Operando photoelectron spectroscopy analysis of graphene field-effect transistors.

In this study, operando photoelectron spectroscopy was used to characterize the performance of graphene field-effect transistors under working conditions. By sweeping the back-gate voltages, the carrier concentration of the graphene channel on the 150 nm Si3N4/Si substrate was tuned. From the C1s core level spectra acquired under the application of different gate voltages, the binding energy shifts caused by electric-field effects were obtained and analyzed. Together with the C1s peak shape information and the photoluminescence spectrum of the Si3N4/Si substrate, the presence of local potential across the x-ray beam spot associated with defects and gate leakage current in amorphous Si3N4was identified. The presence of defects in Si3N4/Si substrate could not only screen the partial electric field generated by the back gate but also serve as long-range scattering centers to the carriers, thus affecting charge transport in the graphene channel. Our findings will help further investigate the dielectric/graphene interface properties and accelerate the utilization of graphene in real device applications.

Optical determination of layered-materials InSe thickness via RGB contrast method and regression analysis.

Indium selenide (InSe) features intriguing thickness-dependent optoelectronic properties, and a simple, and precise way to identify the thickness is essential for the rapid development of InSe research. Here, a red, green, and blue (RGB) color contrast method with regression analysis for quantitative correlation of three optical contrasts from RGB channels with the InSe thickness (1-35 nm), is demonstrated. The lower accuracy of the thickness identification obtained from the individual channels was discussed. Moreover, the effective refractive indices in the three RGB regions can be extracted from the Fresnel equation and numerical analysis by finding the best fit to the experimental optical contrast. After further consideration of the wavelength-dependent refractive indices, the slope of the regression line between the estimated thickness and that obtained from the atomic force microscope was improved from 1.59 ± 0.05 to 0.97 ± 0.02. The complex refractive index spectra of InSe (1-10 layers) generated fromab initionumerical calculation results were also adopted to identify the InSe thickness. Compared to dispersion, the evolution of the band structure had less effect on thickness identification. This work could be extended to other layered materials, facilitate the thickness-dependent study of layered materials, and expedite the realization of their practical applications.

Branched silver nanowires on fluorine-doped tin oxide glass for simultaneous amperometric detection of H2O2 and of 4-aminothiophenol by SERS.

This study introduces a two-step method for the deposition of branched silver nanowires (AgNWs) on fluorine-doped tin oxide (FTO) glass. This material serves as both an active surface-enhanced Raman-scattering (SERS) substrate and as an enzyme-free electrochemical sensor for H2O2. This dual functionality is systematically studied. The AgNWs as the main trunk were first deposited on FTO by spray-coating. Silver branches were then electrochemically produced on the preformed NWs. Scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectrometry were employed to characterize morphology, composition and microstructure. SERS experiments show that the branched AgNW/FTO substrate exhibits excellent performance in detecting 4-aminothiophenol at an ultra-low concentration of 0.1 fM. Simultaneously, this material displays an excellent electrocatalytic response to H2O2 reduction at a concentration as low as 1 µM. The sensor has a rapid response and two linear analytical ranges that extend from 0.25 to 300 µM, and from 0.3 to 2.6 mM of H2O2, respectively. The ultrahigh sensitivity and satisfactory reproducibility highlights the merit of this hierarchical AgNW dendritic structure for sensing applications. Graphical abstract Branched silver nanowires can serve as both an active surface-enhanced Raman scattering substrate and as an electrochemical sensor for H2O2. This dual functionality is systematically investigated.

Coffee consumption was associated with a lower prevalence of airflow limitation in postmenopausal women.

BACKGROUND: Several studies have suggested a potential correlation between menopause and airflow limitation. However, the presence of protective factors in postmenopausal women remains uncertain. Therefore, our study seeks to examine potential protective factors associated with a reduced prevalence of airflow limitation among postmenopausal women. METHODS: Postmenopausal women were recruited from the Taiwan Biobank for this cross-sectional study. Airflow limitation was defined by a forced expiratory volume in the first second (FEV1)/forced vital capacity (FVC) ratio <0.7. The participants were categorized into two groups: non-coffee drinkers and coffee drinkers, and the association between coffee consumption and airflow limitation was examined using binary logistic regression models. RESULTS: A total of 8149 women with available information were enrolled. Compared to the non-coffee drinkers, the coffee drinkers had a significantly lower prevalence of airflow limitation (7% vs. 5%). The odds ratio (OR) for airflow limitation was lower in the coffee drinkers than in the non-coffee drinkers (OR = 0.77; 95% confidence interval [CI] = 0.63 to 0.94) after adjusting for confounding factors. We also examined the association between daily coffee consumption in cups and airflow limitation. The women who consumed ≥2 cups of coffee per day had an OR of 0.74 (95% CI = 0.59 to 0.94) compared to those who did not consume coffee. CONCLUSIONS: Our results suggest that habitual coffee consumption is associated with a reduction in the prevalence of airflow limitation in postmenopausal women, warranting further prospective studies to explore possible causal effects and mechanisms.

