Pentavalent Ions Research Articles

Memory-Enabled Quantum-Dot Light-Emitting Diodes.

Quantum-dot light-emitting diodes (QLEDs) with memory capability can provide multifunctional integration properties in on-chip and intelligent electronic applications. Herein, memory properties are achieved by inserting a tungsten oxide (WOx) film between the ZnO electron-transporting layer and cathode. Pentavalent tungsten ions (W5+) in this nonstoichiometric WOx film can be oxidized to W6+ by storing holes, inducing significant electrons in the adjacent ZnO layer. Hole storage in the WOx layer suppresses electron injection into the quantum dot emissive layer, hence reducing electroluminescence intensity on the onset stage of the QLEDs. This operation-history correlation for the electroluminescence intensity means a memory behavior for the QLEDs. Furthermore, the power efficiency of the devices is greatly improved after inserting the WOx layer due to electrical field-dependent self-adaptive electron injection into the quantum dots (QDs). We anticipate this type of QLEDs have potential applications in on-chip integration applications, such as the optical computing field and storage.

Unraveling the impact of tetravalent and pentavalent ions on the charge dynamics of hematite photoelectrodes for solar water splitting

This study focuses on understanding the impact of tetravalent (Hf4+) and pentavalent (Nb5+) ions in hematite photoelectrodes using a two-step synthesis approach. Structural, morphological, and compositional analyses confirms that Nb5+ is segregated over the hematite crystal surface while Hf4+ is allocated over the crystal surface and between the fluorine-doped tin oxide substrate (FTO)-hematite interface. Our results indicate that the modifier insertion led to substantial improvements in overall efficiency and photoelectrochemical (PEC) performance. However, it creates additional surface states, as evidenced by shifts in the anodic onset potential (Vonset) observed in the linear sweep voltammetry curves. For Nb-modified photoelectrodes, Vonset shift of ∼20 mV with respect to hematite was observed and confirmed by intensity modulated photocurrent spectroscopy (IMPS). For Hf-modified hematite, this Vonset shift is more pronounced (∼30 mV). When combined with NiFeOx, Nb5+ acted synergistically showing a 4-fold efficiency increase compared to hematite and ∼70 mV cathodic shift in the Vonset. Otherwise, NiFeOx showed no significant impact in the Hf4+ modified hematite photoelectrodes, suggesting that Hf4+ role lies in enhancing electron collection at the FTO-hematite interface. This study not only sheds light on the charge dynamics of modified hematite photoelectrodes but also provides strategies for boosting the PEC devices efficiency.

A multifunctional probe based on a heterometallic-organic framework: highly selective detection of 1,3-dinitrobenzene, tryptophan, and visual recognition of pentavalent vanadate ions

Herein, a novel luminescent heterometal-organic framework (HMOF), {[EuZn2(imdc)2(4,4′-bpy) (H2O)4(OH)]·4,4′-bpy}n (1), was synthesized by selecting d-f heterometals and two ligands with abundant coordination sites (H3imdc = 1H-imidazole-4, 5-dicarboxylic acid, 4, 4′-bpy = 4, 4′-bipyridine). The X-ray single crystal diffraction reveals that compound 1 is a three-dimensional framework structure with two kinds of channels, which has good pH fluorescence stability. Compound 1 is demonstrated to be the first known HMOF for selective detection of pentavalent vanadate ions (VO43− or VO3−). It also exhibited high selectivity, sensitivity, and low detection limits for 1,3-dinitrobenzene (1, 3-DNB) and L-tryptophan (L-Trp). More significantly, the portable MOF-based fluorescent paper of compound 1 was also successfully manufactured and might be potentially used as a functional material with naked eye recognition. Furthermore, the fluorescence mechanisms of compound 1 for sensing the above analytes have been elaborated in detail.

