Eu‐, Tb‐, and Dy‐Doped Oxyfluoride Silicate Glasses for LED Applications

Luminescence glass is a potential candidate for the light‐emitting diodes (LEDs) applications. Here, we study the structural and optical properties of the Eu‐, Tb‐, and Dy‐doped oxyfluoride silicate glasses for LEDs by means of X‐ray diffraction, photoluminescence spectra, Commission Internationale de L'Eclairage (CIE) chromaticity coordinates, and correlated color temperatures (CCTs). The results show that the white light emission can be achieved in Eu/Tb/Dy codoped oxyfluoride silicate glasses under excitation by near‐ultraviolet light due to the simultaneous generation of blue, green, yellow, and red‐light wavelengths from Tb, Dy, and Eu ions. The optical performances can be tuned by varying the glass composition and excitation wavelength. Furthermore, we observed a remarkable emission spectral change for the Tb³⁺ single‐doped oxyfluoride silicate glasses. The ⁵D₃ emission of Tb³⁺ can be suppressed by introducing B₂O₃ into the glass. The conversion of Eu³⁺ to Eu²⁺ takes place in Eu single‐doped oxyfluoride aluminosilicate glasses. The creation of CaF₂ crystals enhances the conversion efficiency. In addition, energy transfers from Dy³⁺ to Tb³⁺ and Tb³⁺ to Eu³⁺ ions occurred in Eu/Tb/Dy codoped glasses, which can be confirmed by analyzing fluorescence spectra and energy level diagrams.     

Hyaluronic acid conjugated graphene oxide for targeted drug delivery

Nano-sized graphene oxide (GO) is functionalized with adipic acid dihydrazide to introduce amine groups, and then hyaluronic acid (HA) is covalently conjugated to GO by the formation of amide bonds. The resulting HA-grafted GO (GO–HA) has negligible hemolytic activity and very low cytotoxicity towards HeLa and L929 cells, and it can be effectively taken up by cancer cells through receptor-mediated endocytosis. The histological, hematological and biochemical analysis results suggest no perceptible toxicity of GO–HA in mice at a high exposure level of 10 mg kg⁻¹ and at an exposure time of up to 10 days. Doxorubicin (DOX) can be efficiently loaded on the GO–HA, and the resulting GO–HA/DOX exhibits notable cytotoxicity to HeLa cells. The in vivo drug delivery capability of GO–HA is demonstrated by following the tumor growth in mice after intravenous administration of GO–HA/DOX. The results indicate that GO–HA can efficaciously deliver DOX to the tumors and suppress tumor growth.     

Density and viscosity of the binary polyethylene glycol/CO2 systems

Density of CO₂ saturated solutions of polyethylene glycols (PEGs) of different molecular weight was measured in pressure range from 8.0 MPa up to 47.7 MPa at a temperature of 343 K by a volumetric method. To validate the method density of pure CO₂ was measured at different pressures and a temperature of 293 K. The results were compared to the literature data and the accuracy was better than 2%. The density was between 1.17 g/mL for PEG 1000/CO₂ at 14.5 MPa and 1.78 g/mL for the system PEG 4000/CO₂ at 35 MPa. Further, the data were compared to results, obtained by a gravimetric method using magnetic suspension balance (MSB).Viscosity of CO₂ saturated solutions of polyethylene glycols (PEGs) of different molecular weight at different pressures and at a temperature of 343 K was measured using a high pressure view cell. Also a temperature impact on the viscosity of pure PEGs was observed at ambient pressure. After saturating PEG 1500 with 10 MPa of CO₂ pressure its viscosity decreases from 76.6 mPa s to 2.24 mPa s at 333 K. Further addition of CO₂ and increasing the pressure results in even lower viscosity and the highest viscosity reduction was reached at the highest pressure; at 35 MPa viscosity of the system PEG 1500/CO₂ is only 0.665 mPa s.     

Synthesis of oxygen deficient BiOI for photocatalytic degradation of methyl orange

Oxygen defects are introduced into BiOI by a simple glycerol treatment. This deficient BiOI demonstrated 3.5 times higher photocatalytic performance than the untreated BiOI nanosheets for methyl orange (MO) degradation under visible light irradiation. Moreover, the deficient BiOI nanosheets have excellent cycling stability. The improved efficiency can be ascribed to the significantly enhanced separation efficiency of photogenerated and utilized more solar light.     

c-axis oriented ZnO formed in a rotating magnetic field with various rotation speeds

A rotating magnetic field was used to fabricate c-axis oriented zinc oxide. The influence of rotating speed on orientation structure was also examined. The aligned axes had the largest diamagnetic susceptibility, which axis was difficult to align with a static magnetic field. In c-axis oriented ZnO, the degree of orientation (Lotgering factor) in the green compact ranged from 0.2 to 0.5 along c-axis. The Lotgering factor increased with rotating speed. For all samples with the rotating magnetic field, the degrees of orientation increased up to above 0.9 after sintering at 1573 K.     

