Search

In this article, we provide a comprehensive convergence and stability analysis of a semi-Lagrangian scheme for solving nonlinear Burgers' equations with a high-order spatial discretization. The analysis is for the iteration-free semi-Lagrangian scheme comprising the second-order backward finite difference formula (BDF2) for total derivative and the fourth-order central finite difference for diffusion term along the trajectory. The main highlight of the study is to thoroughly analyze the order of convergence of the discrete $ \ell_2 $-norm error $ \mathcal{O}(h^2+\triangle x^4+ \triangle x^{p+1}/h) $ by managing the relationship between the local truncation errors from each discretization procedure and the interpolation properties with a symmetric high-order discretization of the diffusion term. Furthermore, stability is established by the uniform boundedness of the numerical solution using the discrete Grönwall's Lemma. We provide numerical examples to support the validity of the theoretical convergence and stability analysis for the propounded backward semi-Lagrangian scheme.

The degenerate versions of special polynomials and numbers, initiated by Carlitz, have regained the attention of some mathematicians by replacing the usual exponential function in the generating function of special polynomials with the degenerate exponential function. To study the relations between degenerate special polynomials, $ \lambda $-umbral calculus, an analogue of umbral calculus, is intensively applied to obtain related formulas for expressing one $ \lambda $-Sheffer polynomial in terms of other $ \lambda $-Sheffer polynomials. In this paper, we study the connection between degenerate higher-order Daehee polynomials and other degenerate type of special polynomials. We present explicit formulas for representations of the polynomials using $ \lambda $-umbral calculus and confirm the presented formulas between the degenerate higher-order Daehee polynomials and the degenerate Bernoulli polynomials, for example. Additionally, we investigate the pattern of the root distribution of these polynomials.

Among a remarkably large number of various extensions of polynomials and numbers, and diverse introductions of new polynomials and numbers, in this paper, we choose to introduce two new generalizations of some extended Bernoulli polynomials and numbers by using the Mittag–Leffler function and the confluent hypergeometric function. Then, we investigate certain properties and formulas of these newly introduced polynomials and numbers such as explicit representations, addition formulas, integral formulas, differential formulas, inequalities, and inequalities involving their integrals. Also, by using the theory of umbral calculus, five additional formulas regarding these new polynomials are provided. Furthermore, we propose to introduce four generalizations of the extended Euler and Genocchi polynomials. Finally, three natural problems are poised.

Disulfonated rhodamines are photostable and bright dyes widely used in life science and optical microscopy. However, di-sulfonated dyes were considered cell impermeable and not applicable in living cells. We challenged this assumption with 5 most popular rhodamines (Rho) having two carboxylic acid residues, versatile sulfonation patterns and emitting green (AS488), yellow (Rho530), orange (Rho565) and red (Rho590 and STAR RED) light. The probes comprising one rhodamine entity and a HaloTagTM amine (O2) ligand (x) were prepared and applied for labeling of living, Vimentin-Halo (VIM-Halo) expressing U-2 OS cells. Surprisingly, we observed specific and bright staining with simplest compounds Rho590-x, Rho565-x and Rho530-x bearing two negative charges; they performed well also in stimulated emission depletion (STED) microscopy. Specific staining and red shifts in absorption and emission bands were observed with other probes having one negative charge; they were prepared by native chemical ligation and esterification.

The stability of wild-type p53 is critical for its apoptotic function. In some cancers, wild-type p53 is inactivated by interaction with viral and cellular proteins, and restoration of its activity has therapeutic potential. Here, we identify homeobox Msx1 as a p53-interacting protein and show its novel function as a p53 regulator. Overexpression of homeobox Msx1 induced apoptosis of cancer cells harboring nonfunctional wild-type p53 and suppressed growth of human tumor xenografts in nude mice. The homeodomain of Msx1 functions as a protein-protein interacting motif rather than a DNA-binding domain and is essential for stabilization, nuclear accumulation, and apoptotic function of wild-type p53. The identification of a novel function of Msx1 as a p53 regulator may open new avenues for developing improved molecular therapies for tumors with a nonmutational p53 inactivation mechanism.