Material characteristics of WO3/Bi2O3 substitution on the thermal, structural, and electrical properties of lithium calcium borate glasses

Glasses belonging to the xWO3-(30-x) Bi2O3–15Li2O–15CaO–40B2O3 (0 ≤ x ≤ 10) have been obtained by melt-quenching technique. With increasing the concentration of WO3, an increase in the measured glass transition temperature {T}_{mathrm{g}} and crystallization temperature {T}_{mathrm{c}} are observed, while the values of the thermal expansion coefficient decrease. Due to the unpaired pentavalent ions, the electron spin resonance spectra of glasses doped with {mathrm{WO}}_{3} them show unique signals. The results of Raman spectra show that the glass network is mainly constituted by [{mathrm{BiO}}_{6}], [{mathrm{BO}}_{3}], [{mathrm{BO}}_{4}], and [{mathrm{WO}}_{4}] basic structural units. The activation energies for all studied samples were observed to range from 0.02 to 0.08 eV, and the dielectric constant and the conductivities of the investigated glasses increased with increasing temperature. The electrical behavior of the prepared samples revealed their semiconducting character. The prepared samples are being investigated as potential semiconductor material candidates for use in electronic devices.

New and effective photocatalysts for removal of mordant black 17 and Congo red pollutants: In3+ and Sb5+ doped and codoped TiO2 semiconductor

The incorporation of trivalent (In3+) and pentavalent (Sb5+) ions into nano-sized TiO2 structure critically improved the visible light absorption and the photodegradation characteristics toward mordant black 17 and Congo red (CR) dyes as model organic pollutants. The X-ray diffraction (XRD) proved that pure TiO2 and Ti0·97In0·03O2 powders have a single tetragonal anatase phase structure while Ti0·97Sb0·03O2 and Ti0·94In0·03Sb0·03O2 compositions possess mixed phases of anatase and brookite. The sacnning electron microscope (SEM) images displays that Ti0·94In0·03Sb0·03O2 powder has fine and homogenous particles. The transmission electron microscope (TEM) images confirmed that Ti0.94In0·03Sb0·03O2 powder hasthe lowest mean particles size of 20 nm. The visible light response of TiO2 is significantly enhanced owing to addition of Sb5+ and In3/Sb5+ions. The calculated band gap energies of TiO2, Ti0·97In0·03O2, Ti0·97Sb0·03O2 and Ti0·94In0·03Sb0·03O2 samples are 3.35, 3.21, 2.97 and 2.91 eV, respectively. The engineering of the optical characteristics powerfully boosted the photocatalytic charcteristics of Ti0·97Sb0·03O2 and Ti0·94In0·03Sb0·03O2 catalysts under natural sunlight irradiation. Both samples exhibit photocatalytic efficiencies of 89 and 97% toward 30 ppm mordant black 17 solution under sunlight irradation in 60 min, respectively. As well, Ti0·97Sb0·03O2 and Ti0·94In0·03Sb0·03O2 catalysts show high photo-degradation efficiencies of 81 and 86% toward 15 ppm CR after sunlight irradation for 80 min. The enhanced degradation properties of the nanocrystalline Ti0·94In0·03Sb0·03O2 catalyst may be related to high separation of charge carriers, oxygen vacancies generation and good visible light response. For three cycles, Ti0·94In0·03Sb0·03O2 catalyst reveals high photodegradation activity within 89–97% for 30 ppm mordant black 17 dye under the same circumstances, demonstrating good photostability.

Linear, non-linear refractive index and Judd-Ofelt parameters of Tm2O3-doped P2O5-PbO-WO3 glasses

Lead phosphate glasses within system [40PbO–50P2O5-(10-x) WO3- xTm2O3] doped with different concentration of xTm2O3 ions are equipped and used the rapid cooling mechanism. Produced sets are noticed to soak up highly in the UV domain and ascribed to the concerted aided impurities of iron and participation of lead Pb2+ ions. Subsisting of WO3 exposed clear absorption patterns which are ascribed to appear of W5+ pentavalent ions. Physical parameters such as density (ρ), molar volumes (Vm), refractive index (n), an optical energy gap (Eg) and Urbach energy (ΔE) values of prepared glasses were evaluated. In addition to, the Judd–Ofelt coefficients of the transformation form of oscillator probabilities, fexp., fth, branching ratio, β and radiative lifespans, τ, of many excited sites of Tm3+ have also been computed. Gain cross-section laser transformation stage from 3H6 → 3F3, 3H6 → 3H4, 3H6 → 3H5 and 3H6 →3F4 and induced emission cross-section determined at specific concentrate of Tm2O3 ions across all current glasses. Thus, their spectroscopic characteristics suggest that such Tm3+ doped glasses are an excellent choice for optical purposes.

