[en] Nitrogen was implanted into the chemical vapor deposition (CVD) diamond films, and the electron field-emission properties of the nitrogenated diamond films were investigated. Raman and x-ray photoelectron spectroscopy (XPS) measurement revealed that nitrogen-implantation damaged the structure of diamond film and promoted the formations of sp² C-C and sp² C-N bonding. By increasing the implantation dose, the threshold field of the emission of the diamond film could be lowered from 18 V/μm to 4V/μm. The enhancement of field emission for nitrogen-implanted CVD diamond films was attributed to the increase of the fraction of sp² C bonds and the formation of defect bands within the bulk diamond band gap induced by nitrogen-implantation, which could alter the work function and elevate the Fermi level. Consequently, the energy barrier on diamond surface for electron tunneling was reduced. (authors)

[en] Germanium carbide (Ge_1-xC_x) films have been prepared by RF reactive sputtering a pure Ge(111) target at different flow rate ratios of CH₄/(CH₄+Ar) in a CH₄/Ar mixture discharge, and it has been found that the composition, chemical bonding, optical and mechanical properties of Ge_1-xC_x films are remarkably influenced by the flow rate ratio of CH₄/(CH₄+Ar). The effects of the chemical bonding on the optical and mechanical properties of the Ge_1-xC_x films have been explored. In addition, an antireflection Ge_1-xC_x double-layer coating deposited on both sides of the ZnS substrate wafer has been developed for application as an infrared window. It is shown that the transmittance in the wavelength region between 8 and 12 μm and the hardness of the ZnS substrate have been significantly improved by the double-layer coating

[en] Single crystalline α-Fe₂O₃ ellipsoidal nanoparticles were prepared by a simple hydrothermal method without any requirement of calcination step at high temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to investigate the ellipsoidal structure. The formation and evolution of these ellipsoidal nanoparticles were investigated by SEM, and the results showed that the ellipsoidal structure was achieved through aggregation of nanoparticles while the traditional Ostwald ripening mechanism also played an important role in formation of the initial particles before aggregation and smoothed the morphology of the ellipsoidal nanoparticles after attachment. The as-prepared α-Fe₂O₃ ellipsoidal nanoparticles could catalyze oxidation of almost 100% CO at a temperature of 330 deg. C. The present work shows that the nanostructures of catalyst are important to their catalytic performance besides the traditionally accepted factors, such as high BET surface area

[en] Magnetic MFe₂O₄ (M=Co, Ni, Zn) nanocrystals with a diameter about 30 nm and a nearly spherical shape were synthesized via a simple hydrothermal approach. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy have been used to investigate the as-prepared magnetic MFe₂O₄ (M=Co, Ni, Zn) nanocrystals. Magnetic properties of the as-prepared samples have been detected by a vibrating sample magnetometer at room temperature and the results show that the as-prepared magnetic MFe₂O₄ nanocrystals are a type characteristic of superparamagnetic materials. These superparamagnetic nanocrystals are believed to be promising for wide engineering applications, such as drug delivery, bioseparation, and magnetic resonance imaging

[en] Highlights: • Hierarchical structured Fe₂O₃ microspheres were successfully fabricated using acid leachate of ilmenite as precursor. • A possible formation mechanism was proposed for the hierarchical structured Fe₂O₃ microspheres. • Compared with most reported adsorbents, the Fe₂O₃ microspheres exhibited excellent removal performance for dyes. • Removal mechanism mainly included ion exchange, electrostatic adsorption and pore filling. • This work provided a novel approach for “waste eliminates waste, turning waste to treasure”. A facile method using acid leachate of ilmenite as the precursor has been successfully developed to tailor the structure of Fe₂O₃. The morphology and structure of the final product can be controlled from nanoparticles, microcubes, rhombohedrons to microspheres by varying the synthetic parameters. Detailed characterization showed that the microspheres had a hierarchical structure and was actually consisted of nanoblocks subunits. A possible mechanism was proposed for the formation of the hierarchically structured Fe₂O₃ microspheres. Due to its large surface area and abundant functional groups, the Fe₂O₃ microspheres could efficiently remove organic dyes in aqueous solution. The measured maximum adsorption capacities were 723.8, 150.7, and 54.5 mg/g for Congo red, Methyl orange, and Methylene blue, respectively, which were generally higher than those for Fe₂O₃ with other structures reported in literature. This work provides a novel approach to using waste as the resource for the preparation of low-cost and efficient adsorbent materials.

[en] Paclitaxel (Taxol) is an anticancer taxane drug commonly used in the treatment of nasopharyngeal carcinoma (NPC). However, resistance to paclitaxel is a major difficulty in developing an effective therapy against NPC. MicroRNAs (miRNAs) are known to regulate genes that are involved in drug resistance. We assessed the effects of miR-29c, an miRNA identified in a genome-wide study of Taxol resistance, on genes associated with resistance in NPC cells. We established Taxol resistance in two human NPC cell lines, SUNE-1 and C666-1 (SUNE-1-Taxol and C666-1-Taxol) and found that miR-29c was downregulated and integrin beta-1 (ITGB1) was upregulated in Taxol-resistant NPC cells compared with parental NPC cells. Further investigations using a TUNEL assay and BAX/BCL-2 ratio, found that overexpression of miR-29c and knockdown of ITGB1 can resensitize drug-resistant NPC cells to Taxol and promote apoptosis. In addition, a dual-luciferase reporter assay indicated that ITGB1 is the target of miR-29c. Furthermore, silencing miR-29c markedly increased Taxol-resistant NPC tumor growth in a nude mouse xenograft model while knockdown of ITGB1 reversed this result. Overall, these data demonstrate that miR-29c regulates resistance to Taxol in NPC by targeting ITGB1. Our research indicates that miR-29c may have potential use in Taxol-resistant NPC therapy.

