Thiophene π‐bridge effect on photovoltaic performances of dithienosilole and bithiazole backboned polymers

In this article, two dithienosilole (DTS) and bithiazole (BTz) backboned donor–acceptor (D‐A) copolymers with (poly{5‐(5‐(4,4‐bis(2‐ethylhexyl)‐4H‐silolo[3,2‐b:4,5‐b']dithiophen‐2‐yl)thiophen‐2‐yl)‐4,4'‐dinonyl‐5'‐(thiophen‐2‐yl)‐2,2'‐bithiazole} (PDTS‐DTBTz)) and without (poly{5‐(4,4‐bis(2‐ethylhexyl)‐4H‐silolo[3,2‐b:4,5‐b']dithiophen‐2‐yl)‐4,4'‐dinonyl‐2,2'‐bithiazole} (PDTS‐BTz)) thiophene π‐bridge were synthesized to study the influence of thiophene π‐bridge on their photovoltaic performances. Both polymers show similar band gap, but polymer with thiophene π‐bridge (PDTS‐DTBTz) has a higher molecular weight, narrower polydispersity index (PDI), more planar geometry, higher crystallinity, higher hole mobility, and better miscibility with fullerene (polymer solar cells (PSCs) acceptor). Although PDTS‐BTz polymer based PSCs devices show higher open circuit voltage (V_oc), PDTS‐DTBTz polymer does show higher power conversion efficiency (PCE) with improved short circuit current density (J_sc) and fill factor (FF). The present results indicate that thiophene π‐bridge does contribute to the PSCs performances of dithienosilole and bithiazole backboned copolymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42798.     

Ag Nanoparticles‐Enhanced Photoluminescence in LaPO4: Eu Three‐Dimensional Ordered Macroporous Films

The three‐dimensional ordered macroporous (3DOM) LaPO₄:Eu³⁺ films and Ag nanoparticles (NPs) were prepared via a template‐assisted process and sodium citrate reduction method, respectively. Composite systems consisting of 3DOM LaPO₄:Eu³⁺ films and Ag NPs were obtained by adding the Ag NPs into voids of 3DOM LaPO₄:Eu³⁺ films. The influence of Ag NPs on photoluminescence of 3DOM LaPO₄:Eu³⁺ was investigated. The results show that photoluminescence properties of 3DOM LaPO₄:Eu³⁺ films were enhanced after addition of Ag NPs, which was attributed to the local surface plasmons resonance effect of Ag NPs.     

Co‐electrospun nanofibers of PVA‐SbQ and Zein for wound healing

In this study, electrospun biocompatible nanofibers with random orientation were prepared by physically blending poly(vinyl alcohol)‐stilbazol quaternized (PVA‐SbQ) with zein in acetic acid solution for wound healing. PVA‐SbQ was used as the foundation polymer as well as crosslinking agent, blended with zein to achieve desirable properties such as improved tensile strength, surface wettability, and in vitro degradable properties. Moreover, vaccarin drug was incorporated in situ into electrospun nanofibrous membranes for cell viability and cell attachment. The addition of vaccarin showed great effects on the morphology of nanofiber and enhanced cell viability and proliferation in comparison with composite nanofibers without drug. The presence of PVA‐SbQ, zein, and vaccarin drug in the nanofibrous membranes exhibited good compatibility, hydrophilicity, and biocompatibility and created a moist environment to have potential application for wound healing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42565.     

咪唑型离子液体热物理性质测量

利用自行搭建的热线法液体热导率和热扩散系数装置测试了两种咪唑型离子液体([C₆mIm][BF₄]和[C₄mIm][BF₄])在不同温度下的热导率和热扩散系数。根据文献报道的密度数据获得了样品的比热容。结果表明:两种离子液体的热导率与温度的相关性不大;两种阳离子结构相似的离子液体热扩散率相近, 热扩散率随温度的升高有明显的变化, 本文认为离子液体内部的离子动量分布与温度紧密相关, 离子间的动量交换随温度的升高而增加, 离子动量分布随温度升高逐渐趋于一致, 离子间碰撞产生的动量交换不再明显改变离子的动量, 导致热扩散率的变化随温度升高而减小。     

Preparation,luminescence properties and energy transfer of Ca9Y(PO4)7: Eu2+‐Tb3+ phosphors

Tb³⁺‐doped and Eu²⁺, Tb³⁺ co‐doped Ca₉Y(PO₄)₇ phosphors were synthesized by conventional solid‐state method. Additionally, the luminescence properties, decay behavior and energy transfer mechanism have already been investigated in detail. The green emission intensity of Tb³⁺ ions under NUV excitation is weak due to its spin‐forbidden f‐f transition. While Eu²⁺ can efficiently absorb NUV light and yield broad blue emission, most of which can be absorbed by Tb³⁺ ions. Thus, the emission color can be easily tuned from cyan to green through the energy transfer of Eu²⁺→Tb³⁺ in Ca₉Y(PO₄)₇:Eu²⁺,Tb³⁺ phosphor. In this work, the phenomenon of cross‐relaxation between ⁵D₃ and ⁵D₄ are also mentioned. The energy transfer is confirmed to be resulted from a quadrupole‐quadrupole mechanism.     

