Investigation of catalytic activation of peroxydisulfate on cu-doped mesoporous silica-based particles (Cu-BMS) for efficient degradation of methylene blue

The Cu-doped mesoporous silica-based particles (Cu-BMS) were prepared using an evaporation-induced self-assembly sol-gel procedure as a heterogeneous catalyst for the activation of peroxydisulfate (PDS). The formation of well-organized mesoporous structures with amorphous nature and high surface area of 286 m²/g was demonstrated. The catalytic activity of Cu-BMS in the degradation of Methylene Blue (MB) and the effects of operating parameters, including Cu-BMS dosage, initial PDS amount, initial MB concentration, temperature and initial pH, were investigated in details. The Cu-BMS demonstrated a remarkable catalytic activity (93.5% degradation efficiency within 60 min) and good stability

Luminescent Eu3+-doped transparent alumina ceramics with high hardness

The Eu3+-doped transparent aluminas were prepared by wet shaping technique followed by pressureless sintering and hot isostatic pressing. The effect of dopant amount on microstructure, real in-line transmission (RIT), photoluminescence (PL) properties, hardness and fracture behaviour was studied. The RIT decreased with increasing amount of the dopant. The PL emission spectra of Al2O3:Eu3+ ceramics exhibited predominant red light emission with the highest intensity (under 394 nm excitation) for material containing 0.125 at.% of Eu3+ and colour coordinates (0.645, 0.355) comparable with commercial red phosphors. The doping resulted in hardness increase from 26.1 GPa for undoped alumina to 27.6 GPa for Eu-doped sample. The study of fracture surfaces showed predominantly intergranular crack propagation micro-mechanism

Investigation of catalytic activation of peroxydisulfate on cu-doped mesoporous silica-based particles (Cu-BMS) for efficient degradation of methylene blue

The Cu-doped mesoporous silica-based particles (Cu-BMS) were prepared using an evaporation-induced self-assembly sol-gel procedure as a heterogeneous catalyst for the activation of peroxydisulfate (PDS). The formation of well-organized mesoporous structures with amorphous nature and high surface area of 286 m2/g was demonstrated. The catalytic activity of Cu-BMS in the degradation of Methylene Blue (MB) and the effects of operating parameters, including Cu-BMS dosage, initial PDS amount, initial MB concentration, temperature and initial pH, were investigated in details. The Cu-BMS demonstrated a remarkable catalytic activity (93.5% degradation efficiency within 60 min) and good stability.Alexander Dubček University of Trenčín; Centre for Functional and Surface Functionalized Glass; Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA, (1/0064/21); Horizon 2020, (739566); Univerzita Tomáše Bati ve Zlíně, UTBEuropean Union [739566]; Scientific Grant Agency of the Slovak Republic [VEGA 1/0064/21

Processing and properties of luminescent Cr3+ doped transparent alumina ceramics

Transparent Cr2O3-doped alumina ceramics were prepared by slip casting, followed by pre-sintering in ambient atmosphere and hot isostatic pressing. The effect of dopant concentration on material properties, including microstructure and optical properties was evaluated. Real in-line transmittance in the range of 20–44 % was measured for the ceramics with the mean grain size<520 nm: the transmittance decreased with increasing grain size and Cr content. The excitation spectra consisted of two broad bands with maxima at 404 nm and 558 nm, corresponding to 4A2g4T1g and 4A2g4T2g transitions of Cr3+ ions in octahedral sites of -Al2O3. The intensive deep red narrow emissions under violet/green light excitation, R-lines (2Eg4A2g transition), were observed at 692.5 nm and 693.8 nm, that are very close to ruby single crystal. The highest emission was achieved at the Cr3+ concentration of 0.4 at.%. The luminescence decay curves exhibited single-exponential behaviour with decay times of 3.6 ms

Al2O3–SiC composites prepared by infiltration of pre-sintered alumina with a poly(allyl)carbosilane

The Al2O3/SiC nanocomposites containing 3–8 vol.% SiC were prepared through infiltration and in situ thermal decomposition of a preceramic polymer SiC precursor (poly(allyl)carbosilane) in pre-sintered alumina matrix. The volume fraction of SiC, and the microstructure of composites were adjusted by concentration of the polymer solution, and by the conditions of pyrolysis and sintering. The specimens were densified by pressureless sintering at temperatures between 1550 and 1850 °C in flowing argon. The use of powder bed producing SiO, CO and other volatile species suppressed decomposition reactions in the composites and was vital for their successful densification. The experimental results are discussed against thermodynamic analysis of the system Al2O3/SiC/SiO2 in an inert Ar atmosphere

Sintering of Ce3+-doped yttria nanoparticles prepared by precipitation method

Cerium doped yttrium oxide nanoparticles with various Ce3+ concentrations between 0.001 and 0.010 at% have been synthesised by precipitation method using ammonium hydroxide as a precipitation agent. The synthesised powders are characterised by a mean particle size of ca. 55 nm. Highly dense specimens, with a relative density> 98.8%, were obtained by sintering the green compacts shaped by pressure filtration, at 1550 °C for 3 h in air. The sintering behaviour of Ce3+ doped Y2O3 was studied by constructing Master Sintering Curves (MSC); the results showed that the apparent activation energy of sintering for Ce3+ doped Y2O3 increases with the increase of cerium concentration. The segregation of larger Ce3+ cations in the grain boundaries is likely to be responsible for the increase in the sintering activation energy

