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HfS2/SMoSe, HfS2/SeMoS, ZrS2/SMoSe, and ZrS2/SeMoS heterostructures are promising overall water-splitting photocatalysts.

Direct Z-scheme water-splitting is a promising route to enhancing the photocatalytic performance due to the effective separation of photogenerated carriers while simultaneously preserving the strong oxidation activity of holes and reduction activity of electrons. In this work, the MoSSe/XY

Purpose The pressure sensors can convert external pressure or mechanical deformation into electrical power and signal, which cannot only detect pressure or strain changes but also harvest energy as a self-powered sensor. This study aims to develop a self-powered flexible pressure sensor based on regular nanopatterned polymer films. Design/methodology/approach In this paper, the self-powered flexible pressure sensor is mainly composed of two nanopatterned polymer films and one conductive electrode layer between them, which is a sandwich structure. The regular nanostructures increase the film roughness and contact area to enhance the friction effect. To enhance the performance of the pressure sensor, different nanostructures on soft polymer sensitive layers are fabricated using UV nanoimprint lithography to generate more triboelectric charges. Findings Finally, the self-powered flexible pressure sensor is prepared, which consists of sub-200 nm resolution regular nanostructures on the surface of the elastic layer and an indium tin oxide electrode thin film. By converting the friction mechanical energy into electrical power, a maximum power of 423.8 mW/m2 and the sensitivity of 0.8 V/kPa at a frequency of 5 Hz are obtained, which proves the excellent sensing performance of the sensor. Originality/value The acquired electrical power and pressure signal by the sensor would be processed in the signal process circuit, which is capable of immediately and sustainably driving the highly integrated self-powered sensor system. Results of the experiments show that this new pressure sensor is a potential method for personal pressure monitoring, featured as being wearable, cost-effective, non-invasive and user-friendly.

In this paper, we propose a novel kind of UV click-polymerization thiol-ene copolymers as nanoimprint lithography resists for sub-70 nm resolution patterns. High-precision mold imprint and release are two of the most critical steps of nanoimprint lithography, which requires the resists with properties of excellent conformal replication and low surface energy. Conventional UV-curable resists used in nanoimprint lithography, such as acrylate, epoxy resin, and vinyl ether, cannot satisfy all these properties requirements because they exhibit surface oxygen inhibition during polymerization, or materials fracture and delamination during mold releasing. A novel kind of thiol-ene copolymers have been investigated in this study, which have many properties favorable for use as nanoimprint lithography resists to imprint sub-70 nm and high-aspect-ratio nanostructures. These properties include sufficiently low viscosity and high Young's modulus, low surface energy for easy demolding, polymerization in benign ambient, and in particular, high chemical-etch resistance. These excellent properties give improve nanoimprinting results.

High resolution and high precision polymer nanostructures has unique chemical and physical properties, playing an important role in nano-optics, nano-photonics, and high sensitivity biological detection. This paper demonstrated a novel fabrication method of biological detection chip based on polymer nanostructures via nanoimprint lithography. High precision nanostructures such as nanopillar arrays were prepared on chip film via nanoimprint lithography. The polymer nanostructures were used to enhance adhesion to cancer cells, which is low-cost and suitable for mass production. The replication polymer was biocompatibility materials that has no effect on cells. The experiment results show that the nanopillar arrays chip can adhere lung cancer cells in the size of 10-15 μm to achieve the purpose of filtering and detecting cells. Results of the experiments show that this new biological detection chip has potential applications of cancer detection, targeted therapy, food safety testing, and environmental monitoring.

