In this research article, Na(1−x)Zr2Smx(PO4)3 (x = 0.005–0.05) were synthesized via solution combustion route. The phase purity of the synthesized phosphors were explored by X-ray diffraction and ...Raman Spectroscopy. Rietveld refinement was used to compute the lattice parameters for Sm3+ doped NaZr2(PO4)3. The chemical states and morphological studies of the synthesized phosphors were carried out by X-ray photoelectron spectroscopy and field emission scanning electron microscope, respectively. A strong characteristic emission of Sm3+ ion was identified and the effect of doping concentration on PL spectra was extensively investigated. The bandgap was measured using diffuse reflectance spectra, and it was found in the range of 4.25 – 4.56 eV.
•Vibrational spectroscopy.•UV-visible spectroscopy.•Natural bond orbitals (NBO).•Structure determination. Cr(DDTC)2(OH2)2+.
Diethyldithiocarbamate Cr(III) di-hydrate, Cr(DDTC)2(OH2)2+ was synthesized ...and the analysis of its structure was performed. The calculations as well as its infrared and Raman spectra interpretation were based on the DFT/B3LYP method. The vibrational spectra show a blue shift of the bands in the high energy region (C-H stretching of the -CH3 and -CH2 groups), a result corroborated by the calculated spectra. Besides, the blue shift of the C-H bands of the CH3 and CH2 groups of the complex was interpreted by means of the intermediate hybridization between the sp3 and sp2 orbitals of the carbon atoms whose bonds increased the force constants, shifting the position of the CH bands to the blue. The geometry of the complex produced wave numbers with excellent agreement with the experimental ones, thus indicating that the proposed geometry is correct. Electronic transitions spin allowed (ν1, ν2 and ν3) according to the time-dependent process using the B3LYP functional with basis 6-311G(d,p), and according to the TS diagram they were assigned as: ν12T1g(G)←4A2g (Bu), ν24T2g(F)←4A2g(Ag). ν34T1g(F)←4A2g(Ag). The agreement between the two procedures that led to the assignment was excellent. Natural bond orbital analysis was also carried out as a way to find the hybridization of the carbon atoms of the –CH3 and –CH2 groups. Koopmans’ energy (eV), Mulliken population analysis and assignment for the frontier orbitals of Cr(DDTC)2 (OH2)2+, with the B3LYP method, were also performed.
Display omitted
Display omitted
•Combined electrical-alkali pretreatment for improving sludge anaerobic digestion was proposed.•Combined process enhanced the cell lysis, biopolymers releases, and thus sludge ...disintegration.•Increased solubilization of sludge increased the anaerobic hydrolysis rate.•Increased solubilization does not always induce an improved anaerobic digestion efficiency.
Pretreatment can be used prior to anaerobic digestion to improve the efficiency of waste activated sludge (WAS) digestion. In this study, electrolysis and a commonly used pretreatment method of alkaline (NaOH) solubilization were integrated as a pretreatment method for promoting WAS anaerobic digestion. Pretreatment effectiveness of combined process were investigated in terms of disintegration degree (DDSCOD), suspended solids (TSS and VSS) removals, the releases of protein (PN) and polysaccharide (PS), and subsequent anaerobic digestion as well as dewaterability after digestion. Electrolysis was able to crack the microbial cells trapped in sludge gels and release the biopolymers (PN and PS) due to the cooperation of alkaline solubilization, enhancing the sludge floc disintegration/solubilization, which was confirmed by scanning electron microscopy (SEM) analysis. Biochemical methane potential (BMP) assays showed the highest methane yield was achieved with 5V plus pH 9.2 pretreatment with up to 20.3% improvement over the non-pretreated sludge after 42days of mesophilic operation. In contrast, no discernible improvements on anaerobic degradability were observed for the rest of pretreated sludges, probably due to the overmuch leakage of refractory soluble organics, partial chemical mineralization of solubilized compounds and sodium inhibition. The statistical analysis further indicated that increased solubilization induced by electrical-alkali pretreatment increased the first-order anaerobic hydrolysis rate (khyd), but had no, or very slight enhancement on WAS ultimate methane yield (fd), demonstrating that increased solubilization of WAS from a pretreatment does not always induce an improved anaerobic digestion efficiency.
