Heavy Cations Research Articles

Synthesis, Fluorescence Properties, Molecular Docking Studies, and Analysis of the Crystalline Structure of the Novel 5‐Imino‐7‐Aryl‐5H‐Thiazolo[3.2‐a]Pyrimidine‐6‐Carbonitrile and Its Derivatives

ABSTRACTThis study describes a simple, inexpensive, and effective method for the synthesis of new 5‐imino‐7‐aryle‐5H‐thiazolo[3,2‐a]pyrimidine‐3‐carbonitrile derivatives 4a‐e using a green procedure that does not require the use of heat or a base, creating a strategy that meets both economic and environmental demands. Various synthesized products were characterized via diverse techniques such as 1H‐NMR, infrared (FT‐IR), Mass spectroscopy (MS), and single crystal X‐ray diffraction. Using a fluorescence spectrometer, the 5‐imino‐7‐phenyle‐5H‐thiazolo[3.2‐a]pyrimidine‐3‐carbonitrile 4a has been tested as a potent fluorescent agent in mixture of DMSO/Water at 10−4 M in one hand, and on the other hand the results of our fluorescence evaluation studies with metal ions (Pb(II), Ba(II), Cd(II), Ni(II), Mn(II), Hg(II), Zn(II), Fe(II), Co(II), Cu(II), La(II), Cr(III), and Fe(III)) have shown that this compound exhibits a turn‐on and turn‐off of the fluorescence to 4a compound with these metals, what forms poor to good interaction by these ions. This result represents the emergence of a new potential ligand for the two heavy cations Cd(II) and Pb(II), which are toxic and polluting, and whose detection is currently of high interest. As well, In the molecular docking evaluation study, it was determined that the 4e molecule has an exceptional ability to inhibit the binding energy of the tubulin protein by −9.13 kcal/mmol, compared to other compounds. The results demonstrate the possibilities for a novel oral medication application.

Breakdown of the Total Dipole Moments of Diatomic Molecules into Individual Orbital Contributions.

Quantum chemical results at the CCSD(T)/def2-QZVPP and BP86/def2-QZVPP levels are reported for the neutral and charged diatomic molecules EF, EO- (E = B-Tl), EF+, EO, EN- (E = C-Pb), EO+, and EN (E = N-Bi). The theoretically predicted bond lengths and dipole moments are in good agreement with each other and with the available experimental values. It is shown that the total dipole moment of the molecules can be nicely separated into the contributions of the individual occupied molecular orbitals. The σ lone-pair orbital has a dominating influence on the total dipole moment in the lighter EX systems, where E is an atom of the first or second octal row of the periodic table, but it becomes less influential for the heavier species. The HOMO of the heavy cations PbF+, SbO+, and BiO+ is the degenerate π-bonding orbital, and the σ lone-pair orbital is the HOMO-2. The orbital energies of the (n-1)d AOs of the heavier atoms are in the same range as those of the lowest lying genuine valence orbitals, so the division into nuclear and valence orbitals is not so clear.

Structures and unimolecular chemistry of alkali metal cation complexes with glutathione in the gas phase

This study investigates the unimolecular reactions of glutathione complexes with alkali metal cations in the gas phase through sustained off-resonance irradiation collision-induced dissociation and examines their structures using a combination of infrared multiphoton dissociation spectroscopy and computational techniques. Under soft CID conditions, glutathione complexes with charge-dense cations such as Li⁺, Na⁺, and K⁺ show significant fragmentation of glutathione, while complexes with heavier cations, Rb⁺ and Cs⁺, primarily undergo loss of glutathione. This behavior is attributed to the stronger non-covalent binding between smaller metal cations and glutathione, which competes with the dissociation thresholds of covalent interactions within the peptide complex. Using CREST, a tool for determining trial structures which were submitted to density functional theory calculations, a thorough investigation of the conformational space revealed many possible structures, including pentacoordinated structures for the Na⁺ and K⁺ complexes, as well as tetra-tri-, bi-, and monocoordinated structures along with zwitterionic structures for all metal cation/GSH complexes. For all alkali metal cation complexes, the thermodynamically most stable structures were found to be tetracoordinated A-type structures where the metal cation is bound to the amine nitrogen and three of the carbonyl oxygens—all except O2, the amide between glycine and cysteine. These computed infrared spectra for these lowest energy complexes were also consistent with the experimental vibrational spectra in the fingerprint region. Based on relative energies and the comparison of computed and experimental infrared spectra in the fingerprint region, the tetracoordinate A-type structures are concluded to be the dominant forms of the [M(GSH)]+ complexes in the gas phase.

