New semi-IPN scaffolds based on HEMA and collagen modified with itaconic anhydride

Porous semi-IPN scaffolds were synthesized via free radical copolymerization of collagen modified with itaconic anhydride and 2-hydroxyethyl methacrylate, using ammonium persulfate and N,N,N′,N′-tetramethylethylenediamine as redox initiator system, with the aim of overcoming the high enzymatic degradation rate of native collagen scaffolds. The chemical modification of collagen was confirmed by ¹H NMR and FT-IR spectroscopy. The physico-chemical properties of the resulted matrices were investigated by elemental analysis, SEM, enzymatic degradation and water retention studies. The synthesized scaffolds, obtained through an innovative process, have fine microstructures, controlled water retention degree and enhanced stability against enzymatic digestion compared to native collagen. This may broaden the use of collagen-based scaffolds in tissue engineering, particularly for wound dressings.     

Luminescence excitation spectra of TbX3 (X = Cl, Br, I)

A systematic study of the excitation spectrum of TbX₃ (X = Cl⁻, Br⁻, I⁻) is presented in this work. In general, the excitation spectra of TbX₃ can be divided into three major regions: (1) the short-wave host lattice absorption region, (2) the intermediate absorption region where the Tb³⁺ 4f⁸ → 4f⁷5d¹ interconfigurational excitation transition are located, and (3) the long-wave excitation region where the Tb³⁺ 4f⁸ → 4f⁸ intraconfigurational excitation transition are located. The high spin and the low spin components of the Tb³⁺ interconfigurational excitation transition are clearly identified in the case of TbCl₃. The luminescence of TbX₃ (X = Cl⁻, Br⁻, I⁻) is dominated by emission transitions emanating from the Tb³⁺⁵D₄ state. A comparative study of the optical properties of TbX₃ (X = Cl⁻, Br⁻, I⁻) with the properties of the Tb³⁺ ion in several halide host lattices is presented. Further, a comparative study of the fundamental host lattice optical transitions in terbium halides and other halide materials is also presented.     

Morphology-dependent antibacterial activities of Cu2O

Cubic and octahedral Cu₂O microcrystals were synthesized by the reduction of a copper-ligand complex solution with glucose under microwave irradiation using ethylenediaminetetraacetic acid (EDTA) and N,N,N′,N′-tetramethyl ethylenediamine (TMEDA) as ligands. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) confirmed that the surfaces of the cubic and octahedral of Cu₂O microcrystals had {100} and {111} lattice planes. The antibacterial activity of the Cu₂O microcrystals against E. coli was examined using optical density (OD) methods. The antibacterial activity of the cubic Cu₂O crystals was superior to that of the octahedral Cu₂O crystals. The mechanism of the specific morphology-controlled synthesis of Cu₂O and their morphology-dependent antibacterial activity are discussed.     

Release of BSA from porous matrices constituted of alginate–Ca and PNIPAAm-interpenetrated networks

The synthesis of thermosensitive Interpenetrating Polymer Network (IPN) hydrogels and the release of Bovine Serum Albumin (BSA) from the hydrogels were reported. The hydrogels, constituted of poly(N-isopropyl acrylamide) PNIPAAm network interpenetrated in alginate–Ca²⁺ network, were synthesized in a two-stepped process. In the first step, PNIPAAm network was synthesized from an aqueous solution containing N-isopropyl acrylamide (NIPAAm) monomers and N,N′-methylene-bis-acrylamide (MBAAm) co-monomers, and sodium alginate (SA) (1 or 2% w/v). The concentration of NIPAAm monomers in the hydrogel-forming solution was always 2.5, 5.0 or 10.0% (w/v). In the second step, alginate–Ca²⁺ networks were formed by immersion of the membrane, obtained on the first step, in a 1.0% (w/v) aqueous calcium chloride. The IPN hydrogels were characterized as a function of temperature (from 25 to 45 °C) through the following measurements: drop water contact angle (DWCA), compression elastic modulus (E) and cross-linking density (ν_e). The morphology was investigated using scanning electronic microscopy (SEM). In vitro release of BSA from the hydrogels was monitored by UV–Vis spectroscopy at 22 °C and 37 °C. DWCA results showed a decrease in the hydrogel hydrophilicity when the temperature and/or the PNIPAAm amount on hydrogels were increased. PNIPAAm-loader hydrogels are more compacted and presented elevated rigidity, mainly above 35 °C. This trend was attributed to the collapsing of PNIPAAm chains as the hydrogels were warmed above its Lower Critical Solution Temperature (LCST), which in aqueous solution is ca. 32–33 °C. The amount of BSA released from the alginate–Ca²⁺/PNIPAAm hydrogels changes inversely to both amount of PNIPAAm and temperature. The transport of BSA from the hydrogels was evaluated through a conventional model. In the lesser-compacted hydrogels the release occurs mostly by diffusion. In the more compacted ones the chain relaxation contributes to the BSA release. Thus, the alginate–Ca²⁺/PNIPAAm IPN-typed matrixes may be considered as smart hydrogels for the release of BSA, because the amount and rate of BSA released may be tailored by both the NIPAAm concentration in the hydrogel-forming solution and the control of temperature of hydrogel.     

