The synthesis of Zn2SiO4 doped with Mn2+ ions at different concentrations have been successfully achieved by a conventional sol–gel method. The structure and morphology of the obtained samples were ...characterized by XRD, FTIR, Raman spectroscopy, EDAX, and FE-SEM, TEM. The XRD results of Zn2SiO4 samples with different Mn concentrations showed no obvious differences from the willemite structure. The SEM and TEM results showed the ceramic powders are nanometer sized spherical grains spherical forms and EDAX results confirmed the successful doping of Mn2+ ions into Zn2SiO4 matrix. The optical and dielectric properties of Mn2+ ions doped Zn2SiO4 show an appreciable difference between the levels of Mn2+ doping. The luminescence spectra showed that 0.25mol% Mn2+ in Zn2SiO4 gives a maximum intensity a in the green emission corresponding to the 4T1 (4G) → 6A1(6S) transition for tetrahedral-coordinated Mn2+ (weak crystal field) and at higher levels of Mn2+ doping the green band intensity decreases. The 0.25mol% Mn2+ in Zn2SiO4 also gives the highest ionic conductivity at 373 K. The dielectric constant (ε′), loss tangent (tan δ) and AC conductivity (σac) properties as the function of frequency have also been analyzed and those are strongly dependent on Mn ion concentrations.
Display omitted
•Green luminescence and dielectric nature of Mn2+: Zn2SiO4 nanocomposites reported and discussed.•Both bright green and good conductivity properties of Mn2+: Zn2SiO4 obtained at 0.25mol%.•Uniformly distribution of Mn ions over Zn sites in the host matrix.•Primary characterizations results indicated that these ceramic powders nanometer sized-grains spherical forms with willemite structures.•Spherical shape nanophosphors are favorable in the field display applications.
Mesoporous bioactive glasses have been widely investigated for applications in bone tissue regeneration and, more recently, in soft tissue repair and wound healing. In this study we produced ...mesoporous bioactive glass nanoparticles (MBGNs) based on the SiO2–CaO system. With the intention of adding subsidiary biological function, MBGNs were doped with Zn2+ ions. Zn-MBGNs with 8 mol% ZnO content were synthesized via microemulsion assisted sol-gel method. The synthesized particles were homogeneous in shape and size. They exhibited spherical shape, good dispersity, and a size of 130 ± 10 nm. The addition of zinc precursors did not affect the morphology of particles, while their specific surface area increased in comparison to MBGNs. The presence of Zn2+ ions inhibited the formation of hydroxycarbonate apatite (HCAp) on the particles after immersion in simulated body fluid (SBF). No formation of HCAp crystals on the surface of Zn-MBGNs could be observed after 14 days of immersion. Interestingly, powders containing relatively high amount of zinc released Zn2+ ions in low concentration (0.6–1.2 mg L−1) but in a sustained manner. This releasing feature enables Zn-MBGNs to avoid potentially toxic levels of Zn2+ ions, indeed Zn-MBGNs were seen to improve the differentiation of osteoblast-like cells (MG-63). Additionally, Zn-MBGNs showed higher ability to adsorb proteins in comparison to MBGNs, which could indicate a favourable later attachment of cells. Due to their advantageous morphological and physiochemical properties, Zn-MBGNs show great potential as bioactive fillers or drug delivery systems in a variety of applications including bone regeneration and wound healing.
Display omitted
•Zn doped mesoporous bioactive glass nanoparticles synthesized via microemulsion - sol-gel method.•Synthesized particles were homogeneous in shape and size.•Particles released Zn2+ ions in low concentration and in sustained manner.•Zn-MBGNs improved differentiation of osteoblast-like cells (MG-63).•Zn-MBGNs show potential for hard and soft tissue engineering.
Display omitted
► Novel supported titania photocatalysts by a modified ultrasound-assisted sol–gel technique. ► Glucose photocatalytic selective oxidation to glucaric acid and gluconic acid. ► ...Prepared photocatalysts with high potential for water (phenol removal) purification and solar chemicals production. ► Simplification of conventional multistep synthesis of valuable compounds to a one-pot photocatalytic pathway.
The selective oxidation of glucose and degradation of phenol in liquid phase were studied in the presence of supported TiO2 photocatalysts. Photocatalysts were synthesized by a modified ultrasound-assisted sol–gel method. The fact of supporting TiO2 on zeolite type Y is giving more selective photocatalyst in glucose oxidation toward glucaric acid (GUA) and gluconic acid (GA) (total selectivity approx. 68%, after 10min illumination time and 50%H2O/50%acetonitrile solvent composition) than the unsupported TiO2 and the commercially available photocatalyst Evonik P-25. Photocatalysts worked at room temperature, atmospheric pressure and very short reaction times (up to 15min). Additionally, these photocatalysts were investigated in the mineralization of phenol as a cellulosic industries water contaminant. It was observed that fumed silica is a better option than zeolite as titania support in phenol aqueous degradation.
