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Vertical semiconductor van der Waals heterojunctions are essential for fabricating high-performance photodetectors. However, the range of the spectral response and defect states of semiconductor materials are two critical factors affecting the performance of photodetectors. In this work, the spectral response range of WS2 was changed through WS2 band gap regulation, and a self-powered vertical WS1.08Se0.92/Si heterojunction photodetector with MXene electrode was prepared by synthesizing WS1.08Se0.92 film on Si substrate and vertically stacking Ti3C2T x MXene on the film. Due to the electron collection of MXene and the wonderful junction quality of WS1.08Se0.92/Si, the photodetector can detect near-infrared light in the range of 980–1310 nm, which exceed the detection limit of WS1.08Se0.92. And the device had high sensitivity in the broadband. The responsivity was 4.58 A W−1, the specific detectivity was 4.58 × 1011 Jones, the on/off ratio was 4.95 × 103, and the fast response time was 9.81/9.03 μ s. These properties are superior to previously reported WS2-based photodetectors. Vertical structure, Energy band tuning, and MXene electrode provide a new idea for preparing broadband high-performance and self-powered photodetector. [ABSTRACT FROM AUTHOR]

Ferroelectric polarization plays important roles in catalytic reactions, but the mechanism is still under debate. In this work, 2D ferroelectric MIrSn2S6 is systematically investigated for revealing the effects of ferroelectric polarization on the oxygen evolution reaction (OER) based on density-functional-theory (DFT) calculations. We find that: (1) the adsorption configurations of intermediates, protons, and water strongly depend on the polarization, which in turn affects their bonding patterns and adsorption energies; (2) the paraelectric (PE) state generally shows the highest OER activity (overpotential = 0.54 V) due to its most favorable free energy change; and (3) the capacitances are varied under different polarization states, which affects the reaction kinetics. Our findings illustrate the full picture of the OER process under different polarizations, which may provide insightful understanding on the ferroelectric-enhanced catalytic activity and guide the design of novel ferroelectric catalysts. [ABSTRACT FROM AUTHOR]

Using the no-core fiber (NCF)–seven-core fiber (SCF) interference structure, two curvature sensors of Michelson interference type and Mach–Zehnder interference (MZI) type are proposed, respectively. The curvature sensor based on Michelson interference shows wavelength-modulation characteristics, the sensitivity is about −22.76 nm/m−1 with a linearity of 0.9823, the temperature sensitivity is only 0.054 nm/°C, and the effect of temperature on curvature can be negligible. The MZI sensor based on an enlarged taper-embedded cascaded structure is an intensity-modulated sensor. The sensitivities are −63.6271 dB m/m−1 and 93.3293 dBm/m−1 for the forward and reverse curvature, respectively, and the linearities are 0.9987 and 0.9930, respectively. But the strain sensitivity (8.357 × 10−4 dBm/με) of the MZI sensor is so tiny, which can avoid the strain cross effect. The two sensors can be used in the detection of the curvature at different (temperature/strain) conditions. [ABSTRACT FROM AUTHOR]

Autoclaved aerated concrete (AAC) is widely used for its lightweight, high thermal insulation, and superior machinability. However, its loose and porous microstructure can cause a significant decrease in compressive strength after carbonation and the mechanism of the deterioration remains uncertain. This study delved into the alteration trends of AAC's compressive strength and dry density within carbonation environments. Additionally, a variety of testing techniques were employed to elucidate the microscopic mechanisms. The results showed that when the calcium/silicon ratio (Ca/Si ratio) stood at 0.75, AAC exhibited its highest degree of resistance against carbonation. Microscopic analysis revealed a progression in hydration product characteristics as the Ca/Si ratio increased. The transformation journey encompassed a shift from the initial structure to a needle-like tobermorite configuration and, subsequently, to a flaky structure. The study offers invaluable insights that furnish guidance for enhancing the durability of AAC and broaden the horizons of its potential applications. [ABSTRACT FROM AUTHOR]

A single‐mode‐fiber (SMF)‐multimode‐fiber (MMF)‐tri‐core‐fiber (TCF) Michelson probe structure is proposed for trace detection of canine distemper virus (CDV). One end of the TCF is cut flat and fused with the multimode fiber, and the other end is coated with a silver film to enhance the reflection, and an optic‐fiber sensing probe with SMF‐MMF‐TCF structure is obtained. The (PDDA/PSS)3 multilayer film is modified on the surface of the fiber by layer‐by‐layer self‐assembly method as a polyelectrolyte binder to immobilize CDV antibodies to form a (PDDA/PSS)3/CDV antibody composite membrane for specific detection of CDV antigens. The response‐recovery test of the sensor is performed to verify its repeatability. The detection limit, the sensitivity, and the linear fitting degree for CDV antigen are 0.1236 pg/mL, 1.1776 dB/(pg/mL), and 0.9899, respectively. At the same time, the stability, selectivity, and clinical samples of the sensors were also verified. [ABSTRACT FROM AUTHOR]

In this work, the phosphors of Eu3+ ions doped Ba2.9Sr0.1WO6 were successfully synthesized by the high-temperature solid-state method. The luminescence properties, including the emission and excitation spectra, fluorescent lifetimes, and CIE chromaticity coordinates were characterized. The crystal structure and composite of the samples were investigated by XRD (X-ray diffraction), and HRTEM (high-resolution transmission electron microscope). The emission spectra consist of the characteristic peak of Eu3+ excitation at 393 nm; the leading emission peak at 618 nm can be ascribed to the transition of 7F0 → 5L6. The optimal red emission is achieved by 2 % Eu3+ doping. This red Ba2.9Sr0.1WO6: Eu3+ has good luminescent properties and may have potential application in white LEDs. [ABSTRACT FROM AUTHOR]