The dynamic nature of nanoparticle (NP) aggregation behavior is of paramount interest to many current studies in environmental and toxicological nanoscience. The present study seeks to elucidate the ...influence that different electrolytes have on the aggregation of citrate-coated silver NPs (cit-AgNPs). The use of both UV–vis spectroscopy and dynamic light scattering (DLS, both z-average hydrodynamic diameter (z-dh) and size distribution analysis data) allowed improvement in the data quality and interpretation as compared to other studies using only DLS and reporting solely the z-dh, as the change in the z-dh can be related to analytical errors and uncertainties rather than only aggregation or dissolution of NPs. Divalent cations (CaCl2, Ca(NO3)2, CaSO4, MgCl2 and MgSO4) have stronger influence (ca. 50–65 fold) on aggregation of cit-AgNPs as compared to monovalent cations (NaCl, NaNO3, Na2SO4), as expected. For electrolytes with monovalent cations, there was no specific ion effect of nitrate and sulfate anions. However, the addition of chloride anions resulted in enhanced apparent aggregation, possibly due to the formation of AgCl NPs that sorb/attach to the surface of cit-AgNPs. Suwannee River fulvic acid enhances the stability of cit-AgNPs and shifts the critical coagulation concentrations to higher electrolyte concentrations for all types of electrolytes. Aggregation kinetics in the presence of mixture of monovalent and divalent cations is additive and controlled by the dominant cations. An empirical formula (αmixture=αNa+(50 to 65)Ca) is proposed that reproduces the effect of mixtures of electrolytes in the presence of humic substances and cations that can be used to help predict the aggregation behavior of cit-AgNPs in environmental and ecotoxicological media.
Display omitted
•Potential effect of cations, anions and fulvic acid on aggregation of AgNPs was evaluated.•Aggregation kinetics was assessed using UV–vis and dynamic light scattering methods.•Chloride addition enhanced AgNP aggregation.•Aggregation kinetics appeared additive with mono- and di-valent cations present together.
Examining the emergence of the versified love story as a genre of New Persian literature in the early eleventh century, Love at a Crux situates this literary movement within the broader global ...history of romance.
Present paper reports on an algorithm for calculating the equilibrium composition of several compounds mixture if their total (equilibrium) concentrations and the equilibrium constants of reactions ...between them are known. The algorithm for determining the unknown equilibrium constants from UV–Vis or potentiometric experimental data using minimizing function (maximal likelihood method) is described. The recommendations on the evaluating of equilibrium constants from experimental results are given. The algorithms described are realized as free-of-charge distributed software/scripts bundle/source code.
A free software for equilibrium concentrations calculations or equilibrium constants determination from experimental data was developed. Display omitted
•Calculations of equilibrium concentrations from Ctot and lg K are described.•Determination of lg K from UV–Vis/potentiometric data is described.•Free and open source software for these aims is developed.
In this work the electronic structure of (
E)-4-methoxy-2-(p-tolylimino)methylphenol has been characterized by the B3LYP/6-31G(d) level by using density functional theory. The experimental infrared ...and electronic absorption spectra have been obtained and compared with the theoretically obtained ones. Molecular electrostatic potential map has been evaluated; natural bond orbital and frontier molecular orbitals analysis have been performed from the optimized geometry. The energetic behavior of the title compound has been examined in solvent media using polarizable continuum model. The non-linear optical properties have been computed with the same level of theory. In addition, the changes of thermodynamic properties have been obtained in the range of 100–500
K.
