Impact of high temperatures on aluminoceladonite studied by Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

Upconversion Luminescence and Magnetic Turning of NaLuF4:Yb3+/Tm3+/Gd3+ Nanoparticles and Their Application for Detecting Acriflavine

Fluorescent and magnetic bifunctional NaLuF4:Yb3+/Tm3+/Gd3+ nanocrystals were synthesized by the solvothermal method and subsequent surface modification. By changing the doping concentration of Gd3+, the shape, size, luminescent properties, and magnetic properties of the nanoparticles can be modulated. These NaLuF4:Yb3+/Tm3+/Gd3+ nanocrystals present efficient blue upconversion fluorescence and excellent paramagnetic property at room temperature. Based on the luminescence resonance energy transfer (LRET), upconversion nanoparticles (UCNPs) were confirmed to be an efficient fluorescent nanoprobe for detecting acriflavine. It is easy to derive the concentration of acriflavine from the Integral Intensity Ratio of Green (emission from acriflavine) to Blue (emission from UCNPs) fluorescent signals. Based on this upconversion fluorescent nanoprobe, the detection limit of acriflavine can reach up to 0.32 μg/mL.

DISTANT INFRARED SPECTRAL ANALYSIS OF INDUSTRIAL HOT GAS EJECTION IN ATMOSPHERE

Passive Infrared (IR) Spectral-radiometry of gases in the atmosphere is extremely important today, when pollution of the environment by natural ejections and those produced by human activity is growing very high. Particularly, spectral analysis of hot gas ejections i.e. combustion products from industrial plants is an essential part of ecological monitoring of the atmosphere. In this paper we present the results of IR spectral analysis of hot gas ejections from industrial plants in the spectral range from 2.5 to 5.5µm, at a distance of 3000m. The obtained with a hydrocarbon gas group, SO2, N2 O, CO and CO2 gases, as well as H2 O vapor. Relative content of ejected gases (to CO-CO2 group) per unit time was evaluated by means of an integral intensity ratio for each gas. Distant IR Spectral analysis of hot gas ejections (both industrial firms, and various vehicles) have huge value, in particular at ecological monitoring of an environment.

EVIDENCE OF POLARIZATION SWITCHING INDUCED BY MAGNETIC FIELD IN BiFeO3 THIN FILM

A BiFeO 3 thin film was prepared on the (111) Pt / Ti / SiO 2/ Si substrate by the solution coating method. In order to detect the effect of an external magnetic field on the BiFeO 3 thin film, a fine scan X-ray diffraction with a scan ratio of 0.002°/s was carried out under the magnetic field parallel to the film surface. The result of the in situ analysis of X-ray diffraction for the thin film in the magnetic field indicates that the magnetic field leads to an increase of the integral intensity ratio of [Formula: see text] compared with that under no magnetic field. The increase of [Formula: see text] implies a domain switching under the magnetic field, where the domain switching comes from the decreasing residual tensile stress induced by the magnetostriction of BiFeO 3 in the magnetic field.