With the development of underground engineering, dynamic disasters, such as rock bursts, are becoming increasingly serious. Bolt-grouting combined support is one of the common support methods, aiming at the prevention and control of dynamic disasters in fractured surrounding rock of underground engineering. However, the design of bolt-grouting supports is based mainly on experience, and the antishock characteristics need further study for fractured rock masses reinforced by bolt-grouting, which provides a scientific basis for the design of surrounding rock roadway reinforcement. Therefore, we carried out an experimental study on the dynamic mechanical properties of bolted and grouted red sandstones containing prefabricated fractures with different dip angles. The test results show that the dynamic peak strength and the deformation capacity decrease with increasing of fracture dip angle. Compared with the unreinforced samples, the dynamic peak strength and dynamic peak strain of bolt and grouting reinforced samples are improved, and the reinforced rock samples have higher impact resistance and deformation capacity. As the fracture dip angle increases, the incident energy, reflection energy, and transmission energy all show a decreasing trend. Bolt and grouting play the role of energy absorption and increasing antishock, and the dissipation rate of bolted-grouted rock samples is improved. The failure mode of the unreinforced samples is shear failure, the damage of which is more severe than that of bolt and grouting reinforced samples. For the bolt-grouting samples, tensile failure is observed at a low strain rate, and shear failure occurred at a high strain rate. [ABSTRACT FROM AUTHOR]

BaSr2(PO4)2: 4 %Eu3+, 4 %A (A = Li+, Na+, K+) phosphors were prepared by high-temperature solid-phase method. The crystal structure, photoluminescence properties, thermal stability, chromaticity coordinates, and fluorescence lifetime of the samples were investigated. The excitation and emission spectra of the samples are broadbands and the maximum peak of the emission spectrum is located at 619 nm. Among three charge compensators, the luminescence intensity is optimal for Li+ co-doping case, and the quenching temperature of the typical sample is about 500 K. the fluorescence lifetime τ is 1469.6 ns, and the chromaticity coordinates exhibit a strong red emission. The present phosphor has a potential application for white light-emitting diodes (LEDs) under the near-ultra violet (n-UV) light excitation. [ABSTRACT FROM AUTHOR]

Wide band gap semiconductor nanomaterials have great research prospects in power semiconductor devices, radio frequency devices, optoelectronic sensor devices, and so on. Among them, gallium oxide is considered as the representative material of wide band gap semiconductor nanomaterials as a deep ultraviolet (UV) photoelectric sensing device because of its 4.9 eV band gap width. However, the traditional synthesis of this kind of metal oxide semiconductor nanomaterials by the chemical vapor deposition (CVD) method still has some problems. The experimental process is not easy to achieve due to the high temperature of 960 °C, and the lower photocurrent makes it difficult to read the photoelectric signal for subsequent devices because of the optical response current of the order of nanoampere. In this work, gallium antimonide and indium antimonide were selected as the nutrition reaction materials, while oxygen is used as the oxide materials. InGaO3 nanowire network materials were prepared at a lower temperature of 700 °C and a lower working pressure of 0.2 kPa, the deep UV photoelectric response of the optoelectronic devices was measured, and high performance was obtained at 5 V bias, like at a power of 0.64 μW/cm2, the response is 80.1 A/W, detection is 1.03 × 1014, and the external quantum efficiency is 3.9 × 104. Especially, the photoelectric current 34.1 μA is far larger than that of the level of several nanoampere traditional gallium oxide devices. Its reaction principle is that In and Ga metal nucleate and oxidize on the substrate to form InGaO3 nanowires after antimonide decomposition at 700 °C temperature, which is lower than 960 °C of the traditional CVD reaction method. This mechanism is different from that of traditional graphite and oxide powder reduction, which can save energy. In a word, this research has invented a method for preparing indium doping gallium oxide nanomaterials, which provides a reference for rapid preparation of response materials and low-energy consumption for deep UV photoelectric devices. [ABSTRACT FROM AUTHOR]

Ca9MgLi(PO4)7: 4%Tb3+, 4%R+ (R = Li, Na, K) phosphors were synthesized by a solid-state reaction method. The crystal structure, morphology, composition and luminescent properties of as-prepared samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrometer (EDS), high-angle annular dark field (HAADF) and spectroscopy technique. The effect of a small concentration of charge compensators like Li+, Na+, K+ on Ca9MgLi(PO4)7: Tb3+ phosphor has also investigated. Ca9MgLi(PO4)7: Tb3+, R+ (R = Li, Na, K) exhibit superior blue-green luminescence around 5D4 → 7F5 (543 nm) to Ca9MgLi(PO4)7: Tb3+ and can be effectively excited by 370 nm light, which implies that efficient charge compensation can promote the emitting of Tb3+ in Ca9MgLi(PO4)7. The CIE coordinates and decay lifetimes of typical samples were also studied. The Ca9MgLi(PO4)7: Tb3+, R+ (R = Li, Na, K) have promising application as a blue-green phosphor for near-ultraviolet chip excited white LEDs. [ABSTRACT FROM AUTHOR]

In this paper, a novel carbon monoxide (CO) gas sensor based on α-Fe2O3/MgO is presented and constructed. The endlessly single-mode photonic-crystal fibers (ESPCF) was sandwiched between the four-core fibers (FCF) to form the ESPCF-FCF-ESPCF structure, which was embedded it in the Sagnac loop to construct the Sagnac interferometer. The crystal structure, composition and morphology of α-Fe2O3/MgO sensing film were characterized by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM), respectively. The results indicated that the α-Fe2O3/MgO sensing film was uniformly coated on the outside surface of two ESPCFs, with a thickness of about 1 μm. When these sensing films adsorbed CO, the monitoring wavelength showed blueshift and the maximum sensitivity was 99.42 pm/ppm. The response time and recovery time were respectively 90 s and 100 s respectively. The Sagnac fiber-optic sensor exhibt high sensitivity, good selectivity and strong stability, and it can effectively realize the monitoring of carbon monoxide. [ABSTRACT FROM AUTHOR]

