A facile green synthesis of gold nanoparticles using Canthium parviflorum extract sustainable and energy efficient photocatalytic degradation of organic pollutants for environmental remediation.

Organic dye and nitrophenol pollution from textiles and other industries present a substantial risk to people and aquatic life. One of the most essential remediation techniques is photocatalysis, which uses the strength of visible light to decolorize water. The present study reports Canthium Parviflorum (CNP) leaf extract utilization as an effective bio-reductant for green synthesis of Au NPs. A simple, eco-friendly process with low reaction time and temperature was adopted to synthesize CNP extract-mediated Au-NPs (CNP-AuNPs). The prepared AuNPs characterization involving X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS) surface area analysis, ultraviolet-visible spectroscopy (UV-Vis). XRD results showed that the cubic-structured AuNPs had a crystallite size of 14.12 nm. Assessment of organic dyes performance in degrading brilliant green (BTG) and amido black 10B (AMB) under visible light irradiation highlights an impressive 83.25% and 86% degradation efficiency within 120 min, accompanied by a kinetic rate constant dyes was found to be 0.0828 min⁻1, BTG, and 0.0123 min⁻1, Furthermore, the reduction of 4-nitrophenol by NaBH4 using CNP-AuNPs as a catalyst demonstrated good catalytic performance and rapid degradation at 89.4%. and rate constant 0.099 min-1 followed pseudo-first-order. The LC-MS analysis identified various intermediates during the degradation of the CR dye. Radical trapping experiments suggest that photogenerated free electrons and hydroxyl radicals are crucial for degrading the amido black 10B dye The AuNPs influenced the significant factors responsible for the photocatalytic activity, such as the increase in range of absorbance, increased e- and h+ pair separation, improvement in the charge transfer process, and active site formation, which significantly enhanced the process of degradation. We found that the CNP-AuNPs could effectively remove dyes and nitrophenol from industrial wastewater.

Prognosis of amyotrophic lateral sclerosis patients after tracheostomy invasive ventilation in Korea.

Background: Tracheostomy invasive ventilation (TIV) is applied to a subset of amyotrophic lateral sclerosis (ALS) patients; however, its frequency and impact on prognosis vary across countries. Methods: We conducted a nationwide retrospective cohort study using Korean National Health Insurance claims data. All patients diagnosed with sporadic ALS from 2012 to 2017 were included, with the observation period until 2020. The survival time between the TIV and non-TIV groups was compared using propensity score matching analysis, and prognostic factors were assessed within the TIV group. Results: This study included 3484 ALS patients (mean [standard deviation] age, 62.4 [11.9] years, 60.4% male), among whom 1230 (35.3%) underwent TIV. After 1:1 propensity score matching, the survival duration between the two groups was not significantly different (28 vs. 25 months, p = 0.057). Cox regression indicated that older age (hazard ratios [HRs] for each decade compared to <40 years: 3.89, 3.83, 5.30, 6.78, and 8.40 [≥80 years]; p < 0.005 for all) and lower income (HR, 1.28; 95% confidence interval [CI], 1.09-1.52; p = 0.003) negatively impacted survival, while gastrostomy (HR, 0.57; 95% CI, 0.50-0.66; p < 0.001) and supportive care services (HR, 0.43; 95% CI, 0.32-0.59; p < 0.001) were associated with prolonged survival. Conclusions: TIV was administered to more than one-third of Korean ALS patients without significant survival prolongation. Older age, lower income, lack of gastrostomy, and insufficient supportive care were independent poor prognostic factors for survival, underscoring the importance of comprehensive management for ALS patients.

Improving infra-red polarized imaging efficiency in a bilayer wire-grid polarizer.