Nano-spinel zinc ferrites (ZnFe2O4) with substitution of diamagnetic magnesium (Mg2+) ions were synthesized using solution-gelation (sol-gel) self ignition route. The thermal, structural, spectral, ...optical and N2-physisorption properties of the prepared Zn–Mg ferrite nanoparticles were analyzed by standard characterization techniques. The temperature dependent spinel phase formation and percentage weight loss was studied by thermogravimetric and differential thermal analysis (TG-DTA). The analysis of the room temperature X-ray diffraction (XRD) patterns showed the formation of cubic spinel structure with single phase in the Zn–Mg ferrites. The crystallite size decreasing from 27 nm to 20 nm with Mg2+ substitution confirmed the nanocrystalline formation of the Zn–Mg ferrites. The two characteristics vibrational modes of interstitial sub-lattice sites corresponding to the spinel structure were observed within the desired wavelength range of the FT-IR spectra. The optical band gap values estimated from the UV–Visible data analysis is found to be in the scope of 1.96 eV–2.39 eV. The photoluminescence (PL) spectra showed the broader emission band in the visible region (around 525 nm) for all the samples of Zn–Mg ferrites. The BET isotherms were recorded by the N2 adsorption-desorption and the surface area, pore volume, average pore radius etc surface parameters were deduced. The BET surface area and average pore radius values were obtained in the range of 5.6–24.8 m2/gm and 2.61–4.52 nm respectively.
On-time and accurate estimation of the soil nitrogen mineralization rate (SNMR) is critical for nitrogen (N) management and protecting the environment. This study evaluated the performance of a ...visible-to-near-infrared reflectance (vis-NIR) spectroscopy for predicting SNMR for four texture groups. A total of 62 topsoil samples were collected from 17 management zones distributed over four fields and incubated with seven destructive sampling events. Samples were analysed for total mineral N (NH4++NO3–) content and scanned using a vis-NIR sensor simultaneously at each of the seven-sampling times. Four partial least squares regression models were calibrated and validated for four textural groups (groups- 1– 4) identified over the United State Department of Agriculture (USDA) texture triangle. Prediction accuracies indicated that vis-NIR sensor was moderately to highly accurate for predicting SNMR, while observing variable accuracies across texture groups. The highest accuracy was obtained for group 1 (sandy-loam; coefficient of determination, R2 = 0.90; root mean square error, RMSE = 0.04 mg N kg−1 soil day−1), successively followed by group 2 (mostly loam; R2 = 0.80, RMSE = 0.05 mg N kg−1 soil day−1) group 4 (mostly silt; R2 = 0.66, RMSE = 0.08 mg N kg−1 soil day−1), and group 3 (silt-loam; R2 = 0.44, RMSE = 0.08 mg N kg−1 soil day−1). Variable importance in projection score revealed that the key spectral bands to predict SNMR were in 2150 – 2260 nm and 2470 – 2480 nm, resembling the key bands associated with soil organic compounds and clay minerals. In-advance texture information required for soil stratification is regarded a limitation of the proposed approach. In conclusion, vis-NIR holds potential for a rapid estimation of SNMR when samples are stratified into similar texture groups in advance, however, confirmatory research will be needed to validate the current findings for soils from different origin and under different management.
•Texture based sample stratification enables vis-NIRS to predict soil N mineralization rate.•Vis-NIR sensor can predict soil N mineralization rate at moderate to high accuracy.•The highest prediction accuracy is possible for sandy-loam texture.•Spectral bands of 2150–2260 & 2470–2480 nm are significant for SNMR prediction.
Novel Zn0·95Mn0·05O and Zn0·9Mn0.05M0.05O (M = Al, Bi, Sr, Ag) nanocrystals were prepared via the co-precipitation technique. The X-ray diffraction pattern confirmed the substitution of Mn, Al, Bi, ...Sr, and Ag dopants without altering the basic ZnO structure. The microstructural study was performed by employing the Scherrer plot, Williamson-Hall, and SSP methods. The energy bandgap calculated from UV–vis spectra using different methods observed red-shifted by co-doping. The other optical parameters were also studied and discussed in detail. The FTIR spectra confirmed the presence of Zn–O, and Zn-M–O vibrational modes. Raman spectra demonstrated the presence of ZnO phonon modes, and the Raman shift exhibited the structural defects induced by dopants. The PL spectra showed strong NBE and DLE in the UV and visible region due to extrinsic defects. The IV measurements exhibited the enhancement in the electrical conductivity of ZnO by co-doping. The photocatalytic activity was performed under direct sunlight for methyl orange and methylene blue dyes, and the enhanced degradation efficiency was achieved by co-doping. Furthermore, this article enhances the understanding of tuning the physical properties of ZnO by co-doping and introduces a new class of sunlight-driven photocatalysts.