Adsorption of trivalent and pentavalent arsenic ions from the aqueous stream using natural Bombax ceiba fibers: Insights from density functional theory calculations

Natural fibres have recently emerged as a pool of organic compounds that for different applications. Among several natural products, the fibres of Bombax ceiba contain several naphthalene-based compounds. Hence, Bombax ceiba may exhibit the potential of adsorbing a variety of pollutants. In this study, the adsorption of arsenite (As(III)) and arsenate (As(V)), from the aqueous stream was investigated using density functional theory (DFT) calculations. 1,4-Naphthaquinone, 1-Naphthyl ether, Hemigossypol, and Naphthol were chosen as adsorbent molecules for As(III) and As(V) ions as they form the major portion of the Bombax ceiba fibres. CAM-B3LYP/6-311G level of DFT theory was used to calculate electrostatic potential maps, HOMO-LUMO distributions, chemical potential, and hardness to gain quantitative information on the interactions. The adsorption energies and recovery time were calculated based on the thermodynamic feasibility of the interactions of As(III) and As(V) ions with Bombax ceiba fibres. The results showed that As(III) and As(V) ions adsorbed physically on the Bombax ceiba fibres. The results can be used to further modify naturally occurring Bombax ceiba fibres to develop sustainable solutions.

Acceptor-donor concentration dependent polaronic relaxation, pinned electron defect dipole characteristic and colossal permittivity in co-doped rutile (Zn1/3Nb2/3)xTi(1-x)O2 (x = 0.02, 0.04, 0.06 and 0,08) ceramics

Colossal permittivity with low loss tangent has been achieved by co-substitution of Zn and Nb in TiO2. Incorporation of the divalent and pentavalent ions has been confirmed by structural and Raman spectroscopic analysis. Specific ratio of acceptor-donor pairs led to observation of colossal permittivity (∼104) with a low loss tangent (<0.1). Evidence of localized donor electrons in the dielectric response shows the generation of electron pinned defect dipoles. Low-temperature dielectric relaxation has been observed which correspond to the polaronic conduction following Arrhenius law. As the acceptor-donor content increases, the polaronic relaxation dynamics occurs at higher temperatures. This also reveals that the defect complexes are strongly correlated. Permittivity values corresponding to the loss tangent minima have been compared as a function of acceptor-donor content. Finally, optimum sintering temperature, frequency, measurement temperature, and composition have been identified.

Trace‐element composition of zircon in Kofu and Tanzawa granitoids, Japan: Quantitative indicator of sediment incorporated in parent magma

AbstractZircon is one of the most important minerals in geochronologic research. Isotopic ratios and trace elements in zircons are expected to reflect those of their parent magmas. Many geochemical researchers have proposed various discrimination diagrams for zircon to indicate tectonic setting and to identify source rock. Because most detrital zircons accumulated at river mouths are derived primarily from granitoids, the classification of zircon within granitoids is potentially meaningful. In our research, we focused on sediment involvement during granitoid formation and tried to identify trace‐element compositions in zircon that are sensitive to variation in sediment incorporation. To accomplish this, we examined trace‐element compositions of both the granitoids and the included zircons in the Kofu granitic complex and the Tanzawa tonalitic plutons in Japan. Among the high‐field‐strength elements (Th, U, Ta, Nb, Hf, and rare earth elements), only Nb and Ta concentrations in the granitoids increased as the rate of sediment contribution increased. However, the zircon did not show such trends in Nb and Ta content. Zircon Y and P contents exhibited a positive correlation, indicating that xenotime substitution occurs to some extent. Because P exists as pentavalent ions in igneous systems, its presence likely affects the concentrations of pentads in zircon. When we divided the Nb and Ta contents by the P content, it became clear that zircon Nb/P and Ta/P ratios increase depending on sediment involvement. While some exceptions exist, we found that zircon Yb/Gd ratios also respond to sediment involvement. Our data further demonstrated that zircons in granitoids with significant sediment incorporation are characterized by low Ce/P contents, which is partly attributable to monazite crystallization before zircon saturation. This study demonstrates that combining these element ratios is useful for indicating sediment incorporation.

