Infrared emission properties and energy transfer in ZnO-SiO2:Yb composites

Intense near-infrared emission at 1 μm has been obtained in ZnO-SiO₂:Yb³⁺ composites via a facile sol-gel method upon broadband ultraviolet light excitation. Systematic optical measurements including static and time-resolved photoluminescence have been performed to elucidate the energy transfer from ZnO quantum dots to Yb³⁺ ions. The dependence of energy transfer efficiency on Yb³⁺ concentration has been investigated in detail. Codoping with Li⁺ ions leads to about twice enhancement of the near-infrared luminescence intensity around 1 μm at room temperature. The enhancement in the luminescence intensity could be mostly attributed to the modification of the local symmetry around Yb³⁺ ions by codoping with Li⁺ ions.     

校园媒介建设成新闻专业实习基地的几点探索

新闻学是一门实践性极强的学科,近年来,不少高校的新闻专业学生实习难日渐显现.而新闻学教育利用好高校媒介,把校园媒介打造成本校新闻专业学生的实习基地,可以在一定程度上缓解新闻传播专业学生实习难的现状.     

文字的表情-来自拉丁文字母空白的研究

文字,一群驱赶蛮荒、传载文明、开启智慧的精灵;一群上传神谕、下达民情、中表心意的天使,与创造它们的人类一样有着十分丰富的表情,或喜、或悲、或羞、或酷……当我们被有着不同表情的文字深深吸引时,是否会发现围绕着文字笔画的空白原来正对展现文字的表情发挥着非常重要的作用?这其中拉丁文字母由于其结构的简约性,设计制作的相应简便性,在利用字母空白创造传情字母的实践上,历史悠久且时变时新,非常值得借鉴.     

Breast Fibromatosis after Hydrophilic Polyacrylamide Gel Injection for Breast Augmentation: a Case Report and Review of the Literature

BREAST fibromatosis is a rare kind of lesion.The average incidence is about 2-4 per million every year.1 So far there have been about 100 cases reported altogether.2 In this report, we describe a case of breast fibromatosis developed after hydrophilic polyacrylamide gel (HPG) injection for breast augmenta-Received for publication December 10, 2010.     

Tensile properties and wettability of SAC0307 and SAC105 low Ag lead-free solder alloys

In this article, the tensile properties of low Ag lead-free solder alloys, SAC0307 and SAC105, are examined under various strain rates and temperatures. The wettability of these solders on Cu pad is also characterized by using different fluxes. The SAC305 and Sn37Pb solder alloys are also studied for comparison. Our results show that the properties of all solder alloys are dependent on the strain rate and temperature. The ultimate tensile strength increases monotonously with the increment of strain rate. Both SAC0307 and SAC105 alloys possess lower strength and higher elongation ratio than SAC305 and Sn37Pb alloys. For all the fluxes used in this study, the SAC0307 and SAC105 alloys show the similar wettability to SAC305, whereas worse than that of Sn37Pb alloy. Increasing the activity of the flux does not improve the wettability of the SAC solder alloys on Cu pad effectively.     

The influence of pH and bath composition on the properties of Ni-Co coatings synthesized by electrodeposition

Ni-Co coatings were produced on Cu substrates by electrodeposition from electrolytes with different pH values and different Co²⁺ concentration. The current efficiency increases from 52.1% to 81.2% with the pH increasing from 2.0 to 5.4. It is clearly observed that the content of cobalt in the deposited coatings gradually increases from 9.4% to 19.6% as the pH value varies from 2.0 to 5.4. The Co content in the deposited coatings increases from 16.5% to 72.7% as the molar ratio of CoSO₄/NiSO₄ varying from 1:5 to 1:2 in electrolyte. XRD patterns reveal that the structure of the coatings strongly depends on the Co content in the binary coatings. Both granular and dendritic crystals were investigated by SEM and the different crystallization behaviors were illustrated. The saturation magnetization of the coatings goes up from 96.36 kAm⁻¹ to 136.08 kAm⁻¹ with the pH value increasing from 2.0 to 5.4. The saturation magnetization (M_s) and coercivity (H_c) move up from 144.84 kAm⁻¹ and 15.27 kAm⁻¹ to 175.13 kAm⁻¹ and 125.20 kAm⁻¹ with the increase of Co in the electrolyte, respectively.     

A facile photochemical route for the synthesis of gold nanoparticles

Synthesis of high-quality, water-dispersed gold nanoparticles (AuNPs), has been prepared employing luminol as a special reductant, via direct irradiation of the molecular precursors rather than traditional heat of the solvent. The final quality of the photochemically generated nanomaterial was characterized by transmission electron microscopy, resonance light scattering spectra, and cyclic voltammetry. AuNPs could enhance the chemiluminescence intensity of the luminol-H₂O₂ system, attributing to their catalysis. On the basis, we developed a nanoparticle-based chemiluminescence method for the determination of H₂O₂. The results demonstrated that it was possible to detect hydrogen peroxide in the range of 10⁻⁸–10⁻³ M.     

α-MnO2 nanowires transformed from precursor δ-MnO2 by refluxing under ambient pressure: The key role of pH and growth mechanism

α-MnO₂ nanowires were obtained by reflux treatment of precursor δ-MnO₂ in acidic medium under ambient pressure. The great effects of pH on the transformation of δ-MnO₂ to α-MnO₂ and the concentration of coexistent cations (K⁺, Mn²⁺) was investigated in systematically designed experiments by using powder X-ray diffraction and atomic absorption spectrometry analysis. The specific surface area of the products could be simply controlled by adjusting the initial pH value of the suspension. The micro-morphologies during the transition process from the precursors to final products were characterized by SEM and TEM. A dissolution–recrystallization mechanism was proposed to describe the growth process of the one-dimensional nanowire. MnO_x units or MnO₆ octahedra was formed firstly from the dissolution of outmost surfaces of δ-MnO₂, followed by a rearrangement/crystallization to form one-dimensional α-MnO₂ nanowire. In addition, the time-dependent process of dissolution would take place gradually from the external to internal of the precursor.     

Novel triphenylamine-cored two-photon absorbing dyes for labeling of biomolecules

Two novel, V-shaped and Y-shaped dipicolinate derivatives branched from triphenylamine, {4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl)vinyl]}-N-phenyl-N-{4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl)vinylphenyl]}aniline (1) and {4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl) vinyl]}-N,N-bis {4-[(E)-2-(2,6-dimethoxycarbonyl pyridin-4-yl)vinylphenyl]}aniline (2) were synthesized. These compounds were designed for large two-photon absorption and in particular for labeling of biomolecules. Their linear absorption, fluorescence properties and their two-photon absorption properties as well as two-photon fluorescence cell imaging were examined. When excited at 800 nm, the two-photon absorption cross-section values of chromophores 1 and 2 in THF were 208 GM, 376 GM, respectively. These two-photon absorbing dyes possess reasonable water solubility, strong chelating ability and display a large set of reactivity for coupling to biomolecules, which are apparently due to the two methoxycarbonyl groups in pyridine ring. This work suggests that chromophores 1 and 2 are promising labels potentially applicable for the tracking of biomolecules using two-photon scanning microscopy.