Stabilized Li-rich Mn-based oxide cathode particles with an artificial surface in-Situ-preprocessing

The heavy hybrid anion and cation redox contributes to high discharge capacity for Li-rich Mn-based cathode material, but also raises a number of issues including the low initial coulombic efficiency (ICE), rapid attenuation of capacity and voltage and so on, which have prevented its commercialization for more than a decade. Herein, solid-liquid impregnating is conducted to in-situ-build an artificial surface for Li1.2Mn0.54Ni0.13Co0.13O2 (FLLO) particles, which concurrently constructed a anion-redox-free LiMn1.5Ni0.5O4 (LNMO) shell during FLLO synthesis process that completely encloses the FLLO lattice (A-2%-LNMO-FLLO), presents as solid solution structure between FLLO and LNMO coating interface and exhibits stronger bonding between coatings and FLLO cathode material. DSC, TEM and industry computed tomography (ICT) evidence that LNMO coatings is effectiveness in stabilizing the crystal structure of FLLO from macro and micro aspects, leading to the excellent electrochemical properties, such as A-2%-LNMO-FLLO exhibits a discharge capacity of 278mAh/g under 0.1C, and the capacity retention is 98.5 % after 200 cycles under 1C. Furthermore, the enhancement mechanism on electrochemical properties is investigated from aspects of reaction process and crystal structure stability. This paper can provide a theoretical and experimental support for the practical application of FLLO cathode material.

Polytelluride square planar chain-induced anharmonicity results in ultralow thermal conductivity and high thermoelectric efficiency in Al2Te5 monolayers.

Two-dimensional (2D) metal chalcogenides provide rich ground for the development of nanoscale thermoelectrics, although achieving optimal thermoelectric efficiency is still a challenge. Here, we leverage the unique chemistry of tellurium (Te), renowned for its hypervalent bonding and catenation abilities, to tackle this challenge as manifested in Al2Te3 and Al2Te5 monolayers. While the former forms a straightforward covalent Al-Te network, the latter adopts a more intricate bonding mechanism, enabled by eccentric features of Te chemistry, to maintain charge balance. In Al2Te5, a square planar chain (SPC) known as polytelluride [Te3]2- is neutralized by the covalently bonded [Al2Te2]2+ framework. The hypervalent nature of Te results in bizarre Born effective charges of 7 and -4 for adjacent Te atoms within the square planar chain, a feature that induces significant anharmonicity in Al2Te5 monolayers. Enhanced anharmonic lattice vibrations and the accordion pattern bestow glass-like, strongly anisotropic thermal conductivity to the Al2Te5 monolayer. The calculated κL values of 1.8 and 0.5 W m-1 K-1 along the a- and b-axes at 600 K are one order of magnitude lower than those of Al2Te3, and even lower than monolayers that contain heavy cations like Bi2Te3. Moreover, the tellurium chain dominates the valence band maximum and conduction band minimum of Al2Te5, leading to a high valley degeneracy of 10, and thus a high power factor and figure of merit (zT). Using rigorous first-principles calculations of electron relaxation time, the estimated hole-doped and electron-doped zT of, respectively, 1.5 and 0.5 at 600 K is achieved for Al2Te5. The pioneering zT of Al2Te5 compared to that of Al2Te3 is rooted merely in its amorphous-like lattice thermal transport and its polytelluride chain. These findings underscore the importance of aluminum telluride and polymeric-based inorganic compounds as practical and cost-effective thermoelectric materials, pending further experimental validation.