Red emitting Li2CaSnO4: xEu3+ phosphors were successfully synthesized by the high-temperature solid-state method. The crystal structure, composite and luminescence properties (e.g. the excitation and emission spectra, fluorescent lifetimes, and CIE chromaticity coordinates) of the samples were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), energy dispersive spectrometer (EDS) and spectral analysis technique. The emission spectra consist of the characteristic peak resultant to Eu3+ under the excitation of 395 nm and the dominant emission peak is at 621 nm (7F0→5L6). The optimal red emission was obtained through 4% Eu3+ doping. These new red Li2CaSnO4: Eu3+ phosphors have the potential application for white LEDs. [ABSTRACT FROM AUTHOR]

A cadmium ion (Cd2+) sensor based on polyvinyl alcohol (PVA)/tetraethyl orthosilicate (TEOS)/3-aminopropyl triethoxysilane (APTES) film integrated Mach–Zehnder interferometer was fabricated and evaluated. The three core fiber (TCF) is spliced with two single mode fibers (SMFs), one end of TCF and SMF are spliced with enlarged taper, and the other end of TCF is directly spliced with another SMF. PVA/TEOS/APTES composite film is coated on the surface of TCF. When the Cd2+ is adsorbed by the sensing film, the relative refractive index of TCF cladding changes, the output interference trough wavelength shifts. By monitoring the wavelength shift information of the interference trough, the concentration of Cd2+ will be obtained. In the concentration range of 0–0.4 μM, with the increase of Cd2+ concentration, the interference trough shows a red shift. The sensitivity and the detection limit of the sensor are 7 nm/μM and 0.0143 μM (1.6 ppb), respectively. The sensor has excellent selectivity and good pH stability. It has the advantages of easy preparation, simple structure, and has potential application for the detection of trace Cd2+. [ABSTRACT FROM AUTHOR]

A novel 2D layered material Ti3C2Tx (MXene) is favored by researchers in the application field of optoelectronics due to its tunable work function, great light transmittance, and excellent electrical conductivity. In this work, Ti3C2Tx/n‐germanium (MXene/n‐Ge) Schottky heterostructures are fabricated and investigated. Schottky contacts of MXene with n‐Ge are identified by ultraviolet photoelectron spectroscopy (UPS). Based on the MXene/n‐Ge Schottky junctions, an ultrafast, broadband, and self‐powered photodetector is demonstrated and studied. The MXene/n‐Ge device exhibits excellent photoresponse from ultraviolet to near‐infrared light illumination. In particular, it shows an excellent on/off ratio (≈104), a high responsivity (3.14 A/W), a larger specific detectivity (2.14 × 1011 Jones), and an ultrafast response speed (trise of 1.4 µs and tdecay of 4.1 µs). Moreover, the MXene/n‐Ge Schottky heterostructure photodetector also shows excellent low‐temperature work characteristics of 73 K. It is believed that this work will attract more researchers' attention to MXene in the field of optoelectronic devices. [ABSTRACT FROM AUTHOR]

The allotrope of carbon, biphenylene, was prepared experimentally recently [Fan et al., Science 372, 852–856 (2021)]. In this Letter, we perform first-principles simulation to understand the bonding nature and structure stability of the possible in-plane heterostructure built by graphene and biphenylene. We found that the graphene–biphenylene in-plane heterostructure only exhibits along the armchair direction, which is connected together by strong covalent bonds and energetically stable. Then, the non-equilibrium molecular dynamics calculations are used to explore the interfacial thermal properties of the graphene/biphenylene heterostructure. It is found that the graphene/biphenylene in-plane heterostructure possesses an excellent interfacial thermal conductance of 2.84 × 109 W·K−1·m−2 at room temperature. Importantly, the interfacial thermal conductance presents different temperature dependence under opposite heat flux direction. This anomalous temperature dependence results in increased thermal rectification ratio with temperature about 40% at 350 K. This work provides comprehensive insight into the graphene–biphenylene heterostructure and suggests a route for designing a thermal rectifier with high efficiency. [ABSTRACT FROM AUTHOR]

Keywords: CaSr(WO4)2: Eu3+, Li+; charge compensation; high-temperature solid-state method; optical performance; red phosphor EN CaSr(WO4)2: Eu3+, Li+ charge compensation high-temperature solid-state method optical performance red phosphor 715 722 8 07/05/22 20220701 NES 220701 1 Introduction Luminescent materials doped with rare earth have been widely used in the fields of display, lighting, biological fluorescence imaging and optical information processing [[1]], [[2]], [[3]]. 4 Conclusions The Eu SP 3+ sp doped CaSr(WO SB 4 sb ) SB 2 sb and Eu SP 3+ sp , Li SP + sp co-doped CaSr(WO SB 4 sb ) SB 2 sb phosphors have been successfully synthesized. This phenomenon indicates that the charge compensation by co-doping Li SP + sp ions is an effective way to increase the PL intensity of CaSr(WO SB 4 sb ) SB 2 sb : Eu SP 3+ sp phosphors. [Extracted from the article]

