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Two-dimensional (2D) semiconductors play a crucial role in high-efficiency photocatalysts because of their high surface-to-volume ratio. The surface property is a key part of photocatalysis. In this work, the enhanced photocatalytic behavior of the layered ReS2 with optical polarization along the Re4 nano-diamond-chain (DC) direction (b axis) has been demonstrated. The unpolarized photoconductivity (PC) response of ReS2 with an applied bias along the b axis is approximately 1 order higher than that of the applied bias perpendicular to the b axis. The polarization-dependent PC spectra of E ∥ b also reveal a higher photoresponsivity with respect to those measured along the E ⊥ b polarization for the layered ReS2. This result indicates that stronger polarization dipoles as well as a larger amount of photogenerated carriers and surface states can contribute to the C-plane ReS2 under the illumination of E ∥ b polarized photons. With the special axial effect, the layered ReS2 2D photocatalyst shows much faster ...

A wide gap semiconductor material has attracted attention as a heterophotocatalyst because of its light harvesting nature to be used in alternative energy production for the next generation. We, herein, grow and synthesize ZnS(1–x)Ox series compounds using the chemical vapor transport (CVT) method with I2 serving as the transport agent. Different crystals, such as undoped ZnS and oxygen-doped ZnS0.94O0.06 and ZnS0.88O0.12, revealed different bright palette emissions that were presented in photoluminescence spectra in our previous report. To study the electron–hole pair interaction of this sample series, the near-band-edge transitions of the sample series were characterized in detail by photoconductivity (PC) experiments. Additional results from surface photovoltage (SPV) spectra also detected the surface and defect-edge transitions from the higher oxygen-doped ZnS crystals. PC measurement results showed a red-shift in the bandgap with increasing incorporation of oxygen on ZnS. Consequently, the samples were subjected to photoirradiation by xenon lamp for the degradation of methylene blue (MNB) by acting as heterophotocatalysts. Undoped ZnS emerged as the best photocatalyst candidate with the fastest rate constant value of 0.0277 min–1. In cubic {111} ZnS [{111} c-ZnS], the polarized Zn+ → S– ions may play a vital role as a photocatalyst because of their strong electron–hole polarization, which leads to the mechanism for degradation of the MNB solution.

Flexible optoelectronics devices play an important role for technological applications of 2D materials because of their bendable, flexible and extended two-dimensional surfaces. In this work, light emission properties of layered gallium selenide (GaSe) crystals with different curvatures have been investigated using bending photoluminescence (BPL) experiments in the curvature range between R−1 = 0.00 m−1 (flat condition) and R−1 = 30.28 m−1. A bendable and rotated sample holder was designed to control the curvature (strain) of the layered sample under upward bending uniformly. The curvature-dependent BPL results clearly show that both bandgaps and BPL intensities of the GaSe are curvature dependent with respect to the bending-radius change. The main emission peak (bandgap) is 2.005 eV for flat GaSe, and is 1.986 eV for the bending GaSe with a curvature of 30.28 m−1 (the maximum bending conditions in this experiment). An obvious redshift (i.e. energy reduction) for the GaSe BPL peak was detected owing to the c-plane lattice expansion by upward bending. The intensities of the corresponding BPL peaks also show an increase with increasing curvature. The correlations between BPL peak intensity, shiny area and bond-angle widening of the bent GaSe under laser excitation have been discussed. The lattice constant versus emission energies of the bending GaSe was also analyzed. An estimated lattice constant vs. bandgap relation was present for further application of the layered GaSe in bendable flexible light-emission devices.

Single crystals of oxygen-incorporated ZnS (i.e., ZnS(1–x)Ox series) are environment-friendly wide-band-gap semiconductors available for light-emitting devices and solar cell use. The series of materials has considerable potential for use in visible ultraviolet areas with flexibility for palette emissions. In this study, we grow oxygen-incorporated ZnS series crystals by chemical vapor transport method with iodine (I2) as the transport agent. Three different oxygen-incorporated crystals of undoped ZnS, ZnS0.94O0.06, and ZnS0.88O0.12 are studied. Through structural studies, ZnS doped with oxygen crystallizes in the main sphalerite phase and a little wurtzite structure. The lattice constants of the major cubic phase are determined to be a = 5.43 A (ZnS), 5.41 A (ZnS0.94O0.06), and 5.39 A (ZnS0.88O0.12). Three band-edge excitonic transitions are simultaneously detected by thermoreflectance measurement for the ZnS, ZnS0.94O0.06, and ZnS0.88O0.12 series samples. The energy positions of the band-edge transition...

