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High sensitivity of sensors is extremely significant for precisely monitoring imperceptible changes of motion in real-time, which cannot be achieved by traditional piezoelectric devices. Herein, a hierarchical polyvinylidene fluoride hexafluoropropylene (PVDF-HFP)/ZnO composite nanaofiber piezoelectric sensor with highly sensitivity has been prepared through epitaxial growing ZnO nanosheets on the surface of electrospun PVDF-HFP nanofibers. Systematic investigations have shown that their optimum pressure sensing performance with a sensitivity of 1.9 V kPa−1 and a short response time of 20 ms are achieved for forces from 0.02 to 0.5 N with excellent durability and stability up to 5000 cycles. Moreover, this sensor can precisely detect the imperceptible changes in player’s motions to avoid injury from overtraining. Additionally, a Bluetooth-low-energy that tracks player’s workout and transmits the output signals wirelessly to a smartphone app is utilized. The study provides a feasible approach for high-precision detecting and safety monitoring in the fields of medical, rehabilitation medicine, and workout security.

The weft-knitted reduced graphene oxide (r-GO) textile that is made up of many conductive r-GO coated fibers was successfully prepared dependent on the electrospray deposition technique. Interestingly, the r-GO textile presents negative resistance variation not only in axial direction as the pressure increases but also in transverse direction as the lateral stretch increases which makes it has the advantage to fabricate the reliable sensors based on strain-resistance effect. The transverse-strain and pressure sensors based on the r-GO textiles all show the excellent sensing characteristics such as high sensitivity, reliability, and good durability, etc. The maximum gauge factors (GF) of the transverse-sensor are 27.1 and 153.5 in the x- and y-direction, respectively. And the practical detection range can up to 40% in the x-direction and 35% in the y-direction, respectively. The r-GO textile pressure sensor also shows high sensitivity for a broad pressure range that with a GF up to 716.8 kPa−1 for less than 4.5 kPa region and still has more sensitive pressure sensing characteristics even the pressure goes up to 14 kPa. Based on those good performances of r-GO textile sensors, its potential applications in human body states monitoring have been studied.

Conventional encryptions including single and multiple encryptions still have disadvantages, such as low security, complicated operation process and time consuming. Herein, a dual information encryption mechanism based on the exclusivity of the decryption process is proposed, which uses carbon dots (CDs) as fluorescent inks with two rounds of encryption and decryption to perform dual information encryption. The encryption process is easy to operate, and the decryption process can be completed in a short time (

Superconducting nanofibers have attracted much attention in basic researches and practical applications due to their unique physical properties such as broad phase transition temperature, excellent heat conductivity, and high critical current density, etc. Electrospinning, as a common method to prepare nanofibers, also has many applications for the preparation of superconducting nanofibers. However, a few of the new methods to fabricate superconducting nanofibers via electrospinning still need further investigations. This review firstly introduces several potential electrospinning methods to obtain superconducting nanofibers, then proceeds to summarize the recent progress in the field of electrospun superconducting materials. The preparation process, difficulties and problems, physical properties of the superconducting nanofibers or nanonetworks (such as superconducting transition temperature, critical current density, critical magnetic field strength, fiber morphology, and structure, etc), theoretical analysis of the properties, and the techniques to improve the performance are also reviewed. In addition, some suggestions and prospects for the development and applications of electrospun superconducting materials in the future are discussed.

Stretchable sensors, as the important components of flexible electronic devices, have achieved progress in a variety of applications for monitoring physical or environmental conditions, such as sound, temperature, vibration, and pressure. However, it still remains a challenge to fabricate high performance stretchable humidity sensors. Herein, we present a novel stretchable humidity sensor, which was fabricated based on an ultrastretchable polyaniline composite fiber. Because of the composite fiber with a "twining spring" configuration (cotton fibers twining spirally around a polyurethane fiber) it maintains a stable electrical conductivity up to a strain of 200%. In addition, the conductivity of the composite fiber remains perfectly stable after 5000 cyclic stretching events of 200% strain. Incorporating the humidity sensitive properties of nanostructured polyaniline, the stretchable humidity sensor based on the composite fiber effectively maintains its humidity sensitivity at different elongations.