This research involves a novel axial strain measurement of helical long-period grating by dual-wavelength ratio. The single-mode fiber is spirally processed via the commercial welding machine. There are two obvious resonance dips near 1473 and 1517 nm, with the pitch length around 782 μ m. The experimental results show that both the transmission of dip1 and dip2 rise along with increasing axial strain. The relationships between axial strain versus transmission of resonance dip and axial strain versus transmission of a fixed wavelength are studied separately. They are all linear change with axial strain. This indicates that the axial strain can be measured by the linear relationship between the transmission and axial strain. Furthermore, to eliminate the influence of light source, the dual-wavelength ratio is studied. The experimental results show that the ratio also changes linearly with axial strain. The fixed wavelength can be selected by a filter or a fiber Bragg grating, and the transmission intensity can be measured by a light intensity detector. This exploits a new way to devise high precision, low cost, and gains great potential application in the axial strain sensor.

Using density-functional calculations, we studied the interactions between interstitial impurities (H, O, N, S, and P) and Ni (111) surfaces doped, or not, with Cr, and studied the effect of Cr doping on the dissolution corrosion resistance of Ni(111) surfaces. The aim of this work was to study, at the atomic scale, the effects of Cr on the segregation behaviors of impurities and the synergetic effects between co-doped atoms on the resistance to dissolution corrosion of Ni (111) surfaces. The results indicate that impurities S, P, O, and H prefer to be trapped at near-surface sites, that Cr was uniformly distributed in the Ni crystal and can affect the segregation behavior of impurities S and P to move toward the surface, and it affects impurities N and O such that they shift from the surface to the subsurface. The formation of near-surface Cr nitrides (speculated to be Cr2N based on the results obtained for particular co-doped surfaces) was also noted. Introducing Cr enhances the structural stability of the Ni (111) surface and protects it from being corroded when impurities are present. The elementary processes studied afforded microscopic insights into the formation of a Cr-depleted zone, a phenomenon that leads to local corrosion of the Ni alloy surface. The results of our theoretical calculations explain some of the experimental results previously observed at the atomic scale.

This paper proposed a flexible pressure sensor based on poly(dimethylsiloxane) nanostructures film and report an efficient, simple, and low-cost fabrication strategy via soft nanoimprint lithography. The pressure sensor can convert external pressure or mechanical deformation into electrical signal to detect pressure and strain changes based on the coupling of triboelectrification and electrostatic induction. To enhance the performance of the pressure sensor, it consists of sub-500 nm resolution on the surface of elastic poly(dimethylsiloxane) sensitive layer and an indium tin oxide electrode thin film. When the pressure applied on the nanostructures layer, triboelectrostatic charges are induced. In the experiment, it measures up to sensitivity of 0.8 V/kPa at frequency of 5 Hz. This study results in potential applications such as wearable smart devices and skin-attachable diagnostics sensing systems.

The metallic tortuous hollow ring array in the metallic film is proposed to enhance the modulation efficiency of the graphene based terahertz (THz) amplitude modulation. In the tortuous ring configuration, multimode resonant is excited to enhance the interaction between the THz wave and the graphene. With the change of the chemical potential of the graphene layer, the resonant frequencies are shift and the transmission peaks are tuned. It is enhanced more than 9 times for the amplitude modulation depth of the THz transmission and a maximum modulation efficiency of 74 dB/eV is obtained in the tortuous ring array based modulator. The enhancement of the modulation efficiency will decrease of the applied modulation voltage and will help to the energy saving and device lifetime prolonging.

Because of the influence of hydrogen and the stress corrosion cracking, the damage of metal is quite frequent. It leads to dangerous failures, the loss of property as well as large compensational payments for insurance companies. However, the issue of the precise role of hydrogen in the process is unclear and the mechanism is not available. Based on the binding energy analysis, it was found that H prefers octahedral-like positions for γ-Fe, and could enhance the stability of structure with dissolving into γ-Fe. The higher the concentration of H, the much more remarkable the observation is. Therefore, H is easily soluble in γ-Fe. Under the applied tensile stress, γ-Fe and H doped γ-Fe undergo the stages of elastic and plastic deformations. Meanwhile, H induces γ-Fe phase transition.This process starts from the atomic layer adjacent to H, then gradually extends far. As a consequence, the intergranular embrittlement and cracking happened.

