Modification of titania nanoparticles for photocatalytic antibacterial activity via a colloidal route with glycine and subsequent annealing

Changes in the colloid-chemical and photocatalytic properties of titania nanoparticles by attrition milling in the presence of glycine (Gly) and subsequent heat treatment were examined. By milling at 1500 rpm for 6 h, the average particle size was decreased from 123 to 85 nm, with simultaneous decrease in the specific surface area from 35.1 to 23.5 m2/g. Interfacial reactions between titania and Gly were confirmed by Fourier transform infrared spectroscopy, from the blue shift of the COO− related vibrational bands by 25 cm−1, relative to the same band from the pristine Gly. The bimodal N1s x-ray photoelectron spectroscopy peak similar to that from the reported titania—amino acid complex is another indication of the complex formation with the participation of nitrogen. When the dispersion was dried and calcined at 500 °C in air, the powder exhibited pale yellow color. Diffuse reflectance spectroscopy showed significant visible light absorption, suggesting nitrogen incorporation into titania. The fired product showed high photocatalytic antibacterial activity by irradiation of blue light centered at around 440 nm, using Escherichia coli as a specimen of bacterial species. Thus, the present Gly-modified titania nanoparticles could be used for eliminating indoor bacteria under soft blue illumination. The series of interfacial chemical processes involved are also discusse

Preparation and dielectric properties of CuAlO2 ceramics

Within this work, the focus was on preparation of the delafossite CuAlO2 single phase powder and ceramic with a high density by the solid state synthesis, and on dielectric properties of the as-synthesized ceramic. The reaction between the nanoboehmite γ-AlOOH, with a high specific surface area, and the Cu2O, with the particles below 1 μm, was enhanced by comminution in a high energy mill, which resulted in reduction of the particle size and consequently shorter diffusion paths between constituent powders. The phase pure CuAlO2 powder was synthesized upon heating the reagent powder mixture two times for 10 h at 1100oC in the inert argon atmosphere as confirmed by the X-ray analysis. The ceramic with 86% of theoretical density was obtained after sintering the CuAlO2 powder compact at 1100oC for 2 h in air. According to the X-ray analysis the ceramic sample was single-phase. The bulk of the sample revealed a dense microstructure with a uniform distribution of porosity within the delafossite matrix. However, traces of Cu-rich impurities have been identified at the surface of the pellets by the EDXS analysis. The semiconducting nature of the ceramic sample was confirmed by the temperature dependent dielectric parameters measurements (ε’ and tgδ) in the 10 kHZ-1MHz frequency range between 297 and 473 K

Modification of Titania-Based Nanoparticles for Anode Materials of Li Ion Battery

The present poster contribution aims at optimization of electrochemical properties of titania (N doped anatase TiO2 / N) and Li-Ti ternary oxides (Li4Ti5O12, LTO) with respect to their performance as anode materials in Li-ion battery by using mechanochemical effects

Synthesis of LiFePO4 by mechanical stressing and thermal annealing

Mechanical activation can be regarded as a multi-step process with changes in the energetic parameters and the amount of accumulated energy of solids in each step. Here we report the influence of mechanochemical processing on the synthesis of LiFePO4 powders. The different precursor powders were milled in a planetary mill by using WC vials and 5 mm balls made of the same material. A slightly reductive atmosphere (Ar + 5%H2) was used in both mechanical stressing and thermal annealing so as to prevent the oxidation of iron. All synthesis steps were followed by an X-ray diffractometry and FT-IR spectroscopy. The results were compared with previous findings of precipitated and annealed powder, without mechanochemical treatment

Nanostructure and magnetic anomaly of mechanosynthesized Ce1−x_{1-x}Yx_{x}O2−δ_{2-δ} (x ≤ 0.3) solid solutions

Electromagnetic properties of complex oxide solid solutions containing Ce and Y attract increasing interests due to their high application potential. Their properties are known to be dependent on many factors including grain size and crystal defects. Here we focus on unique features of nanocrystalline Ce$_{1-x}$Y$_{x}$O$_{2-δ}$ (x ≤ 0.3) solid solutions prepared via a mechanosynthesis. Mechanically activated CeO$_{2-δ}$ and mechanosynthesized Ce$_{1-x}$Y$_{x}$O$_{2-δ}$ exhibit room-temperature ferromagnetism. The saturation magnetization reaches maximum for the Ce$_{0.9}$Y$_{0.1}$O$_{2-δ}$ solid solution. XPS and Raman spectra show that Ce$^{Zahl}$4+s are partially reduced to Ce$^{3+}$, with simultaneous introduction of oxygen vacancies accumulated on surface of the solid solutions. An analysis of the experimental magnetization data and the determination of both the spin state and the concentration of magnetic carriers revealed that a small part of the Ce$^{3+}$ spins (<1%) is responsible for the magnetic state of the Ce$_{1-x}$Y$_{x}$O$_{2-δ}$ system. Existence of clusters with a short-range antiferromagnetic order is also suspected

A Unique Mechanochemical Redox Reaction Yielding Nanostructured Double Perovskite Sr2_{2}FeMoO6_{6} With an Extraordinarily High Degree of Anti-Site Disorder

Strontium ferromolybdate, Sr(2)FeMoO(6), is an important member of the family of double perovskites with the possible technological applications in the field of spintronics and solid oxide fuel cells. Its preparation via a multi-step ceramic route or various wet chemistry-based routes is notoriously difficult. The present work demonstrates that Sr(2)FeMoO(6) can be mechanosynthesized at ambient temperature in air directly from its precursors (SrO, α-Fe, MoO(3)) in the form of nanostructured powders, without the need for solvents and/or calcination under controlled oxygen fugacity. The mechanically induced evolution of the Sr(2)FeMoO(6) phase and the far-from-equilibrium structural state of the reaction product are systematically monitored with XRD and a variety of spectroscopic techniques including Raman spectroscopy, (57)Fe Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. The unique extensive oxidation of iron species (Fe(0) → Fe(3+)) with simultaneous reduction of Mo cations (Mo(6+) → Mo(5+)), occuring during the mechanosynthesis of Sr(2)FeMoO(6), is attributed to the mechanically triggered formation of tiny metallic iron nanoparticles in superparamagnetic state with a large reaction surface and a high oxidation affinity, whose steady presence in the reaction mixture of the milled educts initiates/promotes the swift redox reaction. High-resolution transmission electron microscopy observations reveal that the mechanosynthesized Sr(2)FeMoO(6), even after its moderate thermal treatment at 923 K for 30 min in air, exhibits the nanostructured nature with the average particle size of 21(4) nm. At the short-range scale, the nanostructure of the as-prepared Sr(2)FeMoO(6) is characterized by both, the strongly distorted geometry of the constituent FeO(6) octahedra and the extraordinarily high degree of anti-site disorder. The degree of anti-site disorder ASD = 0.5, derived independently from the present experimental XRD, Mössbauer, and SQUID magnetization data, corresponds to the completely random distribution of Fe(3+) and Mo(5+) cations over the sites of octahedral coordination provided by the double perovskite structure. Moreover, the fully anti-site disordered Sr(2)FeMoO(6) nanoparticles exhibit superparamagnetism with the blocking temperature T (B) = 240 K and the deteriorated effective magnetic moment μ = 0.055 μ (B) per formula unit