Self-activated phosphors are capable of generating optical emissions from the internal ion groups of host lattice before externally introducing luminescent ions. However, numerous self-activated phosphors only show luminescence at low temperature due to the thermally activated energy migration among ion groups at room temperature, severely confining their application conditions. In this letter, we propose a strategy to converting the low-temperature luminescence to a room-temperature one through changing the synthesis conditions to induce structural distortions and thus to limit energy migration. Room-temperature self-activated luminescence of Ca2Nb2O7 was accordingly achieved in submicroplates synthesized using the sol–gel method. By further coupling the blue broadband emission from Ca2Nb2O7 submicroplates with the characteristic luminescence of Ln3+ (Pr3+, Sm3+, and Dy3+) dopants, multicolor emissions were successively tuned through adjusting the concentration of Ln3+. Our results are expected to expand the scope of designing room-temperature self-activated phosphors and tuning multicolor emission.

Raman spectroscopy is the prime non-destructive characterization tool for graphene and related layered materials. The shear (C) and layer breathing modes (LBMs) are due to relative motions of the planes, either perpendicular or parallel to their normal. This allows one to directly probe the interlayer interactions in multilayer samples. Graphene and other two-dimensional (2d) crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientation have different optical and electronic properties. In twisted multilayer graphene samples there is a significant enhancement of the C modes due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. Here we show that this applies also to the LBMs, that can be now directly measured at room temperature. We find that twisting does not affect LBMs, quite different from the case of the C modes. This implies that the periodicity mismatch between two twisted layers mostly affects shear interactions. Our work shows that Raman spectroscopy is an ideal tool to uncover the interface coupling of 2d hybrids and heterostructures., ACS Nano, 2015, 9(7), 7440-7449

Graphene and other two-dimensional crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientation have different optical and electronic properties. Probing and understanding the interface coupling is thus of primary importance for fundamental science and applications. Here we study twisted multilayer graphene flakes with multi-wavelength Raman spectroscopy. We find a significant intensity enhancement of the interlayer coupling modes (C peaks) due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. The interlayer coupling results in a Davydov splitting of the C peak in systems consisting of two equivalent graphene multilayers. This allows us to directly quantify the interlayer interaction, which is much smaller compared with Bernal-stacked interfaces. This paves the way to the use of Raman spectroscopy to uncover the interface coupling of two-dimensional hybrids and heterostructures.

Graphene-based micro-tubes (μ-GTs) with good tubular structure were successfully fabricated from commercial graphene oxide dispersion by the electrospray deposition technique and thermal reduction. As a result of the structural changes, the electrical conductivity of the μ-GTs clearly increased as the annealing temperature increased. In particular, the μ-GTs with lower annealing temperatures exhibited distinct semiconductor properties. The electrical conduction mechanism can be explained by the 2-D variable-range hopping model. Furthermore, a transition from semiconductor to semi-metal was found to occur when the annealing temperature exceeded 900 °C, and the electrical conduction mechanism follows the exponential law of temperature in this condition.

Color manipulation of intense multiluminescence from CaZnOS:Mn2+ has been realized by adjusting Mn2+ concentration. Not only the photoluminescence (PL) of Mn2+ emission from 4T1(4G) to 6A1(6S) shows a red shift from yellow to red with increasing Mn2+ concentration, which is in contrast to the fixed PL emission reported by Hintzen et al. (Chem. Mater., 2009), but also mechanoluminescence (ML) and cathodoluminescence (CL) have a similar variation. More attractively, the brightness of multiluminescence is surprisingly intense for all the CaZnOS:Mn2+ with a large-scale Mn2+ doping (0.1–10 mol %). Based on the investigation of crystal field, various spectral results, and PL lifetimes, the red-shift mechanism of multiluminescence reported here has been proposed to arise from the exchange interaction effect of Mn2+ pairs at higher concentrations. In addition to correcting the previous misunderstanding on the emission of CaZnOS:Mn2+, these findings extend the tunable emission window, opening up new opportunities ...

Graphene is a two-dimensional (2D) material with excellent physical properties, and its special charge transport characteristics promote extensive exploration based on graphene electronic devices. In order to determine the effect of the mesostructure on the electromagnetic transport properties of graphene, the temperature dependencies of the resistance and the magnetoresistance (MR) of reduced graphene oxide paper (rGOP) and reduced graphene oxide aerogel fiber (rGAF) were systematically measured. The conduction mechanism was systematically studied, and the graphene paper and aerogel fiber were in accordance with Mott’s 2D and 3D variable-range hopping (VRH) models, respectively. With the decrease of temperature, the transition from small-negative MR to large-positive MR was observed, the influences of wave function shrinkage and quantum interference effects on positive and negative MR were discussed in the framework of hopping conduction.