We applied a thermal-desorption gas-chromatograph mass-spectrometer (TD-GC&ndash, MS) system to identify the marker volatile organic compounds (VOCs) in the aroma of red wine. After obtaining the marker VOC, we utilized surface acoustic waves (SAWs) to develop a highly sensitive sensing system as 'electronic nose' to detect these marker VOC. The SAW chips were fabricated on a LiNbO3 substrate with a lithographic process. We coated sensing polymers on the sensing area to adsorb the marker VOC in a sample gas. The adsorption of the marker VOC altered the velocity of the SAW according to a mass-loading effect, causing a frequency decrease. This experiment was conducted with wines of three grape varieties&mdash, cabernet sauvignon, merlot and black queen. According to the results of TD-GC&ndash, MS, the King brand of red wine is likely to have unique VOC, which are 2-pentanone, dimethyl disulfide, 2-methylpropyl acetate and 2-pentanol, Blue Nun-1 probably has a special VOC such as 2,3-butanedione. We hence used a SAW sensor array to detect the aroma of red wines and to distinguish their components by their frequency shift. The results show that the use of polyvinyl butyral (PVB) as a detecting material can distinguish Blue Nun-2 from the others and the use of polyvinyl alcohol (PVA) can distinguish King from the others. We conducted random tests to prove the accuracy and the reliability of our SAW sensors.

We report on optical examination of structural properties of cubic-In2O3 (c-In2O3) degenerate-semiconducting-oxide thin-film nanostructures grown on Si (100) substrates using vapor transport method driven with vapor–liquid–solid mechanism. Two different types of dense (A) and loose (B) c-In2O3 thin-film nanorods have been, respectively, characterized by photoluminescence (PL), time-resolved photoluminescence (TRPL), thermoreflectance (TR), and Hall and resistivity measurements. Strong excitonic emissions detected from the PL results of the A and B samples identify the high-crystalline quality of the arrow-type c-In2O3 nanorods. Theoretical modeling fits on the TRPL results of the A and B samples characterize and identify defect mechanisms of the nanostructured thin films. Near-band-edge and above-band-edge transitions such as excitons, direct band gap, and Burstein–Moss shift (above direct gap) in the degenerate A and B c-In2O3 have also been detected by TR measurement. Field-emission scanning electron mi...

Crystal growth, characterization, and sensing application of In 2 S 3 and Ga 2 S 3 are demonstrated herein. Single crystals of In 2 S 3 and Ga 2 S 3 were grown by chemical vapor transport method using ICl 3 as the transport agent. The as-grown In 2 S 3 crystals essentially show dark red and Ga 2 S 3 displays transparent and light-yellow colored. X-ray diffraction measurements show tetragonal phase of the as-grown In 2 S 3 crystals while Ga 2 S 3 crystallizes in the monoclinic structure. The optical band edges of In 2 S 3 and Ga 2 S 3 were characterized by absorption and thermoreflectance measurements. The optical band gaps of In 2 S 3 and Ga 2 S 3 are 1.935 eV and 3.052 eV, respectively. The direct gaps of In 2 S 3 and Ga 2 S 3 lie in between red to violet visible region. Photoluminescence (PL) experiments characterize defect and surface-state emissions of the In 2 S 3 and Ga 2 S 3 crystals. The In 2 S 3 can easily form surface oxide in environmental air with an In 2 O 3 growth rate of ∼100 nm/day (i.e. for oxygen sensing). The PL intensity of the In 2 O 3 formed on In 2 S 3 may be a sensing index for oxygen content detection. Besides, Ga 2 S 3 may emit a broadened visible white light (near band edge) due to the existence of intrinsic defects inside the crystal. The Ga 2 S 3 crystal also displays a high-sensitivity photoconductivity change illuminated by a 405 nm laser. According to the experimental results, In 2 S 3 can be an oxygen sensor with the formation of surface oxide (i.e. In 2 O 3 ), while Ga 2 S 3 may possess potential capability in fabrication of blue to UV photodetector.