Supplementary Figures 1-4, with Legends from Homeobox Msx1 Interacts with p53 Tumor Suppressor and Inhibits Tumor Growth by Inducing Apoptosis

We present a new type of degenerate poly-Bernoulli polynomials and numbers by modifying the polyexponential function in terms of the degenerate exponential functions and degenerate logarithm functions. Also, we introduce a new variation of the degenerate unipoly-Bernoulli polynomials by the similar modification. Based on these polynomials, we investigate some properties, new identities, and their relations to the known special functions and numbers such as the degenerate type 2-Bernoulli polynomials, the type 2 degenerate Euler polynomials, the degenerate Bernoulli polynomials and numbers, the degenerate Stirling numbers of the first kind, and $ \lambda $-falling factorial sequence. In addition, we compute some of the proposed polynomials and present their zeros and behaviors for different variables in specific cases.

Research on the degenerate versions of special polynomials provides a new area, introducing the $ \lambda $-analogue of special polynomials and numbers, such as $ \lambda $-Sheffer polynomials. In this paper, we propose a new variant of type 2 Bernoulli polynomials and numbers by modifying a generating function. Then we derive explicit expressions and their representations that provide connections among existing $ \lambda $-Sheffer polynomials. Also, we provide the explicit representations of the proposed polynomials in terms of the degenerate Lah-Bell polynomials and the higher-order degenerate derangement polynomials to confirm the presented identities.

Asymmetric diarylethenes with benzo[b]thiophen-3-yl and 2-thienyl residues having variable oxidation degrees (S and/or SO2) remained unexplored. These photochromes provide reversibly photoswitchable absorbance and multicolor emission modulation. Here we report 18 photochromic 1,2-diarylperfluorocyclopentenes with oxidized and non-oxidized 2-methylbenzo[b]thiophen-3-yl, as well as 5-aryl-3-methylthiophen-2-yl groups. The structure–property relationships were studied for three groups of compounds: non-oxidized, mono-oxidized (to SO2 in the benzothiophene part), and fully-oxidized (to 2 × SO2). The quantum chemistry calculations helped to interpret the substituents’ effects in each group and predict the photophysical properties of yet unavailable photochromes. The photochromic systems with absorbance modulation introduced in this work were designed for the use in diffraction-unlimited writing and reading with light, nanopattering and optical lithography.

This paper analyzes the stability of numerical solutions for a nonlinear Schrödinger equation that is widely used in several applications in quantum physics, optical business, etc. One of the most popular approaches to solving nonlinear problems is the application of a linearization scheme. In this paper, two linearization schemes—Newton and Picard methods were utilized to construct systems of linear equations and finite difference methods. Crank-Nicolson and backward Euler methods were used to establish numerical solutions to the corresponding linearized problems. We investigated the stability of each system when a finite difference discretization is applied, and the convergence of the suggested approximation was evaluated to verify theoretical analysis.

Hybrid nanostructures are promising for ultrasound-triggered drug delivery and treatment, called sonotheranostics. Structures based on plasmonic nanoparticles for photothermal-induced microbubble inflation for ultrasound imaging exist. However, they have limited therapeutic applications because of short microbubble lifetimes and limited contrast. Photochemistry-based sonotheranostics is an attractive alternative, but building near-infrared (NIR)-responsive echogenic nanostructures for deep tissue applications is challenging because photolysis requires high-energy (UV-visible) photons. Here, we report a photochemistry-based echogenic nanoparticle for in situ NIR-controlled ultrasound imaging and ultrasound-mediated drug delivery. Our nanoparticle has an upconversion nanoparticle core and an organic shell carrying gas generator molecules and drugs. The core converts low-energy NIR photons into ultraviolet emission for photolysis of the gas generator. Carbon dioxide gases generated in the tumor-penetrated nanoparticle inflate into microbubbles for sonotheranostics. Using different NIR laser power allows dual-modal upconversion luminescence planar imaging and cross-sectional ultrasonography. Low-frequency (10 MHz) ultrasound stimulated microbubble collapse, releasing drugs deep inside the tumor through cavitation-induced transport. We believe that the photoechogenic inflatable hierarchical nanostructure approach introduced here can have broad applications for image-guided multimodal theranostics.