The optical, plasmonic, and imaging performance of an infra-red polarized system exceeds that of a conventional infra-red detector due to its high resolution and precision. The wire-grid polarizer has large potential for use in an infra-red polarized imaging device owing to its large polarization efficiency. In this study, we theoretically and experimentally investigate a method to improve the polarization efficiency of a wire-grid polarizer. Here, we demonstrated a high-performance wire grid polarizer with a maximum extinction ratio (ER) of 355 using a bilayer structure and dielectric material in the mid-wavelength infra-red (MWIR) region (3000 nm-5000 nm), which is a 4 times higher ER value than that of the monolayer structure. More interestingly, we were able to improve the performance of the bilayer wire-grid polarizer by devising a method to improve the surface roughness using Ar ion milling. The ER for the after-milled sample was 1255, which was markedly larger than that of the before-milled sample. The results of transmittance measurement confirmed that the improvement in the ER was due to the Fabry-Perot (F-P) phenomenon caused by constructive or destructive interference in the bilayer wire-grid structure and the enhancement of the surface smoothness. These results will help design a polarizer structure that will maximize the polarization efficiency and realize a high-performance infrared polarized imaging system.

Polarization-sensitive tunable extraordinary terahertz transmission based on a hybrid metal-vanadium dioxide metasurface.

Thermally tunable extraordinary terahertz transmission in a hybrid metal-vanadium dioxide (VO2) metasurface is numerically demonstrated. The metasurface consists of a metal sheet perforated by square loops, while the loops are connected with strips of VO2. The frequency and amplitude of the transmission resonance are modulated by controlling the conductivity of VO2. For a y-polarized incident field, the resonance transmission peak redshifts from 0.88 to 0.81 THz upon insulator-to-metallic phase transition of VO2. For an x-polarized incident field, the transmission resonance at 0.81 THz is observed in the insulator phase. However, in the metallic phase of VO2, the electromagnetic field is effectively reflected in the 0.5-1.1 THz range with a transmission level lower than 0.14. The proposed metasurface can be utilized as a terahertz modulator, reconfigurable filter, or switch.

Exfoliation of MoS2 Quantum Dots: Recent Progress and Challenges.

Although, quantum dots (QDs) of two-dimensional (2D) molybdenum disulfide (MoS2) have shown great potential for various applications, such as sensing, catalysis, energy storage, and electronics. However, the lack of a simple, scalable, and inexpensive fabrication method for QDs is still a challenge. To overcome this challenge, a lot of attention has been given to the fabrication of QDs, and several fabrication strategies have been established. These exfoliation processes are mainly divided into two categories, the 'top-down' and 'bottom-up' methods. In this review, we have discussed different top-down exfoliation methods used for the fabrication of MoS2 QDs and the advantages and limitations of these methods. A detailed description of the various properties of QDs is also presented.

Temperature-Dependent Exciton Dynamics in a Single GaAs Quantum Ring and a Quantum Dot.

Micro-photoluminescence was observed while increasing the excitation power in a single GaAs quantum ring (QR) at 4 K. Fine structures at the energy levels of the ground (N = 1) and excited (N = 2) state excitons exhibited a blue shift when excitation power increased. The excited state exciton had a strong polarization dependence that stemmed from the asymmetric localized state. According to temperature-dependence measurements, strong exciton-phonon interaction (48 meV) was observed from an excited exciton state in comparison with the weak exciton-phonon interaction (27 meV) from the ground exciton state, resulting from enhanced confinement in the excited exciton state. In addition, higher activation energy (by 20 meV) was observed for the confined electrons in a single GaAs QR, where the confinement effect was enhanced by the asymmetric ring structure.

Hybrid plasmonic slot waveguide with a metallic grating for on-chip biosensing applications.

Designing reliable and compact integrated biosensors with high sensitivity is crucial for lab-on-a-chip applications. We present a bandpass optical filter, as a label-free biosensor, based on a hybrid slot waveguide on the silicon-on-insulator platform. The designed hybrid waveguide consists of a narrow silicon strip, a gap, and a metallic Bragg grating with a phase-shifted cavity. The hybrid waveguide is coupled to a conventional silicon strip waveguide with a taper. The effect of geometrical parameters on the performance of the filter is investigated by 3D finite-difference time-domain simulations. The proposed hybrid waveguide has potential for sensing applications since the optical field is pulled into the gap and outside of the silicon core, thus increasing the modal overlap with the sensing region. This biosensor offers a sensitivity of 270 nm/RIU, while it only occupies a compact footprint of 1.03µm×17.6µm.

