Significant improvement of photocatalytic activity of porous graphitic-carbon nitride/bismuth oxybromide microspheres synthesized in an ionic liquid by microwave-assisted processing

Graphitic-carbon nitride/bismuth oxybromide (g-C₃N₄/BiOBr) porous microspheres have been successfully synthesized by a one-pot ethylene glycol (EG) assisted microwave process in the presence of 1-hexadecyl-3-methylimidazolium bromine ([C₁₆mim]Br). The as-prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and UV–vis diffuse reflectance spectroscopy (DRS). During the reaction process, the ionic liquid acts not only as solvent and Br source but also as a template for fabrication of g-C₃N₄/BiOBr porous microspheres. In addition, the photocatalytic activity of the g-C₃N₄/BiOBr is evaluated by degrading Rhodamine B (RhB) and ciprofloxacin (CIP) under visible-light irradiation. It is found that 12.75 wt% g-C₃N₄/BiOBr microspheres exhibit higher photocatalytic activity than that of the as-prepared BiOBr. A possible photocatalytic mechanism based on the relative band positions of g-C₃N₄/BiOBr has been proposed.     

Facile sonochemical synthesis of BiOBr-graphene oxide nanocomposite with enhanced photocatalytic activity for the degradation of Direct green

The BiOBr-graphene oxide (BiOBr-GO) nanocomposite was successfully synthesized by sonochemical method. The as-synthesized nanocomposite was characterized by Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The effect of incorporation of graphene-oxide with BiOBr on photocatalytic performance of BiOBr under exposure of UV–Visible light irradiation was systematically investigated. The percent removal of Direct green by BiOBr-GO at pH 7 was found to be 91.9% while by pure BiOBr it was 37%. This exhibits that BiOBr-GO shows enhanced adsorption and photocatalytic performance for removal of Direct green under UV–Visible light irradiation. Mechanism of Direct green degradation can be explained by AOP involving heterogeneous photocatalysis. The probable mechanism of photocatalytic degradation and mineralization of Direct green also explained by LC–MS analysis. The mineralization efficiency indicates the 91.7% TOC removal for the degradation of Direct green by BiOBr-GO.     

Rational Design of Porous Nanofiber Adsorbent by Blow‐Spinning with Ultrahigh Uranium Recovery Capacity from Seawater

Highly efficient recovery of uranium from seawater is of great concern because of the growing demand for nuclear energy. The use of amidoxime‐based polymeric fiber adsorbents is considered to be a promising approach because of their relatively high specificity and affinity to uranyl. The surface area, hydrophility, and surface charge of the adsorbent are reported to be critical factors that influence uranium recovery efficiency. Here, a porous amidoxime‐based nanofiber adsorbent (SMON–PAO) that exhibits the highest uranium recovery capacity among the existing fiber adsorbents both in 8 ppm uranium spiked seawater (1089.36 ± 64.31 mg‐U per g‐Ads) and in natural seawater (9.59 ± 0.64 mg‐U per g‐Ads) is prepared by blow spinning. These nanofibers are obtained by compositing polyacrylamidoxime with montmorillonite and exhibit the increased surface area and more exposed functional amidoxime moieties for uranyl adsorption. The residual montmorillonite enhances the hydrophility and reduces the negative surface charge, thereby increasing the contact of the adsorbent with seawater and reducing the charge repulsion between negative amidoxime group and negative uranyl species ([UO₂(CO₃)₃]^4?). The finding of this study indicates that rational design of uranium recovery adsorbents by comprehensive utilizing the key factors that influence uranium recovery performance is a promising approach for developing economically feasible uranium recovery materials.     