La-doped ZnO nanofibers were fabricated via electrospinning and calcination at 800°C. The surface morphology and crystal structure of the La-doped ZnO nanofibers were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photoelectric properties of La-doped ZnO nanofibers were also investigated. It was found that the photoelectric current increased obviously under light illumination (308 nm and 365 nm). However, the photocurrent reduced with increasing La-doping level, which may be ascribed to the increased defects inducing by La-doping.

Electrospinning (e-spinning) still has certain limitations in flexible practicability because its conventional setup is usually quite bulky and excessively dependent on a plug (electric supply). In this article, we report on a battery-operated e-spinning apparatus (BOEA) based on miniaturization and integration. The new device gets liberated from the conventional heavy power supply, achieves the tight integration of functional parts and can be operated by a single hand due to its small volume (10.5 × 5 × 3 cm(3)) and light weight (about 120 g). Different polymers such as polyvinylpyrrolidone (PVP), polycaprolactone (PCL), polystyrene (PS), poly(lactic acid) (PLA) and poly(vinylidene fluoride) (PVDF) were electrospun into fibers successfully, which confirms the stable performance and good real-time control capability of the apparatus. These results demonstrate that the BOEA could be potentially applied in many fields, especially in biomedical fields such as skin damage, wound healing, rapid hemostasis, etc.

A conventional electrospinning setup cannot work without a plug (electricity supply). In this article, we report a self-powered electrospinning setup based on a hand-operated Wimshurst generator. The new device has better applicability and portability than a typical conventional electrospinning setup because it is lightweight and can work without an external power supply. Experimental parameters of the apparatus such as the minimum number of handle turns to generate enough energy to spin, rotation speed of the handle and electrospinning distance were investigated. Different polymers such as polystyrene (PS), poly(vinylidene fluoride) (PVDF), polycaprolactone (PCL) and polylactic acid (PLA) were electrospun into ultrathin fibers successfully by this apparatus. The stability, reliability, and repeatability of the new apparatus demonstrate that it can be used as not only a demonstrator for an electrospinning process, but also a beneficial complement to conventional electrospinning especially where or when without a power supply, and may be used in wound healing and rapid hemostasis, etc.

An SiO2/Si substrate has been widely used to support two-dimensional (2d) flakes grown by chemical vapor deposition or prepared by micromechanical cleavage. The Raman intensity of the vibration modes of 2d flakes is used to identify the layer number of 2d flakes on the SiO2/Si substrate, however, such an intensity is usually dependent on the flake quality, crystal orientation and laser polarization. Here, we used graphene flakes, a prototype system, to demonstrate how to use the intensity ratio between the Si peak from SiO2/Si substrates underneath graphene flakes and that from bare SiO2/Si substrates for the layer-number identification of graphene flakes up to 100 layers. This technique is robust, fast and nondestructive against sample orientation, laser excitation and the presence of defects in the graphene layers. The effect of relevant experimental parameters on the layer-number identification was discussed in detail, such as the thickness of the SiO2 layer, laser excitation wavelength and numerical aperture of the used objective. This paves the way to use Raman signals from dielectric substrates for layer-number identification of ultrathin flakes of various 2d materials.

Titanium dioxide (TiO2) nanorods with anatase phase were successfully fabricated by electrospinning and followed calcination. The TiO2 nanorods were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and UV-visible spectroscopy. The diameter of the TiO2 nanorods was about 60–150 nm and the length was 200 nm–2 μm. Electrical properties under bending were investigated by fixing the device to a curved surface with different curvatures, and the device showed a fast and stable resistance response to curvature changing. Photoelectric properties were studied by irradiation with different light intensities. The device exhibited a short response time (∼10 s) and a high sensitivity (∼103) which increased with the light intensity increasing. These results indicate that electrospun anatase TiO2 nanorods have potential applications in flexible photodetectors and solar cells.