The tribological performances and rolling lubrication properties of SiO2/graphene combinations as water-based lubricant additives were evaluated using a reciprocating ball-on-plate tribometer and two-high rolling mill. The results obtained therein revealed that dispersion of the SiO2/graphene combinations in water is conducive to the reduction of the friction coefficient and wear volume and the increase in the load-bearing capacity, which were superior to the results obtained for the graphene nanofluids or SiO2 nanofluids separately. In the best case, the addition of 0.1 wt% nano-SiO2 mixed with 0.4 wt% graphene in water reduced the friction coefficient by 48.5% and the wear volume by 79% compared with the addition of 0.5 wt% graphene. Transmission electron microscopy images of the SiO2/graphene combinations additives after friction testing showed that nano-SiO2 supports the graphene layers as pillars and prevent assembly between the graphene layers. The synergistic effect of the components considerably enhanced the SiO2/graphene combination. Additionally, the preliminary application of the SiO2/graphene combination nanofluids in magnesium alloy rolling effectively decreased the rolling force and improved the surface quality of sheets.

We have calculated and discussed the electronic and optical properties of two-dimensional (2D) CdS/g-C6N6 heterostructures by using hybrid density functional of HSE06. The CdS and g-C6N6 can form CdS/g-C6N6 heterostructures through weak van der Waals (vdW) interactions. The CdS/g-C6N6 composites are indirect bandgap semiconductors and type-II heterostructures. The visible light absorbtion of CdS/g-C6N6 composites is obviously improved, and the band alignment is beneficial for spontaneous water redox reactions. Furthermore, the electrons migrating from CdS layer to g-C6N6 leads to the built-in electric field formation, which promotes the effective separation of photogenerated carriers. These factors imply CdS/g-C6N6 composites are promising visible light water-splitting photocatalysts.

Twist measurement based on the transmission of fixed wavelength of a helical long-period fiber grating is studied. The single-mode fiber is spiraled by a welding machine. There are two resonance dips near 1473 nm and 1517 nm, with the pitch length around 782 μm. The experimental results show that the transmission near 1473 nm decreases along with contra-direction twist and increases along with co-direction twist. In contrast, the transmission near 1517 nm decreases along with co-direction twist and increases along with contra-direction twist. The relationships between the twist and the resonance wavelength, the twist and the transmission of resonance dips, the twist and the transmission of fixed wavelengths are studied, respectively. They all show linear relationship with the twist, and the slopes are about 100 nm·mm/rad, 36 dB·mm/rad, and 46 dB·mm/rad, respectively. The dual-wavelength ratio is studied, and the ratio also shows linear relationship with the twist. The twist sensitivity of I1463.3 nm/I1526.5 nm is about 0.79 each 0.01 rad/mm. This has great potential application in twist sensors.

We report a temperature measurement method based on fixed wavelength transmission intensity of long-period fiber grating. Relative to wavelength or edge filtering, this method has obvious advantages in measurement accuracy and cost. The relationship between the transmission intensity and temperature at a fixed wavelength is simulated based on the theory of long-period fiber grating coupling mode. The results show that the transmission intensity of the fixed wavelength is linearly related to the temperature with the appropriate parameters. In the experiment, the transmission spectrum shows two resonant peaks at 1485 and 1538 nm. Two fixed wavelengths at 1480.4 and 1549.7 nm were selected, and the results show a linear relationship between transmission intensity and temperature. The temperature sensitivity of the transmission intensity at 1480.4 nm is about 0.0544 dB / ° C, which means the value of I1480.4 nm / I0 changes by 1.3% for every 1°C. To eliminate the influence of light source and enhance the measurement sensitivity, the ratio of the transmission intensity of two fixed wavelengths was selected to carry out the temperature measurement. The temperature sensitivity of the ratio of I1480.4 nm / I1549.7 nm was 0.0729 dB / ° C, that is, the light intensity ratio changed by 1.7% when the temperature changed by 1°C. A more reasonable design of long-period fiber grating and a more appropriate selection of fixed wavelength should be able to obtain higher temperature sensitivity.