Splitting upconversion emission and phonon‐assisted population inversion of Ba2Y(BO3)2Cl:Yb3+, Er3+ phosphor

Upconversion (UC) peak of ⁴S_3/2→⁴I_15/2 transition of Er³⁺ is close to that of ²H_11/2→⁴I_15/2 transition. The UC emission splitting of Er³⁺ caused by coordination fields of host results in that it is difficult to confirm which transitions (⁴S_3/2→⁴I_15/2 or ²H_11/2→⁴I_15/2) are responsible for the splitting UC emission peaks. In this work, the UC luminescence peaks located at 524, 540, 551, 565, 662, 677, and 683 nm were observed in the Ba₂Y(BO₃)₂Cl:Yb³⁺, Er³⁺ phosphor upon the 980 nm excitation. The 524 and 540 nm UC emissions intensity were increased, while the 551 and 565 nm UC emissions intensity were decreased with the temperature increasing from 323 to 573 K, which is attributed to the phonon‐assisted population inversion from the ⁴S_3/2 to ²H_11/2 level. The temperature dependence of UC emission spectra demonstrated that the 524 and 540 nm UC emissions are from ²H_11/2→⁴I_15/2 transition, and 551 and 565 nm UC emissions are from the ⁴S_3/2→⁴I_15/2 transition. Temperature sensing property was characterized by the UC intensity ratio of the ²H_11/2→⁴I_15/2 transition to ⁴S_3/2→⁴I_15/2 transition. The Ba₂Y(BO₃)₂Cl:Yb³⁺,Er³⁺ phosphor has potential application as the non‐contact temperature sensor.     

Au nanoparticles embedded inverse opal photonic crystals as substrates for upconversion emission enhancement

Photonic crystals (PCs) with periodic dielectric structures are capable to control the propagation of photons when photon energy is in the region of photonic band gap. The upconversion luminescence (UCL) of nanocrystals coated on the PCs surface can be enhanced by the PCs effects. While surface plasmon resonance (SPR) of noble metal nanoparticles (NPs) is being extensively applied to enhance the UCL properties of nanocrystals. However, the PCs or SPR effect are developed separately for the UCL enhancement. In this work, we present a facile preparation method of the Au NPs embedded inverse opals, which was used as substrates to improve the UCL properties of NaYF₄:Yb³⁺, Er³⁺ NPs. The significant luminescence enhancement of NaYF₄:Yb³⁺, Er³⁺ upconverting NPs was obtained by the coupling between the SPR of Au NPs and PCs effects from Au NPs embedded inverse opals substrates. The finding demonstrated that the Au NPs embedded inverse opals as substrates may be useful for the enhanced UCL of other phosphors, producing novel photonic devices.     

Effect of TeO2 on Near‐Infrared Emission from Bismuth Centers in Borogermanate Glasses

Bi‐doped xTeO₂–(60?x)GeO₂–15B₂O₃–20MgO–5Al₂O₃ glasses were prepared by the conventional melt‐quenching method and their absorption and fluorescence spectra were characterized. Broadband near‐infrared (NIR) emission from Bi centers centered around 1240 nm with a full width at half maximum (FWHM) of 250 nm was observed, and the position of the emission peak strongly depends on the excitation wavelength. Increasing TeO₂ concentration results in the strong coloration of the glass, leading to the reduction and finally, complete quenching of the NIR emission. Based on Raman, X‐ray photoelectron spectroscopy and transmission microscopy observation, the coloration of the glass at high TeO₂ concentration can be ascribed to the precipitation of elemental Te nanoparticles of around 3–8 nm, which effectively suppresses the NIR emission by reabsorption. The precipitation of Te nanoparticles in an oxide glass may find novel applications in photonics and relevant fields.     

Preparation of the projectile rotating band and its performance evaluation

Alternative materials are being investigated as substitution of the traditional copper rotating band, in order to solve problems associated with their mechanical and physical properties. Meanwhile, new processes for joining the rotating band on the projectile body have also to be developed because of different material physical properties. In this paper, swaging, welding, and newly developed spraying technologies for fabricating rotating band are analyzed, respectively. Quasi-static and dynamic engraving methods are presented for evaluating the performance of as-prepared rotating band. The former was performed on an 810 Material Testing System and the latter was carried out by using a specially developed gas-gun-based impact test rig. Hoop and axial direction strain gauges were positioned on the exterior of the barrel to monitor the effect of the rotating band on the barrel during engraving process. It is suggested that aluminum bronze coating prepared by the High Velocity Arc Spraying (HVAS) process should be a good candidate for application to a rotating band of medium- and large- caliber projectiles. The measured strains were found to be dependent on a set of variables, such as loading rate, band material and structure, forcing cone and rifling (land and groove) structure, bore condition (oiled or dry), etc. The loading rate has been verified as the most important factor and the essential difference among quasi-static engraving, dynamic engraving, and actual firing.