Searching for highly‐efficient electrocatalysts for water splitting has been greatly endowed due to the huge demand for green energy sources. Two‐dimensional (2D) materials are widely explored for the purpose because of their unique physical and chemical properties, abundant active sites, and easy fabrication. Here, we present a new family of 2D M4B6X6 (2D Boridenes) and investigate their physical and chemical properties for their potential applications into electrocatalysis based on first‐principles calculations. We demonstrate that 2D M4B6X6 (M=Cr, Mo, and W; X=O and F) are dynamically, thermodynamically, and mechanically stable, and show intriguing electronic and catalytic properties. Importantly, we find that M4B6O6 are intrinsically active for oxygen evolution reaction (OER). Our results demonstrate that: (1) the adsorbate‐escape mechanism dominates the OER process with a low overpotential of 0.652 V on Cr4B6O6; (2) the partial surface‐oxidization can improve the catalytic performance of M4B6F6 dramatically; and (3) the surface reconstruction greatly affects the OER performance of M4B6X6. Our findings illustrate that the surface reconstruction is critical to the OER activity, which may provide a new strategy on the design of 2D materials for electrocatalysis and offer theoretical insight into the catalytic mechanism. [ABSTRACT FROM AUTHOR]

As a common geological structure, rock joints have a great influence on the mechanical properties and stability of rock mass engineering. The shear constitutive model of the rock joint and its calculation methods have played an important role in theoretical and experimental research. Most of the existing elastic–plastic shear constitutive models of the rock joint are simplified to linear form or only considering hardening behavior, while the shear test results show that the post-peak nonlinear softening curve is the most common form for shear curves. Therefore, based on Barton shear strength criterion, the shear stress softening is characterized by the change of the post-peak joint roughness coefficient (JRC), and an increment elastic–plastic constitutive model reflecting the shear stress softening is established. According to the constraint condition of constant normal stress, the increment model of the normal deformation with shear deformation is obtained. Based on principle of the implicit return mapping algorithm, an algorithm for the shear softening elastic–plastic constitutive model in the stress space is established. The applicability and rationality of the model and algorithm are verified by a large number of the joint shear experiment results under different conditions. The established elastic–plastic constitutive model provides an effective reference for correctly evaluating the shear deformation characteristics of the joint. [ABSTRACT FROM AUTHOR]

Keywords: -Fe2O3/ZrO2; fluoride-ion sensor; Michelson interferometer; no-core fiber; thin-core fiber EN -Fe2O3/ZrO2 fluoride-ion sensor Michelson interferometer no-core fiber thin-core fiber 269 278 10 03/11/22 20220301 NES 220301 1 Introduction In recent years, more attention has been paid to the study of anions in solutions because of the important applications in the fields of biology, environment, and industrial production [[1]]. The Michelson interference intensity can be expressed as [[16]], HT ht Graph (1)in which I I i SB core sb and I I i SB cladding sb are, respectively, the propagation intensities of core mode and cladding mode in TCF. Fiber-optic Michelson interferometer based on -Fe2O3/ZrO2 sensing membrane and its application in trace fluoride-ion detection. [Extracted from the article]

A novel fiber-optic surface plasmon resonance (SPR) hydrogen sulfide gas sensor based on silver/3-aminpropyltriethoxysilane/cuprous oxide modified graphene sheets (Ag/APTES/ ${\text{Cu}}_{x}\text{O}$ (${x}=1$ , 2)-MGS) composite membrane coated no-core fiber (NCF) was proposed and fabricated. The NCF is sandwiched between two segments of multi-mode fiber (MMF), forming the fiber-optic sensing unit with MMF1-NCF-MMF2 structure. The comparative experiment of sensing performance of two sensors coated respectively by Ag/APTES and Ag/APTES/ ${\text{Cu}}_{x}\text{O}$ (${x}=1$ , 2)-MGS film is investigated in detail. The results show that the sensor with Ag/APTES/ ${\text{Cu}}_{x}\text{O}$ (${x}=1$ , 2)-MGS film has better sensing performance for hydrogen sulfide in the concentration range of 10–60 ppm. After adsorption of hydrogen sulfide, the resonance wavelength of the sensor with Ag/APTES/ ${\text{Cu}}_{x}\text{O}$ (${x}=1$ , 2)-MGS film shows the red shift, and the total shift is about 132.642 nm. In the concentration range of 10–40 ppm, the sensitivity is 3385.67 pm/ppm, the detection limit is 0.56±0.12 ppm, and the response time is 27 s. The sensor has good temperature, humidity, time stability and excellent selectivity, and can be potentially used in the trace hydrogen sulfide detection. [ABSTRACT FROM AUTHOR]

In this work, the spectra of two fiber-optic Fabry–Perot sensors in parallel and series connection were studied. The spectrum of the parallel structure is a simple superposition of the two sensors' spectrum, and that of the series structure can be regarded as the interference occurring in two Fabry–Perot sensors successively. The sensors' optical path difference can be obtained and separated by using the theoretical formula to fit the normalized spectrum of parallel or series structure, which showed that two or more Fabry–Perot sensors can be simultaneously demodulated by the spectrum fitting method. [ABSTRACT FROM AUTHOR]

A reflective fiber-optic surface plasmon resonance (RFSPR) sensor was proposed for detection of cadmium ion (Cd2+) in water based on polyvinyl alcohol/titanium dioxide (PVA/TiO2) composite sensing film. The silver (Ag) was deposited on the side and end surfaces of plastic cladding multimode fiber (PCMF), and then uniform PVA/TiO2 was coated on the outside surface of Ag covered PCMF. The Ag films on the end face and the side face of the fiber are respectively playing the roles in enhancing light reflection and exciting SPR effectively. The Ag-PVA/TiO2 composite film is served as the sensing film of Cd2+. The results show that the sensor can detect 0- $1~\mu \text{M}$ Cd2+ in aqueous solution. The maximum sensitivity of Cd2+ is 315.2 nm/ $\mu $ M, and the minimum detection concentration is $0.006~\mu $ M (about 0.76 ppb), which is much less than that (3 ppb) of the international standard. This assay for Cd2+ detection possesses high sensitivity, excellent selectivity and good stability. The fiber- optic method might become a potential Cd2+ detection tool in aqueous solution. [ABSTRACT FROM AUTHOR]