We report an effective method to fabricate poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)–polyvinyl pyrrolidone (PEDOT:PSS–PVP) fiber arrays doped with ionic liquid (IL). The twisted microropes were obtained by twisting the electrospun aligned polymer fiber arrays. It was found that the twisted rope exhibited higher electrical conductivity (∼1.8 × 10−4 S cm−1) after IL doping (1.96 wt%) than those without doping (∼0.8 × 10−5 S cm−1), and its conductivity was linearly correlated with strain up to 35% (which is one magnitude larger than previous reports) and showed repeatable cycle loops of tensile-resilience. The extensible rate could reach up to more than 90%, considerably higher than that of ropes without IL doping (∼17%). The results indicate that the twisted PEDOT:PSS–PVP ropes may be used as elastic semiconductors and stretchable sensors.

Mixed-valence Eu-doped CaZr(PO4)2 was prepared in air atmosphere by a two-step solid-state reaction for the first time. The reduction of Eu3+ to Eu2+ in air atmosphere was observed in the second synthesis step via the use of NH4H2PO4 and the first-step product CaZrO3:Eu3+ to synthesize CaZr(PO4)2:Eu, which strengthens the evidence linking the tetrahedral anion groups PO4 with the Eu reduction. This reduction mechanism is explained by a charge compensation model. The luminescence measurements indicate that the obtained phosphors exhibit a broad bluish-green fluorescence of Eu2+ and a sharp orange-red emission of Eu3+ on 200–350 nm ultraviolet (UV) excitations. A tunable white luminescence covering the whole visible spectrum is realized based on the gradual reduction of Eu3+ to Eu2+ with increasing the sintering time. The optimal white luminescence excited at 247 nm presents the CIE color coordinates of (0.322, 0.305), a correlated color temperature of 6243 K, and a good thermal stability. Furthermore, energy transfer from Eu2+ to Eu3+ is found in CaZr(PO4)2:Eu. Our investigation of CaZr(PO4)2:Eu may provide a practical basis to design and fabricate novel phosphors for white light-emitting diodes (W-LEDs).

Due to a variety of outstanding properties, such as large surface area, high length-to-diameter ratio, flexible surface functionality, tunable surface morphologies and superior mechanical performance, electrospun ultrathin fibers are suitable for flexible and stretchable devices, which have aroused much attention nowadays. In this review, we aim to summarize recent developments in the fabrication of flexible/stretchable electronic devices via electrospinning, including strain and pressure sensors, supercapacitors, organic field-effect transistors, and transparent electrodes, which are the key components of flexible/stretchable devices. Moreover, in order to further improve the performance of these devices, some challenges facing electrospun fibers (e.g. production on large scale, precise deposition and flexibility improvement of electrospun inorganic fibers) and subsequent integration for flexible/stretchable electronic devices have also been discussed.

Self-activated phosphors are capable of generating optical emissions from the internal ion groups of host lattice before externally introducing luminescent ions. However, numerous self-activated phosphors only show luminescence at low temperature due to the thermally activated energy migration among ion groups at room temperature, severely confining their application conditions. In this letter, we propose a strategy to converting the low-temperature luminescence to a room-temperature one through changing the synthesis conditions to induce structural distortions and thus to limit energy migration. Room-temperature self-activated luminescence of Ca

MoS2 flakes have attracted much attention due to their attractive properties. Optical reflectance techniques can prove to be very powerful techniques to study some of the thickness dependent physical properties, e.g. A and B excitonic peaks. Here, we measured reflection spectra of MoS2 flakes on SiO2/Si substrate in the broad wavelength range of 400-800 nm and studied the emission wavelength of A and B excitons as a function of the layer number. Moreover, we calculated the optimized SiO2 thickness to avoid the substrate-related interference effect influencing the investigation of exciton properties.

Uniaxially aligned and cross-aligned arrays of ultrafine polymer fibers have been fabricated by a novel and effective centrifugal electrospinning setup with rotating polymer solution jets. Comparing with conventional electrospinning (10–30 kV) and centrifugal spinning (4,000–12,000 rpm), this technique only requires a lower working voltage (2.8–6.0 kV), a slower rotational speed (360–540 rpm), and a shorter spinning distance (2.0–4.0 cm). In addition, the influences of experimental parameters such as working voltage, rotational speed, collecting distance, and solution concentration on the alignment of the as-spun fibers are investigated using image analysis techniques. It is found that the working voltage and rotational speed mainly influence the perpendicular and linear velocities of the fibers, respectively. The polymer fibers tend to show higher alignment degree when these two velocities are very close. Optimum conditions (working voltage 3.0 kV, rotational speed 420 rpm, collecting distance 2.5 cm, and solution concentration 18 wt%) to maximize alignment degree (~97%) of polystyrene fibers are also obtained.

