Oxygen Vacancy-Enhanced Centrosymmetric Breaking of SrFeO3- x for Piezoelectric-Catalyzed Synthesis of H2O2.

Normally, only noncentrosymmetric structure of the materials can potentially be piezoelectric. Thus, it is limited in the field of piezoelectricity for the centrosymmetric structure of the material. In this work, the performance of piezoelectricity is successfully achieved from centrosymmetric SrFeO3- x by modulating oxygen vacancies, which have a surface piezoelectric potential up to 93 mV by using Kelvin-probe force microscopy (KPFM). Moreover, the piezoelectric effects of SrFeO3- x are also evaluated by piezoelectric catalytic effect and density functional theory calculations (DFT). The results show that the piezo-catalytic degradation of tetracycline reaches 96% after 75 min by ultrasonic mechanical vibration and the production of H2O2 by SrFeO3- x piezoelectric synthesis could reach 1821 µmol L-1. In addition, the DFT results indicate that the intrinsic effect of oxygen vacancies effectively promotes the adsorption and activation of O2 and H2O as well as intermediates and improves the piezoelectric catalytic activity. This work provides an effective basis for realizing the piezoelectricity of centrosymmetric materials and regulating the development of piezoelectric catalytic properties.

Enhanced Visible-Photocatalytic Activities in Strong Acids and Strong Alkalis of Flexible Iron-SrTiO3 Nanofibrous Membranes.

Traditional SrTiO3 (STO) materials have high brittleness and poor deformation resistance. In this work, macroscopically flexible iron-doped SrTiO3 (SFTO) nanofibrous membranes were prepared by electrospinning and calcination, which can be easily isolated and can maintain integrity to recycle as photocatalysts. Moreover, the SFTO nanofibrous membranes showed enhanced photocatalytic performance under strong acids (pH = 2) and strong alkalis (pH = 12). The SFTO nanofibrous membranes increased the catalytic rate of Congo red (CR) dye by about 10 times in visible light. The mechanism of photocatalytic activity enhancement was discussed by the combined effects of hydroxyl radicals and superoxide radicals. The successful preparation of SFTO nanofibrous membranes has offered a simple and economical approach to photocatalysis as well as environmental remediation.

Transparent Polyurethane Nanofiber Air Filter for High-Efficiency PM2.5 Capture.

Fine particulate matter (PM) has seriously affected human life, such as affecting human health, climate, and ecological environment. Recently, many researchers use electrospinning to prepare nanofiber air filters for effective removal of fine particle matter. However, electrospinning of the polymer fibers onto the window screen uniformly is only achieved in the laboratory, and the realization of industrialization is still very challenging. Here, we report an electrospinning method using a rotating bead spinneret for large-scale electrospinning of thermoplastic polyurethane (TPU) onto conductive mesh with high productivity of 1000 m2/day. By changing the concentration of TPU in the polymer solution, PM2.5 removal efficiency of nanofiber-based air filter can be up to 99.654% with good optical transparency of 60%, and the contact angle and the ventilation rate of the nanofiber-based air filter is 128.5° and 3480 mm/s, respectively. After 10 times of filtration, the removal efficiency is only reduced by 1.6%. This transparent air filter based on TPU nanofibers has excellent filtration efficiency and ventilation rate, which can effectively ensure indoor air quality of the residential buildings.

Piezoluminescence from ferroelectric Ca3Ti2O7:Pr3+ long-persistent phosphor.

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.

Multicolor Tuning in Room-Temperature Self-Activated Ca2 Nb2 O7 Submicroplates by Lanthanide Doping.

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 Ca2 Nb2 O7 was accordingly achieved in submicroplates synthesized using the sol-gel method. By further coupling the blue broadband emission from Ca2 Nb2 O7 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.

Electrospun Aligned Fibrous Arrays and Twisted Ropes: Fabrication, Mechanical and Electrical Properties, and Application in Strain Sensors.

Electrospinning (e-spinning) is a versatile technique to fabricate ultrathin fibers from a rich variety of functional materials. In this paper, a modified e-spinning setup with two-frame collector is proposed for the fabrication of highly aligned arrays of polystyrene (PS) and polyvinylidene fluoride (PVDF) nanofibers, as well as PVDF/carbon nanotube (PVDF/CNT) composite fibers. Especially, it is capable of producing fibrous arrays with excellent orientation over a large area (more than 14 cm × 12 cm). The as-spun fibers are suspended and can be easily transferred to other rigid or flexible substrates. Based on the aligned fibrous arrays, twisted long ropes are also prepared. Compared with the aligned arrays, twisted PVDF/CNT fiber ropes show enhanced mechanical and electrical properties and have potential application in microscale strain sensors.

A battery-operated portable handheld electrospinning apparatus.

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.

Electrical transport properties of an isolated CdS microrope composed of twisted nanowires.

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.

Self-powered electrospinning apparatus based on a hand-operated Wimshurst generator.

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.