Charge Localization and Magnetic Correlations in the Refined Structure of U3O7.

Atomic arrangements in the mixed-valence oxide U3O7 are refined from high-resolution neutron scattering data. The crystallographic model describes a long-range structural order in a U60O140 primitive cell (space group P42/n) containing distorted cuboctahedral oxygen clusters. By combining experimental data and electronic structure calculations accounting for spin-orbit interactions, we provide robust evidence of an interplay between charge localization and the magnetic moments carried by the uranium atoms. The calculations predict U3O7 to be a semiconducting solid with a band gap of close to 0.32 eV, and a more pronounced charge-transfer insulator behavior as compared to the well-known Mott insulator UO2. Most uranium ions (56 out of 60) occur in 9-fold and 10-fold coordinated environments, surrounding the oxygen clusters, and have a tetravalent (24 out of 60) or pentavalent (32 out of 60) state. The remaining uranium ions (4 out of 60) are not contiguous to the oxygen cuboctahedra and have a very compact, 8-fold coordinated environment with two short (2 × 1.93(3) Å) "oxo-type" bonds. The higher Hirshfeld charge and the diamagnetic character point to a hexavalent state for these four uranium ions. Hence, the valence state distribution corresponds to 24/60 × U(IV) + 32/60 U(V) + 4/60 U(VI). The tetravalent and pentavalent uranium ions are predicted to carry noncollinear magnetic moments (with amplitudes of 1.6 and 0.8 μB, respectively), resulting in canted ferromagnetic order in characteristic layers within the overall fluorite-related structure.

Appearance of pentavalent Fe ion as a result of a charge disproportionation in Fe-substituted Li2MnO3

20% Fe substituted Li2MnO3 (Li1+x(Fe0.2Mn0.8)1-xO2, 0 < x < 1/3) was prepared using coprecipitation–calcination method. X-ray Rietveld analyses showed that most Fe and Mn ions were on both 4g and 2b sites and small amount of them occupy on 2c and 4h sites in monoclinic Li2MnO3-type structure. Neutron Rietveld analysis revealed that Mn ion was mainly on the 4g site, whereas Fe ion was on both 4g and 2b sites. Temperature dependence of magnetization detected a cusp at 30 K for the sample, originating from its antiferromagnetic nature. The 57Fe Mössbauer spectrum at 300 K consisted of two symmetric doublets with different isomer shifts. From the isomer shifts, Fe ion existed as 3+δ and 4+δ states (0 < δ < 1). Below 200 K, the Fe4+δ component split to two doublets having two isomer shift values assigned as 4+ and 5+ states. At 3 K, the spectrum consisted of magnetically ordered 3+, 4+, and 5+ irons and paramagnetic 4+ state iron. The magnetically ordered pentavalent and tetravalent Fe ions can be stabilized at a highly distorted octahedral 4g site, whereas magnetically ordered trivalent and paramagnetic tetravalent Fe ions exist mainly on the less distorted octahedral 2b site.

The impact of γ-irradiation on Cd-B2o3 glass doped WO3: New evidences by TL and ESR spectroscopy

A well resolved Thermoluminescence (TL) glow peak at ~168 °C was observed in Cd-borate glass doped WO3. The maximum TL intensity was observed for 1.5 mol% of WO3+ doped samples and thereafter decreases. The variation of gamma exposure (0.025→2 kGy) on TL glow curves of Cd-borate glass showed linear and sub-linear behavior supported by track interaction model (TIM). Here γ-irradiated sample shows the formation of shallow trap (surface trapping) beside the formation of deep trapping. The composition dependence of the g ≈ 1.94 ESR absorption line intensity shows a decrease with increasing WO3 content, which is attributed to a fall in the ratio of the number of unpaired pentavalent ions W5+ ions to the number of W6+ ions. The effect of gamma irradiation doses on TL and ESR studies show high response with dose which indicates that these glass samples may be useful for TL dosimetry.