A novel reflective magnetic field sensor is presented and experimentally demonstrated. The sensing probe is fabricated by splicing a section of uncoated four-core fiber (FCF) between two sections of no-core fibers (NCFs), and the end face of the last NCF is coated by silver. The sensor structure is sealed in a magnetic fluid (MF)-filled capillary, so that the NCF–FCF–NCF magnetic field sensing probe structure is obtained. The NCF is used to excite the high-order modes of the FCF's cladding. Combined with the adjustable refractive index of MF, the sensor is sensitive to the magnetic field and temperature. Experimental results indicate that the presented sensor can measure the low magnetic field and high magnetic field. In the low magnetic field ranges of 0–10 mT and 10–18 mT, the wavelength near 1548 nm varies linearly with the magnetic field intensity, and the sensitivities are −7.43 pm mT−1 and −60 pm mT−1, respectively. The sensitivity of the interference intensity is −0.30782 dB mT−1 in the low magnetic field intensity range of 0–18 mT. The sensor under low magnetic field is also affected by temperature. In the temperature range of 20 °C–70 °C, the temperature sensitivity of the wavelength shift around 1548 nm is 62.33 pm °C−1, and the corresponding sensitivities of the interference intensity are −0.03888 dB °C−1 and −0.02076 dB °C−1 in the range of 30 °C–50 °C and 50 °C–70 °C, respectively. However, the effect of temperature on the sensor in the high magnetic field (18–36 mT) can be ignored. Within the high magnetic field intensity range of 26–36 mT, the sensitivity of the interference intensity near 1598 nm is −1.20993 dB mT−1. The dual-parameter matrix is used to eliminate the cross-sensitivity of temperature in the low magnetic field. This sensor, with the advantages of easy fabrication, high sensitivity and low cost, has the potential application in the magnetic field monitoring. [ABSTRACT FROM AUTHOR]

A novel liquid refractive index sensor based on the connected single-mode fiber (SMF), no-core fiber (NCF), four-core fiber (FCF), and silver mirror (SM) to form an SMF–NCF–FCF–SM Michelson probe structure is proposed and fabricated. The change of light field in the probe structure has been simulated by the light-beam propagation method. The theoretical results show that light is excited in the NCF and couples into the cores and cladding of FCF at the junction of NCF and FCF. The interference fringes are generated between the cladding modes and core modes of FCF. The sensitivities of the probe in NaCl, sucrose, and glycerol are 171.75 dB/RIU, 121.41 dB/RIU, and 207.50 dB/RIU, respectively. The temperature sensitivity is 0.05 nm/°C, and the intensity change of temperature (≤0.046 dB/°C) is very small and has little effect on the liquid refractive index. Thus, the cross-sensitivity of temperature for the liquid refractive index can be removed. The proposed probe structure has the advantages of easy fabrication, good stability, and linear response, having potential application in the liquid refractive index monitoring environments. [ABSTRACT FROM AUTHOR]

Using a segment of thin-core fiber (TCF), multimode fiber (MMF) and single-mode fiber (SMF), a fiber-optic sensor based on the SMF-MMF-TCF-MMF-SMF structure is fabricated and experimentally demonstrated. Based on the layer-by-layer self-assembly method, neodymium modified chitosan (Nd/CTS)/polymethyl methacrylate (PMMA) film is coated on the TCF surface, a Mach-Zehnder interferometer (MZI) sensor for fluoride-ion detection is obtained. With the increase of the fluoride-ion concentration, the monitoring trough shows redshift. Also, the high sensitivity of 14.145 nm/ppm, the rapid response time (about 60 s), the good logarithmic linear relationship (${R}^{2}=0.97175$) at the concentration range of 0.002–0.04 ppm with high selectivity for fluoride ion are achieved. The sensor has the advantages of easy fabrication, good selectivity, low-temperature cross-sensitivity, and good stability, which is suitable for sensitive detection of trace fluoride ion. [ABSTRACT FROM AUTHOR]

A novel hydrogen sulfide (H2S) gas sensor based on multimode interference is proposed and presented. The sensor is constructed by a 30 mm no-core fiber (NCF) and two 30 mm thin-core fibers (TCFs). The first part of the TCF is excited by the high-order modes, in the second part of TCF, the basic core and high-order modes are coupled to the last single-mode fiber, which can induce inter-mode interference. Titanium dioxide–zinc oxide (TiO2–ZnO) composite film is coated on the outside surface of the NCF by the dip-coating method. The experimental results indicate that there is a good linear relationship between the wavelength shift and the different H2S gas concentrations. The sensor has a sensitivity of 21.26 pm ppm−1 in the gas range of 0–50 ppm H2S. In addition, the TiO2–ZnO composite sensing membrane has good selectivity for H2S gas. The response and recovery times are about 90 s and 115 s, respectively. The sensor has the advantages of simple structure, high sensitivity, easy manufacture and could be used in toxic H2S gas monitoring. [ABSTRACT FROM AUTHOR]