В настоящей работе приводятся результаты измерения температурной зависимости сопротивления твердых растворов Ga(1-х)MnхAs со значением х=0.0156. Установлено, что температурные зависимости сопротивления, измеренные вдоль кристаллических осей [110] и [110] в области температур ниже 150 К, носят существенно различный характер. Показано, что при температурах ниже температуры Кюри данные различия могут быть связаны с анизотропией магнитных свойств эпитаксиального слоя Ga(1-х)MnхAs, тогда как при температурах выше температуры Кюри, наблюдаемые различия могут быть связаны с анизотропией подвижности носителей заряда, возникающей из-за наличия в объеме эпитаксиального слоя пространственно ориентированных структур.

Photoelectrochemical water splitting is an environmentally benign way to store solar energy. Properties such as fast charge recombination and poor charge transport rate severely restrict the use of BiVO4 as a photoanode for photoelectrochemical water splitting and many attempts were made to improve the current performance limit of the photoanode. To address these disadvantages, a highly efficient BiVO4/Bi2S3 heterojunction was fabricated applying facial anion-exchange (AE) and successive ionic layer adsorption and reaction (SILAR). The deposition of Bi2S3 on BiVO4 nanoworms by both AE and SILAR was confirmed through morphological, structural, and optical analyses. The morphological analysis indicated that Bi2S3 grown through SILAR has relatively more crystalline-amorphous phase boundaries than Bi2S3 generated using the anion-exchange method. The highest photocurrent density was observed for the SILAR-coated Bi2S3 on BiVO4, which is three times the value of the pristine BiVO4 measured under 1 sun illumination (100 mW cm−2 with Air mass (AM) 1.5 filter) in a 0.5 M Na2SO4 electrolyte at 1.6 V vs. RHE. In addition, the deposition of Bi2S3 through AE results in a twofold higher photocurrent density compared to uncoated BiVO4. The comparison of the two cost-effective AE and SILAR methods to deposit Bi2S3 on BiVO4 showed a negative shift in the flat band Mott-Schottky values, which coincides with the drifted onset potential values of the current density-voltage (J–V) curve. Furthermore, photoelectrochemical impedance spectroscopy (PEIS) analyses and band alignment studies revealed that SILAR-grown Bi2S3 creates an effective heterojunction with BiVO4, which leads to an efficient charge transfer.

In this paper, we give a necessary condition for two virtual knots to be related by a finite sequence of twist moves by using the affine index polynomial, which is a Vassiliev invariant of degree [Formula: see text]. Trapp showed that a numerical Vassiliev invariant of degree [Formula: see text] has a polynomial growth of degree [Formula: see text] on a twist sequence of knots, which can be extended to a twist sequence of virtual knots. We calculate the growth of the affine index polynomial for a twist sequence of virtual knots and find the difference of the affine index polynomials of two virtual knots, which are related by a twist move. Moreover, we give a lower bound for the number of twist moves needed to transform [Formula: see text] to [Formula: see text] if [Formula: see text] and [Formula: see text] are virtual knots related by a finite sequence of twist moves.

The temperature dependence of the anisotropy of the magnetotransport properties of GaMnAs epitaxial layers featuring ferromagnetic order is investigated. The anisotropy of negative magnetoresistance that is unrelated to the presence of uniaxial anisotropy and the orientation of the hard magnetization axis is observed. This anisotropy may result from the occurrence of spatially oriented structures in GaMnAs that emerge in the bulk of the epitaxial layer during growth.

A hydrogen breath test is a non-invasive and safe diagnostic tool to explore the functional gastrointestinal disorders. For the diagnosis of small intestinal bacterial overgrowth syndrome as well as carbohydrate malabsorption such as fructose, lactose, and sorbitol malabsorption, a hydrogen breath test is considered one of the gold criterions. Since the more sensitive hydrogen sensor enables the more accurate prediction about the disease, many efforts have been to the development of the high performance H2 sensor. Herein, we fabricate the pn-junction type composite sensors using single wall carbon nanotube (SWCNT) and zinc oxide and thoroughly investigate their hydrogen sensing properties at various temperatures. We discuss the origin of sensing performance enhancement mechanism in the composite sensors, while the composite sensor with high H2 sensing performance, linearity, repeatability, and selectivity can be prepared.