Over 1000 km FSK heterodyne transmission system experiment usingerbium-doped optical fiber amplifiers and conventional single-modefibers

The influence of spontaneous emission noise on coherent transmission systems using multistage erbium-doped optical fiber amplifiers is experimentally examined. A frequency-shift keying (FSK) heterodyne transmission experiment was successfully performed at 560 Mb/s through 1028 km of fiber using ten cascaded fiber amplifiers and conventional single-mode fibers with a zero dispersion wavelength of around 1.3 μm. In the experiment, no transmission penalty due to accumulated spontaneous emission noise or to fiber chromatic dispersion was observed     

多探头光纤倏逝波生物传感器及其性能研究

利用光纤倏逝波原理,以输出波长为635 nm的半导体激光器为光源,研制成功一台具有5个探头的光纤生物传感器.该传感器5个光纤探头对纯净Cy5荧光染料溶液的检测灵敏度均达0.01 nmol/L,在同一浓度下信噪比的相对标准偏差小于10%,5个探头的信噪比曲线几乎重合,且与商品化生物芯片扫描仪同时检测得到的结果一致;检测到了抗原抗体特异性反应的动态过程.本传感器具有较高的检测灵敏度、良好的响应一致性和生物特异性,可用于多重生物物质的检测.     

Transversal Load Sensing With Fiber Bragg Gratings in Microstructured Optical Fibers

We present fiber Bragg grating based transversal load sensing with a highly birefringent microstructured optical fiber. For the bare fiber, the change of the Bragg peak separation under a transverse line load was simulated with a finite-element model and experimentally verified. We also show that microstructured optical fibers with fiber Bragg gratings can be successfully embedded in a carbon fiber reinforced composite material. The linear dependence of the Bragg peak separation to a transversal stress in the composite sample was measured to be 15.3 pm/MPa.      

Long-span single-mode fiber transmission characteristics in long wavelength regions

Experimental and analytical results on high-speed optical pulse transmission characteristics for long-span single-mode fibers by using InGaAsP lasers, emitting at 1.1, 1.3, and 1.5 μm, as well as a Ge-APD are reported. At 1.1 μm, 400 Mbit/s transmission experiments were successfully carried out with 20 km repeater spacing. At 1.3 μm, where single-mode fiber dispersions approach zero, error rate characteristics showed that optical power penalties at 100 Mbits/s and 1.2 Gbits/s are negligible even after 30 and 23 km fiber transmission, respectively. It was confirmed that a 1.6 Gbit/s transmission system has 15 km repeater spacing. At 1.5 μm, where silica fibers have ultimately minimum loss, single-mode fiber transmission experiments were carried out at 100 Mbits/s with about 30 km repeater spacing. 400 Mbit/s transmission characteristics using 20 km fibers were also studied. Fiber bandwidths, measured by optical pulse broadenings after 20 km transmission, were 24, 140, and 37 GHz . km . nm at 1.1, 1.3, and 1.5 μm, respectively. Progress in lasers, fibers, and optical delay equalizers at 1.5μm will bring about large-capacity transmission systems having about 150 km repeater spacing. These results reveal fiber dispersion characteristics in the long wavelength region essential to high data rate single-mode fiber transmission system design.     

Growth and photoreactive properties of a- and c-axis cerium-doped strontium barium niobate single-crystal fibers

The authors report on the photorefractive properties of cerium-doped strontium barium niobate (Ce:SBN60) single-crystal fibers grown by the laser-heated pedestal growth method. Single-crystal fibers, 250 mu m in diameter, were successfully grown along both the a- and c-axes. The diffraction efficiency and grating formation time results for each fiber in two beam coupling experiments are compared, with emphasis on their crystal orientation and relevant figure of merit. It is found that the hologram efficiency of the a-axis fiber is larger than that of the c-axis fiber and that its grating formation time is faster. The results suggest that Ce-doped SBN single-crystal fiber grown along the a-axis is a promising candidates for holographic storage, parallel data processing, and phase-conjugation mirrors.<>     

Novel multi-heterostructured Pt-BiOBr/TiO2 nanotube arrays with remarkable visible-light photocatalytic performance and stability