Ultrasound-promoted sol–gel methodology is giving promising supported TiO2 photocatalysts for water purification and solar chemicals production.
We report the synthesis of nanostructured SnO2 by a simple inexpensive sol–gel spin coating method using m-cresol as a solvent. This method facilitates rapid synthesis at comparatively lower ...temperature enabling formation of nanostructures suitable for gas-sensing applications. Various physicochemical techniques have been used for the characterization of SnO2 thin films. X-ray diffraction analysis confirmed the single-phase formation of tetragonal SnO2 having crystallite size 5–10nm. SnO2 showed highest response (19%) with 77.90% stability toward 100ppm nitrogen dioxide (NO2) at 200°C. The response time of 7s and recovery time of 20min were also observed with the same operating parameters. The probable mechanism is proposed to explain the selective response toward nitrogen dioxide. Impedance spectroscopy studies showed that the response to nitrogen dioxide is mainly contributed by grain boundaries. The reproducibility and stability study of SnO2 sensor confirmed its candidature for detection of NO2 gas at low concentration (10–100ppm) and lower operating temperature.
STEM-HAADF image of 2%WO3/TiO2 catalyst, the small lightest zones represents WO3 clusters. Display omitted
► To evaluate the WO3/TiO2 photocatalytic activity, this is one of the first studies that ...were carried out using solar energy for degradation of an organophosphorous pesticide. ► The sol–gel technique for the 2%WO3/TiO2 synthesis, allowed the incorporation of WO3 clusters on anatase TiO2 surface, with a good homogeneity in spatial and size distribution. ► The morphological and electronic properties obtained in the coupled WO3/TiO2 catalyst give as a result better performance of the composite than bare TiO2 for malathion degradation under solar light radiation.
In this study, TiO2 modified with WO3 (2wt.%) was prepared by the sol–gel method, and its photocatalytic activity (PCA) under solar irradiation was evaluated using malathion as the model contaminant. The catalyst was synthesized using tetra butyl orthotitanate (TBT) and ammonium p-tungstate (ApT) as precursors. For comparison, bare TiO2 was also prepared by the sol–gel process. The resulting photocatalysts were characterized by XRD, BET, DRUV–vis, FE-SEM, TEM and STEM. The synthesized TiO2 materials exhibited a crystalline anatase phase with an average particle size of 20nm. Results of malathion degradation using solar light, indicated that 2%WO3/TiO2 showed better catalytic performance than sol–gel TiO2, achieving a complete degradation after 2h, while TOC abatement was 63% after 5h. These results suggest that 2%WO3/TiO2 catalyst is a promising material for solar photocatalytic treatment of water contaminated by pesticides.
SrBixLaxFe12-2xO19 (0.0≤x≤0.5) hexaferrites were synthesized by sol-gel auto combustion technique. The influence of Bi and La substitutions on structural, magnetic and optical properties were ...investigated by X-ray diffraction (XRD), Furrier transformed infrared (FT-IR), Vibrating sample magnetometer (VSM) and Percent diffuse reflectance spectroscopy (DR %). XRD analysis confirmed the single phase formation for all the samples, the purity of the products was also confirmed by FT-IR. The specific magnetization (σ-H) curves revealed the ferromagnetic nature of the samples. The extrapolated specific saturation magnetization (σs) decreases from 63.45emu/g to 49.84emu/g with increasing Bi, La substitutions. Similar decrement is observed from 32.6emu/g to 25.8emu/g at remnant magnetization (σr). The average crystallite size varies in a range of (43.28–51.40)nm. The coercive fields are between 4682 and 5315Oe. Magnetic anisotropy was assigned as uniaxial and calculated effective anisotropy constants (Keff) are between 5.57×105 Ergs/g and 4.03×105 Ergs/g. The observed high magnitudes of intrinsic coercivity (Hci) above 16,000Oe confirm hard magnetic nature of the samples. The Tauc plots were used to extrapolate the direct optical energy band gap (Eg) of hexaferrites. The Eg values decreased from 1.81 to 1.68eV with increasing Bi, La contents.
The emissions at the three biological windows are due to the energy transfer of Yb3+ → Ln3+ → Cr3+ under 980 nm excitation.
Display omitted
•The phosphors emit in NIR-1, NIR-2 and NIR-3 ...simultaneously.•The emissions have good thermal stability.•The fluorescence intensity ratio of Er3+ in NIR-3 can be used to measure temperature.
Until now, the emissions of most biological phosphors were located at a single biological window. By utilizing energy transfer of Yb3+ → Ln3+ → Cr3+, we have successfully developed a phosphor emitting in the first, second and third biological windows simultaneously. The luminescences have good thermal stability because of forming the thermal cycle among Ho3+ and Cr3+. And temperature measurement can be realized in NIR-3.
PDF