A presentation based on the helical long-period grating (H-LPFG) affected by the change of temperature and twist has been demonstrated. There are two resonant peaks near 1451 nm (resonant peak 1) and 1519 nm (resonant peak 2) when the pitch length is about 757 μm. The resonant peak 1 is caused by second-order diffraction coupling between the fundamental mode and the LP110 cladding mode, and the resonant peak 2 is caused by first-order diffraction coupling between the fundamental mode and the LP15 cladding mode. Their temperature sensitivities are 72 pm/℃ and 45 pm/℃, respectively. The resonant peak 1 twist sensitivities are − 138 nm·mm/rad with co-direction twist and 133 nm·mm/rad with contrary-direction twist, but the resonant peak 2 is insensitive to twist. This indicates that at the resonant peak 2, the H-LPFG can measure temperature without cross-impact by twist. Therefore, this can be applied to measure temperature and twist at the same time.

The single-mode fiber provided by YOFC inc is employed for spiral processing by commercial welding machine. It can clearly see the periods structure under the light, but there is no obvious deformation of the fiber core, cladding and surface morphology under a microscope. There is an obvious resonant peak near 1560 nm, half peak width is about 25 nm, the depth of the resonant peak closed to –26 dB, when the period is about 411 μm. It agrees with theoretical calculation results according to the long-period fiber grating coupled-mode theory. The resonance wavelength is caused by coupling between the fundamental mode and the LP14 mode. The responsivities of the helically twisted long-period fiber gratings (H-LPFG) for the temperature is measured, the resonance wavelength is linear with temperature, the slope is 86 pm/℃. Because it is easy to inscribe by commercial welding machine, and has a strong resonance peak, it has potential applications as the temperature sensor.

In the present work, a systematic analysis of the microscopic plastic deformation mechanism and mechanical properties of interstitial impurities (H, O, N, S, and P) and Ni doped, or not doped, with Cr, was conducted based on generalized stacking fault energy curves generated via first-principles calculations. Focus has been put on the effects of Cr on plastic deformation for Ni doped interstitial impurities, upon the GPFE curve, with the aim to investigate the effects of Cr on the deformation mode and mechanical properties for doped Ni systems. It is found that a solid solution of Cr caused the tendency of partial dislocation in Ni. The evaluation of the Rice criterion reveals that Cr tends to decrease the ductility in Ni, and it cannot reverse interstitial H promoting the probability of cleavage fracture in Ni, while increases the ductility of O, P and S doped Ni, particular in O doped Ni, due to increasing the value of ductility D remarkably, so possibly changes the tendency of cleavage fracture. Besides, the solid solution of Cr is beneficial in promoting the dissociation of dislocation into fragments more easily in Ni, and enhances dislocation nucleation, while O, N, and S impurities have a slower rate of partial dislocation emission in Ni when interacting with Cr. Furthermore, Cr promotes the probability of twinning in Ni, and probably switches the deformation mechanism of H doped Ni from dislocation mediated slipping to twinning. Our study provides important insights toward the understanding and control of dislocation dynamics in doped Ni.

Using hybrid density functionals, we study the interfacial interactions and electronic properties of ZnO/AlN composites with the consideration of rotation angles and biaxial strains in order to enhance the photocatalytic performance for water-splitting. The different rotated composites, and -2% strained, original, and 2% strained ZnO/AlN composites can be easily prepared owing to the negative interface formation energies. The bandgaps and band alignments of ZnO/AlN composites can be significantly tuned by biaxial strains. Particularly, the appropriate bandgap for visible light absorption, proper band alignment for spontaneous water-splitting, and the formed electric field promoting photoinduced carrier separation make the 2% strained ZnO/AlN composite a potential candidate for photocatalytic water-splitting. This work shines some light on designing two dimensional heterostructured photocatalysts.