Using a segment of thin-core fiber (TCF), multimode fiber (MMF) and single-mode fiber (SMF), a fiber-optic sensor based on the SMF-MMF-TCF-MMF-SMF structure is fabricated and experimentally demonstrated. Based on the layer-by-layer self-assembly method, neodymium modified chitosan (Nd/CTS)/polymethyl methacrylate (PMMA) film is coated on the TCF surface, a Mach-Zehnder interferometer (MZI) sensor for fluoride-ion detection is obtained. With the increase of the fluoride-ion concentration, the monitoring trough shows redshift. Also, the high sensitivity of 14.145 nm/ppm, the rapid response time (about 60 s), the good logarithmic linear relationship (${R}^{2}=0.97175$) at the concentration range of 0.002–0.04 ppm with high selectivity for fluoride ion are achieved. The sensor has the advantages of easy fabrication, good selectivity, low-temperature cross-sensitivity, and good stability, which is suitable for sensitive detection of trace fluoride ion. [ABSTRACT FROM AUTHOR]

An ultraviolet curable glue (UCG)-filled microprobe Fabry–Perot fiber temperature sensor, which based on the two-beam interference principle, is proposed and fabricated. In the range of 25.7–250 °C, the average sensitivity and average linear correlation coefficient of the sensor are −41.69 pm/°C and 0.98558, respectively. Under the same temperature, the maximum fluctuation (0.56 pm) of the trough's wavelength and the standard error (0.0023 ± 0.04%) are obtained. The proposed interferometer exhibits excellent stability and has a potential application in the field of temperature monitoring. [ABSTRACT FROM AUTHOR]

Taking the concrete as an example, this paper studies the shear characteristics of the cohesive soil and rigid base. A series of shear tests are conducted by the refitted DSJ-2 electric four-joint equal stress direct shear apparatus. The results in the shear tests are contrastively analyzed. The results show that under the condition of simple shear tests, the constitutive relation of structural interface between the clay and concrete is rigid, and the residual strength is obvious. Under the condition of direct shear tests, the shear stress-displacement curves present hyperbolic connection. There is obvious strain hardening phenomenon, no obvious peak strength and residual strength. Under the two experimental conditions, the peak shear strength of the interface increases with an increase in the normal stress. With increasing moisture content, the peak shear strength of the interface decreases. The internal friction angle and cohesion of the structural interface decrease with increasing moisture content, and the relationship between internal friction angle, cohesion of the structural interface and moisture content are nonlinear. The peak shear strength of the direct shear tests is greater than that of the simple shear tests. [ABSTRACT FROM AUTHOR]

A novel fiber temperature sensing head based on the Fabry–Perot interference principle is proposed and fabricated. Its temperature sensing is performed by using the thermal expansion of titanium wire fixed in a quartz capillary. The rationality of ignoring high-order reflected light was verified by the experiment. The spectra of heating and cooling processes were measured for three times in the temperature range of 1 ∼ 50 °C, showing the high consistency and stability. This sensor requires only 25 nm scanning width of the optical spectrum analyzer. Its sensitivity of the Fabry–Perot cavity optical length changing with temperature is approximately −66.7 nm °C−1, and the accuracy can reach 0.1 °C by utilizing the binomial empirical formula instead of the linear one. [ABSTRACT FROM AUTHOR]

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A novel strain and temperature sensor based on the fiber Bragg grating (FBG) cascaded two-tapered four-core fiber (FCF) Mach–Zehnder interference (MZI) is proposed and fabricated. The two optical fiber tapers, acting respectively as a beam splitter and a coupler, are able to produce interference phenomena, so the high interference extinction ratio (above 20 dB) can be obtained. The attenuation peak at 1562 nm and the FBG center wavelength at 1550 nm in the transmission spectra are, respectively, selected to represent MZI and FBG as the monitoring wavelengths. The results indicate that the sensitivities of MZI to strain and temperature are −1.83 pm μϵ−1 and 46.93 pm C−1, respectively, and those of FBG to strain and temperature are 1.26 pm μϵ−1 and 10.58 pm C−1, respectively. Both the FBG and MZI exhibit insensitivity to the refractive index. The cascaded sensor has good linearity and is applied to measure the strain and temperature simultaneously. [ABSTRACT FROM AUTHOR]

Silicon-based Schottky heterojunction photodetectors are promising due to their compatibility with the semiconductor process. However, the applications of these devices are usually limited to wavelengths shorter than 1.1 µm due to the low absorption of electrode materials at infrared. In this report, silicon-based compound semiconductor heterojunction photodetectors with graphene transparent electrodes are fabricated. Due to the high absorption of InSb at infrared, as well as the good transparency and excellent electrical conductivity of the graphene, the as-prepared photodetectors show a broadband photoresponse with high performance which includes a specific detectivity of 1.9 1012 cm Hz1/2 W−1, responsivity of 132 mA W−1, on/off ratio of 1 105, rise time of 2 µs, 3 dB cut-off frequency of 172 kHz, and response wavelengths covering 635 nm, 1.55 µm and 2.7 µm. This report proves that graphene as a transparent electrode has a great effect on the performance improvement of silicon-based compound semiconductor heterojunction photodetectors. [ABSTRACT FROM AUTHOR]

The experimental results show that the creep properties of the rocks are affected by the initial damage, and the damage evolution also has a significant impact on the time-dependent properties of the rocks during the creep. However, the effects of the initial damage and the damage evolution are seldom considered in the current study of the rocks' creep models. In this paper, a new nonlinear creep damage model is proposed based on the multistage creep test results of the sandstones with different damage degrees. The new nonlinear creep damage model is improved based on the Nishihara model. The influences of the initial damage and the damage evolution on the components in the Nishihara model are considered. The creep damage model can not only describe the changes in three creep stages, namely, the primary creep, the secondary creep, and the tertiary creep, but also reflect the influence of the initial damage and the damage evolution on creep failure. The nonlinear least squares method is used to determine the parameters in the nonlinear creep damage model. The consistency between the experimental data and the predicted results indicates the applicability of the nonlinear damage model to accurately predict the creep deformation of the rocks with initial damage. [ABSTRACT FROM AUTHOR]