Doping Effects of Pentavalent Metal Ions (Nb5+ or Ta5+) on the Redox Stability and Electrochemical Properties of La0.6Sr0.4FeO3‐δ for Use as Interconnectors in Solid Oxide Fuel Cells

In this work, pentavalent metal ions of Nb or Ta are doped in the Fe sites of La0.6Sr0.4FeO3−δ (LSFO), and the doping effects on the redox stability and electrochemical properties of LSFO are investigated. Nb‐ or Ta‐doped LSFO is synthesized by a citric acid‐based sol–gel process and solid‐state reaction. The doping of metal ions in LSFO is confirmed by powder XRD and Rietveld refinements. The oxidation states of the doped metal ions are also confirmed by X‐ray photoelectron spectroscopy. In a stability test in a reducing atmosphere of H2, the undoped LSFO shows structural deterioration, whereas the doping of pentavalent metal ions leads to an enhancement in the structural stability of LSFO. Electrical conductivity measurements show that the LSFO compounds with 10 mol % Nb or Ta show the highest conductivity value under conditions of air or H2. Long‐term stability tests show that all the metal‐doped LSFO are much more stable than LSFO.

Dual regulation of Li+ migration of Li6.4La3Zr1.4M0.6O12 (M = Sb, Ta, Nb) by bottleneck size and bond length of M−O

AbstractBottleneck size is the minimum Li+ migration channel of Li7La3Zr2O12 (LLZO) and it greatly influences the Li+ conductivity. Doping different elements on the Zr site of LLZO can adjust the bottleneck size and improve the Li+ conductivity. However, the regulation mechanism is not clear. In this work, Li6.4La3Zr1.4M0.6O12 (M = Sb, Ta, Nb) has been prepared and the bottleneck size has been adjusted by doping different pentavalent ions. The results manifest that the cell parameter and bottleneck size decrease with the rise of the radius of doped pentavalent ions. This is because larger pentavalent ion leads to larger bond length of M–O, and weaker covalent component between M5+ and O2‐, corresponding, the formal charge on the M5+ become larger, and the bond length of La–O slightly decreases due to the coulomb repulsion between La3+ and M5+ increase. While, the activation energy drop firstly and then rise with the rise of bottleneck size because of the migration of Li+ not only relate to the size of the migration channel but also to the strength of M–O covalent bonding. The bottleneck size and bond length of M–O synergistically affect the migration of Li+.

Synthesis and characterization of electrical features of bismuth manganite and bismuth ferrite: effects of doping in cationic and anionic sublattice: Materials for applications