Unique multiple heterojunction of Pt-BiOBr/TiO2 nanotube arrays (Pt-BiOBr/TNTAs) was achived by successively loading both Pt nanoparticles (NPs) and BiOBr nanoflkes (NFs) on surface of ordered and spaced TiO2 nanotubes (NTs) using anodization followed by solvothermal and sequential chemical bath deposition (S-CBD) method. The fabricated Pt-BiOBr/TNTAs were fully characterized, and the photocatalytic (PC) activity and stability of Pt-BiOBr/TNTAs toward degradation of methyl orange (MO) under visible-light irradiation (λ>400 nm) were evaluated. The results reveal that multiple heterostructures of Pt/TiO2, Pt/BiOBr and BiOBr/TiO2 are constructed among TNTAs substrate, Pt NPs and BiOBr NFs, and the hybrid Pt-BiOBr/TNTAs catalyst exhibits remarkable visible-light PC activity, favourable reusability and long-term stability. The combined effect of several factors may contribute to the remarkable PC performance, including strong visible-light absorption by both Pt NPs and BiOBr NFs, lower recombination rate of photo-generated electrons and holes attributed to the multiple heterojunction, microstructures for facile light injection and adsorption as well as efficient mass transport, and larger specific surface area for enhancing light absorption, increasing the effective contact area between the absorbed dye molecules and catalyst and benefiting the molecule transport of reactants or products. This work has been supported by the National Natural Science Foundation of China (Nos.51402078 and 51302060), Anhui Provincial Natural Science Foundation (No.1408085QE85), and the Young Scholar Enhancement Foundation (Plan B) of Hefei University of Technology in China (No.JZ2016HGTB0711). E-mail:jqliu@hfut.edu.cn      

Infrared optical fibers with vapor-deposited cladding layer

Core-cladding structures constructed for KRS-5 polycrystalline and As₂S₃ glass infrared fibers by means of vapor deposition are discussed. In order to obtain high-numerical-aperture fibers, KRS-6 and AsS₃, respectively, have been used as cladding materials. A CO₂ laser beam of 15-20 W has been successfully transmitted through the KRS-5 fiber. For the As₂S₃ fiber an absorption loss due to Teflon coating has been reduced, and a loss of 0.13 dB/m has been achieved     

光纤光栅与法珀微腔温度应变双参量传感器

针对光纤应变传感器的温度-应变交叉敏感性问题,研究了一种结合光纤布拉格光栅(FBG)与法布里-珀罗(FP)微腔的光纤FBG-FP混合型温度应变双参量传感器.该传感器由两根垂直切割的单模光纤穿入一段石英毛细管(Glass capillary),并在石英毛细管两端固定制成,其中一根光纤端面附近预刻FBG,两根光纤端面间距为...     

Measurements for enhanced bandwidth performance over 62.5-/spl mu/m multimode fiber in short-wavelength local area networks

The Telecommunications Industry Association (TIA) FO-2.2.1 Working Group on the modal dependence of bandwidth has conducted industrywide interlaboratory comparisons on measurements aimed at improving the bandwidth performance of short-wavelength, laser-based, multimode-fiber local area networks (LANs). Measurements of both transceiver encircled flux and fiber restricted-mode-launch bandwidth can together successfully predict an enhanced system performance, provided that the proper limiting criteria are selected. System performance is determined by a measurement of effective bandwidth and/or intersymbol interference. Recommendations for source and fiber selection criteria come from a risk analysis based on an extensive multilaboratory comparison involving 95 fibers and 69 laser transceivers. For this paper, enhanced system performance is defined as a performance that allows operation at a data rate of at least one gigabit per second over a 500-m length of 62.5/125-/spl mu/m graded-index glass fiber.     

含光纤编织复合材料试件的制作与实验研究

编织结构复合材料克服了层合结构复合材料层间强度低,损伤容限低等缺点,光纤传感器由于与复合材料有良好的相容性等优点,已广泛应用于层合结构复合材料,文章通过实验研究了光纤偏入编织复合材料试件的工艺以及含光纤试件的成型工艺。将光纤成功地编入三维编织复合材料试件并通过树脂传递模塑（RTM）工艺成型。并对编入试件的光纤在试件受弯时的传感性能进行了研究,     

Fabrication of multiple parallel suspended-core optical fibers by sheet-stacking

We demonstrate the fabrication of a novel type of optical fibers with multiple parallel air-suspended cores by the sheet-stacking method. Using this technique we have constructed optical fibers with up to 10 parallel micron-size suspended cores. No extra scattering loss from the fabrication process was observed in a fabricated dual air-suspended core fiber. The sheet-stacking method opens the way towards using a wide range of optical glasses for manufacturing multiple parallel suspended-core specialty optical fibers with novel optical functionalities such as dispersion tunability. Fusion splicing has also been successfully used to connect such a multiple core fiber with a conventional silica fiber.     