A series of WO3/multiwalled carbon nanotube (MWCNT) nanocomposite sensors was fabricated by bar-coating slurries using different ratios of MWCNTs to WO3 nanoparticles. The morphology, composition, and structure of the fabricated nanocomposites were examined using electron microscopy, X-ray diffraction, ultraviolet and X-ray photoelectron spectroscopy, Raman spectroscopy, and nitrogen adsorption-desorption measurements, with the aim of completely identifying the physical and electronic structures of the nanocomposites. The effects of the different ratios of the nanocomposites on the electrical conductance and NO2 gas sensing properties were examined and compared with the morphological investigation results. The synergetic properties of the nanocomposite sensors were a result of the combined effect of low-doped semiconducting WO3 and metallic MWCNTs. Because nanoscale sensors exhibit a maximal response on the scale of their depletion depth, individual components with conductivities that are either too low or too high cannot meet the condition. Meanwhile, their mixture can establish the required condition for the maximal response which appears as a synergetic effect. Based on this effect, the optimal nanocomposite sensor (0.5 wt% MWCNT) showed a response of ~18 for 5 ppm NO2 at 150 °C with short response/recovery times (~87 s /~300 s). The synergetic effect in nanocomposite sensors cannot be explained by the interfacial Schottky barrier model, which has been used for sensors of agglomerated particles.

Afterglow is superior to other optical modalities for biomedical applications in that it can exclude the autofluorescence background. Nevertheless, afterglow has rarely been applied to the high-contrast "off-to-on" activatable sensing scheme because the complicated afterglow systems hamper the additional inclusion of sensory functions while preserving the afterglow luminescence. Herein, a simple formulation of a multifunctional components-incorporated afterglow nanosensor (MANS) is developed for the superoxide-responsive activatable afterglow imaging of cisplatin-induced kidney injury. A multifunctional iridium complex (Ir-OTf) is designed to recover its photoactivities (phosphorescence and the ability of singlet oxygen-generating afterglow initiator) upon exposure to superoxide. To construct the nanoscopic afterglow detection system (MANS), Ir-OTf is incorporated with another multifunctional molecule (rubrene) in the polymeric micellar nanoparticle, where rubrene also plays dual roles as an afterglow substrate and a luminophore. The multiple functions covered by Ir-OTf and rubrene renders the composition of MANS quite simple, which exhibits superoxide-responsive "off-to-on" activatable afterglow luminescence for periods longer than 11 min after the termination of pre-excitation. Finally, MANS is successfully applied to the molecular imaging of cisplatin-induced kidney injury with activatable afterglow signals responsive to pathologically overproduced superoxide in a mouse model without autofluorescence background.

STEM learning systems in which the roles of all subjects are unequal, may have a detrimental impact on student learning in neglected subject roles. Therefore, STEM learning packages should have sub-activities that assist students to see the interdependence of all disciplines, especially in mathematics. The nature of the content makes it quite difficult to link it to the mission of STEM. As a result, both teachers and learners are not explicitly aware of the role of mathematics in STEM. Mathematics should not be seen as a simple component in the design of STEM activities, but rather as a vital and necessary aspect. STEM activities based on packaging material problems were developed in this study. The goal is to promote student awareness of the role of mathematics in STEM activities. Seventy-one students, aged 16 and 17 years old, participated in a one-day STEM camp. When the activities were completed, it was found that assessment of student awareness of the role of mathematics in STEM activities was positive. Moreover, teamwork was assessed by groupmates. The evaluation results showed that their behavior was satisfactory. These results indicate that the developed activities are useful for STEM learning in classroom contexts that lack clear tasks reflecting the role of mathematics. Interested instructors can integrate this activity into one sub activity in their own classroom STEM learning packages as appropriate.

Hematite-based photoanode (α-Fe

Organolead halide perovskite nanocrystals (NCs) have emerged as promising materials for various optoelectronic applications. However, their practical applications have been limited due to low struc...

Thin film consisting of hierarchical cadmium oxide nanonecklaces has been synthesized through room temperature chemically deposited cadmium hydroxide nanowires as template followed by air annealing. Formation of thin film has been confirmed with aid of structural, surface morphological, valence state and optical, studies performed by X-ray diffraction, Raman analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV–visible spectroscopy. Air annealing at 330 °C has enhanced the photo electrochemical power conversion efficiency of the CdO as photoanode to 0.21% configured through platinum as counter electrode and polyiodide as a liquid electrolyte. Complete device performance have been correlated through rate of recombination, and electron life time. The schematic energy band alignment also has been comprehended herein.