The influence of Al2O3 concentration on the NaYF4 crystallization in oxyfluoride glass–ceramics

[EN] The influence of Al2O3 addition on the precipitation of NaYF4 crystals in oxyfluoride glasses has been investigated through the thermal, structural, and optical characterization of the parent glasses and corresponding glass–ceramics (GCs). The high-resolution transmission electron microscopy analysis of the GC with 5 mol% of Al2O3 shows the presence of phase-separated droplets about 69 nm in size containing several NaYF4 nanocrystals with the diameter of about 10–15 nm. Raman and magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy were used to examine the structural changes attributed to the addition of Al2O3. The 19F MAS-NMR analysis indicated that fluorine atoms are present in different chemical environments (Na–F, Na–Si–F, Na–Al–F, and NaYF4). The increasing amount of Al2O3 reduces the crystallization of NaYF4 phase due to the increased fraction of fluorine bound in Na–Al–F environments. The visible luminescence investigation of the glasses and GCs demonstrated that the intensity of Er3+ ions emission transitions in the GCs was higher than that of the parent glass. This difference was attributed to the presence of Er3+ ions bound in NaYF4 crystalline phase. Further evidence that the Er3+ ions were present in NaYF4 phase was provided by the fact that the excited level Er3+:4S3/2 lifetime was increased in GCs as compared to parent glass.European Union Horizon 2020, Grant/Award Number: 739566; Slovak Grant Agency, Grant/Award Number: VEGA 1/0476/22; RIS3 SK, Grant/Award Number: ITMS2014+:313011W442; European Regional Development FundPeer reviewe

Crystallization kinetics of binary Yb2O3-Al2O3 glass

The ytterbium aluminum garnet composition YbAG (62.5 mol.% Al2O3, 37.5 mol.% Yb2O3) was prepared in the form of glass microspheres by flame synthesis. Precursor powder for flame synthesis with high homogeneity was prepared by modified sol-gel Pechini method. XRD pattern of prepared glass microspheres indicated predominantly amorphous nature of the sample. Detailed study of morphology of the microspheres by scanning electron microscopy revealed the presence of a small fraction of partially or fully crystallized microspheres. The high-temperature X-ray powder diffraction analysis (HT XRD) was carried out in the temperature interval 750-1450 degrees C: The temperature dependence of phase composition was determined. Crystallization of Yb3Al5O12-ytterbium aluminum garnet phase-was observed in the temperature range 900-1200 degrees C. The DSC analysis with heating rates 2, 4, 6, 8, 10 degrees C min(-1)in temperature interval 25-1200 degrees C was performed in N(2)atmosphere to study thermal behavior and crystallization kinetics of prepared glass microspheres. The two exothermic effects at 918 and 939 degrees C were observed, which were attributed to Yb(3)Al(5)O(12)crystallization. The crystallization kinetics of prepared sample was examined with the use of JMAK model, and the kinetic triplet-frequency factorA = (1.8 +/- 2.2) 10(+28)min(-1)(for the first peak),A = (1.2 +/- 1.6) 10(+55)min(-1)(for the second peak), apparent activation energyE(app) = (6.4 +/- 0.1) 10(+02) kJ mol(-1)(for the first peak),E-app = (1.3 +/- 0.1) 10(+03)kJ mol(-1)(for the second peak) and the Avrami coefficientm = 3 (for the first peak) andm = 2 (for the second peak)-was determined using RSS,Radj2, AIC andW(AIC)criteria

A novel interplay between the ubiquitin-proteasome system and serine proteases during Drosophila development.

The concentrations of the Drosophila proteasomal and extraproteasomal polyubiquitin receptors fluctuate in a developmentally regulated fashion. This fluctuation is generated by a previously unidentified proteolytic activity. In the present paper, we describe the purification, identification and characterization of this protease (endoproteinase I). Its expression increases sharply at the L1-L2 larval stages, remains high until the second half of the L3 stage, then declines dramatically. This sharp decrease coincides precisely with the increase of polyubiquitin receptor concentrations in late L3 larvae, which suggests a tight developmental co-regulation. RNAi-induced down-regulation of endoproteinase I results in pupal lethality. Interestingly, we found a cross-talk between the 26S proteasome and this larval protease: transgenic overexpression of the in vivo target of endoproteinase I, the C-terminal half of the proteasomal polyubiquitin receptor subunit p54/Rpn10 results in transcriptional down-regulation of endoproteinase I and consequently a lower level of proteolytic elimination of the polyubiquitin receptors. Another larval protease, Jonah65A-IV, which degrades only unfolded proteins and exhibits similar cross-talk with the proteasome has also been purified and characterized. It may prevent the accumulation of polyubiquitylated proteins in larvae contrary to the low polyubiquitin receptor concentration