A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10,000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polyvinylpyrrolidone (PEDOT:PSS/PVP) composite nanofibers were successfully fabricated via electrospinning and used as a quartz crystal microbalance (QCM) sensor for detecting CO gas. The electrical property of individual PEDOT:PSS/PVP nanofibers was characterized and the room temperature resistivity was at the magnitude of 105 Ω·m. The QCM sensor based on PEDOT:PSS/PVP nanofibers was sensitive to low concentration (5–50 ppm) CO. In the range of 5–50 ppm CO, the relationship between the response of PEDOT:PSS nanofibers and the CO concentration was linear. Nevertheless, when the concentration exceeded 50 ppm, the adsorption of the nanofiber membrane for CO gas reached saturation and the resonant frequency range had no change. Therefore, the results open an approach to create electrospun PEDOT:PSS/PVP for gas sensing applications.

Color manipulation of intense multiluminescence from CaZnOS:Mn2+ has been realized by adjusting Mn2+ concentration. Not only the photoluminescence (PL) of Mn2+ emission from 4T1(4G) to 6A1(6S) shows a red shift from yellow to red with increasing Mn2+ concentration, which is in contrast to the fixed PL emission reported by Hintzen et al. (Chem. Mater., 2009), but also mechanoluminescence (ML) and cathodoluminescence (CL) have a similar variation. More attractively, the brightness of multiluminescence is surprisingly intense for all the CaZnOS:Mn2+ with a large-scale Mn2+ doping (0.1–10 mol %). Based on the investigation of crystal field, various spectral results, and PL lifetimes, the red-shift mechanism of multiluminescence reported here has been proposed to arise from the exchange interaction effect of Mn2+ pairs at higher concentrations. In addition to correcting the previous misunderstanding on the emission of CaZnOS:Mn2+, these findings extend the tunable emission window, opening up new opportunities ...

Transition-metal dichalcogenide (TMD) semiconductors have been widely studied due to their distinctive electronic and optical properties. The property of TMD flakes is a function of its thickness, or layer number (N). How to determine N of ultrathin TMDs materials is of primary importance for fundamental study and practical applications. Raman mode intensity from substrates has been used to identify N of intrinsic and defective multilayer graphenes up to N=100. However, such analysis is not applicable for ultrathin TMD flakes due to the lack of a unified complex refractive index ($\tilde{n}$) from monolayer to bulk TMDs. Here, we discuss the N identification of TMD flakes on the SiO$_2$/Si substrate by the intensity ratio between the Si peak from 100-nm (or 89-nm) SiO$_2$/Si substrates underneath TMD flakes and that from bare SiO$_2$/Si substrates. We assume the real part of $\tilde{n}$ of TMD flakes as that of monolayer TMD and treat the imaginary part of $\tilde{n}$ as a fitting parameter to fit the experimental intensity ratio. An empirical $\tilde{n}$, namely, $\tilde{n}_{eff}$, of ultrathin MoS$_{2}$, WS$_{2}$ and WSe$_{2}$ flakes from monolayer to multilayer is obtained for typical laser excitations (2.54 eV, 2.34 eV, or 2.09 eV). The fitted $\tilde{n}_{eff}$ of MoS$_{2}$ has been used to identify N of MoS$_{2}$ flakes deposited on 302-nm SiO$_2$/Si substrate, which agrees well with that determined from their shear and layer-breathing modes. This technique by measuring Raman intensity from the substrate can be extended to identify N of ultrathin 2D flakes with N-dependent $\tilde{n}$ . For the application purpose, the intensity ratio excited by specific laser excitations has been provided for MoS$_{2}$, WS$_{2}$ and WSe$_{2}$ flakes and multilayer graphene flakes deposited on Si substrates covered by 80-110 nm or 280-310 nm SiO$_2$ layer., Comment: 10 pages, 4 figures. Accepted by Nanotechnology

La-doped p-type ZnO nanofibers were successfully synthesized by electrospinning, followed by calcination. The microstructure and morphology of the La-doped ZnO nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The field effect curve of individual nanofibers confirms that the resulting La-doped ZnO fibers are p-type semiconductors. The doping mechanism is discussed. Furthermore, crossed p-n homojunction nanofibers were also prepared based on electrospun La-doped p-type ZnO and n-type pure ZnO fibers. The current-voltage curve shows the typical rectifying characteristic of a p-n homojunction device. The turn-on voltage appears at about 2.5 V under the forward bias and the reverse current is impassable.