In this research, thermal desorption tendon with gas chromatography-mass spectrum (TD-GC-MS) system has been used to find the marker of VOCs in variety grape of red wines After finding out the proper markers, we utilize the principle of surface acoustic wave (SAW) to develop a highly sensitive electronic nose sensing array system for the detection of red wines. This reported experiments with three varieties of grape including cabernet sauvignon, merlot, and blackqueen which were widely grown in Taiwan. Experiment results demonstrate that the blackqueen grape variety possibly has unique VOCs, which are Acetic acid, methyl ester, 2-Pentanone, Disulfide, dimethyl, Acetic acid, 2-methylpropyl ester. However, using SAW array gas sensor cannot discriminate these red wines because the polymer has poor selectivity to the marker VOCs.

ZnO nanorods (NRs) incorporating a graphene layer were fabricated on silicon substrates. The graphene layer was placed on top and bottom of ZnO to form graphene/ZnO NRs/Si and ZnO NRs/graphene/Si nanocomposites. To characterize these nanocomposites, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were used, as well as contact angle measurements to study hydrophilic properties. Finally, OD600 bacterial growth tests were performed to investigate the bacterial suppression capabilities. Results indicate that the ZnO NRs/graphene/Si nanocomposite exhibits the strongest bacterial suppression capability among the studied nanostructures.

ZnS is an environmentally friendly wide-band-gap semiconductor possessing a direct gap larger than ZnO, which makes it more promising for application in ultraviolet (UV) optoelectronics and solar-energy conversion applications. However, highly crystalline ZnS is usually obtained by elegant epitaxial growth, such as with pulsed laser vaporization, molecular beam epitaxy, and metal–organic chemical vapour deposition, in a thin-film form. A high-quality ZnS substrate crystal has been rarely achieved to date. Herein, we demonstrate a high-grade cubic ZnS (c-ZnS) substrate crystal with a longer range order grown by a chemical vapour transport (CVT) method. Photoluminescence (PL), transmittance, contactless electroreflectance (CER), and transmission electron microscopy were performed for qualification of the c-ZnS substrate. The transparency of the c-ZnS substrate crystal (∼0.6 mm thick) was about 81% at λ = 400 nm and 92% at λ = 600 nm. Strong and complete series excitonic emissions were detected from the ZnS substrate crystal by PL, indicating the high crystallinity of the CVT-grown ZnS. Band-edge free-exciton emission of the ZnS substrate showed an intense emission around 3.68 eV at 300 K. The temperature dependences of the band-edge excitonic emissions from 10 to 300 K were analyzed and are herein discussed in terms of sustaining the high crystalline quality of the c-ZnS substrate. An initially-formed Cu/ZnS Schottky solar cell was also tested using the c-ZnS substrate. Under the illumination of a 325 nm laser (i.e. a power density of P ∼ 48 mW cm−2), a significant photovoltage of ∼0.6 V could be generated from the original Cu/ZnS Schottky solar cell.

High-k NdTaO4 dielectrics annealed with various temperatures were first deposited on polycrystalline silicon substrates. Material and electrical characterizations were performed. To examine the crystalline structures, X-ray diffraction patterns were analyzed. Electrical measurements including current–voltage characteristics, constant current stress, and the Weibull plots show that annealing could enhance the breakdown voltages, lower the trapping rate, and strengthen the reliability. Results indicate that annealing at 900 °C may optimize the dielectric performance. This dielectric shows promise for future gate material or flash memory integrated with current NdTaO4-based optical devices.

In this study, CeO2 was used as a trapping layer in metal oxide high-K-oxide-Si (MOHOS)-type memory devices. This trapping layer underwent annealing to enhance memory performance. Multiple material analyses indicate that annealing enables enhanced crystallization and suppresses silicate formation. MOHOS-type flash memory devices incorporating a CeO2 charge trapping layer annealed at 950 °C exhibited a large memory window of 4.7 V, as well as a fast program and erase speed. Our research indicates that MOHOS-type memory devices utilizing CeO2 show great promise for future industrial flash memory applications.