The description of rock creep by existing rheological models mainly focuses on the first two stages of creep. However, the description of the accelerated creep stage is rare, which is contrary to the common study of soft rock failure in engineering applications. Therefore, the study of the accelerated creep stage is an important research direction at present. In this paper, a new model that can describe accelerated creep is proposed on the basis of the Nishihara model, and creep constitutive relation of the model is deduced via relevant laws. The parameters of the model are obtained by the whole rheological curves of the sandy mudstone of the diversion tunnel of a hydropower station and the strongly weathered sandstone in the bottom of the Xiangjiaba dam foundation. A fitting analysis of the theoretical results and experimental data indicates that the fitting results are highly consistent; the correlation coefficients are all above 0.98, which shows the rationality and correctness of the model. The nonlinear viscoelastic-plastic model proposed in this paper can accurately describe the accelerated creep stage of rock, and its applicability is obviously broader than that of the traditional Nishihara model. This nonlinear viscoelastic-plastic model can be used to not only predict the critical sliding of a rock mass in slope, tunnel and hydraulic engineering but also enrich the theory of rock rheology. [ABSTRACT FROM AUTHOR]

Copyright of Zeitschrift für Naturforschung Section A: A Journal of Physical Sciences is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Creep characteristics of rock mass are related not only to the confining pressure but also to the degree of internal fracture damage. Revealing the creep characteristics of rock mass under different confining pressures and degrees of damage is of great significance for selecting a reasonable supporting time and optimum supporting strategy in engineering. Sandstone is the main medium of the coal seam roof in the Jushan Mine and has poor physical and mechanical properties. To study the creep behavior of sandstone, triaxial creep tests and simulations are conducted under different confining pressures and degrees of damage. The results show that the appearance of the creep stage is related not only to the stress but also to the confining pressure and the degree of damage. With an increase in the confining pressure or the degree of damage, the creep parameters will have clear change, especially under high stress level. The creep parameters and confining pressures show different changing laws, and there are also different relationships between the creep parameters and the degrees of damage. Three surface equations are proposed to visually describe the variation in the creep parameters with the confining pressure and the degree of damage. The sudden increase in cracks is affected by both the confining pressure and the degree of damage, and it can be used as an early warning of rock failure. Thus, the influence of the confining pressure and damage should be simultaneously considered in the long-term stability of rock mass. [ABSTRACT FROM AUTHOR]

A highly sensitive hydrogen sulfide gas sensor based on NH2-rGO-coated thin-core-fibre (TCF) Michelson interferometer (MI) is proposed and evaluated. Two sections of TCFs are alternately sandwiched between three single-mode-fibres (SMFs). A Faraday rotator mirror (FRM) is fixed to the end of the last SMF to reflect the light signal and enhance the interference. Then the structure SMF-TCF-SMF-TCF-SMF-FRM (STSTS-F) is successfully constructed. NH2-rGO, as sensing film, is coated on two TCFs and is used to detect traces of hydrogen sulfide gas. Raman spectra and XPS analysis show that NH2-rGO has been successfully synthesised. The thickness of the NH2-rGO film coated on the TCF surface is about 500 nm. By introducing 0–60 ppm hydrogen sulfide gas into the chamber, with the increase in concentration of the gas, the monitoring trough exhibits a blue shift. Our experimental results show that the sensor has good linearity (R2 = 0.98096) and selectivity for hydrogen sulfide gas. The sensitivity is 21.3 pm/ppm, and the response and recovery times are about 72 and 90 s, respectively. The sensor has the advantages of high sensitivity, high selectivity, and small size, enabling the detection of trace hydrogen sulfide in toxic gas environments. [ABSTRACT FROM AUTHOR]

Novel green phosphors Zn3Al2Ge2O10: Mn2+ were successfully synthesised at high temperature under weak reducing atmosphere. X-ray diffraction results indicate that the samples have like-spinel structure. The morphology, chemical states, and the composition of the dopants in the host were analysed with high-resolution transmission electron microscopy, energy dispersive spectrum, high-angle annular dark-field, and X-ray photoelectron spectroscopic techniques. The photoluminescence spectra show that the emission peak is at 537 nm (under excitation at λex = 334 nm), which is the strong green emission resulting from the 4T1 (4G)-6A1 (6S) transition of Mn2+ ion. The full width at half maximum broadband of the strongest broad emission is about 50 nm. The Zn3Al2Ge2O10 doped with 4 mol% Mn2+ appears to have the highest emission intensity after thermal treatment at 1250 °C for 5 h. The CIE coordinates are x = 0.279, y = 0.625, corresponding to green region, and the decay time is 4.88 μs. The results indicate that the phosphors may be used as a trichromatic fluorescent material. [ABSTRACT FROM AUTHOR]

A hydrogen sulfide (H2S) gas sensor based on copper (Cu) nanoparticle deposited graphene oxide (GO) composite membrane with two waist-enlarged tapers is proposed. Three segments of the single-mode fibres (SMFs) are sequentially fused to obtain two waist-enlarged bitapers of Mach–Zehnder interferometer (MZI). When the light of a broadband light source transmits through the first bitaper, some light enters the fiber cladding; the lights of core mode and cladding mode are coupled at the second taper and an MZI is successfully fabricated. The copper/graphene oxide (Cu/GO) composite sensing film is coated on the surface of the second SMF, and the effective refractive index of the coating is changed when the sensitive film adsorbs the target gas. The correlation between the gas concentration and the wavelength shift is achieved and the H2S can be measured effectively. The results show that a uniform Cu/GO film is successfully coated on the surface of the fiber, and when the thickness of the sensitive film is about 1.2 μm, the sensor has a sensitivity of 4.42 pm/ppm and a good linearity and selectivity for H2S in the range of 0–60 ppm, and the limit of detection is 2.79 ppm. The response time and recovery time are approximately 31 and 48 s, respectively. The sensor has the advantages of small volume, low cost, simple structure, and easy manufacture and so on, which is suitable for on-line monitoring of H2S. [ABSTRACT FROM AUTHOR]

