石墨烯/橡胶纳米复合材料研究进展

石墨烯结合了碳纳米管导电和黏土片层的结构特征,为发展高性能、多功能聚合物纳米复合材料提供了新的方向.石墨烯/橡胶纳米复合材料近年来引起广泛关注.众多研究结果表明石墨烯是橡胶的理想填料之一,为高性能橡胶改性提供了新途径.本文介绍了石墨烯/橡胶纳米复合材料的3种主要制备方法,即乳液共混法、溶液共混法和机械混炼法,以及材料的物理机械性能、电学性能、气体阻隔性能和热学性能,并分析了该类材料的发展前景和存在问题.     

Low‐Dimensional Carboxylate‐Bridged GdIII Complexes for Magnetic Refrigeration

Four carboxylate‐bridged Gd^III complexes ( 1 – 4 ) with 1D/2D structures have been synthesized by using the hydrothermal reaction of Gd₂O₃ with various carboxylate ligands. Compounds 1 and 2 contained the same [2n] Gd^III? OH ladders, but with different crystallographically independent Gd^III ions, whilst the structures of compounds 3 and 4 were composed of [Gd₄(μ₃‐OH)₂(piv)₈(H₂O)₂]²⁺ units and 1D ladder Gd^III chains, respectively. Antiferromagnetic interactions occurred in compounds 1 – 3 , owing to their small Gd? O? Gd angles, whereas ferromagnetic coupling occurred in compound 4 , in which the Gd? O? Gd angles were larger. These complexes exhibited a distinct magnetocaloric effect (MCE), which was affected by their different magnetic densities and exchange interactions. Among these compounds, complex 4 presented the largest MCE (?ΔS_m^max=43.6 J kg^?1 K^?1), the lowest M_w/N_Gd ratio (the highest magnetic density), and weak ferromagnetic coupling. Therefore, a lower M_w/N_Gd ratio and weaker exchange interactions (a smaller absolute value of θ) between Gd^III ions resulted in a larger MCE for the Gd^III complexes.     

Sonocrystallization Yields Monoclinic Paracetamol with Significantly Improved Compaction Behavior

Ultrasound‐assisted crystallization (sonocrystallization) was used to prepare a mixture of nano‐ and micrometer‐sized crystals of the monoclinic form of paracetamol—a widely used analgesic known for its particularly problematic mechanical behavior under compression (i.e. poor tabletability). The nano‐ and micrometer‐sized crystals yielded a powder which exhibits elastic moduli and bulk cohesions that are significantly higher than those observed in samples consisting of macrometer‐sized crystals, thus leading to enhanced tabletability without the use of excipients, particle coating, salt, or cocrystal formation. Experimental compaction and finite element analysis were utilized to rationalize the significantly improved compaction behavior of the monoclinic form of paracetamol.     

Imidazolin‐2‐ylidenaminophosphines as Highly Electron‐Rich Ligands for Transition‐Metal Catalysts

A variety of chemical transformations benefit from the use of strong electron‐donating ancillary ligands, such as alkylphosphines or N‐heterocyclic carbenes when electron‐rich metal centers are required. Herein, we describe a facile and highly modular access to monodentate and bidentate imidazolin‐2‐ylidenamino‐substituted phosphines. Evaluation of the phosphine’s electronic properties substantiate that the formal replacement of alkyl or aryl groups by imidazolin‐2‐ylidenamino groups dramatically enhance their donor ability beyond that of alkylphosphines and even N‐heterocyclic carbenes. The new phosphines have been coordinated onto palladium(II) centers, and the beneficial effect of the novel substitution patterns has been explored by using the corresponding complexes in the palladium‐catalyzed Suzuki–Miyaura cross‐coupling reaction of non‐activated aryl chloride substrates.     