The thermoelectric transport properties of a parallel-coupled double quantum dot (PCDQD) system with side-coupled quantum dots (QDs) is investigated by using the Keldysh non-equilibrium Green's function technique. The thermoelectric quantities, including the thermal conductance, thermopower, and thermoelectric figure of merit denoted by ZT, are sensitive to the inter-dot coupling strength. With the help of side-coupled QD, unusual double Fano resonances are created in the conductance spectra to largely enhance the thermoelectric effect at low-temperature. Benefited from the coexistence of local bipolar effect and Fano resonance, the ZT can be improved by one-fold higher than that of original PCDQD system. Moreover, when the asymmetry parameter α, which indicates the geometric arrangement of coupled QDs with a given lead, takes appropriate value, the optimization of ZT can be achieved at high temperature. Our work suggests that the side-coupled QDs scheme holds promise for the designing of high-efficiency thermoelectric conversion devices.

The influence of interface structure on the photoelectric properties of InGaN light-emitting diodes grown on (0001) polar, (11–22) semi-polar, and (11–20) nonpolar planes is studied. Nonpolar and semi-polar interface structures are characterized by reduced polarization-related electric fields and suppressed QCSE. The energy bands of the structures grown on these orientations are undistorted, and QWs have more rectangular shapes. Consequently, these structures do not undergo separation of the electron and hole wavefunctions typical of c-plane structures. The simulation results suggest that potoelectric properties and efficiency drop is markedly improved when the polar interface structure is replaced by nonpolar or semi-polar interface structures.

The electrical and optical properties of InGaN LEDs with different threading dislocation densities (TDDs) were investigated. LEDs with low TDDs exhibited low forward voltage and high injection efficiency compared with LEDs with high TDDs. The effect of TDDs on the electrical properties of InGaN LEDs was attributed to efficient carrier injection into the QWs brought about by increased transverse carrier mobility in the InGaN layer resulting from reductions in carrier scattering around dislocation cores. In terms of optical properties, LEDs with low TDDs exhibited high peak efficiency and substantial efficiency droops under increased current densities, whereas LEDs with high TDDs showed low peak efficiency and minimal droops under the same condition. These trends can be explained by the correlations of high TDDs with increased dominance of nonradiative recombination and pronounced suppression of peak efficiency under low current densities.

Nano-conglutination technology is a nonconventional nanofabrication technique to use adhesive materials to “stick” nanostructures, which relies on excellent properties of adhesive materials. In this article, we propose a novel hybrid material based on thiol-ene system as the adhesive material for nano-conglutination technology. Thiol-ene system is a kind of UV-curable polymer via “click reaction” to form cross-linked network, which is low viscosity, rapid polymerization rate, high Young’s modulus, and low cost. High-resolution nanostructures such as nano-bowl and nanopillar arrays with sub-200 nm resolution are achieved using thiol-ene adhesive material via nano-conglutination technology. Special reactions of thiols with reactive carbon-carbon double bonds happen in the crosslink process, which make the thiol-ene system be enough low viscosity to keep conformal with the stuck nanostructures and be enough high rigid to easily separate from the mold and keep the original arrangement of nanostructures. This study promotes nanostructures for potential applications of optical, electronics, and photonic devices due to the surface plasmon resonance, surface enhanced Raman spectroscopy, electrical effect, and nonlinear optical response.

To enhance the modulation of the terahertz wave in graphene based modulators, the hollow metallic structures are proposed in our works. With the field localization and enhancement raised by the resonant of the hollow metallic structures, the interaction between the graphene and the terahertz wave is enhanced. It leads to the modulation enhanced when the conductance of graphene is tuned by applied voltage. The samples with hollow square ring array structure and hollow H-cross array structure is discussed with simulations and experiments. The results indicate that the maximum modulation enhancement is achieved near the resonant frequencies.

