Temperature dependence of the dielectric function and critical points of α-SnS from 27 to 350 K.

We report the temperature dependence of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of biaxial α-SnS in the spectral energy region from 0.74 to 6.42 eV and temperatures from 27 to 350 K using spectroscopic ellipsometry. Bulk SnS was grown by temperature gradient method. Dielectric response functions were obtained using multilayer calculations to remove artifacts due to surface roughness. We observe sharpening and blue-shifting of CPs with decreasing temperature. A strong exciton effect is detected only in the armchair direction at low temperature. New CPs are observed at low temperature that cannot be detected at room temperature. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that contains the Bose-Einstein statistical factor and the temperature coefficient for describing the electron-phonon interaction.

Parameterization of Dielectric Functions and Phase Transitions of SrTiO3 from 26 to 674 K.

We present parameters that allow the dielectric function (ε = ε1 + iε2) of perovskite SrTiO3 (STO) to be calculated for spectral range from 0.74 to 6.42 eV and temperatures from 26 to 674 K. The ε data of STO were reproduced from a previous report. We use the Tauc-Lorentz model to express ε of STO analytically for each temperature. The ε spectra are successfully parameterized with six Tauc-Lorentz components and a pole. To obtain ε data for arbitrary energies and temperatures over the range given above, we interpolated the parameterized results using cubic polynomials. It is well known that STO has phase transitions near 40 and 105 K, which are reflected well in our modeling. Our data allow complex refractive indices to be calculated at any temperature for device design.

Parameterized optical properties of InxAl1-xP alloys.

We report values of parametric-model (PM) parameters that can be used to obtain dielectric functions (refractive indices) from 1.5 to 6.0 eV for ${{\rm In}_x}{{\rm Al}_{1 - x}}{\rm P}$InxAl1-xP alloys of arbitrary compositions $x$x. Using reported pseudo-dielectric data for several In compositions, we extract their dielectric functions by multilayer calculations, then parameterize them with PM lineshapes that well describe the asymmetric nature of their critical point (CP) contributions. We follow the ${E_0}$E0 fundamental bandgap as a function of $x$x, and determine the composition of the indirect-to-direct crossover.

The Preparation and Characterization of MnFe2O4-Decorated Expanded Graphite for Removal of Heavy Oils from Water.

Recently, many methods have been developed to efficiently eliminate oil spills due to its long-term harmful effects on marine life and human health. Expanded graphite (EG) has been considered as an excellent platform to remove contaminated oil from aqueous solution through a facile adsorption route. As an innovative approach, the decoration of magnetic components, namely, MnFe2O4, into graphite layers was taken into account for facilitating phase separation under magnetic field which resulted into an easy collection of the used adsorbents in a large scale. The expanded graphite/manganese ferrite composites were prepared from Vietnamese graphite flakes via a two-stage process. Characterization was performed using Scanning Electron Microscope (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), X-Ray Powder Diffraction (XRD), Vibrating Sample Magnetometer (VSM), Energy-Dispersive X-ray (EDS), and nitrogen adsorption/desorption analysis. The adsorption behavior of EG-MnFe2O4 for widespread used heavy oils, including diesel oil and crude oil, was investigated under the effects of adsorption conditions, i.e., contact time, loaded oil dosage, and salinity of mixing oil and water. The obtained results showed successful incorporation of MnFe2O4 into graphite sheets and no considerable change on the worm-like structure of EG. The results also showed that incorporated manganese ferrites enhanced the magnetism EG up to 16 emu/g, which made the recovery of used adsorbent conveniently. The EG-MnFe2O4 adsorbents exhibited the strong adsorption ability toward diesel oil (32.20 ± 0.46 g DO/g EG) and crude oil (33.07 ± 0.33 g CO/g EG). In brief, EG-MnFe2O4 material provides a potential and promising platform with high performance for oil spill removal.

A Parametric Model for Temperature Dependence of Dielectric Function of AlSb Film.

We present analytic representation of dielectric function (ɛ ═ ɛ1 + iɛ2) data from 1.7 to 5.0 eV for the temperature from 300 to 803 K of oxide-free AlSb that are the closest representation to date of the intrinsic bulk dielectric response ɛ of the material. Pseudodielectric functions 'ɛ' were measured on a 1.5 µm thick film grown on (001) GaAs by molecular beam epitaxy. Data were obtained with the film in situ to avoid surface oxidation artifacts. The dielectric function parametric model and multilayer calculation were performed to obtain pure dielectric function and fundamental bandgap (E0) of the AlSb film. The ɛ spectrum was successfully reconstructed by seven polynomials and a pole, which can be used to determine ɛ for arbitrary temperatures. Our results should be useful for device design based on AlSb.

Temperature Dependence of the Dielectric Response and Critical Point Energies of Bi1.85Gd0.15Te3.