[en] Although the role of ion bombardment on electrical conductivity and optical reflectivity of transition metal nitrides films was reported previously, the results were controversial and the mechanism was not yet well explored. Here, we show that proper ion bombardment, induced by applying the negative bias voltage (V_b), significantly improves the electrical conductivity and optical reflectivity in rocksalt hafnium nitride films regardless of level of stoichiometry (i.e., in both near-stoichiometric HfN_1_._0_4 and over-stoichiometric HfN_1_._1_7 films). The observed improvement arises from the increase in the concentration of free electrons and the relaxation time as a result of reduction in nitrogen and hafnium vacancies in the films. Furthermore, HfN_1_._1_7 films have always much lower electrical conductivity and infrared reflectance than HfN_1_._0_4 films for a given V_b, owing to more hafnium vacancies because of larger composition deviation from HfN exact stoichiometry (N:Hf = 1:1). These new insights are supported by good agreement between experimental results and theoretical calculations. (orig.)

[en] Full-color multi-level transmittance-modulated films have important applications in many emerging fields, such as decorative smart windows and camouflage laser-protection windows. However, the existing transmission-modulated films cannot obtain rich colors due to the limitation of selective absorption. Although the traditional selective reflection-enhanced Fabry-Perot (FP) cavity has rich colors, it cannot obtain the transmission-modulated properties due to the use of a metal reflective layer. Herein, we design an asymmetric FP cavity with a pair of high- and low-activation energy chalcogenide phase change materials as the reflective layer (named as “PCM pair” FP cavity), achieving a combination of full color and multi-level transmittance modulation in a thin film. This is attributed to the “PCM pair” having the coupling effect of selective reflection enhancement and gradient absorption that traditional FP cavities do not have. According to simulations and experiments of ITO/“PCM pair” (“PCM pair” = GeTe/Sb₂Te₃), we prove that the gradient absorption is attributed to the multi-stage change of “PCM pair” from amorphous to crystalline state. This increases carrier absorption and induces additional interface absorption, thus resulting in four-level transmittance modulation. The selective reflectivity enhancement is due to light interference effect between “PCM pair” and ITO with different thicknesses, which realizes full-color modulations. Based on new insights into the activation energy, we propose the design principles of “PCM pair” and present a materials map. Therefore, this study provides the new FP cavity and candidate materials for the problem that the color and transmittance modulation cannot be integrated in a thin film.

[en] This work reports the first synthesis of CuO-CeO₂ binary oxides with a plate-like morphology by a solvothermal method. The as-prepared CuO-CeO₂ nanoplates calcined at 400 ^oC were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectrum, and tested for catalytic oxidation of dilute benzene in air. Various structural characterizations showed that large amounts of copper species were exposed on the CuO-CeO₂ nanoplate surface. The effect of the synthesis conditions on the structure of the product, as well as the growth process of the nanoplates, has been studied and discussed. The CuO-CeO₂ nanoplates exhibited an excellent catalytic activity for benzene oxidation despite its relatively low surface area and could catalyze the complete oxidation of benzene at a temperature as low as 240 ^oC.

[en] Highlights: • BNTM ceramics were prepared for the first time by solid-state reaction route. • Crystal structure changes from mixed phases to tetragonal then to cubic phase. • BN6TM meets the Y5V specification, and all of the Mn ions exist as Mn²⁺. • The role of $2N{d}_{Ba}^{·}-M{n}_{Ti}^{″}$ defect complexes was investigated. (Ba_1−xNd_x) (Ti_0.97Mn_0.03)O₃ (BNTM) (x = 0.01, 0.02, 0.04, 0.06) ceramics were prepared using a conventional cold-pressing ceramic technique. The structure, valence state and dielectric properties were investigated using XRD, RS, SEM, TEM, EPR, and dielectric temperature and frequency measurements. XRD, RS analysis coupled with SEM and TEM observations indicate that the samples have a coexistence of tetragonal and hexagonal phase at room temperature as x ≤ 0.02 and become a single phase in the tetragonal as x = 0.04 and in the cubic as x = 0.06 (air-sintered, 1400 °C/12 h). It reveals that Nd³⁺ ions can suppress hexagonal phase effectively and benefit the formation of single-phase ceramics. Improvement of dielectric properties is accompanied by the structural evolution. Particularly a cubic ceramic with x = 0.06, the dielectric-peak temperature is found to shift to room temperature, meeting the EIA Y5V specification with tan δ < 0.04. Up to x = 0.04, the phase transition remains first order. The valence state of Mn ions was analyzed by EPR. It is found that Mn ions transform from high valence (+3 and + 4) to low valence (+2) with the increase of Nd concentration, and all of the Mn ions exist as Mn²⁺ when x = 0.06. The unit cell volume and dielectric-peak temperature of BNTM decrease nonlinearly with increasing x, which can be ascribed to the incorporation of Nd ions and the formation of $2N{d}_{Ba}^{·}-M{n}_{Ti}^{″}$ donor-acceptor defect complexes.