Creation of high density ensembles of nitrogen-vacancy centers in nitrogen-rich type Ib nanodiamonds.

This work explores the possibility of increasing the density of negatively charged nitrogen-vacancy centers ([NV(-)]) in nanodiamonds using nitrogen-rich type Ib diamond powders as the starting material. The nanodiamonds (10-100 nm in diameter) were prepared by ball milling of microdiamonds, in which the density of neutral and atomically dispersed nitrogen atoms ([N(0)]) was measured by diffuse reflectance infrared Fourier transform spectroscopy. A systematic measurement of the fluorescence intensities and lifetimes of the crushed monocrystalline diamonds as a function of [N(0)] indicated that [NV(-)] increases nearly linearly with [N(0)] at 100-200 ppm. The trend, however, failed to continue for nanodiamonds with higher [N(0)] (up to 390 ppm) but poorer crystallinity. We attribute the result to a combined effect of fluorescence quenching as well as the lower conversion efficiency of vacancies to NV(-) due to the presence of more impurities and defects in these as-grown diamond crystallites. The principles and practice of fabricating brighter and smaller fluorescent nanodiamonds are discussed.

Efficacy of the visual cognitive assessment test for mild cognitive impairment/mild dementia diagnosis: a meta-analysis.

Background: Mild cognitive impairment (MCI) is an intermediate stage between normal ageing and dementia. The early identification of MCI is important for timely intervention. The visual cognitive assessment test (VCAT) is a brief language-neutral screening tool for detecting MCI/mild dementia. This meta-analysis evaluated the diagnostic efficacy of the VCAT for MCI/mild dementia. Methods: Medline, Embase, Google Scholar, and Cochrane Library were searched from their inception until August 2023 to identify studies using VCAT to diagnose MCI/mild dementia. The primary outcome was to assess the diagnostic accuracy of the VCAT for detecting MCI/mild dementia through area under the receiver operating characteristic curve (AU-ROC) analysis. The secondary outcome was to explore the correlation between VCAT scores and MCI/mild dementia presence by comparing scores among patients with and without MCI/mild dementia. Pooled sensitivity, specificity, and area under the curve (AUC) were calculated. Results: Five studies with 1,446 older adults (mean age 64-68.3 years) were included. The percentage of participants with MCI/mild dementia versus controls ranged from 16.5% to 87% across studies. All studies were conducted in Asian populations, mostly Chinese, in Singapore and Malaysia. The pooled sensitivity was 80% [95% confidence interval (CI) 68%-88%] and the specificity was 75% (95% CI 68%-80%). The AU-ROCC was 0.77 (95% CI 0.73-0.81). Patients with MCI/mild dementia had lower VCAT scores than the controls (mean difference -6.85 points, p < 0.00001). Conclusion: VCAT demonstrated acceptable diagnostic accuracy in distinguishing MCI/mild dementia in cognitively normal older adults. As a language-neutral and culturally unbiased tool, the VCAT shows promise in detecting MCI/mild dementia. Further studies in non-Asian populations are required. Systematic review registration: https://www.crd.york.ac.uk/prospero/, identifier: CRD42023453453.

Antioxidant, Anti-α-Glucosidase, Antityrosinase, and Anti-Inflammatory Activities of Bioactive Components from Morus alba.