Improving the wear resistance of UHMWPE implants by in situ precipitation of hyaluronic acid using supercritical fluid technology

Recently, the increase in the number of patients who require a hip or knee implant, combined with the reduction of age at which this implant is demanded, emphasizes the urgent need for the development of new materials with enhanced mechanical and tribological properties. In this work, a new technique called supercritical in situ precipitation (SCisP) has been employed to manufacture a blend made of ultra-high molecular weight polyethylene with added vitamin E (UHMWPE_vit) plus a hyaluronic acid (HA) derivative. The precipitation of the HA derivative within the pores of a porous UHMWPE_vit preform allows getting a blend after the post-processing of the SCisP product. Blend characterization results report the reduction of friction coefficient and wear rate in comparison to reference UHMWPE_vit, probably due to the improvement in the wettability that hyaluronic derivative produces. Manufacturing times and raw material consumption have been drastically reduced by SCisP in comparison to processes reported up to now. Moreover, preliminary studies varying the conditions of the process, i.e. the type of hyaluronic acid derivative, solvent and number of injections, establish the basis of this technique for further development and open an interesting route in the manufacture of medical devices.     

Effects of 90° domain switching on electric generation properties of PZT ceramic

The influence of domain switching on the electric generation properties of lead zirconate tinatate (PZT) ceramic has been investigated after static and cyclic loadings under various conditions. A PZT ceramic of size ϕ8.0 mm×0.17 mm, consisting of a tetragonal lattice structure, i.e., c/a≠1.014, was used. Domain switching occurred as a result of the applied stress, where three different switching modes were employed: (I) simple 90° switching; (II) 90° switching with 90° rotation; and (III) 90° switching with 180° rotation. The rates of the switching mode were different: the simple switching mode (Mode I) was 20%; and both complicated switching modes (Mode II and III) were 40%. The extent of 90° domain switching was different depending on the grain and where the direction of the tetragonal structure (c-axis direction) was affected, e.g., the closer the parallel between the c-axis and the stress direction, the stronger the domain switching. The electric generation voltage increased with increasing applied cyclic stress; however, that voltage dropped suddenly as the stress value was close to its elastic limit. This is due to the 90° domain switching. Such domain switching (reduction of the electric voltage) occurred in the early cyclic stage.     

Detection of aluminium by energy dispersive X-ray microanalysis at high accelerating voltages with semi-thin sections of biological sample

Aluminium (Al) was detected in semi-thin sections of three organs, the duodenum, liver and kidney, of ddY strain mouse by energy dispersive X-ray microanalysis at high accelerating voltages around 300 kV. Firstly, to determine the conditions best for detecting Al, several adult ddY mice were injected intraperitoneally with aluminium chloride (AlCl3) and the duodenums were fixed, embedded and sectioned at various thicknesses and subjected to energy dispersive X-ray microanalysis at various accelerating voltages from 100 to 400 kV. From the results obtained, 1.0 microm-thick sections observed at 300 kV resulted in the highest peak-counts/background ratios and were shown to be the most suitable for X-ray microanalysis. Secondly, ddY mice aged four weeks were administered orally with 2% AlCl3 at pH 2.5 for two weeks and the three organs (duodenum, liver and kidney) were subjected to X-ray microanalysis under the same condition found above. The results were compared with light microscopic Al staining of the same tissues. Aluminium was detected in lysosomes of the three kinds of tissues with higher sensitivity by energy dispersive X-ray microanalysis by light microscopic observation. From the results, it was suggested that Al dissolved in acidic water was absorbed in the duodenum and accumulated in the liver and kidney.     

The study of metal ion release and cytotoxicity in Co–Cr–Mo and Ti–Al–V alloy in total knee prosthesis – scanning electron microscopic observation

We surgically retrieved two cobalt(Co)–chromium(Cr)–molybdenum(Mo) and five titanium(Ti)–aluminum(Al)–vanadium(V) alloy knee prostheses from patients because of mechanical failure and pain. We examined the distribution of the small particles which were released from the Co–Cr–Mo and Ti–Al–V alloys using a backscattered scanning electron microscopy (SEM). In addition we analyzed the metals in the artificial knee joints and the tissues adjacent to them using energy dispersive X-ray spectroscopy (EDS). We demonstrated that a myriad of fine particles, produced by the abrasion of both Co–Cr–Mo and Ti–Al–V alloys, accumulated in the synovial cells. As Co–Cr–Mo alloys disintegrate easily in the cells, Co dissolves from the peripheral areas of them, although Cr remains within the cells. In contrast Ti–Al–V alloys are very stable in the synovial cells. From these findings we conclude that the Co–Cr–Mo alloys are hazardous to the body as the alloys release Co which enters the body. In contrast the Ti–Al–V alloys are very stable and are patently safer. Artificial joints, however, are still in considerable need of improvement.     

Cyclic oxidation behaviour of cerium implanted AZ31 magnesium alloys

AZ31 samples were implanted with 90 keV cerium ions with a dose of 1 × 10¹⁷ ions/cm². Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and Glancing angle X-ray diffraction (GAXRD) were used in order to investigate the characterization of elements in the implanted surface. The results indicate that after cerium implantation a pre-oxidation layer with double structure was formed. The influence of cerium implantation on the cyclic oxidation behaviour of AZ31 samples was studied at 773 K in air for 96 h, and the morphologies of the oxide scales were examined by scanning electron microscopy (SEM). It was found that the oxidation resistance of the implanted sample has been improved. The mechanisms to explain the experimental results were also proposed.