Ictal Swearing as a Lateralizing Value for the Dominant Hemisphere in Temporal Lobe Epilepsy.

Ictal swearing, as an epileptic manifestation, has rarely been reported. Despite its poor localization value and unclear mechanism, several previous studies have reported that it frequently originates from the temporal lobe and more often from the non-dominant hemisphere. Herein, we report a case of a 41-year-old right-handed man with a history of stereotypical manifestation of ictal swearing with a left (dominant) hemisphere origin, confirmed by video electroencephalography monitoring. Reasonable suspicion that repetitive swearing could be a manifestation of seizures is important for clinicians not to misdiagnose the disease.

Optical characteristics of type-II hexagonal-shaped GaSb quantum dots on GaAs synthesized using nanowire self-growth mechanism from Ga metal droplet.

We report the growth mechanism and optical characteristics of type-II band-aligned GaSb quantum dots (QDs) grown on GaAs using a droplet epitaxy-driven nanowire formation mechanism with molecular beam epitaxy. Using transmission electron microscopy and scanning electron microscopy images, we confirmed that the QDs, which comprised zinc-blende crystal structures with hexagonal shapes, were successfully grown through the formation of a nanowire from a Ga droplet, with reduced strain between GaAs and GaSb. Photoluminescence (PL) peaks of GaSb capped by a GaAs layer were observed at 1.11 eV, 1.26 eV, and 1.47 eV, assigned to the QDs, a wetting-like layer (WLL), and bulk GaAs, respectively, at the measurement temperature of 14 K and excitation laser power of 30 mW. The integrated PL intensity of the QDs was significantly stronger than that of the WLL, which indicated well-grown GaSb QDs on GaAs and the generation of an interlayer exciton, as shown in the power- and temperature-dependent PL spectra, respectively. In addition, time-resolved PL data showed that the GaSb QD and GaAs layers formed a self-aligned type-II band alignment; the temperature-dependent PL data exhibited a high equivalent internal quantum efficiency of 15 ± 0.2%.

Comparative Chemico-Physical Analyses of Strain-Free GaAs/Al0.3Ga0.7As Quantum Dots Grown by Droplet Epitaxy.

We investigate the quantum confinement effects on excitons in several types of strain-free GaAs/Al 0 . 3 Ga 0 . 7 As droplet epitaxy (DE) quantum dots (QDs). By performing comparative analyses of energy-dispersive X-ray spectroscopy with the aid of a three-dimensional (3D) envelope-function model, we elucidate the individual quantum confinement characteristics of the QD band structures with respect to their composition profiles and the asymmetries of their geometrical shapes. By precisely controlling the exciton oscillator strength in strain-free QDs, we envisage the possibility of tailoring light-matter interactions to implement fully integrated quantum photonics based on QD single-photon sources (SPSs).

Optical shaping of the polarization anisotropy in a laterally coupled quantum dot dimer.

We find that the emission from laterally coupled quantum dots is strongly polarized along the coupled direction [1 1 ¯ 0], and its polarization anisotropy can be shaped by changing the orientation of the polarized excitation. When the nonresonant excitation is linearly polarized perpendicular to the coupled direction [110], excitons (X1 and X2) and local biexcitons (X1X1 and X2X2) from the two separate quantum dots (QD1 and QD2) show emission anisotropy with a small degree of polarization (10%). On the other hand, when the excitation polarization is parallel to the coupled direction [1 1 ¯ 0], the polarization anisotropy of excitons, local biexcitons, and coupled biexcitons (X1X2) is enhanced with a degree of polarization of 74%. We also observed a consistent anisotropy in the time-resolved photoluminescence. The decay rate of the polarized photoluminescence intensity along the coupled direction is relatively high, but the anisotropic decay rate can be modified by changing the orientation of the polarized excitation. An energy difference is also observed between the polarized emission spectra parallel and perpendicular to the coupled direction, and it increases by up to three times by changing the excitation polarization orientation from [110] to [1 1 ¯ 0]. These results suggest that the dipole-dipole interaction across the two separate quantum dots is mediated and that the anisotropic wavefunctions of the excitons and biexcitons are shaped by the excitation polarization.

