Highly enhanced degradation of dye with well-dispersed TiO2 nanoparticles under visible irradiation

TiO₂ nanoparticles were prepared through a facile flame method. The samples were characterized by means of X-ray diffraction, transmission electron microscopy, zeta potential measurement and transmittance spectrum. Compared with TiO₂ P-25, smaller particle size, less agglomeration and well dispersion are shown for the prepared TiO₂ particles. The photosensitized catalytic activity of as-prepared TiO₂ was investigated upon its degradation of Rhodamine B under visible light irradiation. It is found that the optical characteristics of TiO₂ have great influence on the photosensitized catalytic activity due to its crystalline forms, smaller size, higher surface area and well dispersion.     

Effects of Bi doping on the optical properties of Er:Y2O3

The influences of Bi³⁺ doping on the optical properties of Er³⁺:Y₂O₃ are investigated under UV and IR excitations. The emission intensity of Er³⁺ is remarkably enhanced by the introduction of Bi³⁺ under both two excitations. The emission enhancement under UV excitation originates from the energy transfer from Bi³⁺ to Er³⁺, while under IR excitation it can be attributed to the modification of the local crystal field around the Er³⁺.     

Optical band gap tuning of discontinuous [SnO2/Mn]n multilayers

Multilayers (ML) of [SnO₂/Mn]_n were deposited by RF-magnetron sputtering on quartz substrates at room temperature using metal targets. The XRD pattern and the XRR show amorphous and discontinuous nature of ML respectively. The transmittance (at 550 nm) as well as the estimated optical band gap (E_g) decreases with the increase in the number of bilayers. The present study shows that the optical properties of the present ML can be tuned by changing the n value.     

A facile route to VN and V2O3 nanocrystals from single precursor NH4VO3

V₂O₃ and VN nanocrystals have been synthesized by the decomposition of the precursor NH₄VO₃ and following nitridation in an autoclave with metallic Na flux at 450–600 °C. X-ray powder diffraction (XRD) recorded the evolution process of the reaction from precursor NH₄VO₃ to hexagonal V₂O₃ and then to NaCl-type VN. In addition, the products were characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).     

Dielectric relaxation and ionic conductivity studies of [N(CH3)4]2Cu0.5Zn0.5Cl4

WO₃-doped zinc titanate ceramics were prepared by conventional mixed-oxide method combined with a chemical processing. The effects of WO₃ additions on the phase structure and phase transitions of zinc titanate ceramics were investigated by high-temperature X-ray diffractometry (HTXRD) and transmission electron microscopy (TEM). The results showed that the major phase of zinc titanate ceramics transformed from zinc orthotitanate phase to zinc metatitanate phase with the amounts of WO₃ additions increasing. Small WO₃ (<1.00 mass%) addition accelerated the transition of ZnTiO₃ to Zn₂TiO₄, while excessive WO₃ addition restrained the transition. HTXRD showed that WO₃ enhanced the stability of Zn₂Ti₃O₈ and weakened the stability of ZnTiO₃. A precipitate within the Zn₂TiO₄ matrix was observed. Viewed along the orientation of Zn₂TiO₄, the precipitate was found to have a rectangular shape and to be nanometer level in size; its composition was concluded to be Zn₂Ti₃O₈. The dielectric properties of WO₃-doped zinc titanate ceramics were measured at different frequencies. The results showed the decreasing tendency with the increasing measuring frequencies for both the dielectric constants and the loss tangents, and there existed maximum values when the amount of WO₃ was 0.50 mass%.     

Preparation, characterization and the electrogenerated chemiluminescence behavior of WO3 nanocrystals

The (WO₃)_NCs/Nafion film electrode was prepared by immobilizing the synthesized WO₃ NCs on the surface of a glassy carbon electrode (GCE) with the help of Nafion. The ECL emission of the electrode in aqueous solution was affected by the buffer solution with respect to the pH and composition. And the strongest ECL was observed in an NH₃-NH₄Cl buffer with pH being 8.2. Only a weak ECL peak at 1.14 V which was originated from the annihilation process between oxidized and reduced species of WO₃ NCs was found. By adding coreactant triproplamine (TPrA) in buffer solution, an additional ECL peak at 1.13 V which was attributed to the electron-transfer reaction between the oxidized WO₃ NCs and reduced intermediate of TPrA was observed. The (WO₃)_NCs/Nafion film electrode exhibits excellent ECL property and good stability, which would promote the potential application of WO₃ NCs as a luminescence material for solid-state ECL detection.     