Photocatalytic water-splitting for hydrogen generation is a promising way to solve the energy crisis, yet the design of efficient photocatalysts is still a challenge. By utilization of first principles calculations, we predict the photocatalytic properties of monolayer boron phosphide (BP) based BP/XY

To convert the polarization of terahertz waves pumped by a femtosecond laser in a terahertz time domain system, a broadband anisotropic metamaterial is proposed. The metamaterial is constructed with a single-layer gapped metallic ring array, which supports different resonant modes in orthogonal directions. With the aid of simulations and measurements, the anisotropy of the terahertz transmission is demonstrated and discussed. The experimental results of THz transmission in the metamaterial indicate that the anisotropic band is as wide as 0.56 THz, which accords well with our theoretical prediction.

Bi3.15Nd0.85Ti2.99Mn0.01O12 (BNTM) thin films with (200)-orientations, (117)-orientations, and mixed-orientations were prepared by sol-gel methods. The influence of orientations on polarization fatigue behaviors of BNTM thin films were systematically investigated at both low and elevated temperatures. It was found that the changed trends of the polarization fatigue of (200)-oriented and (117)-oriented BNTM thin films at elevated temperatures were opposite. The fatigue properties become exacerbated for the (200)-oriented ones and become improved for the (117)-oriented ones, while the reduction of remanent polarization first decreases and then increases for the mixed-oriented ones. It can be assumed that the different roles played by domain walls and interface layer with increasing T in these thin films have caused such differences, which was certified by the lower activation energies (0.12–0.13 eV) of (200)-oriented BNTM thin films compared to those of BNTM thin films (0.17–0.31 eV) with other orientations through the temperature-dependent impedance spectra analysis. With the aid of piezoresponse force microscopy (PFM), the non-neutral tail-to-tail or head-to-head polarization configurations with greater probabilities for (117)-oriented and mixed-oriented thin films were found, while a majority of the neutral head-to-tail polarization configurations can be observed for (200)-oriented ones.

In this paper, effective fabrication of high-resolution diffractive optical elements on a polymer substrate is demonstrated using roller nanoimprint lithography. A nanoscale diffraction grating mold, which can generate a random laser pattern, is fabricated by scan-and-repeat projection lithography. The mold is imprinted to a thin polymer on the soft substrate via roller nanoimprint lithography, which has high efficiency, high fidelity, and high throughput for mass production. This fabrication process can produce high-resolution nanostructures while reducing the cost substantially. We obtained large-area polymer diffractive optical elements with a flexible substrate, which can generate high-quality diffraction random lattice patterns with sub-250 nm resolution for an 808-nm wavelength laser. The diffractive optical elements have about 83.2% diffraction efficiency and 99.7% uniformity of random pattern intensity. It is believed that this fabrication technique can promote practical applications of diffractive optical elements, such as laser wavefront correction, face and activity recognition, and optical communication.In this paper, effective fabrication of high-resolution diffractive optical elements on a polymer substrate is demonstrated using roller nanoimprint lithography. A nanoscale diffraction grating mold, which can generate a random laser pattern, is fabricated by scan-and-repeat projection lithography. The mold is imprinted to a thin polymer on the soft substrate via roller nanoimprint lithography, which has high efficiency, high fidelity, and high throughput for mass production. This fabrication process can produce high-resolution nanostructures while reducing the cost substantially. We obtained large-area polymer diffractive optical elements with a flexible substrate, which can generate high-quality diffraction random lattice patterns with sub-250 nm resolution for an 808-nm wavelength laser. The diffractive optical elements have about 83.2% diffraction efficiency and 99.7% uniformity of random pattern intensity. It is believed that this fabrication technique can promote practical applications of diffractiv...

A wideband terahertz anisotropy metamaterial with the structure of metallic strip-split ring array is discussed. The anisotropy property of transmission is achieved due to the structure of split and strip embed in the ring is different in the orthogonal directions. With theory simulations and experiments, the transmission and resonant differences excited by the structure between the different directions are analyzed. The polarization conversion measurement reveals that the anisotropy band of the metamaterial is between 0.2-0.9 THz. And the experimental results are accord well with the theory calculations.