The root bark of Morus alba L. (Mori Cortex) is used to treat diuresis and diabetes in Chinese traditional medicine. We evaluated different solvent extracts and bioactive components from the root bark of Morus alba L. for their antioxidant, anti-α-glucosidase, antityrosinase, and anti-inflammatory activities. Acetone extract showed potent antioxidant activity, with SC50 values of 242.33 ± 15.78 and 129.28 ± 10.53 µg/mL in DPPH and ABTS radical scavenging assays, respectively. Acetone and ethyl acetate extracts exhibited the strongest anti-α-glucosidase activity, with IC50 values of 3.87 ± 1.95 and 5.80 ± 2.29 µg/mL, respectively. In the antityrosinase assay, the acetone extract showed excellent activity, with an IC50 value of 7.95 ± 1.54 µg/mL. In the anti-inflammatory test, ethyl acetate and acetone extracts showed significant anti-nitric oxide (NO) activity, with IC50 values of 10.81 ± 1.41 and 12.00 ± 1.32 µg/mL, respectively. The content of the active compounds in the solvent extracts was examined and compared by HPLC analysis. Six active compounds were isolated and evaluated for their antioxidant, anti-α-glucosidase, antityrosinase, and anti-inflammatory properties. Morin (1) and oxyresveratrol (3) exhibited effective antioxidant activities in DPPH and ABTS radical scavenging assays. Additionally, oxyresveratrol (3) and kuwanon H (6) showed the highest antityrosinase and anti-α-glucosidase activities among all isolates. Morusin (2) demonstrated more significant anti-NO and anti-iNOS activities than the positive control, quercetin. Our study suggests that the active extracts and components from root bark of Morus alba should be further investigated as promising candidates for the treatment or prevention of oxidative stress-related diseases, hyperglycemia, and pigmentation disorders.

Physiological exophoria did not increase the incidence of myopia in rural school children in Taiwan.

ABSTRACT: This study evaluated the incidence rate and risk factors for developing myopia in elementary school students in Chiayi, Taiwan. This prospective cohort study comprised 1816 students without myopia (grades 1 to 5 in Chiayi County). The students underwent a noncycloplegic ocular alignment examinations using an autorefractometer and completed a questionnaires at baseline and at a 1-year follow-up. A univariate logistic regression was used to assess the effects of the categorical variables on new cases of myopia. A multinomial logistic regression was then conducted. A chi-squared test was used to compare new cases of myopia in terms of ocular alignment. A Cox hazard ratio model was then used to validate factors associated with changes in ocular alignment. A P value of <.05 was considered significant. In 370 participants with new cases of myopia out of 1816 participants, a spherical error of -1.51 ±â€Š0.6 diopters was noted at follow-up. The baseline ocular alignment was not a significant risk factor for developing myopia (exophoria vs orthophoria: OR 1.26, 95% CI 0.97-1.62; other vs. orthophoria: OR 1.15, 95% CI 0.73-1.82). However, new cases of myopia (HR 1.36, 95% CI 1.14-1.61), and baseline ocular alignment (exophoria vs orthophoria: HR 3.76, 95% CI 3.20-4.42; other vs orthophoria: HR 3.02, 95% CI 2.05-4.45) were associated with exophoria at follow-up. This study provided epidemiological data on the incidence of myopia in elementary school students in Chiayi, Taiwan. It also demonstrated that physiological exophoria does not predispose patients to developing myopia.

Thermal treatment using microwave irradiation for the phytosanitation of Xylella fastidiosa in pecan graftwood.

Pecan bacterial leaf scorch caused by Xylella fastidiosa is an emerging disease for the U.S. and international pecan industries and can be transmitted from scion to rootstock via grafting. With the expanse of global transportation and trade networks, phytosanitation is critical for reducing the spread of economically significant pathogens, such as X. fastidiosa. We developed and evaluated thermal treatments using microwave irradiation and microwave absorbers [sterile deionized water (dH2O) and carbon nanotubes (CNTs)] as novel disinfectant methods for remediating X. fastidiosa in pecan scions. Partial submergence of scions in dH2O or CNT dispersions resulted in the transport of microwave absorbers in the xylem tissue via transpiration but did not compromise plant health. The microwave absorbers effectively transferred heat to the scion wood to reach an average temperature range of 55-65°C. Microwave radiation exposure for 6 sec (3 sec for two iterations) of CNT- or dH2O-treated scions reduced the frequency of X. fastidiosa-positive in pecan scions without negatively affecting plant viability when compared to the control group (dH2O-treated with no microwave). The efficacy of the new thermal treatments based on microwave irradiation was comparable to the conventional hot-water treatment (HWT) method, in which scions were submerged in 46°C water for 30 min. Microwave irradiation can be employed to treat X. fastidiosa-infected scions where the conventional HWT treatment is not feasible. This study is the first report to demonstrate novel thermal treatment methods based on the microwave irradiation and microwave absorbers of dH2O and CNT as an application for the phytosanitation of xylem-inhabiting bacteria in graftwood.

Two-photon fluorescence correlation spectroscopy of lipid-encapsulated fluorescent nanodiamonds in living cells.