ZnO nanorods were deposited on silicon substrate using sol-gel hydrothermal methods. The seed layer was first grown by sol-gel methods and then annealed at temperatures of 300ºC, 400ºC, 500ºC and 600ºC. Multiple material and optical analyses including field-emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, photoluminescence spectra, and Raman spectra were conducted to examine the growth orientation and material properties. Results indicate that the ZnO nanorods annealed at a proper temperature of 400ºC could enhance orientation and material quality.

Layered-type α- and γ-In 2 Se 3 crystals were simultaneously grown by chemical vapor transport (CVT) method using ICl 3 as the transport agent. The crystalline state, surface state, and structural polytype of the as-grown In 2 Se 3 were observed by high-resolution transmission electron microscopy (HRTEM). The direct band edges of α- and γ-In 2 Se 3 were evaluated by thermoreflectance (TR) measurements. For α-In 2 Se 3 , a surface oxidation layer α-In 2 Se 3−3 x O 3 x (0 ≤ x ≤ 1) can easily form on the crystal face in environmental air by oxygen detection (∼250 nm/day). The surface formation oxide can be easily removed by laser treatment ( λ = 266 nm, P = 60 mW) and the oxygen detection can be repeated again. For γ-In 2 Se 3 , the HRTEM and Raman measurements reveal amorphous and polycrystalline state existing in the as-grown crystals. The amorphous effect renders erasable optical-memory switching of γ ↔ α inter-phase transition occurred inside the γ-In 2 Se 3 layer with laser heating treatment. The phase transition of In 2 Se 3 is fast and easily by using the laser treatment. The phase transformation of γ ↔ α was verified by Raman and TR measurements. The optical-memory switching and oxygen detection behavior for the as-grown γ- and α-phase In 2 Se 3 are demonstrated herein.

In this study, we address process how the ZnO nanorods were deposited on GaN substrates with spin-coating by using the hydro-thermal methods. After ZnO was spin coated, the samples were annealed with different temperatures to incorporate with Au nano particles. Multiple material analyses, such as the field emission scanning electron microscopy (FESEM), the energy dispersive X-ray spectroscopy (EDX) and the X-ray diffraction (XRD) analyses were carried out to characterize the Au nanoparticles/ZnO nanorods/GaN nanocomposites.

Multilayer InSe with a thickness above ~20 nm is a direct semiconductor proposed for solar-energy conversion and to use in flexible optoelectronics. We demonstrate herein a superior 1000-nm light emission and absorption capability of two-dimensional (2D) multilayer InSe studied by photoluminescence (PL) and photoconductivity (PC) experiments. Layered crystals of InSe have been grown by chemical vapor transport method using ICl3 as a transport agent. Polarized Raman measurement confirmed 2 H e crystalline phase of the as-grown crystals. For 2D flexible applications, the bending photoluminescence (BPL) result of InSe (t ≈ 30 nm) showed an enhancement in light intensity with respect to that of the flat PL condition. It might be because the cylinder surface area under bending (convex) is larger than that of the flat surface under the same laser excitation condition. Besides, the luminescence efficiency of BPL is also enhanced owing to the widening of emission solid angle of each Se-In-In-Se unit in the InSe as compared to that of the flat PL condition. The emission wavelength is about 1000 nm at room temperature. Furthermore, for the PC study, photoresponsivity spectrum of a Ag-InSe-Ag multilayer photoconductor demonstrates a prominent peak absorption at 1.1 ~ 1.3 eV, matching well with the direct-free-exciton energy of the multilayer InSe. All the experimental results demonstrate that 2D multilayer InSe is a promising 1000 nm light emitter and absorber available for potential optoelectronics applications.

In order to investigate the filterability of artificial fiber, salts were added to the fiber for particulate removal. In addition, nanofibers were prepared for particle filtration efficiency assessment, and Nylon 6 nanofibers were prepared by electrospinning. Scanning electron microscopy (SEM) was used for analyzing the fiber characteristics. Furthermore, the single-factor experimental method was used to study the optimal material preparation method and operating parameters, including content of different salts (NaCl and KCl), with Nylon 6 nanofibers for particle removal. The particle removal efficiency of pure Nylon 6 nanofibers was about 95%. The removal efficiencies of Nylon 6 nanofibers containing NaCl and KCl were 99% and 98%, respectively. It was found that the removal efficiency of nanofibers was decreased with increasing content of salts in Nylon 6 nanofibers.