Conducting polypyrrole (PPY) nanowires doped with p-toluene sulfonamide (PTSA) were synthesized by a template-free self-assembly method. Electrical transport characteristics, i.e. current-voltage (I-V) behavior, of an individual PPY/PTSA nanowire have been explored in a wide temperature range from 300 down to 40 K. The fitting results of I-V curves indicated that the electrical conduction mechanism can be explained by the space-charge-limited current (SCLC) theory from 300 down to 100 K. In this temperature range, traps play an important role for this non-crystalline system. The corresponding trap energy and trap concentration have also been calculated based on the SCLC theory. Interestingly, there is no trap at 160 K, different from other temperatures. The obtained carrier mobility for the polymer nanowires is 0.964 cm(2) V(-1) s(-1) on the basis of trap free SCLC theory. In the temperature range of 80-40 K, little current can flow through the nanowire especially at lower voltages, however, the current follows the equation I ∞ (V/Vt-1)(ζ) at higher bias, which could be attributed to Coulomb blockade effect. Additionally, the differential conductance dI/dV curves also show some clear Coulomb oscillations.

CdS is one of the important II-VI group semiconductors. In this paper, the electrical transport behavior of an individual CdS microrope composed of twisted nanowires is studied. It is found that the current–voltage (I-V) characteristics show two distinct power law regions from 360 down to 60 K. Space-charge-limited current (SCLC) theory is used to explain these temperature- and electric-field-dependent I-V curves. The I-V data can be well fitted by this theory above 100 K, and the corresponding carrier mobility, trap energy, and trap concentration are also obtained. However, the I-V data exhibit some features of the Coulomb blockade effect below 80 K.

Edges naturally exist in a single-layer graphene sample. Similarly, individual graphene layers in a multilayer graphene sample contribute their own edges. We study the Raman spectrum at the edge of a graphene layer laid on n layer graphene (nLG). We found that the D band observed from the edge of the top graphene layer exhibits an identical line shape to that of disordered (n+1)LG induced by ion-implantation. Based on the spectral features of the D and 2D bands, we identified two types of alignment configurations at the edges of mechanically-exfoliated bilayer and trilayer graphenes, whose edges are well-aligned from their optical images., 9 pages, 2 figures

A variety of up-and-coming applications of piezoluminescence in artificial skins, structural health diagnosis, and mechano-driven lightings and displays recently have triggered an intense research effort to design and develop new piezoluminescent materials. In this work, we deduced and verified an efficient piezoluminescence in ferroelectric Ca3Ti2O7:Pr3+ long-persistent phosphor, in view of three fundamental elements forming piezoluminescence – piezoelectricity, luminescent centers and carrier traps. Under the stimulation of mechanical actions including compression and friction, Ca3Ti2O7:Pr3+ shows an intense red emission from 1D2-3H4 transition of Pr3+. On the basis of investigations on structural and optical characteristics especially photoluminescence, persistent luminescence and thermoluminescence, we finally proposed a possible piezoluminescent mechanism in Ca3Ti2O7:Pr3+. Our research is expected to expand the horizon of existing piezoluminescent materials, accelerating the development and application of new materials.

The quantum confinement in atomic scale and the presence of interlayer coupling in multilayer make the electronic and optical properties of 2D materials (2DMs) be dependent on the layer number (N) from monolayer to multilayer. Optical properties of 2DMs have been widely probed by several optical techniques, such as optical contrast, Rayleigh scattering, Raman spectroscopy, optical absorption, photoluminescence, and second harmonic generation. Here, it is reviewed how optical properties of several typical 2DMs (e.g., monolayer and multilayer graphenes, transition metal dichalcogenides) probed by these optical techniques significantly depend on N. Further, it has been demonstrated how these optical techniques service as fast and nondestructive approaches for N counting or thickness determination of these typical 2DM flakes. The corresponding approaches can be extended to the whole 2DM family produced by micromechanical exfoliations, chemical-vapor-deposition growth, or transfer processes on various substrates, which bridges the gap between the characterization and international standardization for thickness determination of 2DM flakes.