Dynamics of fluorescent diamond nanoparticles in HeLa cells has been studied with two-photon fluorescence correlation spectroscopy (FCS). Fluorescent nanodiamond (FND) is an excellent fluorescent probe for bioimaging application, but they are often trapped in endosomes after cellular uptake. The entrapment prohibits FCS from being performed in a time frame of 60 s. Herein, we show that the encapsulation of FNDs within a lipid layer enhances the diffusion of the particles in the cytoplasm by more than one order of magnitude, and particles as small as 40 nm can be probed individually with high image contrast by two-photon excited luminescence. The development of the technique together with single particle tracking through one-photon excitation allows probing of both short-term and long-term dynamics of single FNDs in living cells.

Observing second-order nonlinear optical properties by symmetry breaking in centrosymmetric furan-containing oligoaryl cyclophandienes.

Centrosymmetric furan-containing cyclophandienes 3 and 4, synthesized by our furan annulation protocol, have been shown to exhibit extraordinarily large Stokes shifts and second-order nonlinear optical beta values. The beta values for 3 and 4 measured at 1.32 mum are 208 and 530x10(-30) esu, respectively. The beta values of 3 and 4 are similar to those of respective cyclophenes 1 a and 7 in which strong hyperpoarizable interactions between two twisted pi-systems (oligoaryl and bridging double bond) might take place. Symmetry breaking due to the resonance contribution (cf. 2) and the unique structural features of 3 and 4 has been used to account for this unusual photophysical behavior.

Promoting Dual Electronic and Ionic Transport in PEDOT by Embedding Carbon Nanotubes for Large Thermoelectric Responses.

Thermoelectric (TE) energy conversion with nontraditional organic materials is promising in wearable electronics and roll-to-roll manufacturing because of mechanical flexibility, lightweight, and easy processing. Although typical organic materials have a benefit of low thermal conductivity that creates a large temperature gradient, relatively small thermopower (or Seebeck coefficient) often requires copious number of TE legs to fabricate practical TE devices. Here, we show that hybrids of poly(3,4-ethylenedioxythiophene)-tosylate (PEDOT-Tos) and carbon nanotubes (CNTs) can produce extremely large thermopower, ∼14 mV/K at room temperature by a chemical reduction. With decent electrical conductivity, an extraordinary power factor of ∼1200 µW/m K2 at room temperature was observed. The large power factor could be attributed to prominent dual electronic and ionic conduction, which is likely to be promoted by embedding the CNTs in PEDOT  due to the improvement in the carrier mobility, in comparison with the inferior and widely varying  TE properties of PEDOT-only samples in the literature. While a higher CNT concentration gave a larger electronic contribution, a longer reduction or a lower CNT concentration provided a larger ionic contribution. Meanwhile, well-separated CNTs created CNT junctions intervened by PEDOT-Tos, suppressing the thermal transport. Further research utilizing the high TE responses could greatly help to develop practical wearable and/or mass-producible thermal energy harvesting and storage devices.

Novel Organic Schottky Barrier Diode Created in a Single Planar Polymer Film.

An organic Schottky barrier diode is created in a single planar PEDOT:Tos film by treating a half of the PEDOT:Tos film with TDAE vapor. Current is rectified in one direction by the Schottky barrier at the junction. The unique planar structure made of a single film greatly reduces defects, resulting in a remarkably high current density with a high rectification ratio, as well as making it suitable for ink-jet-type or roll-to-roll printing techniques.

Thermally Driven Large N-Type Voltage Responses from Hybrids of Carbon Nanotubes and Poly(3,4-ethylenedioxythiophene) with Tetrakis(dimethylamino)ethylene.

Hybrids of carbon nanotubes (CNTs) and poly(3,4-ethylenedioxythiophene) (PEDOT) treated by tetrakis(dimethylamino)ethylene (TDAE) have large n-type voltages in response to temperature differences. The reduced carrier concentration by TDAE reduction and partially percolated CNT networks embedded in the PEDOT matrix result in high thermopower and low thermal conductivity. The high electron mobility in the CNTs helps to minimally reduce the electrical conductivity of the hybrid, resulting in a large figure-of-merit.

Completely organic multilayer thin film with thermoelectric power factor rivaling inorganic tellurides.

Composed exclusively of organic components, polyaniline (PANi), graphene, and double-walled nanotubes (DWNTs) are alternately deposited from aqueous solutions using a layer-by-layer assembly. The 40 quadlayer thin film (470 nm thick) exhibits electrical conductivity of 1.08 × 10(5) S m(-1) and a Seebeck coefficient of 130 µV K(-1) , producing a thermoelectric power factor of 1825 µW m(-1) K(-2) .

