Nanoparticle structure, surface structure and crystal chemistry

Waychunas, Glenn A.; Kim, C.S.; Gilbert, Benjamin; Zhang, H.; Banfield, Jillian F.

doi:10.1016/j.gca.2006.06.1505

Cited by 3 publications

(1 citation statement)

References 4 publications

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“…3 4 Compared with the pure nano-TiO 2 , the nano-TiO 2 coated magnetic particles are alternative candidates for heterogeneous photocatalysis owing to their multifunctional surfaces and magnetically separable properties. Various TiO 2 -related core-shell magnetic nanoparticles such as TiO 2 / -Fe 2 O 3 , 5 6 TiO 2 /Fe 3 O 4 , 7-10 TiO 2 /CoFe 2 O 4 , 11 12 TiO 2 /NiFe 2 O 4 , 13 14 have been extensively investigated. However, in most cases the photocatalytic activity was lower than that of the single phase nano-TiO 2 due to the heterojunction effect, in which the electronic interaction usually takes place between the TiO 2 coating and iron-contained oxide core.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Core–Shell Nano-TiO2/Al2O3/NiFe2O4 Microparticles with Enhanced Photocatalytic Activity

Jing

Han²,

Wang³

et al. 2013

j. nanosci. nanotech.

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The core-shell nano-TiO2/Al2O3/NiFe2O4 microparticles of 5-8 microm were prepared by the heterogeneous precipitation followed by calcination treatment. The morphologies, structure, crystalline phase, and magnetic property were characterized by optical biomicroscopy (OBM), scanning electron microscopy (SEM), X-ray diffractometry (XRD) and vibrating sample magnetometer (VSM) respectively. The photocatalytic activity was evaluated by degrading methyl orange solution either under UV light and sunlight. The results indicate that the nano-TiO2 layer consists of needle-like nanoparticles and the intermediate layer of Al2O3 avoids the nano-TiO2 agglomeration, shedding and uneven loading. The nano-TiO2/Al2O3/NiFe2O4 composite particles show high magnetization of 31.5 emu/g and enhanced photocatalytic activity to completely degrade 50 mg/L methyl orange solution either under UV light and sun light. The enhanced activity of the composite is attributed to the unique structure, insulation effect of Al2O3 intermediate layer and the hybrid effect of anatase TiO2 and NiFe2O4. The obtained catalyst may be magnetically separable and useful for many practical applications due to the improved photocatalytic properties under sunlight.

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Section: Introductionmentioning

confidence: 99%

Magnetic Core–Shell Nano-TiO2/Al2O3/NiFe2O4 Microparticles with Enhanced Photocatalytic Activity

Jing

Han²,

Wang³

et al. 2013

j. nanosci. nanotech.

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Powders versus Thin Film Preparation

2010

Clean by Light Irradiation

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The chapter briefly outlines the sulphate, the chloride, the flame pyrolysis, the sol-gel, the hydrothermal, the solvothermal, the sol, the laser pyrolysis and the microwave methods for the preparation of the three most important powdered TiO2 phases (anatase, brookite and rutile). Some of these preparations can be used to prepare thin films of TiO2 on various types of supports. The techniques described for the films obtainment are: the dip-coating, the spin-coating, the flow coating, the (plasma) spray drying, the spray-pyrolysis methods, the physical vapour deposition, the chemical vapour deposition, the chemical bath deposition, the thermal or the anodic oxidation and the electrophoretic techniques. Some examples from the literature are commented by considering the photocatalytic activity both of powders and films.

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Properties of atoms under pressure: Bonded interactions of the atoms in three perovskites

Gibbs

Wang

Hin

et al. 2012

The Journal of Chemical Physics

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The crystal structures for the three perovskites, CaSnO(3), YAlO(3), and LaAlO(3), were geometry optimized at the density functional theory level for a wide range of simulated isotropic pressures up to 80 GPa. The connections between the geometry optimized bond lengths, R(M-O), the values of the electron density, ρ(r(c)), the local kinetic, G(r(c)), potential, V(r(c)), energy densities, H(r(c)), and the Laplacian, ∇(2)(r(c)), at the bond critical points, r(c), for the M-O nonequivalent bonded interactions were examined. With increasing pressure, ρ(r(c)) increases along four distinct trends when plotted in terms of the Al-O, Ca-O, Sn-O, Y-O, and La-O bond lengths, but when the bond lengths were plotted in terms of ρ(r(c))/r where r is the periodic table row number of the M atoms, the data scatter along a single trend modeled by the power law regression expression R(M-O) = 1.41(ρ(r(c))/r)(-0.21), an expression that is comparable with that obtained for the bonded interactions for a large number of silicate and oxides crystals, R(M-O) = 1.46(ρ(r(c))/r)(-0.19) and that obtained for a relatively large number of hydroxyacid molecules R(M-O) = 1.39(s/r)(-0.22) where s is the Pauling bond strength of a bonded interaction. The similarity of the expressions determined for the perovskites, silicate and oxides crystals, and hydroxyacid molecules suggest that the bonded interactions in molecules and crystal are not only similar and comparable. The close correspondence of the expressions for the perovskites, the silicate and oxide crystals, and the molecules indicates that Pauling bond strength and ρ(r(c)) are comparable measures of the bonded interactions, the larger the accumulation of the electron density between the bonded atoms the larger the value of s, the shorter the bond lengths. It also indicates that the bonded interactions that govern the bond length variations behave as if largely short ranged. Like ρ(r(c))/r, the values of G(r(c))/r, V(r(c))/r, ∇(2)(r(c))/r likewise correlate in terms of R(M-O) in a single trend. With increasing pressure, the value of V(r(c)) decreases at a faster rate than G(r(c)) increases consistent with the observation that ρ(r(c)) increases with increasing pressure thereby stabilizing the structures at high pressures. As evinced by the well-developed power law trends between R(M-O) and the bond critical point properties, the bulk of the bonded interactions for the perovskites are concluded to change progressively from closed-shell to intermediate polar covalent interactions with increasing pressure. A well-developed trend between the ratios ∣V(r(c))∣ /G(r(c)) and H(r(c))/ρ(r(c)) is consistent with this conclusion. The employment of a positive value for the Laplacian alone in distinguishing between closed shell and polar covalent bonded interactions is unsatisfactory when 2G(r(c)) > ∣V(r(c))∣ > G(r(c)).

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Nanoparticle structure, surface structure and crystal chemistry

Cited by 3 publications

References 4 publications

Magnetic Core–Shell Nano-TiO<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB>/NiFe<SUB>2</SUB>O<SUB>4</SUB> Microparticles with Enhanced Photocatalytic Activity

Magnetic Core–Shell Nano-TiO<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB>/NiFe<SUB>2</SUB>O<SUB>4</SUB> Microparticles with Enhanced Photocatalytic Activity

Powders versus Thin Film Preparation

Properties of atoms under pressure: Bonded interactions of the atoms in three perovskites

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