Nonlinear saturable absorption of the sodium borosilicate glass containing Bi2S3 nanocrystals using Z-scan technique

The sodium borosilicate glass containing Bi₂S₃ nanocrystals is prepared by employing both sol-gel and atmosphere control methods. The third-order nonlinear optical absorption of the glass is investigated in detail using the open-aperture Z-scan technique at the wavelength of 770 nm with a pulse width of 200 fs. The results show that the transformation from saturable absorption to reverse saturable absorption in the glass is observed with the increase of the input light intensity of the laser used. The mechanism of the third-order nonlinear optical absorption is discussed preliminarily in the glass. Meanwhile, XRD, XPS, TEM, (S)TEM, EDAX, HRTEM, and SAED are used to characterize the microstructures of the glass.     

Formation of nanoparticles and nanorods via UV irradiation of AgNO3 solutions

The synthesis of silver nanoparticles via UV irradiation of AgNO₃ solutions was controlled by using UV–vis absorption spectra and TEM (transmission electron microscope) images. The UV–vis absorption method is good enough for the general control of synthesis process, and TEM images give us information about size of formed species. For investigated solutions of silver nitrate in ethanol and water, we observed formation of large nanoparticles (size about 100 nm) and nanorods (100 nm in length). Moreover, there was effort to confirm evidence of formation of these particles by using TOF mass spectrometer. Due to laser desorption/ionization process there is only evidence of small silver nanoparticles Ag_x, x ≤ 4 (clusters), and variety of silver compounds Ag_xN_yO_z (x ≤ 5, y ≤ 2, z ≤ 3).     

Synthesis and optical properties of Yb0.6Y1.4O3 transparent ceramics

Transparent yttrium oxide ceramics doped with 30 at.% ytterbium were successfully produced by a combination of pre-sintering and hot isostatic pressing. The influence on the final transparency of different densification states and porosity configurations obtained by varying pre-sintering conditions were investigated by optical and electron microscopy. Our results show that densification prior to the final stage of sintering is necessary to limit final porosity. Samples showing open porosity were found to lead to pore entrapment because of the diffusion of argon inside the glass capsule during hot isostatic pressing. Transmittance measurements showed that the valence charge of the ytterbium ions was 3+ at the end of the process, indicating no effect of reduction when pre-sintering in vacuum was employed.     

Magnetic and photoluminescence properties of Fe3O4@SiO2@YP1−xVxO4:Dy nanocomposites

In this paper, we report on the bifunctional Fe₃O₄@SiO₂@YP_0.1V_0.9O₄:Dy³⁺ nanocomposites were prepared by the solvothermal method and sol-gel method. The structure, photoluminescence (PL) and magnetic properties of the nanocomposites were characterized by means of X-ray diffraction, scanning electron microscope, transmission electron microscope, PL excitation and emission spectra and vibration sample magnetometry. It is shown that Fe₃O₄@SiO₂@YP_0.1V_0.9O₄:Dy³⁺ nanocomposites with a core-shell structure present excellent fluorescent and magnetic properties. Additionally, the effects of the magnetic field on the luminescence properties of nanocomposites were discussed.     

Characterization and sintering of BaZrO3 nanoparticles synthesized through a single-step combustion process

Barium zirconate (BaZrO₃) nanoparticles synthesized by a self-sustained single-step combustion process is reported in this paper. In this process, a phase pure nanopowder of BaZrO₃ has been obtained by the combustion of an aqueous solution containing Ba and Zr ions by using citric acid as complexing agent and liquor ammonia as fuel, thus giving rise to phase pure BaZrO₃ nanopowder in a single-step combustion without any further calcination. The X-ray diffraction studies have shown that the as-prepared powder was single phase, crystalline, and has a cubic perovskite structure (ABO₃) with a lattice constant a = 4.19 Å. The average particle size calculated from FWHM is 30 nm. The phase purity of BaZrO₃ nanopowder has been examined using differential thermal analysis (DTA), thermo gravimetric analysis (TGA) and Fourier transform of infrared spectroscopy (FTIR). The transmission electron microscopic investigation has shown that the particle size of the as-prepared powder was in the range 30–50 nm with a mean size of 40 nm. The nano BaZrO₃ has been sintered to a density of 99% of the theoretical density at 1650 °C in 2 h without the use of any sintering aids. The morphology of the sintered pellets has been studied with scanning electron microscopy (SEM). The dielectric constant (_r) and loss factor (tan δ) values obtained at 10 MHz for a well-sintered barium zirconate pellet has been found to be 32.2 and 1 × 10⁻⁴, respectively, at room temperature.     