Intrachain energy transfer in silylene-spaced alternating donor-acceptor divinylarene copolymers.

Silylene-spaced donor-acceptor divinylarene copolymers are synthesized by hydrosilylation of bisalkynes 7 with bisvinylsilanes 3; efficient intrachain energy transfer between donor-acceptor chromophores is observed.

Large enhancements in optoelectronic efficiencies of nano-plastically stressed conjugated polymer strands.

The photoluminescence (PL) of well dispersed molecules of a conjugated polymer, poly[2-methoxy-5-((2'-ethylhexyl)oxy)-1,4-phenylene-vinylene] (MEH-PPV), in an optically inert matrix manifested dramatic increases when the individual molecular strands were fully stretched. The PL increase rose with stretching and may reach several folds when the mechanical strain of the matrix polymer went beyond 550%. Strong polarization effects indicate that stretching individual polymer chains was responsible for the PL enhancement. This effect was attributed to suppression of electron-phonon interactions in the stress-rigidified polymer chain segments and may be useful for efficiency-enhanced polymer-based optoelectronic devices.

Objective-type dark-field system applied to multi-wavelength capillary electrophoresis for fluorescent detection and analysis.

This paper presents an advanced diascopic illumination technique for simultaneous multi-wavelength fluorescence excitation and detection without using any spatial filter sets. The proposed system includes a home-built dark-field condenser comprising a high N.A. objective and a light stop-film to excite fluorescence and an ultraviolet-visible-near infrared (UV-VIS-NIR) spectrometer to detect emitted signals. Since no direct light source enters the optical detection system, no complex optical filter is required for multi-wavelength fluorescence detection. This study also designs an optimized stop-film pattern to obtain the best performance in exciting fluorescent samples and reduce background light. Experimental results show that the proposed system can effectively increase the fluorescent signal and simultaneously detect a mixed sample composed of 2',7'-dichlorofluorescein, Rhodamine B, Atto610, and Atto647N. Furthermore, this proposed system successfully separates and detects a mixed bio-sample composed of three single-stranded DNA samples labeled with Cy3, FITC, and Alexa647 fluorescence in a single channel. A simple and fast calculation removes noise and fluorescent cross-effect for conveniently observing the electropherograms. The proposed system has a measured detection limit up to 5x10(-8)M (S/N=3) while detecting a standard fluorescence of 2',7'-dichlorofluoresein, which is capable of detecting fluorescence samples in general applications. The proposed method provides a simple and straightforward way to detect multi-wavelength fluorescence for CE analysis.

Two-photon excited fluorescence of nitrogen-vacancy centers in proton-irradiated type Ib diamond.

Two-photon fluorescence spectroscopy of negatively charged nitrogen-vacancy [(N-V)-] centers in type Ib diamond single crystals have been studied with a picosecond (7.5 ps) mode-locked Nd:YVO(4) laser operating at 1064 nm. The (N-V)- centers were produced by radiation damage of diamond using a 3 MeV proton beam, followed by thermal annealing at 800 degrees C. Prior to the irradiation treatment, infrared spectroscopy of the C-N vibrational modes at 1344 cm(-1) suggested a nitrogen content of 109 +/- 10 ppm. Irradiation and annealing of the specimen led to the emergence of a new absorption band peaking at approximately 560 nm. From a measurement of the integrated absorption intensity of the sharp zero-phonon line (637 nm) at liquid nitrogen temperature, we determined a (N-V)- density of (4.5 +/- 1.1) x 10(18) centers/cm3 (or 25 +/- 6 ppm) for the substrate irradiated at a dose of 1 x 1016) H(+)/cm(2). Such a high defect density allowed us to observe two-photon excited fluorescence and measure the corresponding fluorescence decay time. No significant difference in the spectral feature and fluorescence lifetime was observed between one-photon and two-photon excitations. Assuming that the fluorescence quantum yields are the same for both processes, a two-photon absorption cross section of sigma(TPA) = (0.45 +/- 0.23) x 10(-50) cm(4).s/photon at 1064 nm was determined for the (N-V)- center based on its one-photon absorption cross section of sigma(OPA) = (3.1 +/- 0.8) x 10(-17) cm2 at 532 nm. The material is highly photostable and shows no sign of photobleaching even under continuous two-photon excitation at a peak power density of 3 GW/cm(2) for 5 min.