A paramagnetic NiTi substrate was coated with diamagnetic carbon materials, i.e., graphene, graphene oxide (GO), and carbon nanotubes (CNTs), in order to reduce magnetic resonance (MR) image artifacts of NiTi implants. The present study focused on the effect of magnetic susceptibility variations in NiTi caused by the carbon coating on MR image artifacts. In the case of the graphene and GO coatings, the reduction of the magnetic susceptibility was greater along the perpendicular direction than the parallel direction. In contrast, the CNT coating exhibited a larger reduction along the parallel direction. The reduction of magnetic susceptibility measured in CNT-coated NiTi (CNT/NiTi) was smaller than the theoretical prediction especially when measured along the parallel direction, because CNTs on the NiTi surface were randomly arranged, rather than in a single direction. MR image artifacts were substantially reduced in all carbon-coated NiTi specimens, which is due to the reduction of magnetic susceptibility in NiTi by the carbon coating. This method can also be applied to other paramagnetic bio-metallic materials such as Co-Cr.

A flexible transparent electrode film is fabricated by coating the conductive polymer PEDOT:PSS using a solution-shearing process on PET film in which silver nanoparticles are embedded in intaglio grids patterned by a roll-to-roll thermal imprinting method. The composite electrode shows a sheet resistance of 20 Ω square−1 and a light transmittance of 82.9% at room temperature. An all-solution polymer solar mini sub-module is fabricated on the flexible electrode by further depositing ZnO and P3HT:PC61BM layers using the optimized solution-shearing process with subsequent printing of PEDOT:PSS and flat-screen printing of silver. The structure and morphology of the solution-shearing processed films examined by XRD and AFM show smoother surfaces and higher crystallinity than those of conventional spin-coated films. The solution-shearing-processed flexible polymer solar mini sub-module fabricated on an area of 36 cm2 shows a power conversion efficiency of 1.87% under an AM 1.5G solar simulator. Therefore, the solution-shearing process toward large-area flexible polymer solar module fabrication is successfully demonstrated.

In this study, we develop a numerical method for solving the coupled viscous Burgers’ equations based on a backward semi-Lagrangian method. The main difficulty associated with the backward semi-Lagrangian method for this problem is treating the nonlinearity in the diffusion-reaction equation, whose reaction coefficients are given in terms of coupled partial derivatives. To handle this difficulty, we use an extrapolation technique which splits the nonlinearity into two linear diffusion-reaction boundary value problems. In the proposed backward semi-Lagrangian method, we use fourth-order finite differences to discretize the diffusion-reaction boundary value problems and employ the so-called error correction method to solve the highly nonlinear initial value problems. Our overall algorithm is completely iteration-free and computationally efficient. We demonstrate the numerical accuracy and efficiency of the present method by comparing our numerical results with analytical solutions and other numerical solutions based on alternative existing methods.

Photoelectrochemical (PEC) water splitting process is thoroughly revisited based on the energy diagram to elucidate the experimental observations. The TiO2 nanorod structure is studied as the model system for the photoanode of the PEC cell due to its stability in both acidic and basic solutions. The photocurrents with the external bias are examined under the various electrolytes of H2SO4, NaCl, and NaOH. The energy diagrams of the whole PEC system related to the water splitting process are interactively constructed in three-electrode configuration with the vacuum level as the common reference. Electrode potentials and photocurrents measured with the external bias in dark and under light are systematically correlated with the energy diagram of the PEC system. The pH dependent flat-band potential is explained by applying the pH dependent Helmholtz layer potential at the interface. In addition, the distribution of the applied potential in the PEC system during the water splitting process is understood by in-depth understanding of the energy band diagram.

A UV-light-activated TiO2 thin film gas sensor composed of nanoparticles is reported for H2S detection at room temperature. TiO2 nanoparticulate thin films were fabricated by bar coating of a mixture of TiO2 powder and acetic acid. The morphology and structural properties of the films were examined by scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy, and absorption spectroscopy. The nil response to H2S was significantly enhanced by UV light irradiation in the response levels and response/recovery kinetics. The effect of the sensor conductance and light intensity towards sensor optimization was discussed. The sensor exhibited high gas selectivity, repeatability, and linearity for practical applications of the sensor, but the interference of humidity on the sensing process needs to be solved. The results exhibited a simple way to detect parts per million concentrations of H2S at room temperature.