Visible light photocatalytic performance of hierarchical BiOBr microspheres synthesized via a reactable ionic liquid

Hierarchical BiOBr microspheres were synthesized via a one-pot solvothermal process in the presence of ethylene glycol and 1-butyl-3-methylimidazolium bromide ([BMIM]Br) as a reactable ionic liquid. The products were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance absorption spectra, nitrogen adsorption–desorption measurements, and photoluminescence spectroscopy. The photocatalytic activity of BiOBr microspheres was evaluated in terms of the degradation of Rhodamine B (RhB), methyl orange (MO), and 4-chlorophenol (4-CP) under visible light irradiation. We found that the solvothermal temperature had important effects on the crystallinity, crystallite size, optical property, adsorptive performance, and photocatalytic activity of BiOBr microspheres. BiOBr microspheres with a specific surface area of 15.7 m² g⁻¹ prepared at 160 °C exhibited the best adsorption and photocatalytic performance for RhB degradation in aqueous solution. However, this sample showed hardly any activity for photodegradation of 4-CP. Tests using radical scavengers confirmed that h⁺ and O₂⁻ were the main reactive species during RhB degradation. A possible mechanism for photocatalysis by BiOBr microspheres is proposed.     

Nonlinear Sagnac interferometer switch and its applications

Ultrafast all-optical switching based on the optical Kerr effect in a Sagnac interferometer which consists of a dichroic polarization-maintaining fiber coupler and dispersion-shifted polarization-maintaining fiber loop is reported. This nonlinear Sagnac interferometer switch has the advantage of high stability originating from completely balanced interfering arms. In addition, because dispersion-shifted fibers were used, increases in switching power and switching time were prevented. Moreover, polarization fluctuation was completely suppressed due to the all-polarization maintaining fiber configuration. The required switching power for complete switching was measured to be 1.8 W for a 200-m-long fiber. All-optical time division demultiplexing and logic operations, including inversion and operation, using the nonlinear Sagnac interferometer switch were successfully demonstrated at 5 Gb/s     

Subwavelength Dielectric-Fiber-Based THz Coupler

We demonstrate a terahertz (THz) directional coupler for future THz applications including THz power dividers, THz communications, and THz fiber-endoscopes. By using subwavelength polyethylene fibers, we successfully established a single-mode fiber-based THz directional coupler. Unlike traditional directional couplers, the demonstrated subwavelength directional fiber coupler shows less dependency on the overlapped length of two fibers and the delivered THz frequency in our interested minimal-attenuation wavelength regime. By tuning the geometry, we also show the feasibility to control the coupling ratio.      

新型多芯光纤的模场特性分析

为了实现高功率、高亮度的光纤激光输出,研究了新型多芯光纤组束技术,基于大模场倏逝波,采用时域有限差分数值模拟方法,对多芯光纤(包含多根微纳纤芯或包含多根微纳芯和大芯径纤芯)的模场特性进行了数值仿真和理论分析。结果表明,以一定方式排列的微纳光纤束阵列中多根微纳纤芯可以很好耦合;当多根微纳芯和大芯径纤芯组束时,微纳纤芯能够有效地平坦模场。这一结果对于高功率光纤激光器和放大器的进一步发展很有帮助。     

Tm-doped mode-locked fiber lasers

Ultrashort pulse fiber lasers are increasingly used in various areas for scientific as well as industrial purposes. In contrast to ultrashort pulse lasers based on ytterbium- and erbium-doped fibers, the dispersion of silica fibers in the amplification band of thulium-doped fibers around 2 μm is typically anomalous, which has fundamental impact on the pulse propagation. In this paper, mode-locked thulium-doped fiber lasers operating in different pulse propagation schemes are presented. The transfer of various concepts into the 2 μm wavelength range, which have been successfully applied for pulse parameter scaling in the 1 and 1.5 μm spectral region, are discussed on the basis of experimental and numerical results.