Surface implantation of ionically conductive polyhydroxyethylaniline on cation exchange membrane for efficient heavy metal ions separation

Extraction of heavy metal ions from aqueous could enable recycling of wastewater and reusing of high-value ion resources. Recently, electrodialysis (ED) technology has been applied in the removal of heavy metal ions from wastewater, however, developing high-efficient and stable heavy metal ions selective cation exchange membrane (CEM) remains an elusive challenge. Herein, we demonstrate the fabrication of high-efficient cations selective CEM with the surface implantation of ionically conductive polyhydroxyethylaniline (PANI-OH) on a commercial CEM membrane (CTG) containing sulfonic acid groups via the electrostatic attraction. Implanted hydrophilic and positively charged PANI-OH facilitates fast and selective transfer of Cu2+ over Zn2+ cations through the membrane. Meanwhile, the synergistic effect of rigid conjugate structure and hydrogen-bond interaction of PANI-OH renders the resultant membrane CTG-PANI-OH with stable structure and separation performance. As such, the Cu2+/Zn2+ permselectivity of CTG-PANI-OH membrane is ~1.70, which is about 190 % of that of the pristine CTG membrane. This work provides a facile design and strategy for the construction of high-efficient cations selective CEMs with great application prospects in the purification and extraction of heavy metal ions from wastewater.

Structural and Electrical Characterization of LaSrAl1-xMgxO4-δ Layered Perovskites Obtained by Mechanical Synthesis.

This work presents the structural and electrical characterization of K2NiF4-type layered perovskites of LaSrAl1-xMgxO4-δ composition to be used as oxide-ion electrolytes for a solid-oxide fuel cell (SOFC). These perovskites were prepared by mechano-chemical synthesis (ball milling), an alternative to traditional synthesis methods such as citrate-nitrates and solid-state reaction. With these methods, two things are avoided: first, the use of nitrate salts, which are more environmentally harmful than oxide precursors, and second, it saves the series of long thermal treatments associated with solid-state reactions. After grinding the precursors, nanometric particles were obtained with a combination of crystalline regions and amorphous regions; this effect was determined by XRD and TEM, showing that Mg has a positive effect on the phase formation by only mechanical synthesis. R2C4: After sintering, it was found by XRD that the sample x = 0.1 only presents the diffraction peaks corresponding to the desired phase, which shows a phase purity greater than 97%, even higher than that of the standard undoped sample. For x = 0.2 and 0.3, there was a segregation of impurities, possibly by the local migration of La and Sr heavy cations; this was determined by SEM and EDS. The electrical characterization of the sintered pellets was carried out by electrochemical impedance spectroscopy, which determined that the incorporation of Mg in the structure improves the ionic conductivity by three orders of magnitude, obtaining conductivities of 1.6 mS/cm at 900 °C for x = 0.2. Although the improvement in conductivity is considerable, many challenges such as densification, the segregation of impurities, and the study of mechanical and thermal properties must be carried out on these materials to endorse them as solid electrolytes in SOFC.

Overcoming the cyan gap for full‐spectrum lighting using cation‐substitution‐induced rigid Ca2YZr2Al3O12:Ce3+

AbstractMixing multicolor phosphors for simulating the full spectrum of sunlight illumination is a popular solution to obtain high‐quality white light. However, there is still a need to overcome the cyan gap in the emission spectrum. In this work, a series of garnet Ca2Y0.94–xLuxZr2–yHfyAl3O12:6%Ce3+ (abbreviated as CY0.94–xLuxZr2–yHfyA:Ce3+) cyan phosphors are designed and prepared by substituting Y3+ and Zr4+ in Ca2YZr2Al3O12:6%Ce3+ with Lu3+ and Hf4+ with smaller ionic radius and larger mass. Under 405 nm violet light excitation, the optimized Ca2Y0.88Lu0.06Hf2Al3O12:6%Ce3+ (CY0.88Lu0.06Hf2A:Ce3+) shows a bright cyan emission band in the range of 430–750 nm with the peak at 477 nm. Importantly, the emission intensity and thermal stability properties of CY0.88Lu0.06Hf2A:Ce3+ were significantly improved by 58% and 47% compared to those of pure Ca2YZr2Al3O12:Ce3+. Small and heavy cation substitution could induce highly stable rigid structure, thus enhancing emission intensity and stability. The color rendering index increases from 84.5 to 92.0 after supplementing CY0.88Lu0.06Hf2A:Ce3+ phosphor in white light‐emitting diode devices combining commercial red, green, and blue phosphors with a violet chip, indicating its practical application in full‐spectrum lighting. The present study provides promising strategies for the design and development of efficient cyan materials for high‐quality full visible spectrum light‐emitting diode lighting.