Electrical conduction mechanism of an individual polypyrrole nanowire at low temperatures.

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.

Primary cerebellar paraganglioma: a pediatric case report and review of the literature.

BACKGROUND: Only four cases of primary intracerebellar paragangliomas have been reported in the literature to date. Because of its rarity, primary intracerebellar paraganglioma still presents a diagnostic challenge for both radiologists and neurosurgeons, and the optimal therapeutic modality is still debatable for its hypervascularity and location. PATIENTS: We report a 16-year-old boy with pathology-proven primary intracerebellar paraganglioma who presented with dull headache, dizziness, and gait disturbance, and underwent gross total resection. Further, we review all reported cases of primary intracerebellar paraganglioma in the English literature and discuss its clinical profile, neuroradiological features, and treatment modalities. RESULTS: His symptoms improved following tumor removal without radiotherapy, and postoperative neuroimaging thirteenth months after surgery showed no recurrence. In the literature, all four patients were stable in the follow-up period including three with complete resection and one with partial resection plus adjuvant radiotherapy. CONCLUSION: Surgical resection is the treatment modality most often used for primary intracerebellar paraganglioma; radiation therapy may be used when there is residual tumor or recurrence. Angiography may help to clarify the vessel architecture for reducing intraoperative bleeding when primary intracerebellar paraganglioma is considered.

Fabrication of curled conducting polymer microfibrous arrays via a novel electrospinning method for stretchable strain sensors.

Stretchable strain sensors based on aligned microfibrous arrays of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)-poly(vinyl pyrrolidone) (PEDOT:PSS-PVP) with curled architectures have been fabricated by a novel reciprocating-type electrospinning setup with a spinneret in straightforward simple harmonic motion. The incorporation of PEDOT:PSS into PVP is confirmed by Raman spectra, which improves the room-temperature conductivity of the composite fibers (1.6 × 10(-5) S cm(-1)). Owing to the curled architectures of the as-spun fibrous polymer arrays, the sensors can be stretched reversibly with a linear elastic response to strain up to 4%, which is three times higher than that from electrospun nonwoven mats. In addition, the stretchable strain sensor with a high repeatability and durability has a gauge factor of about 360. These results may be helpful for the fabrication of stretchable devices which have potential applications in some fields such as soft robotics, elastic semiconductors, and elastic solar cells.

Pediatric isolated oculomotor nerve schwannoma: a new case report and literature review.

Isolated schwannoma arising from the oculomotor nerve occurs rarely, and only 12 children with oculomotor nerve schwannoma without neurofibromatosis have been sufficiently documented. This article presents a 3-year-old boy in which a large isolated parasellar oculomotor nerve schwannoma causing parent nerve dysfunction. Complete resection of the tumor was achieved via a right pterion approach, but he developed complete palsy of the third nerve postoperatively, which had an incomplete recovery in 12-month follow-up. We review the pertinent literature about pediatric oculomotor nerve schwannoma and discuss its clinical features and management.

Self-assembly of a three-dimensional fibrous polymer sponge by electrospinning.

In this paper, we report a quick approach to self-assemble three-dimensional (3D) spongiform nanofiber stacks via electrospinning, which usually fabricates 2D non-woven fiber mats. Through controlling experimental conditions, cone-like polystyrene fiber stacks can be self-assembled on aluminum foil within 30 min. The stacks are able to reach a height of more than 10 cm. Moreover, conversion between the 3D fiber stack and 2D thin film can be controlled. The formation mechanism of the self-assembled fiber stacks and the influence of experimental conditions have also been explored. The 3D fiber stacks may be promising for applications in many fields such as tissue engineering, electrodes of battery, and filtration, etc.

Corpus callosum: a favorable target for rSFV-mediated gene transfer to rat brain with broad and efficient expression.

Recombinant Semliki Forest virus (rSFV), as a new kind of neurotropic vector system, has great potential of gene therapy for stroke. However, very little is known about its transduction characteristics in cerebral cortex or corpus callosum (CC) in vivo, which are common targets for gene transfer in experimental stroke therapy. Here, we investigate and compare rSFV-mediated gene expression at above two brain regions in rat; 2.0 x 10(7) IU of rSFV encoding green fluorescent protein (rSFV-GFP) was locally injected into CC or cerebral cortex in two groups. At 36 h following injection, the number of GFP-positive cells, GFP distribution volume, and GFP expression level were examined in the rat brain of each group using continuous frozen sections and enzyme-linked immunosorbent assay. rSFV vector displayed noticeably different transduction patterns in CC and cerebral cortex in vivo. CC injection of vector increased GFP-positive cell number by 802%, GFP transduction volume by 958%, and GFP expression level by 508% compared with cortical injection (all P < 0.01). We concluded that rSFV CC delivery significantly enhances transduction efficiency in rat brain with its ability to achieve transgene extensive transduction and abundant expression, and CC may be a favorable target for improving rSFV-based gene delivery efficiency to brain.