Synthesis of zinc-gallate phosphors by biomineralization and their emission properties.

Reduction of target species by microorganisms and their subsequent precipitation into sparingly soluble mineral phase nanoparticles have been referred to as microbially mediated nanomaterial synthesis. Here, we describe the microbially mediated production of nano-dimensioned spinel structured zinc-gallate (ZnGa2O4) phosphors exhibiting different emission performance with varying substituted elements. Interestingly, in the microbially mediated phosphor production described herein, there were no reducible metal- and non-metal species composing the target minerals. By varying substituted elements, zinc-gallate phosphors present typical red, green, and blue (RGB) emission. An apparent whitish emission was accomplished by blending phosphors. A promising potential for white light produced by biosynthesized mixtures of Cr-, Mn-, and Co- substituted zinc-gallates representing RGB emissions was evidenced. Microbial activity supplied a reducing driving force and provided appropriate near neutral pH and reduced Eh conditions to thermodynamically precipitate spinel structured nanomaterials from supersaturated divalent and trivalent cations. This result complemented conventional biomineralization concepts and expanded the realm of biomanufacturing nanomaterials for further applications. STATEMENT OF SIGNIFICANCE: This study substantiated that circumstances of a suitable pH/Eh derived from bacterial activity, divalent/trivalent ion supply, buffering capacity, and supersaturation could precipitate spinel structure nanoparticles. Even though live or dead cells with membrane could enhance the nuclei generation, the spinel structured phases were produced regardless of existence of live or dead cells and reducible metal or non-metal species incorporating into the produced solid phases. This finding led to production of a series of metal-substituted zinc-gallates with specific RGB emission that can result in whitish light using simple blending. We believe our findings could expand the realm of nanomaterial synthesis using low cost, highly scalable bio-nanotechnology.

Post-thermal-Induced Recrystallization in GaAs/Al0.3Ga0.7As Quantum Dots Grown by Droplet Epitaxy with Near-Unity Stoichiometry.

Here, we investigate the stoichiometry control of GaAs/Al0.3Ga0.7As droplet epitaxy (DE) quantum dots (QDs). Few tens of core nonstoichiometries in the Ga(As) atomic percent are revealed in as-grown "strain-free" QDs using state-of-the-art atomic-scale energy-dispersive X-ray spectroscopy based on transmission electron microscopy. Precise systematic analyses demonstrate a successful quenching of the nonstoichiometry below 2%. The control of the chemical reactions with well-controlled ex situ annealing sheds light on the engineering of a novel single-photon source of strain-free DE QDs free of defects.

Gate- and Light-Tunable pn Heterojunction Microwire Arrays Fabricated via Evaporative Assembly.

One-dimensional (1D) nano/microwires have attracted considerable attention as versatile building blocks for use in diverse electronic, optoelectronic, and magnetic device applications. The large-area assembly of nano/microwires at desired positions presents a significant challenge for developing high-density electronic devices. Here, we demonstrated the fabrication of cross-stacked pn heterojunction diode arrays by integrating well-aligned inorganic and organic microwires fabricated via evaporative assembly. We utilized solution-processed n-type inorganic indium-gallium-zinc-oxide (IGZO) microwires and p-type organic 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) microwires. The formation of organic TIPS-PEN semiconductor microwire and their electrical properties were optimized by controlling both the amounts of added insulating polymer and the widths of the microwires. The resulting cross-stacked IGZO/TIPS-PEN microwire pn heterojunction devices exhibited rectifying behavior with a forward-to-reverse bias current ratio exceeding 102. The ultrathin nature of the underlying n-type IGZO microwires yielded gate tunability in the charge transport behaviors, ranging from insulating to rectifying. The rectifying behaviors of the heterojunction devices could be modulated by controlling the optical power of the irradiated light. The fabrication of semiconducting microwires through evaporative assembly provides a facile and reliable approach to patterning or positioning 1D microwires for the fabrication of future flexible large-area electronics.