Extractable latex yield from Taraxacum kok-saghyz roots is enhanced by increasing rubber particle buoyancy

Taraxacum kok-saghyz (TK) is a leading alternative rubber-producing plant that produces natural rubber (NR) latex in laticifers within its roots. Unlike the tropical rubber tree, Hevea brasiliensis, TK can be grown in temperate regions, such as the northern United States, as the basis of a domestic rubber production industry. To support such an industry, efficient, scalable rubber extraction techniques are needed. In this study, aqueous extraction was used to recover TK natural rubber latex (TNRL) from four harvests of greenhouse-produced TK roots with a new technique that improves rubber particle buoyancy in root homogenate by chelation. The new method includes harvest, cleaning, and homogenization of freshly harvested roots, followed by centrifugation, vacuum collection of latex, and purification. Treatment of homogenate with ethylenediaminetetraacetic acid (EDTA), a divalent cation chelator, allowed more than twice as much latex to be extracted from fresh homogenate. EDTA-treated rubber particles contained lower concentrations of divalent cations than untreated ones in fresh homogenate and homogenate stored for two weeks. Long term (three months) storage of root homogenate similarly yielded more latex than fresh homogenate and had low divalent cation rubber particle concentrations, indicating that heavy cations had slowly leached from the particles into the aqueous medium during storage. Rubber particle size was larger in this treatment suggestive of rubber particle agglomeration but this was prevented and reversed by EDTA. Removal of divalent cations via chelation increased particle packing density of particles in concentrated latex and appeared to increase the gel content of dried latex samples. Molecular characterization of dried samples of purified TNRL established that the rubber was of the high molecular weight needed for product manufacturing.

Groundwater quality in the vicinity of a dumpsite in Lagos metropolis, Nigeria

Inappropriate management of municipal solid waste dumpsites is a major cause of groundwater contamination in developing countries, but the extent of the problem is not known. This study investigated groundwater quality in the vicinity of Olusosun dumpsite in Lagos, Nigeria, the most populous city in sub-Saharan Africa. During 2020, monthly groundwater samples were collected in 17 wells and boreholes used as drinking water sources, and analysed for 20 physico-chemical parameters. Differences between sites and seasons were statistically assessed, together with changes in water quality index (WQI). The results indicated that heavy metals (Pb2+, Ni+, Mn2+, Fe2+, Cr6+), cations (Ca2+, Mg2+, K+), total hardness and pH were the main parameters impairing water quality. Drinking water quality standards from both the World Health Organization and Nigeria government were exceeded more often in the wet season than in the dry season. Some groundwater properties were negatively correlated with distance to dumpsite (e.g., Fe2+, Pb2+, NO3−). Significant differences between sites were identified, but with no clear spatial trend. WQI varied from excellent (6%–24% of the sites over the study period) to unsuitable for drinking water purposes (12%–18%), with good quality prevailing at most sites (35%–47%). Although groundwater quality declined at 24% of the sites over 2020, the results indicated improvements compared with previous decades. Remediation strategies must be implemented to safeguard public health and the sustainability of water resources.

Upgrading of conventional water treatment plant by nanofiltration for enhanced organic matter removal