The electrical, magnetic, and structural features of bismuth manganite (BM), e.g., BiMnO3, and bismuth ferrite (BF), e.g., BiFeO3, are reviewed. Induced multiferroicity and enhanced magnetoelectric coupling are required for various modern device applications. BM and BF were synthesized using standard high-temperature sintering and processes such as sol–gel, hydrothermal, or wet chemical methods combined with annealing. The size and morphology of the nanoscale particles were controlled, although they were usually inhomogeneous. BF exhibits structurally stable antiferromagnetic (AFM) and ferroelectric (FE) phases in wide temperature ranges. Ferromagnetic (FM) order was induced in a thick shell around the AFM core of the nanoscale BF particles, which was attributed to a size effect related to surface strains and disorder. BM exhibited both structurally stable and unstable phases. The BiMnO3, Bi12MnO20, and BiMn2O5 structures are nonferroelectric. The perovskite BiMnO3 form was synthesized under high hydrostatic pressure. FM order occurs in BM at low temperatures. Bi(MnFe)O3 solid solution samples exhibited competition between AFM and FM ordering. Doping can decrease the content of unavoidable secondary phases. Doping in the Bi ion sublattice can stabilize the crystal lattice owing to local strains caused by the difference in ionic radius between Bi and the dopant. Doping in the Fe and Mn sublattices affects the electrical features. The main achievement of substitution with tetra- and pentavalent ions is compensation of the oxygen vacancies. In turn, leakage current suppression enables switching of FE domains and polarization of the samples. A significant enhancement of magnetoelectric coupling was observed in composites formed from BF and other FE materials. The leakage currents can be diminished when an insulator polymer matrix blocks percolation. The potential applicability is related to enhanced magnetoelectric coupling. The constructed devices meet the size effect limitations for FE and FM ordering. Resistive switching suggests possible use in nonvolatile memories and gaseous sensors. The sensors can be used for hydrophones and for photovoltaic and photoluminescence applications, and they can be constructed from multiphase materials. Bulk multiferroic solid solutions, composites, and nanoheterostructures have already been tested for use in sensors, transducers, and read/write devices for technical purposes.

Optical, FTIR and ESR Spectral Investigations of Tungsten Ions in Barium Phosphate Host Glass and Effects of Gamma Irradiation

Tungsten oxide (0.25 – 3% WO3) doped barium phosphate glasses were prepared by the conventional melting annealing procedure. Spectroscopic FTIR infrared and ESR measurements were applied at 0 and 10 Mrad doses of gamma irradiations. The UV-Visible spectrum of the base glass consists of distinct ultraviolet peaks that can be correlated with trace ferric (Fe3+ ions) impurities. UV-Visible absorption spectra of WO3 – doped glasses show similar ultraviolet absorption as the base glass and a very broad visible band settled at about 720 nm and with the high content sample (3% WO3) two peaks are identified at 602 and 790 nm on the very broad visible absorption band. These additional broad band accompanied by the bluish color to the samples support the assumption of the formation or presence of pentavalent tungsten ions because of the reducing nature of the phosphate host glass. Gamma irradiation produces some extension of the UV absorption of the undoped glass spectrum accompanied by the generation of an induced visible broad band centered at 520 nm. These extra induced changes are related to some photochemical reactions leading to the partial oxidation of some ferrous ions to ferric ions through the radiation effect. The induced broad visible band is assumed to be related to the formation of phosphorus oxygen hole centers (POHC) or nonbridging oxygen hole centers (NBOHC) from interaction of gamma rays on the phosphate network. Gamma irradiation of WO3 doped glasses reveals the increase of the intensity of the very broad band and in the high content sample (3% WO3), a new induced band is generated at about 411 nm. These changes are assumed to be related to some photochemical reactions involving the conversion of some W6+ ions to W5+ ions by capturing electrons or by photo-reduction of W6+ ions to W4+ ions and thus imparting the additional peak at 411 nm. FTIR results of the studied glasses reveal the appearance of vibrational modes due to phosphate network groups mainly of metaphosphate units or P–O–P linkages as the response of the chemical composition 50% BaO – 50% P2O5. The infrared results of the radiative samples have no notable changes due to compactness of the phosphate with noticeable amount of heavy Ba2+ ions which seem to retard the passage of liberated electrons or positive holes during the irradiation process and thus the network structure remains unaffected. ESR spectra of WO3 – doped glasses reveal distinct signals due to the unpaired pentavalent ions which are stable towards irradiation due to the existence of a high content of the heavy Ba2+ ions which block the passage of negative and positive holes during irradiation.