Photocatalytic effects for the TiO2-coated phosphor materials

This study investigated the photocatalytic behavior of the coupling of TiO₂ with phosphorescent materials. A TiO₂ thin film was deposited on CaAl₂O₄:Eu²⁺,Nd³⁺ phosphor particles by using atomic layer deposition (ALD), and its photocatalytic reaction was investigated by the photobleaching of an aqueous solution of methylene-blue (MB) under visible light irradiation. To clarify the mechanism of the TiO₂-phosphorescent materials, two different samples of TiO₂-coated phosphor and TiO₂–Al₂O₃-coated phosphor particles were prepared. The photocatalytic mechanisms of the ALD TiO₂-coated phosphor powders were different from those of the pure TiO₂ and TiO₂–Al₂O₃-coated phosphor. The absorbance in a solution of the ALD TiO₂-coated phosphor decreased much faster than that of pure TiO₂ under visible irradiation. In addition, the ALD TiO₂-coated phosphor showed moderately higher photocatalytic degradation of MB solution than the TiO₂–Al₂O₃-coated phosphor did. The TiO₂-coated phosphorescent materials were characterized by transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and X-ray photon spectroscopy (XPS).     

Thermally stable triphenylene-based hole-transporting materials for organic light-emitting devices

The thermally stable hole transport layer (HTL) materials, 1,4-bis[(N,N′-di(2-naphthyl)-N,N′-diphenyl)aminophenyl]triphenylene (NPAPT) and 1,4-bis[(N,N′-di(2-naphthyl)-N,N′-diphenyl) aminophenyl]-2,3-diphenyl triphenylene (NPAPPT), were synthesized and the device performances of the organic light-emitting diodes (OLEDs) with NPAPT and NPAPPT as a hole transport layer were investigated. The glass transition temperatures of NPAPT and NPAPPT could be enhanced to 153 °C and 157 °C by the introduction of a rigid triphenylene backbone in the main chain. The use of NPAPT and NPAPPT as a HTL for OLEDs lowered the driving voltage and enhanced the light-emitting efficiency. The power efficiencies of triphenylene-based devices with tris(8-hydroxyquinoline)aluminum as an emitting material could be improved by 20% compared with that of N,N′-di(naphthalene-1-yl)-N,N′-diphenyl benzidine based devices.     

Synthesis and luminescent characteristic of Eu-doped (Gd,Lu)2O3 nanopowders

Eu³⁺ doped (Gd,Lu)₂O₃ nanopowders with particle sizes ranging from 20 to 70 nm were synthesized by the co-precipitant method using mixed precipitants, namely the mixture of ammonium hydroxide (NH₃⋅H₂O) and ammonium hydrogen carbonate (NH₄HCO₃). The precipitate precursor prepared by this method was believed to possess a basic carbonate composition and its thermal decomposition of the (Gd,Lu)₂O₃:Eu³⁺ powders were investigated by Thermogravimetric analysis and differential thermal analysis (TG-DTA). This preparation was followed by a calcination process at 800-1100 °C and corresponding phosphor structure were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Photoluminescence measurement of the (Gd,Lu)₂O₃:Eu³⁺ particles show typical red emission at the 612 nm corresponding to the ⁵D₀ → ⁷F₂ transition. We found that the optimal Eu³⁺ molar doping concentration, calcined temperature and reaction time were 7 mol%, 1000 °C, and 2 h, respectively, which is helpful to obtain the final transparent ceramics with excellent properties.     

Ar assisted carbidization of TiO2 (1 1 0) supported Mo nanoparticles by decomposition of C2H4

Ar⁺ assisted carbidization of Mo nanoparticles supported on TiO₂ (1 1 0) is studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In order to activate the diffusion of carbon into the bulk of Mo nanoparticles we applied Ar ions (1 keV) during the exposure of C₂H₄. XPS exhibited that the decomposition of C₂H₄ at 850 K accompanied by ion bombardment results in an almost complete carbidization of nanocrystalline Mo while this treatment performed without ion bombardment results only in the carbidization of the particle surface. The modification of the crystallinity of the Mo-carbide particles was deduced from STM measurements.     

