the devices with V-OH exhibited better long-term stability compared to that of the devices without V-OH. Thus, we found that it is possible to enhance the efficiency of PSCs by a simple approach without the need for complicated methods of device fabrication.

Ice-Binding Protein Derived from Glaciozyma Can Improve the Viability of Cryopreserved Mammalian Cells.

Ice-binding proteins (IBPs) can inhibit ice recrystallization (IR), a major cause of cell death during cryopreservation. IBPs are hypothesized to improve cell viability after cryopreservation by alleviating the cryoinjury caused by IR. In our previous studies, we showed that supplementation of the freezing medium with the recombinant IBP of the Arctic yeast Glaciozyma sp. (designated as LeIBP) could reduce post-thaw hemolysis of human red blood cells and increase the survival of cryopreserved diatoms. Here, we showed that LeIBP could improve the viability of cryopreserved mammalian cells. Human cervical cancer cells (HeLa), mouse fibroblasts (NIH/3T3), human preosteoblasts (MC3T3-E1), Chinese hamster ovary cells (CHO-K1), and human keratinocytes (HaCaT) were evaluated. These mammalian cells were frozen in dimethyl sulfoxide (DMSO)/fetal bovine serum (FBS) solution with or without 0.1 mg/ml LeIBP at a cooling rate of -1°C/min in a -80°C freezer overnight. The minimum effective concentration (0.1 mg/ml) of LeIBP was determined, based on the viability of HeLa cells after treatment with LeIBP during cryopreservation and the IR inhibition assay results. The post-thaw viability of mammalian cells was examined. In all cases, cell viability was significantly enhanced by more than 10% by LeIBP supplementation in 5% DMSO/5% FBS: viability increased by 20% for HeLa cells, 28% for NIH/3T3 cells, 21% for MC3T3-E1, 10% for CHO-K1, and 20% for HaCaT. Furthermore, addition of LeIBP reduced the concentrations of toxic DMSO and FBS down to 5%. Therefore, we demonstrated that LeIBP can increase the viability of cryopreserved mammalian cells by inhibiting IR.

Effect of polyelectrolyte electron collection layer counteranion on the properties of polymer solar cells.

Polyviologen (PV) derivatives are known materials used for adjusting the work function (WF) of cathodes by reducing the electron injection/collection barrier at the cathode interface. To tune and improve device performance, we introduce different types of counteranions (CAs), such as bromide, tetrafluoroborate, and tetraphenylborate, to a PV derivative. The effective WF of the Al cathode is shown to depend on the size of the CA, indicating that a Schottky barrier can be modulated by the size of the CA. Through the increased size of the CA from bromide to tetraphenylborate, the effective WF of the Al cathode is gradually decreased, indicating a decreased Schottky barrier at the cathode interface. In addition, the change of the power conversion efficiency (PCE) and the short circuit current (Jsc) value show good correlation with the change of the WF of the cathode, signifying the typical transition from a Schottky to an Ohmic contact. The turn-on electric field of the electron-only device without PV was 0.21 MV/cm, which is dramatically higher than those of devices with PV-X (0.07 MV/cm for PV-Br, 0.06 MV/cm for PV-BF4, and 0.05 MV/cm for PV-BPh4) This is also coincident with a decrease in the Schottky barrier at the cathode interface. The device ITO/PEDOT/P3HT:PCBM/PV/Al, with a thin layer of PV derivative and tetraphenylborate CA as the cathode buffer layer, has the highest PCE of 4.02%, an open circuit voltage of 0.64 V, a Jsc of 11.6 mA/cm2, and a fill factor of 53.0%. Our results show that it is possible to improve the performance of polymer solar cells by choosing different types of CAs in PV derivatives without complicated synthesis and to refine the electron injection/collection barrier height at the cathode interface.

Preparation of flexible organic solar cells with highly conductive and transparent metal-oxide multilayer electrodes based on silver oxide.

We report that significantly more transparent yet comparably conductive AgOx films, when compared to Ag films, are synthesized by the inclusion of a remarkably small amount of oxygen (i.e., 2 or 3 atom %) in thin Ag films. An 8 nm thick AgOx (O/Ag=2.4 atom %) film embedded between 30 nm thick ITO films (ITO/AgOx/ITO) achieves a transmittance improvement of 30% when compared to a conventional ITO/Ag/ITO electrode with the same configuration by retaining the sheet resistance in the range of 10-20 Ω sq(-1). The high transmittance provides an excellent opportunity to improve the power-conversion efficiency of organic solar cells (OSCs) by successfully matching the transmittance spectral range of the electrode to the optimal absorption region of low band gap photoactive polymers, which is highly limited in OSCs utilizing conventional ITO/Ag/ITO electrodes. An improvement of the power-conversion efficiency from 4.72 to 5.88% is achieved from highly flexible organic solar cells (OSCs) fabricated on poly(ethylene terephthalate) polymer substrates by replacing the conventional ITO/Ag/ITO electrode with the ITO/AgOx/ITO electrode. This novel transparent electrode can facilitate a cost-effective, high-throughput, room-temperature fabrication solution for producing large-area flexible OSCs on heat-sensitive polymer substrates with excellent power-conversion efficiencies.

Nonconjugated anionic polyelectrolyte as an interfacial layer for the organic optoelectronic devices.

A nonconjugated anionic polyelectrolyte, poly(sodium 4-styrenesulfonate) (PSS-Na), was applied to the optoelectronic devices as an interfacial layer (IFL) at the semiconducting layer/cathode interface. The ultraviolet photoelectron spectroscopy and the Kelvin probe microscopy studies support the formation of a favorable interface dipole at the organic/cathode interface. For polymer light-emitting diodes (PLEDs), the maximum luminance efficiency (LEmax) and the turn-on voltage (Von) of the device with a layer of PSS-Na spin-coated from the concentration of 0.5 mg/mL were 3.00 cd/A and 5.5 V, which are dramatically improved than those of the device without an IFL (LEmax = 0.316 cd/A, Von = 9.5 V). This suggests that the PSS-Na film at the emissive layer/cathode interface improves the electron injection ability. As for polymer solar cells (PSCs), the power conversion efficiency (PCE) of the device with a layer of PSS-Na spin-coated from the concentration of 0.5 mg/mL was 2.83%, which is a 16% increase compared to that of the PSC without PSS-Na. The PCE improvement is mainly due to the enhancement of the short-circuit current (12% increase). The results support that the electron collection and transporting increase by the introduction of the PSS-Na film at the photoactive layer/cathode interface. The improvement of the efficiency of the PLED and PSC is due to the reduction of the Schottky barrier by the formation of a favorable interface as well as the better Ohmic contact at the cathode interface.

Preparation and characterization of the antibacterial Cu nanoparticle formed on the surface of SiO2 nanoparticles.

Cu deposition on the surface of spherical SiO2 nanoparticles was studied to achieve the hybrid structure of Cu-SiO2 nanocomposite. SiO2 nanoparticles served as seeds for continuous Cu metal deposition. The chemical structure and morphology were studied with X-ray photoelectron spectroscopy (XPS), scanning electron microscope energy dispersive X-ray (SEM-EDX), and a transmission electron microscope (TEM). The antibacterial properties of the Cu-SiO2 nanocomposite were examined with disk diffusion assays. The homogeneously formed Cu nanoparticles on the surface of SiO2 nanoparticles without aggregation of Cu nanoparticles showed excellent antibacterial ability.