Development and Precision Molding of Optical Glasses with High Refractive Index for Optical Applications

The structure and optical properties of phosphate glasses containing bismuth or niobium oxides for subwavelength structure (SWS) optical elements were studied. The glasses containing a large amount of bismuth and niobium oxides had refractive indexes higher than 1.8 and low deformation temperatures. However, these high refractive index glasses were yellowish due to the electronic transition in trivalent bismuth ions and pentavalent niobium ions. The structure of the glasses was investigated by X-ray, IR, and Raman spectroscopy. NbOx and BiOx formed clusters as the bismuth and niobium oxide content increased. The results showed that the local structure around bismuth and niobium ions was related to the coloration. Based on these results, we developed high refractive index glasses that were used for precision molding to fabricate periodic SWSs. One-dimensional periodic SWSs were fabricated on the glass surface by a precision molding method using a SiC mold on which the reverse of the SWS pattern was carved and a flat SiC mold. One-dimensional SWSs with a high aspect ratio were fabricated on one surface of the glass plate. The niobium phosphate glass plates with the one-dimensional SWS showed phase retardation higher than 1/8l between TE- and TM-polarized beams at 400 nm, demonstrating that a wavelength plate can be fabricated by our precision molding technique.

Chemical synthesis and characterization of Nb–ZrO2

The effects of doping of ZrO with pentavalent ions have been insufficiently studied, given that some results indicate that doping does not suppress the monoclinic-tetragonal transformation of the material. To assess the influence of Nb and the calcination conditions on the morphology of ZrO2 in this study, ZrO2:Nb was prepared with dopant concentrations of 2.5mol%, 5.0mol% and 7.5mol%, and was microwave and conventionally calcined at temperatures of 500–1000°C. The XRD results revealed the presence of the orthorhombic, tetragonal and monoclinic phases of ZrO2 and the orthorhombic phase of Nb2Zr6O17. The Rietveld refinement indicated a volumetric fraction of more than 96% of the orthorhombic phase. Raman vibrational modes indicate the presence of tetragonal phase in all the samples and coexistence with other phases at higher temperatures. SEM micrographs of niobium-doped zirconia powders indicated the growth of particles with sizes varying from 1μm to 20μm, in response to increasing heat treatment temperatures and Nb content. The nitrogen adsorption–desorption isotherms of the sample revealed the presence of IV and V type isotherms characteristic of mesoporous materials. The average pore diameter distribution vs. incremental pore volume confirmed the existence of mesopores, whose average diameter was influenced by both dopant and temperature.

Elasticity and mechanical instability of charged lipid bilayers in ionic solutions.

We use coarse-grained Monte Carlo simulations to study the elastic properties of charged membranes in solutions of monovalent and pentavalent counterions. The simulation results of the two cases reveal trends opposite to each other. The bending rigidity and projected area increase with the membrane charge density for monovalent counterions, while they decrease for the pentavalent ions. These observations can be related to the counterion screening of the lipid charges. While the monovalent counterions only weakly screen the Coulomb interactions, which implies a repulsive Coulomb system, the multivalent counterions condense on the membrane and, through spatial charge correlations, make the effective interactions due to the charged lipids attractive. The differences in the elastic properties of the charged membranes in monovalent and multivalent counterion solutions are reflected in the mechanisms leading to their mechanical instability at high charge densities. In the former case, the membranes develop pores to relieve the electrostatic tensile stresses, while in the latter case, the membrane exhibits large wavelength bending instability.

Iron crosslinked alginate as novel nanosorbents for removal of arsenic ions and bacteriological contamination from water

Fixed-bed column studies were conducted to evaluate performance of Fe (III) crosslinked alginate nanoparticles for the removal of pentavalent arsenic ions [As (V)] from aqueous environments. The study involved observing the influences of column bed depth, influent As (V) concentration and influent flow rates on the removal of arsenic ions. The total adsorbed quantity, equilibrium uptake and total percentage removal of arsenic were determined from the breakthrough curves obtained at different flow rates, initial metal ion concentration and bed heights. The results showed that column demonstrate fairly well performance at the lowest flow rate. Also, column bed capacity and exhaustion time were found to increase with increasing bed height. When initial metal ion concentration was increased from 0.5mg/L to 1.5mg/L, the corresponding adsorption bed capacity decreases from 0.066 to 0.022mg/g. The Bed Depth Service Time (BDST) model was used to analyze the experimental data and the model parameters were evaluated. Good agreement of the experimental breakthrough curves with the model predictions was observed.