Exciton Dipole-Dipole Interaction in a Single Coupled-Quantum-Dot Structure via Polarized Excitation.

We find that the exciton dipole-dipole interaction in a single laterally coupled GaAs/AlGaAs quantum dot structure can be controlled by the linear polarization of a nonresonant optical excitation. When the excitation intensity is increased with the linearly polarized light parallel to the lateral coupling direction [11̅0], excitons (X1 and X2) and local biexcitons (X1X1 and X2X2) of the two separate quantum dots (QD1 and QD2) show a redshift along with coupled biexcitons (X1X2), while neither coupled biexcitons nor a redshift are observed when the polarization of the exciting beam is perpendicular to the coupling direction. The polarization dependence and the redshift are attributed to an optical nonlinearity in the exciton Förster resonant energy transfer interaction, whereby exciton population transfer between the two quantum dots also becomes significant with increasing excitation intensity. We have further distinguished coupled biexcitons from local biexcitons by their large diamagnetic coefficient.

Multibit MoS2 Photoelectronic Memory with Ultrahigh Sensitivity.

A novel multibit MoS2 photoelectronic nonvolatile memory device is developed by synergistically combining rational device designs and the efficient transfer of large-area MoS2 flakes. The MoS2 photoelectronic memory exhibits excellent memory characteristics, including a large programming/erasing current ratio that exceeds 107 , multilevel data storage of 3 bits (corresponding to eight levels), performance stability over 200 cycles, and stable data retention over 104 s.

Synthesis and Characterization of Multiwalled Carbon Nanotubes/Poly(HEMA-co-MMA) by Utilizing Click Chemistry.

The hybrid material consisting of multi walled carbon nanotubes (MWNTs) and poly(2-hydroxyethylmethacrylate-co-methylmethacrylate) [poly(HEMA-co-MMA)] was synthesized by a combination of RAFT and Click chemistry. In the primary stage, the copolymer poly(HEMA-co-MMA) was prepared by applying RAFT technique. Alkynyl side groups were incorporated onto the poly(HEMA-co-MMA) backbone by esterification reaction. Then, MWNTs-N3 was prepared by treating MWNTs with 4-azidobutylamine. The click coupling reaction between azide-functionalized MWNTs (MWNTs-N3) and the alkyne-functionalized random copolymer ((HEMA-co-MMA)-Alkyne) with the Cu(I)-catalyzed [3+2] Huisgen cycloaddition afforded the hybrid compound. The structure and properties of poly(MMA-co-HEMA)-g-MWNTs were investigated by FT-IR, EDX and TGA measurements. The copolymer brushes were observed to be immobilized onto the functionalized MWNTs by SEM and TEM analysis.

Highly Conductive PEDOT:PSS Films with 1,3-Dimethyl-2-Imidazolidinone as Transparent Electrodes for Organic Light-Emitting Diodes.

Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT: PSS) films as transparent electrodes for organic light-emitting diodes (OLEDs) are doped with a new solvent 1,3-dimethyl-2-imidazolidinone (DMI) and are optimized using solvent post-treatment. The DMI doped PEDOT: PSS films show significantly enhanced conductivities up to 812.1 S cm(-1) . The sheet resistance of the PEDOT: PSS films doped with DMI is further reduced by various solvent post-treatment. The effect of solvent post-treatment on DMI doped PEDOT: PSS films is investigated and is shown to reduce insulating PSS in the conductive films. The solvent posttreated PEDOT: PSS films are successfully employed as transparent electrodes in white OLEDs. It is shown that the efficiency of OLEDs with the optimized DMI doped PEDOT: PSS films is higher than that of reference OLEDs doped with a conventional solvent (ethylene glycol). The results present that the optimized PEDOT: PSS films with the new solvent of DMI can be a promising transparent electrode for low-cost, efficient ITO-free white OLEDs.

An Organic Vertical Field-Effect Transistor with Underside-Doped Graphene Electrodes.

High-performance vertical field-effect transistors are developed, which are based on graphene electrodes doped using the underside doping method. The underside doping method enables effective tuning of the graphene work function while maintaining the surface properties of the pristine graphene.