Additional file 1 Table S1. EGFR mutation subtypes.

Additional file 3 Table S3. Drug-related serious adverse events.

Additional file 2 Table S2. Univariate and multivariate Cox proportional hazard analysis for progression-free survival in patients harboring epidermal growth factor receptor mutation and received tyrosine kinase inhibitors.

During the past few decades, photoelectrochemical (PEC) water splitting has attracted significant attention because of the reduced production cost of hydrogen obtained by utilizing solar energy. Significant efforts have been invested by the scientific community to produce stable ternary metal oxide semiconductors, which can enhance the stability and increase the overall production of oxygen. Herein, we present the ternary metal oxide deposition of ZnCo2O4 as a route to obtain a novel photocatalyst layer on BiVO4 to form BiVO4/ZnCo2O4 a novel composite photoanode for PEC water splitting. The structural, topographical, and optical analyses were performed using field emission scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy, and UV–Vis spectroscopy to confirm the structure of the ZnCo2O4 grafted over BiVO4. A remarkable 4.4-fold enhancement of the photocurrent was observed for the BiVO4/ZnCo2O4 composite compared with bare BiVO4 under visible illumination. The optimum loading of ZnCo2O4 over BiVO4 yields unprecedented stable photocurrent density with an apparent cathodic shift of 0.46 V under 1.5 AM simulated light illumination. This is also evidenced by the flat-band potential change through Mott–Schottky analysis, which reveals the formation of p-ZnCo2O4 on n-BiVO4. The improvement in the PEC performance of the composite with respect to bare BiVO4 is ascribed to the formation of thin passivating layer of p-ZnCo2O4 on n-BiVO4 which improves the kinetics of interfacial charge transfer. Based on our study, we have gained an in-depth understanding of the BiVO4/ZnCo2O4 composite as high potential in efficient PEC water splitting devices.

Background: Excessive alveolar epithelial cell(AEC) death by repeated injury play a role in the pathogenesis of lung fibrosis. Recently reports show defective lipid metabolism in AEC contributes to development or progression of lung fibrosis and normal lipid metabolism relies on proper mitochondrial function. Fatty acid synthase(FASN) is key enzyme catalyzes the conversion of acetyl-CoA and malonyl-CoA to saturated fatty acids. Objectives: We investigated whether regulation of FASN expression in AECs modulate severity of lung fibrosis and to find its possible mechanism. Methods: We generated FASN knock-down, overexpression stable cell lines and human FASN transgenic (TG) mice, with conditionally induced alveolar epithelium to overexpress FASN. Cell proliferation and apoptosis assay were performed treated with bleomycin(BLM). Lung fibrosis was established by BLM inhaled FASN TG mice. Measurement and Results: We found that FASN protein was mainly expressed at AECs in controls but significantly reduced in IPF lung. Knockdown of FASN significantly increased but overexpression of FASN attenuate apoptotic cell death. FASN overexpression reduces BLM-induced loss of mitochondrial membrane potential and downregulate mitochondrial ROS production. FASN TG mice dramatically attenuated BLM-induced lung inflammation and fibrosis. Conclusions: These findings suggest that defective FASN production may associated with IPF pathogenesis and augmentation of FASN in the lung may have therapeutic potential in preventing lung fibrosis. This study was supported by National research foundation of Korea grant 2019R1A2C1006351.

Photoelectrochemical water splitting is an environmentally benign way to store solar energy. Properties such as fast charge recombination and poor charge transport rate severely restrict the use of BiVO

Recently, III-nitride semiconductor nanostructures, especially InGaN/GaN quantum well nanorods (NRs), have been established as a promising material of choice for nanoscale optoelectronics and photoelectrochemical (PEC) water-splitting applications. Due to the large number of surface states, III-nitride NRs suffer from low quantum efficiency. Therefore, control of the surface states is necessary to improve device performance in real-time applications. In this work, we investigated the effect of hydrogen plasma treatment on the optical properties of InGaN/GaN single-quantum-well (SQW) NRs. The low-temperature photoluminescence (PL) studies revealed that yellow and green emissions overlapped and the yellow band is more dominant in the pristine InGaN/GaN SQW NRs. However, the emission corresponding to yellow luminescence was strongly suppressed and the green emission is more intensified in hydrogenated InGaN/GaN SQW NRs. Furthermore, the time-resolved PL spectroscopy studies revealed that the carrier lifetimes of hydrogenated InGaN/GaN SQW NRs are relatively short compared to the pristine InGaN/GaN SQW, indicating the effective reduction of non-radiative centers. From the PEC measurement, the photocurrent density of hydrogenated InGaN/GaN SQW NRs in the H2SO4 solution is found to be 5 mA cm-2 at -0.48 V versus reversible hydrogen electrode, which is 3.5-fold larger than that of pristine ones. These findings shed new light on the significance of surface treatment on the optical properties and thus nanostructured photoelectrodes for PEC applications.