Structural impact of tungsten ions on ZnO-Sb2O3-As2O3 glass system

Five glasses in the quaternary system 5 ZnO-(50 − x) As₂O₃-45 Sb₂O₃: x WO₃ with the values of x ranging from 0 to 20 mol% (in steps of 5 mol%) are prepared. The samples are characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS) and differential thermal analysis (DTA) techniques. The DTA studies have indicated that the glass forming ability decreases with the increasing content of WO₃. A number of studies, like, spectroscopic (optical absorption, IR, Raman, ESR spectra) and dielectric studies (dielectric constant ?, loss tan δ, a.c. conductivity σ_a.c.) over a wide range of frequency and temperature and dielectric break down strength at room temperature, have been carried out and are analysed in the light of different oxidation states and environment of tungsten ions in these glasses. These glasses have potential photonic applications.     

Optical study of praseodymium dicarboxylate [Pr(H2O)]2[O2C(CH2)3CO2]3.4H2O

Praseodymium dicarboxylate, [Pr(H₂O)]₂[O₂C(CH₂)₃CO₂]₃.4H₂O]–glutarate, Pr[glut], is synthesized by hydrothermal techniques. The title compound crystallizes in the monoclinic space group C2/c (No. 15). The rare earth cation is coordinated by nine oxygen atoms, eight oxygen atoms from the carboxylate groups and one from the water molecule. The local symmetry of Pr site is low, C_s. The absorption spectra of Pr[glut] are recorded from the visible to the far IR domain at 300, 77 and 9 K. Under various Ar⁺ laser excitations no emission is detected from ³P₀ and ¹D₂ excited levels of Pr³⁺ ion. In the low temperature absorption spectra only one electronic line is recorded for ³H₄→³P₀ transition. It confirms a unique local environment for the rare earth ion in Pr[glut]. The utility of the ‘barycenter curves’ in the attribution of electronic lines is demonstrated. Energy level scheme of 36 Stark components is deduced from the absorption spectra. The parametric calculation was performed on the whole 4f² (Pr³⁺) configuration with the starting set of crystal field parameters obtained previously for the Eu³⁺ ion in the isostructural compound. Eight free ion and nine phenomenological crystal field parameters in C_2v symmetry reproduce quite well several electronic levels of Pr³⁺ ion experimentally observed in Pr[glut]. A good r.m.s. standard deviation of 14.8 cm⁻¹ is obtained.     

A facile method to prepare MoS2 with nanolameller-like morphology

MoS₂ nanolamellers were synthesized by a one-step oxidation-reduction reaction in solution, in which the (NH₄)₂MoS₄ and H₂C₂O₄·2H₂O were used as reactants and then calcined at 800 °C under N₂ for 1 h. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The diameter and nanoplate thickness of the obtained MoS₂ nanolamellers were approximately 80 nm and 20-30 nm, respectively. These novel structures of nanolamellers had potential applications in solid lubricants.     

Ba4In2−x(CO3)1+xO6−2.5x and Ba4In0.8Cu1.6(CO3)0.6O6.2—new indium oxycarbonates closely related to n=3 Ruddlesden–Popper phases

