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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 (

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.

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.

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.

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 ...

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.

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.

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.

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 ...

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.

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.