This research demonstrated the development of graphene oxide (GO)-gold nanocrystals (AuNCs) composite-modified glassy carbon electrode (GCE) for the sensitive detection of dopamine (DA), uric acid (UA), and 4-aminophenol (4-AP). The GO was synthesized by modified Hummer's method, which was utilized to prepare GO-AuNCs composites by in situ synthesis method using sodium l (-) malate as a reducing agent. Morphological, X-ray diffraction, and spectral analysis revealed the homogeneous formation of AuNCs with high crystallinity and purity on the GO surface and the sizes of the NCs were decreased with increasing the concentrations of sodium l (-) malate. The optimal GCE/GO-AuNCs sensor exhibited excellent electrocatalytic activity towards the oxidation of DA, UA, and 4-AP. The sensor showed interference-free and selective detection of DA and UA with sensitivities of ca. 30.3 and 17.28 μA/cm2/μM, respectively, and detection limits of ca. 28 and 50 nM, respectively, with wider dynamic ranges, measured by differential pulse voltammetry (DPV) technique. Whereas, it displayed a sensitivity and detection limit of ca. 5.70 μA/cm2/mM and 0.017 nM, respectively, for the detection of 4-AP, using current density (J)-voltage (V) measurement method. The sensor also revealed excellent stability, reproducibility, and recoveries of DA, UA, and 4-AP in real samples.

The novel photoelectrochemical cell with very high photocurrent density (>35 mA/cm2) is demonstrated by nanoscale architecturing of TiO2/CdS/CdSe multi-core-shell nanorods. While dimensions of constituting layers, i.e. TiO2 nanorod templates, CdS, and CdSe shell layers, are optimized by thorough investigation of optical and photoelectrochemical responses of each layer, high light absorption through the nanorod geometry and facile transport of the photo-generated electrons and holes along the high conduction path of CdSe and CdS result in the high photoelectrochemical performances. In addition, the microscopic model for the electron and hole transport in the core-shell nanorod is elaborated using the energy band diagram. The demonstration of the high performance PEC electrode as well as the platform to optimize PEC electrodes are highlighted in the current work.

ZnO thin-films with precisely controlled thicknesses were fabricated by the atomic layer deposition and their NO gas sensing properties were investigated at different temperatures, and in particular, under light irradiation of various energy and intensity at room temperature with and without Au catalyst. The molecular dynamics of NO and O2 during the response and recovery cycles in relation with the NO sensing performance in air environment was elaborated using the energy diagram modelled for adsorption and desorption kinetics of the gas molecules. The blue light irradiation combined with Au catalytic effect greatly enhanced the NO response rate, but delayed the recovery rate in the air environment via molecular dynamic interference from the environmental oxygen. The optimum condition for NO sensing was obtained for the film thickness, light energy and intensity. Critical issues for the stable sensor operation such as concentration dependence, gas selectivity, and humidity effect were also reported.

Vertically-standing, few-layer MoS2 flakes were uniformly and conformally grown on closely-packed TiO2 nanowire substrates using metal-organic chemical vapor deposition. The TiO2/MoS2 heterostructures exhibited remarkably improved photoelectrochemical (PEC) performance and long-term stability owing to enhanced photogenerated electron–hole separation and transfer properties across the heterojunction. Due to the built-in heterojunction potential, the onset potential of TiO2/MoS2 heterostructures was cathodic-shifted to −0.3 V, thereby resulting in maximum PEC reactivity at approximately zero potential. In contrast, MoS2 flakes on fluorine-doped tin oxide substrates exhibited an onset potential of approximately 0.3 V. Furthermore, PEC performance was critically affected by the size of the vertically-standing MoS2 flakes, indicating that controlled conformal growth of MoS2 flakes on appropriate nanostructures is essential to exploit these nanostructures as efficient, non-toxic, inexpensive, and earth-abundant PEC electrodes.