The complex dielectric function and band-edge critical point structures of Bi1.85Gd0.15Te3 are reported for temperatures from 28 to 300 K and energies from 0.74 to 6 eV, obtained on bulk Bi1.85Gd0.15Te3 by rotating-compensator spectroscopic ellipsometry. The critical point (CP) energies are determined using numerically calculated second energy derivatives of the data. At low temperature, eight CP structures are identified, while only four CPs are observed at room temperature. As temperature decreases, we also observe blue shifts and significantly enhanced CP structures relative to those obtained at room temperature. The temperature dependence of the CPs are determined by fitting the data to the temperature coefficient and a phenomenological expression that contains the Bose-Einstein statistical factor.

Temperature Dependence of the Dielectric Function of Monolayer MoSe2.

The dielectric function [Formula: see text] of monolayer molybdenum diselenide (MoSe2) is obtained and analyzed at temperatures from 31 to 300 K and at energies from 0.74 to 6.42 eV. The sample is a large-area, partially discontinuous monolayer (submonolayer) film of MoSe2 grown on a sapphire substrate by selenization of pulsed laser deposited MoO3 film. Morphological and optical characterizations verified the excellent quality of the film. The MoSe2 data were analyzed using the effective medium approximation, which treats the film and bare substrate regions as a single layer. Second derivatives of ε with respect to energy were numerically calculated and analyzed with standard lineshapes to extract accurate critical-point (CP) energies. We find only 6 CPs for monolayer MoSe2 at room temperature. At cryogenic temperatures 6 additional structures are resolved. The separations in the B- and C-excitonic peaks are also observed. All structures blue-shift and sharpen with decreasing temperature as a result of the reducing lattice constant and electron-phonon interactions. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that contains the Bose-Einstein statistical factor and the temperature coefficient.

Polychlorobenzenes and polychlorinated biphenyls in ash and soil from several industrial areas in North Vietnam: residue concentrations, profiles and risk assessment.

Polychlorinated benzenes (PCBzs) including penta- and hexachlorobenzene can be unintentionally formed from thermal processes in different industrial activities, and very little information is available on the contamination and emission characteristics of these new persistent organic pollutants from industries in Vietnam. In this study, contamination of PCBzs (including penta- and hexachlorobenzene, named PeCBz and HCB, respectively) and PCBs (including CB-28, 52, 101, 153, 138, 180) in fly ash, bottom ash and soil from combustion processes of waste incineration, metallurgy (steel making and zinc production) and cement production from several provinces in the Northern Vietnam, including Hai Duong, Hanoi, Bac Ninh, Hai Phong and Thai Nguyen, was preliminary investigated. The PCBzs concentrations in fly ash, bottom ash and soil ranged from 2.7 to 100 ng g(-1), from 2.7 to 159 ng g(-1) and from 0.28 to 33.9 ng g(-1), respectively. Relatively high residues of PeCBz in fly ash and bottom ash from municipal waste incinerators in some provinces from the Northern Vietnam were encountered. Total PCBs concentrations ranged from 18.0 to 8260 ng g(-1), from 1.0 to 10600 ng g(-1) and from 14.5 to 130 ng g(-1) for the fly ash, bottom ash and soil, respectively. Daily intakes of PeCBz, HCB and PCBs through soil ingestion and dermal exposure estimated for children ranged 0.33-9.93 (mean 3.14), 0.39-21.1 (mean 4.9) and 6.09-1530 ng/kg bw/day (mean 346), respectively; and these intakes were about 4.7-5.4 times higher than those estimated for adult. The intakes of PeCBz and HCB were relatively low, while those for PCBs exceeded WHO TDI for some samples.

Occurrence, fate and antibiotic resistance of fluoroquinolone antibacterials in hospital wastewaters in Hanoi, Vietnam.

Occurrence and behavior of fluoroquinolone antibacterial agents (FQs) were investigated in hospital wastewaters in Hanoi, Vietnam. Hospital wastewater in Hanoi is usually not treated and this untreated wastewater is directly discharged into one of the wastewater channels of the city and eventually reaches the ambient aquatic environment. The concentrations of the FQs, ciprofloxacin (CIP) and norfloxacin (NOR) in six hospital wastewaters ranged from 1.1 to 44 and from 0.9 to 17 micrgl(-1), respectively. Total FQ loads to the city sewage system varied from 0.3 to 14 g d(-1). Additionally, the mass flows of CIP and NOR were investigated in the aqueous compartment in a small wastewater treatment facility of one hospital. The results showed that the FQ removal from the wastewater stream was between 80 and 85%, probably due to sorption on sewage sludge. Simultaneously, the numbers of Escherichia coli (E. coli) were measured and their resistance against CIP and NOR was evaluated by determining the minimum inhibitory concentration. Biological treatment lead to a 100-fold reduction in the number of E. coli but still more than a thousand E. coli colonies per 100ml of wastewater effluent reached the receiving water. The highest resistance was found in E. coli strains of raw wastewater and the lowest in isolates of treated wastewater effluent. Thus, wastewater treatment is an efficient barrier to decrease the residual FQ levels and the number of resistant bacteria entering ambient waters. Due to the lack of municipal wastewater treatment plants, the onsite treatment of hospital wastewater before discharging into municipal sewers should be considered as a viable option and consequently implemented.