Investigations of phase relations in the Ba-rich part of the In₂O₃–BaO(CO₂)–CuO pseudo-ternary system at 900 °C have revealed the existence of new indium–copper oxycarbonate – Ba₄In_0.8Cu_1.6(CO₃)_0.6O_6.2. Rietveld refinement of the X-ray powder diffraction data combined with infrared studies gives evidence that this phase is a oxycarbonate crystallising in the tetragonal structure (space group I4/mmm) with unit cell parameters: a=4.0349(1) Å and c=29.8408(15) Å. In the binary part of the In₂O₃–BaO(CO₂) system we have identified the occurrence of Ba₄In_2−x(CO₃)_1+xO_6−2.5x oxycarbonate solid solution showing a crystal structure also described by I4/mmm space group, but with the unit cell parameters: a=4.1669(1) Å and c=29.3841(11) Å for x=1. The existence range of this phase, −0.153<x<0.4, includes chemical compositions of earlier found phases: Ba₅In_2+xO_8+0.5x with 0≤x≤0.45 (known as the -solid solution), as well as the binary Ba₄In₂O₇ phase. The crystal structures of both new oxycarbonates are isomorphic and related to n=3 member of the Ruddlesden–Popper family.     

Correlation between the surface state and optical properties of S6 site and C2 site in nanocrystalline Eu:Y2O3

Eu³⁺ doped Y₂O₃ nanocrystals are synthesized via precipitation and hydrothermal methods. With the increase of hydrothermal temperature, the number of surface states decreases when nanorods are formed. The decrease of surface states induces the increase in the ratio of S₆ site to C₂ site, and meanwhile results in the spectral red-shift of charge transfer band as well as the enhancement of red emission. The results indicate that the surface states and optical properties have close correlations.     

Influence of niobium doping on phase composition and defect-mediated photoluminescence properties of Eu-doped TiO2 nanopowders synthesized in Ar/O2 thermal plasma

Nb⁵⁺:Eu³⁺-codoped TiO₂ nanopowders for chemical composition adjustment have been synthesized via Ar/O₂ radio-frequency thermal plasma. X-ray diffraction (XRD) results reveal that all the resultant powders exhibited mixture polymorphs of anatase (mean size: ∼45 nm) as the major phase and rutile (mean size: ∼71 nm). Rutile formation was promoted by the Eu³⁺ doping but suppressed by the Nb⁵⁺ addition. Combined observation using FE-SEM and TEM indicates that all the plasma-synthesized powders had a majority of facet-shaped particles (several nanometers) and a small proportion of nearly spherical crystals (∼150 nm). For the defect-mediated photoluminescence (PL) emission through the energy transfer from the TiO₂ host to the Eu³⁺ activator, the PL intensity originating from the ⁵D₀ → ⁷F₂ electronic transition weakened but that from the ⁵D₀ → ⁷F₁ electronic transition strengthened with increasing Nb⁵⁺ content. This may be a result of the decrease in the oxygen vacancy defects in the TiO₂ host lattice, as revealed by the joint means of UV-vis absorption spectra and excitation and emission spectra.     

Annealing driven performance and optical effects in nanocrystalline SnO2 thin films induced by pulsed delivery

Tin dioxide thin films were prepared successfully by pulsed laser deposition techniques on glass substrates. The thin films were then annealed for 30 min from 50 °C to 550 °C at 50 °C intervals. The influence of the annealing temperature on the microstructure and optical properties of SnO₂ thin films was investigated using X-ray diffraction, optical transmittance and reflectance measurements. Various optical parameters, such as optical band gas energy, refractive index and optical conductivity were calculated from the optical transmittance and reflectance data recorded in the wavelength range 300-2500 nm. We found that the SnO₂ thin film annealed at temperatures up to 400 °C is a good window material for solar cell application. Our experimental results indicated that SnO₂ thin films with the high optical quality could be synthesized by pulsed laser deposition techniques.     

Solvents for growing Al2(WO4)3 single crystals from high-temperature solutions

The crystallization conditions of Al₂(WO₄)₃ from Li₂O–WO₃ solvents (molar ratio 30.0:70.0, 32.5:67.5, 35.0:65.0, 45.0:55.0 and 55.0:45.0) as well as from Na₂O–WO₃ solvents (molar ratio 25.0:75.0, 27.5:72.5, 30.0:70.0 and 32.5:67.5) have been investigated. The concentration and temperature regions of crystallization of Al₂(WO₄)₃ and the density, viscosity as well as the solution losses due to evaporation have been established. On the basis of the data obtained it has been concluded that the most suitable solvent for growing Al₂(WO₄)₃ single crystals is Na₂O–WO₃ with a molar ratio of 27.5:72.5.