A novel sucrose sensor based on graphene-coated optical fibre with waist-enlarged bitapers as Mach-Zehnder interferometer is proposed and demonstrated. The sensor is formed by arc fusion splicing a photonic crystal fibre (PCF) sandwiched between two single-mode fibres (SMFs). The intermodal interference is achieved by two waist-enlarged fibre tapers at the coupling points between the PCF and two SMFs. The result shows that the dips of transmission spectra exhibit blue shift with the concentration increase of the sucrose, and the sensor has a high linear response (R2 = 0.98233) to sucrose with an excellent sensitivity of 3.36 pm/ppm in the range of 0–230 ppm. Additionally, the surface adsorption mechanism is also discussed. Such easily fabricated, cost-effective and small volume fibre interferometer could be used for sucrose sensing applications. [ABSTRACT FROM AUTHOR]

A novel fiber-optic carbon monoxide sensor based on a thin-core Mach–Zehnder fiber modal interferometer is presented and fabricated. This interferometer contains a short section of thin-core fiber spliced in two standard single-mode fibers, and the fast response to carbon monoxide is achieved via the construction of carbon monoxide sensing membrane on the outside surface of the thin-core fiber by using the dip-coating technique. The prepared sensing film is characterized by scanning electron microscopy, energy dispersion spectrum (EDS), spectroscopic analysis technology, and so on. Experimental results show that the thickness of the polyaniline (i.e., PANI)/Co3O4/CuO composite film, is about 360 nm with a compact and uneven appearance. The EDS indicates that the elements C, N, O, Cu, and Co are existed and agree well with the components of PANI/Co3O4/CuO. With the increasing concentration of carbon monoxide, the interference spectra appear blue shift. A high sensitivity of 2.87 pm/ppm and a good linear relationship are obtained within a measurement range from 0 to 70 ppm. In addition, there is an excellent selectivity for carbon monoxide. This interferometer has the advantages of high sensitivity and safety in flammable and explosive situations and could be used in the safety monitoring field of carbon monoxide gas. [ABSTRACT FROM AUTHOR]

Engineering research has shown that the surrounding rock of deep roadways experienced many times of post-peak cyclic loading and unloading. So studying on rock mechanical characteristics of post-peak loading and unloading is helpful to control the deep surrounding rocks. The test using RMT-150B rock mechanics testing system, to experiment on the mechanical properties of sandstone of post-peak cyclic loading and unloading. The results show that: the stress-strain curves of post-peak cyclic loading and unloading have significant plastic hysteretic loops. The area of plastic hysteretic loops gloss back. The enveloping outer enclosure of cycle loading curve is the similar as the stress-strain curves of strain softening stage when the samples failure, which shows that post-peak failure of rocks have significant memory. With the increase of cycles, the cumulative deterioration parameters are gradually increased, and the ultimate bearing capacity, elastic of loading section of samples and cumulative deterioration parameters conform with the exponential attenuation function with constant term. With the increase of surrounding pressure, the total energy, dissipated energy and elastic energy of samples are gradually increased. With the increase of cycles, the total energy, dissipated energy and elastic energy of samples all are gradually decreasing, the rate of reduction decreases gradually. The samples exist in vertical splitting and transverse shear combination failure under the post-peak uniaxial cycles, or exist in shear failure under the post-peak triaxial cycles. The shear plane exists slip traces. [ABSTRACT FROM AUTHOR]

A series of new red-orange emission phosphors Na2BaMg(PO4)2:Pr3+ were synthesised by a high-temperature solid-state reaction. The crystal structure and photoluminescence properties of these samples were characterised by X-ray diffraction and spectroscopic measurements. This compound holds P3̅m1 space group of the trigonal system with the lattice parameters of hexagonal cell a=0.5304(3) nm and c=0.6989(3) nm. The phosphor emits the strongest peak at 606 nm when excited by 449 nm. The average Commission Internationale de l’Eclairage chromaticity coordinates calculated for the phosphors are (0.52, 0.46). The results demonstrate the potential application of these phosphors in solid-state lighting and other fields. [ABSTRACT FROM AUTHOR]

The novel green terbium single-doped or terbium and sodium codoped barium zinc phosphate phosphors were successfully synthesized by a high temperature solid-state reaction. Terbium single-doped and terbium and sodium codoped barium zinc phosphate phosphors can be efficiently excited by near ultraviolet (n-UV) light, and the emission spectrum consists of four main emission peaks at 495, 545, 589, and 622 nm. By increasing the terbium concentration, the emission signal of the phosphor can reach the maximum at 0.09 molar terbium, then the content quenching occurs. By introducing the charge compensator sodium ions into the terbium-doped barium zinc phosphate phosphors, its emission signal can be obviously enhanced. The Commission International de l’Eclairage chromaticity coordinates of the two typical samples are (0.30, 0.47) and (0.31, 0.48), which are both in the green region. The decay time and quantum yield of the typical sample are 365.84 µs and 0.49, respectively. All the results indicate that terbium single-doped and terbium and sodium codoped barium zinc phosphate are promising green phosphors for near ultraviolet pumped white light-emitting diodes. [ABSTRACT FROM AUTHOR]