Tailoring bifunctional hybrid organic–inorganic nanoadsorbents by the choice of functional layer composition probed by adsorption of Cu2+ ions

Spherical silica particles with bifunctional (≡Si(CH2)3NH2/≡SiCH3, ≡Si(CH2)3NH2/≡Si(CH2)2(CF2)5CF3) surface layers were produced by a one-step approach using a modified Stöber method in three-component alkoxysilane systems, resulting in greatly increased contents of functional components. The content of functional groups and thermal stability of the surface layers were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and 13C and 29Si solid-state NMR spectroscopy revealing their composition and organization. The fine chemical structure of the surface in the produced hybrid adsorbent particles and the ligand distribution were further investigated by electron paramagnetic resonance (EPR) and electron spectroscopy of diffuse reflectance (ESDR) spectroscopy using Cu2+ ion coordination as a probe. The composition and structure of the emerging surface complexes were determined and used to provide an insight into the molecular structure of the surfaces. It was demonstrated that the introduction of short hydrophobic (methyl) groups improves the kinetic characteristics of the samples during the sorption of copper(II) ions and promotes fixation of aminopropyl groups on the surface of silica microspheres. The introduction of long hydrophobic (perfluoroctyl) groups changes the nature of the surface, where they are arranged in alternately hydrophobic/hydrophilic patches. This makes the aminopropyl groups huddled and less active in the sorption of metal cations. The size and aggregation/morphology of obtained particles was optimized controlling the synthesis conditions, such as concentrations of reactants, basicity of the medium, and the process temperature

Luminescence and vacuum ultraviolet excitation spectroscopy of samarium doped SrB₄O₇

Abstract Sm²⁺ and Sm³⁺ co-doped SrB₄O₇ could be utilized in several high-level optical devices and fundamental knowledge about the optical behavior of these materials benefits the development of luminescent applications. Herein, we report luminescence and its vacuum ultraviolet (VUV) excitation spectra in samarium doped SrB₄O₇. Both, Sm²⁺ and Sm³⁺ luminescence centers have been examined and distinguished in the emission and the excitation spectra investigated under synchrotron radiation. The contribution of either Sm²⁺ or Sm³⁺ emission lines into the emission spectra heavily depended on the excitation energy, and strong f-f transitions of both Sm²⁺ and Sm³⁺ were detected. At 10 K, a broad intrinsic luminescence in the UV range was detected and attributed to the radiative transition of either bound or self-trapped exciton in SrB₄O₇. The optical behavior, including e.g. inter-configurational f-d transitions of Sm(n+) were elucidated with first-principles calculations. Partial density of states well represents the changes of the electronic states that are related to the samarium doping, which in turn explains the emerging features in excitation spectra. In summary, the obtained results clarify the excitation and emission behavior of samarium doped SrB₄O₇

Effect of magnesium ferrite doping with lanthanide ions on dark-, visible- and UV-driven methylene blue degradation on heterogeneous Fenton-like catalysts

Abstract The catalytic behavior of magnesium ferrites doped with lanthanide ions (La³⁺, Ce³⁺, Sm³⁺, Gd³⁺, and Dy³⁺) on Methylene Blue (MB) degradation using Fenton process was studied. A slow increase in cubic Fd3m crystalline structure parameters and increase in crystallite size of doped samples magnesium ferrites were observed. A dramatic decrease in catalytic activity of catalysts obtained at 600 °C as compared to catalysts obtained at 300 °C was explicitly observed and this was grossly attributed to the elimination of surface hydroxyl groups as ascertained by FT-IR analysis. The initial magnesium ferrite demonstrated the highest catalytic activity under dark- (kˈ 0.0555 min⁻¹) and visible-light (kˈ 0.1029 min⁻¹) conditions. Catalytic efficiency of the lanthanides doped catalysts under UV-irradiation in accordance with the maximum appearance rate constant kˈ decreased in the following order Ce³⁺ > Dy³⁺ > La³⁺ ≈ MgFe₂O₄ > Sm³⁺ > Gd³⁺. The most active ferrites provided up to 99% of MB degradation in 60 and 20 min for visible- and UV-driven Fenton processes. Findings obtained from this study were observed to be competitive with other heterogeneous Fenton catalysts