The in-plane shear ($C$) modes between neighbor layers of 2-4 layer graphenes (2-4LGs) and the corresponding 2-4 layer graphene scrolls (2-4LGSs) rolled up by 2-4LGs at edges are investigated by Raman scattering. In contrast to the result that only one $C$ mode is observed in 3-4LGs, all the $C$ modes of 3-4LGs are observed in 3-4LGSs, whose frequencies agree with the theoretical prediction by the force-constant and linear chain models. The results indicate that the $C$ mode intensity of 2-4LGSs is resonantly enhanced by the electronic transition gaps of band structures of 2-4LGS structures at edges, which makes it possible to observe all the $C$ modes. Indeed, for a simple assumption, the calculated band structures of twisted ($n+n$)LGs ($n=2$,3,4) show parallel conduction and valence bands and the corresponding Van Hove singularities in the joint density of states along $\ensuremath{\Gamma}$-M, $\ensuremath{\Gamma}$-K and/or K-M directions. The intensity resonance of the $C$ modes provides direct evidence to explain how the band structure of few layer graphenes can be sensitive to local stacking configurations. This result can be extended to $n$ layer graphene ($ng4$) for understanding the basic phonon and electronic properties of multilayer graphenes. This observation of all the $C$ modes in graphene scrolls can be foreseen in other two-dimensional materials with similar scroll structures.

The ideal edges of bilayer graphene (BLG) are that the edges of the top and bottom graphene layers (GLs) of BLG are well-aligned. Actually, the alignment distance between the edges of the top and bottom GLs of a real BLG can be as large as the submicrometer scale or as small as zero, which cannot be distinguished using an optical microscope. Here, we present a detailed Raman study on BLG at its edges. If the alignment distance of the top and bottom GLs of BLG is larger than the laser spot, the measured D mode at the edge of the top GL of BLG shows a similar spectral profile to that of disordered BLG. If the alignment distance is smaller than the laser spot, the D mode at a real BLG edge shows three typical spectral profiles similar to that at the edge of SLG, that of the well-aligned edge of BLG, or a combination of both. We show the sensitivity and ability of Raman spectroscopy to acquire the alignment distance between two edges of top and bottom GLs of BLG as small as several nanometers, which is far beyond the diffraction limit of a laser spot. This work opens the possibility to probe the edge alignment of multi-layer graphene.

To study the preventive effects of jinghua weikang capsule (JWC) on nonsteroidal anti-inflammatory drugs (NSAIDs) induced injury to the mucosa of the small intestine.Thirty-two Wistar rats were randomly divided into four groups, i.e., the blank control group, the model group, the JWC group, and the esomeprazole group. Diclofenac was administered to rats in the model group, the JWC group, and the esomeprazole group at the daily dose of 15 mg/kg. JWC and esomeprazole was respectively given to those in the JWC group, and the esomeprazole group one day ahead. Normal saline was given to rats in the blank control group. Rats were killed 3 days later. The pathological changes of the small intestine were observed by hematoxylin and eosin stain.Compared with the blank control group, the general score for the small intestine (4.63 +/-0.52 vs 0.00 +/-0. 00) and the pathological score (4.00 +/-0.90 vs 0.00 +/-0. 00) obviously increased in the model group, showing statistical difference (P0.05). Compared with the model group, the general score for the small intestine (1.88 +/-0.99) and the pathological score (2.11 +/-1.11) obviously decreased in the JWG group, showing statistical difference (P0.05). Compared with the model group, the general score for the small intestine (2.75 +/-1.28) and the pathological score (2. 30 +/-0.94) obviously decreased in the esomeprazole group, showing statistical difference (P0.05).JWC could prevent NSAIDs induced injury to the mucosa of the small intestine.