X‐ray Radiation‐Controlled NO‐Release for On‐Demand Depth‐Independent Hypoxic Radiosensitization

Multifunctional stimuli‐responsive nanotheranostic systems are highly desirable for realizing simultaneous biomedical imaging and on‐demand therapy with minimized adverse effects. Herein, we present the construction of an intelligent X‐ray‐controlled NO‐releasing upconversion nanotheranostic system (termed as PEG‐USMSs‐SNO) by engineering UCNPs with S‐nitrosothiol (R‐SNO)‐grafted mesoporous silica. The PEG‐USMSs‐SNO is designed to respond sensitively to X‐ray radiation for breaking down the S N bond of SNO to release NO, which leads to X‐ray dose‐controlled NO release for on‐demand hypoxic radiosensitization besides upconversion luminescent imaging through UCNPs in vitro and in vivo. Thanks to the high live‐body permeability of X‐ray, our developed PEG‐USMSs‐SNO may provide a new technique for achieving depth‐independent controlled NO release and positioned radiotherapy enhancement against deep‐seated solid tumors.     

Bond strengths evaluation of laser ceramic bracket debonding

Ceramic brackets often used for an orthodontic treatment can lead to problems such as enamel tear outs because of their low fracture resistance and high bond strengths. Therefore the aim of our study was to investigate the positive laser radiation effect on bracket debonding. Moreover, the influence of the enamel shape surface under the bracket and laser radiation power on the debonding strength was investigated. The source of the radiation was the longitudinally diode-pumped Tm:YAP laser operating at 1997 nm. To eliminate the tooth surface roughness the flat enamel surface was prepared artificially and the bracket was bonded on it. The debonding was accomplished by Tm:YAP laser radiation with different the power value while recording the temperature rise in the pulp. To simulate the debonding process in vivo the actual bond strength was measured by the digital force gauge. The results were analyzed by scanning electron microscope.     

Separation and characterization of clindamycin phosphate and related impurities in injection by liquid chromatography/electrospray ionization mass spectrometry

A simple high‐performance liquid chromatography/electrospray ionization tandem mass spectrometric (HPLC/ESI‐MS/MS) method has been developed for the rapid identification of clindamycin phosphate and its degradation products or related impurities in clindamycin phosphate injection. Detection was performed by quadrupole time‐of‐flight mass spectrometry (Q‐TOFMS) via an ESI source in positive mode. Clindamycin phosphate and its related substances lincomycin, 7‐epilincomycin‐2‐phosphate, lincomycin‐2‐phosphate, clindamycin B, clindamycin B‐2‐phosphate, and clindamycin were identified simultaneously by HPLC/ESI‐MS/MS results. Based on the MS/MS spectra of their quasi‐molecular ions, the fragmentation pathways of clindamycin phosphate and its related substances were compared and proposed, which are specific and useful for the identification of the lincosamide antibiotics and related impurities. The method was rapid, sensitive and specific and can be used to identify clindamycin phosphate and its related impurities in clindamycin phosphate injection without control compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

556 nm黄光激光器激光反射镜的研制

从激光晶体低增益谱线的运转机理出发,对LD泵浦NdYAG,LBO腔内倍频556 nm激光器所使用的光学薄膜进行了研制.在激光反射镜的设计上,为保证基频光1 112 nm的高效振荡,并获得高的倍频556 nm激光输出,对膜系要求进行了深入分析.采用离子束反应溅射和离子辅助沉积的方法,运用时间监控膜厚法成功置备出556 nm激光器所使用的特殊的全介质激光反射膜,在国内首次实现了1 112 nm激光高效振荡,通过LBO腔内倍频,在2 W的LD泵浦功率下获得102 mW 556 nm激光输出.     

Preparation of PMMA Foam by Supercritical CO_2 with Ethanol

Supercritical (SC) CO2 can plasticize many amorphous polymers, which reduce the glass transition temperature of the polymers significantly. Recently, it was used as blowing agent to foam amorphous materials such as poly(methyl methacrylate) (PMMA)1,2, polystyrene (PS)3, polycarbonate (PC)4 and poly(ethylene terephthalate) (PET)4. In this foaming process, a polymer is saturated with SC CO2, and followed by rapid depressurization to atmospheric pressure. The microcellular foams can be ob…