Preparation and characterization of N–I co-doped nanocrystal anatase TiO2 with enhanced photocatalytic activity under visible-light irradiation

N–I co-doped TiO₂ nanoparticles were prepared by hydrolysis method, using ammonia and iodic acid as the doping sources and Ti(OBu)₄ as the titanium source. The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible diffuse reflection spectroscopy (UV–vis DRS). XRD spectra show that N–I–TiO₂ samples calcined at 673 K for 3 h are of anatase structure. XPS analysis of N–I–TiO₂samples indicates that some N atoms replace O atoms in TiO₂ lattice, and I exist in I⁷⁺, I⁻ and I⁵⁺ chemical states in the samples. UV–vis DRS results reveal that N–I–TiO₂ had significant optical absorption in the region of 400–600 nm. The photocatalytic activity of catalysts was evaluated by monitoring the photocatalytic degradation of methyl orange (MO). Compared with P25 and mono-doped TiO₂, N–I–TiO₂ powder shows higher photocatalytic activity under both visible-light (λ > 420 nm) and UV–vis light irradiation. Furthermore, N–I–TiO₂ also displays higher COD removal rate under UV–vis light irradiation.     

VUV spectroscopy of wide bandgap materials

In this paper we will present VUV spectroscopy experiments performed at the Superlumi station of Hasylab, DESY, Hamburg, on samples of BaF₂ crystals activated with Ce and BaF₂, (Ba,La)F₂ crystals activated with Er. The results of these experiments include time resolved luminescence and luminescence excitation spectra obtained under wavelength selective VUV and UV excitation by pulsed synchrotron radiation.We will reveal the information provided by the VUV/UV excitation spectra of the Ce³⁺ 5d → 4f as well as Er³⁺ 4fⁿ⁻¹5d → 4fⁿ and 4fⁿ → 4fⁿ emissions on energy transfer mechanisms from the fluoride host to the rare earth ion. We will demonstrate that the fast energy transfer channels involve bound excitons while the generation of free electrons and holes leads to slower processes dependant on hole and/or electron trapping.We will demonstrate that differences between the excitation spectra of the 5d → 4f emission in Ce and 4f¹⁰5d → 4f¹¹ emission in Er activated BaF₂ are generated by the coupling of the 4f → 5d transition to the 4f¹⁰ core of the Er³⁺ ion. We will also identify the additional band, absent for Ce, which is due to the exchange split high spin (HS) state of the 4f¹⁰5d configuration responsible for the slow decay of the excited Er³⁺ ions in BaF₂ and (Ba,La)F₂.Finally we will provide evidence and explain why the dominant VUV 4f¹⁰5d → 4f¹¹ Er³⁺ emission in BaF₂ is spin-forbidden and slow while in the mixed (Ba,La)F₂ crystals it is spin-allowed and fast.     

Effect of Pb(Zn1 / 2W1 / 2)O3 introduction on perovskite development and dielectric properties of (Ba,Pb)TiO3

Powders of a Pb(Zn_1 / 2W_1 / 2)O₃-introduced BaTiO₃-PbTiO₃ system were prepared. A two-step calcination route of a B-site precursor method was employed to promote perovskite formation. The overall effects of the Pb(Zn_1 / 2W_1 / 2)O₃ incorporation on changes in crystalline aspects as well as dielectric properties were explored.     

Dechlorination of 3,3′,4,4′-tetrachlorobiphenyl in aqueous solution by hybrid Fe0/Fe3O4 nanoparticle system

The kinetics and efficiency of 3,3′,4,4′-tetrachlorobiphenyl (PCB77) degradation in aqueous solution by hybrid Fe⁰/Fe₃O₄ nanoparticle system were investigated. The results showed that nano-sized Fe⁰ and Fe₃O₄ could efficiently degrade PCB77, and the residual rate of PCB77 by nano-sized Fe⁰ and Fe₃O₄ were 67.70% ± 0.42% and 82.26% ± 2.96%, respectively after 240 min of reaction (for 5 mg·L^?1 PCB77 and 5 g·L^?1 nanoparticles). The combined use of nanoscale Fe⁰ and Fe₃O₄ could enhance the degradation of PCB77. The dose ratios of nano-sized Fe⁰ and Fe₃O₄ significantly affected the PCB77 degradation rate. At Fe⁰/Fe₃O₄ ratios of 1:0.1, 1:0.2 and 1:1, the residual rates of PCB77 were 6.46%, 10.23% and 38.20%, respectively. The PCB77 degradation efficiency was also greatly affected by solution pH, and was maximised at pH 6.8. The degradation of PCB77 by Fe⁰/Fe₃O₄ nanoparticle was a dechlorination process, and the chlorion concentration increased with the decreasing residual rate of PCB77 accordingly. Fe₃O₄ provided Fe²⁺ and Fe³⁺ for enhancing the PCB77 degradation by nanoscale Fe⁰, suggesting a synergy between Fe⁰ and Fe₃O₄.     