Hydrogen sulfide (H2S) is an extremely toxic gas and comes under the classification of chemical asphyxiants. To date, numerous metal oxide-based gas sensors have been developed for the detection and quantification of H2S. However, high sensing temperature, low sensitivity, humidity dependence, and very high response/recovery time severely limit their practical applications. Herein, we prepared hierarchical mesoporous nickel oxide (NiO) nanodisks and boron–nitrogen co-doped reduced graphene oxide (rGO)-NiO (NiOBNG) nanodisk composites for H2S sensing. The as-prepared materials were investigated by several techniques to determine their morphologies, crystal structures, phase purity, and compositions. The sensing response of the NiOBNG sensor to 100 ppm H2S at 150 °C was ∼82, and the detection limit of the sensor was ∼24 ppb. The NiOBNG sensor showed 2- and 3-fold stronger response compared to pristine rGO incorporated NiO and bare NiO nanodisk sensors. The enhanced sensing performance of the NiOBNG sensor is attributed to the presence of several catalytically active sites provided by boron and nitrogen doped rGO in the NiOBNG nanocomposite. The ease of the synthesis procedure, excellent sensitivity, selectivity, rapid response, high stability, and ambient temperature operation make for intriguing, promising practical applications of our NiOBNG sensor, especially in explosive environments and medical diagnosis.

In gas sensors, metal oxide semiconductors have been considered as favorable resistive-type toxic gas sensing materials. However, the higher temperature operation of metal oxides becomes a barrier for their wide range of applications in explosive and flammable gas environments. In this regard, great efforts have been devoted to reducing the operating temperature of the sensor. We demonstrated a chemical resistor-type NO gas sensor based on p-i-n GaN nanorods (NRs) consisting of InGaN/GaN multi-quantum wells (MQW). The sensor exhibited superior NO gas sensing performance to p-type GaN NRs. Furthermore, it also showed a remarkably improved response and fast recovery under UV irradiation (λ = 367 nm) of different UV intensities (7 to 20 mw cm-2) under reverse bias. The sensing performance of MQW-embedded p-i-n GaN NRs was enhanced with the boosted response by 4-fold at 35 °C under UV irradiation. The significant decrease in the resistance of the sensor under UV irradiation was mainly due to the extraction of photo-generated carriers under reverse bias, which can enhance the ionization of oxygen molecules. In addition, the effect of relative humidity (30%-60%) on the gas sensing performance was also manifested in this study. The selectivity of the sensor was determined by using other gases (NO, NO2, O2, NH3, H2S, CO, and H2), which exhibited a low response towards all tested gases other than NO. The experimental results demonstrated that p-i-n GaN NRs with InGaN/GaN MQW is a promising material for the detection of NO gas. Specific emphasis was laid on the enhanced response of p-i-n GaN NRs in reverse bias under UV irradiation.

We report a water-soluble turn-on type diarylethene SO3-BPDBTEO that reversibly switches its fluorescence on and off upon light stimuli. We note that the two sodium sulfonate groups enable SO3-BPDBTEO to exhibit excellent photo-switching properties in aqueous solution over a wide range of pH between 3 and 10. We demonstrated that SO3-BPDBTEO could be applied to conventional fluorescence imaging of mammalian cell lines such as HeLa cell at various pH conditions with low cytotoxicity. We also examine its feasibility for super-resolution fluorescence imaging as a photoswitching probe.

We present a backward semi-Lagrangian method with third-order temporal accuracy for solving the guiding center problem. For solving highly nonlinear characteristic curves, we propose an iteration-free L ( α ) -stable method equipped with an error correction technique and a classical collocation method. As a discretization of the Poisson equation, we adopt the fourth-order centered differential scheme and the Shortley–Weller discretization depending on the boundary of the domain, and apply the local cubic interpolation polynomial for the evaluation of the density and the potential at the non-grid foot points of the characteristics. The novelty of the proposed method is its good stability as well as its outstanding computational cost compared to those of the recently developed high-order Adams–Moulton method. Furthermore, based on several numerical tests, we conclude that the proposed method exhibits excellent performance for long-time stable simulations and allows for large temporal step sizes.