Resolving failure origins of AlGaN/GaN light emitting diodes (LED) has received intensive study recently. In this study, formation of GaCO3 caused by carbon contamination may result in deformation of the electrode near the surface and degrade the device. The electrochemical reactions may cause device damages. Degradation in electrical properties is observed in I-V characteristics. Forward-bias and reverse-bias EL images are used to trace the damaged areas. Furthermore, focus ion beam (FIB), scanning electron microscope (SEM), energy dispersive X-ray diffraction (EDX) are applied to examine the damaged areas. Results indicate that formation of GaCO3 may deform the electrode, generate the reverse-bias EL and cause the degradation.

Unlike canonical pre-mRNAs, animal replication-dependent histone pre-mRNAs lack introns and are processed at the 3'-end by a mechanism distinct from cleavage and polyadenylation. They have a 3' stem loop and histone downstream element (HDE) that are recognized by stem-loop binding protein (SLBP) and U7 snRNP, respectively. The N-terminal domain (NTD) of Lsm11, a component of U7 snRNP, interacts with FLASH NTD and these two proteins recruit the histone cleavage complex containing the CPSF-73 endonuclease for the cleavage reaction. Here, we determined crystal structures of FLASH NTD and found that it forms a coiled-coil dimer. Using solution light scattering, we characterized the stoichiometry of the FLASH NTD-Lsm11 NTD complex and found that it is a 2:1 heterotrimer, which is supported by observations from analytical ultracentrifugation and crosslinking.

Multilayer InSe with a thickness above 20 nm is a direct semiconductor for flexible-optoelectronics use. We show a superior 1000-nm light emission and absorption capability of 2D multilayer InSe studied by photoluminescence and photoconductivity herein.

ReS2 and ReSe2 have recently been enthusiastically studied owing to the specific in-plane electrical, optical and structural anisotropy caused by their distorted one-layer trigonal (1 T) phase, whereas other traditional transition-metal dichalcogenides (TMDCs, e.g. MoS2 and WSe2) have a hexagonal structure. Because of this special property, more and versatile nano-electronics and nano-optoelectronics devices can be developed. In this work, 2D materials in the series ReS2−x Se x (0 ≤ x ≤ 2) have been successfully grown by the method of chemical vapor transport. The direct and indirect resonant emissions of the complete series of layers can be simultaneously detected by polarized micro-photoluminescence (μPL) spectroscopy when the thickness of the ReS2−x Se x is greater than ~70 nm. When it is less than 70 nm, only three direct excitonic emissions—E 1 ex, E 2 ex and E S ex—are detected. For the thick (bulk) ReS2−x Se x , more stacking of the ReX2 monolayers even flattens and shifts the valence-band maximum from Γ to the other K- or M-related points, thus leading to the coexistence of direct and indirect resonant light emissions from the c-plane ReX2. The transmittance absorption edge of each bulk ReX2 (a few microns thick) usually has a lower energy than those of the direct E 1 ex and E 2 ex excitonic emissions to form indirect absorption. The coexistence of direct and indirect emissions in ReX2 is a unique characteristic of a 2D layered semiconductor possessing triclinic low symmetry.

Multianalyte CeO2 biosensors have been demonstrated to detect pH, glucose, and urine concentrations. To enhance the multianalyte sensing capability of these biosensors, CF4 plasma treatment was applied to create nanograin structures on the CeO2 membrane surface and thereby increase the contact surface area. Multiple material analyses indicated that crystallization or grainization caused by the incorporation of flourine atoms during plasma treatment might be related to the formation of the nanograins. Because of the changes in surface morphology and crystalline structures, the multianalyte sensing performance was considerably enhanced. Multianalyte CeO2 nanograin electrolyte–insulator–semiconductor biosensors exhibit potential for use in future biomedical sensing device applications. Keywords: Multianalyte biosensor, CeO2 nanograin, EIS, CF4 plasma treatment, Membrane surface