Synthesis and Upconversion Emission of β-Ca2SiO4: (Er3+, Yb3+)

The β-Ca₂SiO₄: (Er³⁺, Yb³⁺) powders were synthesized by the simple solid-state process. The obtained samples were given characterizations of X-ray diffraction, Fourier-transform infrared, transmission electron microscopy, and luminescence. The samples have monoclinic parawollastonite phase and irregular morphology. Under the excitation at 980 nm, the obtained β-Ca₂SiO₄: (Er³⁺, Yb³⁺) samples show the intense upconversion (UC) emission. The dosage of Yb³⁺ has obvious influence on the emission intensities of β-Ca₂SiO₄: (Er³⁺, Yb³⁺) samples. Also, the emission intensity increases gradually with the increasing pump power from 350 to 600 mW. On the basis of luminescent properties of samples, we can conclude that the UC emission originates from the biphotonic process.     

Photocatalytic degradation of formaldehyde by nanostructured TiO2 composite films

Interest in the photocatalytic oxidation of formaldehyde from contaminated wastewater is growing rapidly. The photocatalytic activity of the nanocrystalline Fe³⁺/F^? co-doped TiO₂–SiO₂ composite film for the degradation of formaldehyde solution under visible light was discussed in this study. The films were characterised by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy, X-ray diffraction (XRD), BET surface area, UV–Vis absorption spectroscopy, and photoluminescence spectroscopy. The FE-SEM results revealed that the Fe³⁺/F^? co-doped TiO₂–SiO₂ film was composed of uniform round-like nanoparticles or aggregates with the size range of 5–10 nm. The XRD results indicated that only the anatase phase was observed in the film. Compared with a pure TiO₂ film and a singly modified TiO₂ film, the Fe³⁺/F^? co-doped TiO₂–SiO₂ composite film showed the best photocatalytic properties due to its strong visible light adsorption and diminished electrons-holes recombination.     

Yellow-emitting phosphor of Sr3B2O6:Eu for application to white light-emitting diodes

This work focuses on the development of Eu²⁺-doped strontium (Sr)-borate as a yellow-emitting phosphor and its application to the fabrication of white light-emitting diodes (LEDs). Synthesis of Eu²⁺-doped Sr-borate phosphors was finely tuned for obtaining the efficient yellow luminescence through varying host composition, Eu concentration, and firing temperature. The 1300 °C-fired Eu²⁺-doped Sr₃B₂O₆, which was found to be the most efficient candidate to date, was used for white LED fabrication. Their optical properties were evaluated, resulting in warm white lights with CIE chromaticity coordinates of (0.340–0.372, 0.287–0.314) and color rendering indices of 75–77 under the forward currents of 5–40 mA.     

Simulations of Si and SiO2 etching in SF6 + O2 plasma

Chemical etching of Si and SiO₂ in SF₆ + O₂ plasma is considered. The concentrations of plasma components are calculated using values extrapolated from experimental data. Resulting calculations of plasma components are used for the calculation of Si and SiO₂ etching rates. It is found that the reaction constants for reactions of F atoms with Si atoms and SiO₂ molecules are equal to (3.5 ± 0.1) × 10⁻² and (3.0 ± 0.1) × 10⁻⁴, respectively. The influence of O₂ addition to SF₆ plasma on the etching rate of Si is quantified.     

Scintillation and optical properties of Pb-doped YCa4O(BO3)3 crystals

This communication reports optical properties and radiation responses of Pb²⁺ 0.5 and 1.0 mol%-doped YCa₄O(BO₃)₃ (YCOB) single crystals grown by the micro-pulling-down (μ-PD) method for neutron scintillator applications. The crystals had no impurity phases according to the results of X-ray powder diffraction. These Pb²⁺-doped crystals demonstrated blue-light luminescence at 330 nm because of Pb²⁺¹S₀-³P_0,1 transition in the photoluminescence spectra. The main emission decay component was determined to be about 250-260 ns under 260 nm excitation wavelength. When irradiated by a ²⁵²Cf source, the relative light yield of 0.5% Pb²⁺-doped crystal was about 300 ph/n that was determined using the light yield of a reference Li-glass scintillator.     

Preparation and characterization of CuIn1 − xGaxSe2 − ySy thin film solar cells by rapid thermal processing

This paper describes the synthesis and characterization of CuIn_1 − xGa_xSe_2 − yS_y (CIGSeS) thin-film solar cells prepared by rapid thermal processing (RTP). An efficiency of 12.78% has been achieved on ~ 2 µm thick absorber. Materials characterization of these films was done by SEM, EDS, XRD, and AES. J-V curves were obtained at different temperatures. It was found that the open circuit voltage increases as temperature decreases while the short circuit current stays constant. Dependence of the open circuit voltage and fill factor on temperature has been estimated. Bandgap value calculated from the intercept of the linear extrapolation was 1.1-1.2 eV. Capacitance-voltage analysis gave a carrier density of 4.0 × 10¹⁵ cm^− 3.