We report the synthesis and characterization of a bulk diluted magnetic semiconductor (La${}_{1\ensuremath{-}x}$Ba${}_{x}$)(Zn${}_{1\ensuremath{-}x}$Mn${}_{x}$)AsO (0 $\ensuremath{\leqslant}$ $x$ $\ensuremath{\leqslant}$ 0.2) with a layered crystal structure identical to that of the 1111-type FeAs superconductors. No ferromagnetic order occurs with (Zn,Mn) substitution in the parent compound LaZnAsO without charge doping. Together with carrier doping via (La,Ba) substitution, a small amount of Mn substituting for Zn results in ferromagnetic order with ${T}_{C}$ up to $\ensuremath{\sim}$40 K, although the system remains semiconducting. Muon spin relaxation measurements confirm the development of ferromagnetic order in the entire volume, with the relationship between the internal field and ${T}_{C}$ consistent with the trend found in (Ga,Mn)As and the 111-type Li(Zn,Mn)As and the 122-type (Ba,K)(Zn,Mn)${}_{2}$As${}_{2}$ systems.

Growth of epitaxial graphene on the C-face of SiC has been investigated. Using a confinement controlled sublimation (CCS) method, we have achieved well controlled growth and been able to observe propagation of uniform monolayer graphene. Surface patterns uncover two important aspects of the growth, i.e. carbon diffusion and stoichiometric requirement. Moreover, a new "stepdown" growth mode has been discovered. Via this mode, monolayer graphene domains can have an area of hundreds of square micrometers, while, most importantly, step bunching is avoided and the initial uniformly stepped SiC surface is preserved. The stepdown growth provides a possible route towards uniform epitaxial graphene in wafer size without compromising the initial flat surface morphology of SiC., 18 pages, 8 figures

We report polarization resolved photoluminescence from monolayer MoS2, a two-dimensional, non-centrosymmetric crystal with direct energy gaps at two different valleys in momentum space. The inherent chiral optical selectivity allows exciting one of these valleys and close to 90% polarized emission at 4K is observed with 40% polarization remaining at 300K. The high polarization degree of the emission remains unchanged in transverse magnetic fields up to 9T indicating robust, selective valley excitation., Comment: 5 pages, 3 figures

Because of novel features in their structural, electronic, magnetic and optical properties, especially potential applications in nanoelectronics, the few-layer graphene intercalation compounds (FLGICs) have been intensively studied recently. In this work, the dielectric constant of the doped graphene of stage-1 FeCl3-GIC is obtained by fitting the optical contrast spectra. And fully intercalated stage-1 FeCl3-FLGICs were prepared by micromechanical cleavage method from graphite intercalation compounds (GICs) for the first time. Finally, we demonstrated that the thickness of stage-1 FeCl3-GICs by micromechanical cleavage can be determined by optical contrast spectra. This method also can be used to other FLGICs, such as SbCl5-FLGICs and AuCl5-FLGICs, etc.

A two-dimensional honeycomb lattice harbours a pair of inequivalent valleys in the k-space electronic structure, in the vicinities of the vertices of a hexagonal Brillouin zone, K±. It is particularly appealing to exploit this emergent degree of freedom of charge carriers, in what is termed 'valleytronics'. The physics of valleys mimics that of spin, and will make possible devices, analogous to spintronics, such as valley filter and valve, and optoelectronic Hall devices, all very promising for next-generation electronics. The key challenge lies with achieving valley polarization, of which a convincing demonstration in a two-dimensional honeycomb structure remains evasive. Here we show, using first principles calculations, that monolayer molybdenum disulphide is an ideal material for valleytronics, for which valley polarization is achievable via valley-selective circular dichroism arising from its unique symmetry. We also provide experimental evidence by measuring the circularly polarized photoluminescence on monolayer molybdenum disulphide, which shows up to 50% polarization., The monolayer transition-metal dichalcogenide molybdenum disulphide has recently attracted attention owing to its distinctive electronic properties. Cao and co-workers present numerical evidence suggesting that circularly polarized light can preferentially excite a single valley in the band structure of this system.

Barium titanate (BTO) nanofibers were synthesized by electrospinning and followed calcination. The morphologies and microstructures of the nanofibers were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Calcinating temperature and process greatly influenced the surface morphology of the nanofibers. In addition, parallel BTO nanofibers were also successfully produced by a centrifugal electrospinning technique. And the humidity sensing properties of the nanofibers were measured. The results showed an ultrafast response time (~0.5 s) and a recovery time (~0.4 s) to humidity at room temperature, which revealed excellent humidity sensitivity performance.