Natural organic matter (NOM) is responsible for a variety of problems in water, including taste, odor, and color. If NOM is present in treated water, it can also promote microbial growth in water distribution systems. Another problem related with NOM is that it combines with chemicals such as chlorine in water resulting in the formation of disinfection by-products (DBPs). With the DBP regulations becoming more stringent, several advanced treatment methods started to be applied to enhance NOM removal. Pilot-scale advanced treatment tests employing tight nanofiltration (T-NF) membrane with high ion rejection capacity and loose nanofiltration (L-NF) membrane with low ion rejection capacity were conducted in this study in order to remove total organic carbon (TOC) having an average concentration of 2 mg/L at the sand filter effluent of a full-scale drinking water treatment plant and to avoid DBP production. The cost of incorporating membrane processes into the treatment process scheme was also determined during the study, in addition to the experimental studies. At constant 6 bar, the average fluxes for the T-NF and L-NF were determined to be 12.7 and 7.6 L /m2 h, respectively. L-NF had a TOC removal efficiency of 96.0%, which is quite similar to the removal efficiency achieved by T-NF (96.3%). Heavy metals, anions, and cations removal efficiency in T-NF membranes were greater than in L-NF, as expected. The removal efficiencies of Cl-, and Fe on T-NF membrane were determined to be 90.3 ± 2.2% and 69.6 ± 5.6, respectively, which are much greater than those achieved in L-NF membrane The total cost of 400,000 m3/d L-NF membrane system upgrade is calculated as 28,901,262 $/y including capital and operation and maintenance (O&M) costs, while in T-NF is calculated as 28,074,282 $/y. The total cost of NF upgrading is estimated to be around 0.191–0.198 $/m3, which is nearly 50% of the cost of the conventional treatment plant. When upgrading a conventional treatment system with this type of membrane system, additional expenses are typically incurred, resulting in a higher total cost; however, the resultant water quality is significantly improved.

COHERENCE ASSEMBLY IN STRUCTURES WITH HEAVY METAL CLUSTERS

A crystallographic analysis of two structures, monoclinic Nа8[{Re4(PO)4}(CN)12]⋅18H2O⋅CH3OH (I) and orthorhombic [(C6H5)4P]4 [Ta6I12(CN6)] (II), in which clusters of heavy atoms are significantly rarefied in space, so that their mutual arrangement cannot be explained only in terms of chemical interaction, has been performed. In structure I the crystallographic planes with a high atomic density (“skeletal” planes) are located in the regions with dhkl = 10–5.5 Å and dhkl 3 Å. The planes in which atomic groups [Re4(PO)4] (playing the role of unified bulk objects) are concentrated are in fact selected in the first region. In the second region, ordering is implemented at the level of individual atoms. A crystallographic analysis showed that the structure basis is determined by the sites of heavy Re cations. A striking fact is that there are 1152 subcells and only 32 Re atoms per unit cell in this structure; i.e., only the fraction of 1/144 provides the basis of structure stability. In structure II “skeletal” planes are also absent in the range of dhkl from ∼7 to ∼4 Å. The planes in the range of large dhkl characterize cluster ordering, whereas the planes in the range of small dhkl characterize ordering of separate atoms. The geometry and local symmetry of the cluster group (Та6 octahedron) dictates the basis of translational symmetry—unified sublattice of sites, most of which are free of these atoms. The considered structures demonstrate the key role of heavy atoms in the formation of translational symmetry—the fundamental difference of the crystalline state from other condensed states. The newly formed structure retains partially local symmetry of cores (templates) of atomic groups, bound by strong chemical interactions, including the interactions between heavy and light atoms. The process of formation of a crystal structure from randomly oriented and randomly located templates—coherence assembly—is implemented according to the laws of dynamics of elastic media, where masses of atoms rather than their chemical characteristics are important.

Structure and reactivity assessment of dioctahedral montmorillonite during provoked variable sequential cation exchange process via XRD modelling approach

The intrinsic cation exchange capacity (CEC) of clays is a crucial characteristic that offers a tool to assess their overall chemical properties. For the confinement of industrial and radioactive waste, clays are deployed as geological barriers, hence it is important to consider how they will react under external stresses. With respect to the electronegativity rate and cation ionic potential, the impact of a series of sequential cation exchange processes with heavy metals exchangeable cations was the main emphasis of this work. Using X-ray diffraction (XRD) profile modeling to assess interlayer space (IS) deformation and highlight geochemical alteration, the structural reactivity of Na-rich montmorillonite was investigated. To determine the ideal structural characteristics defining IS configuration, the study contrasted estimated reflections produced from theoretical models with those produced experimentally from 00l reflections. Per each exchanged cation, the results showed a partial CEC saturation and a heterogeneous mixed layer structure (MLS), with heterogeneous hydration behavior continuing to exist regardless the type of exchangeable cation. The established chemical constraint had no effect on the cation hydration sphere for Co (II), Ni (II), Mg (II), Cu (II), and Zn (II) exchangeable cations. However, significant interlamellar water molecule development was observed for the Cd (II), Pb (II), and Ba (II) cations, indicating a major alteration in the discretization of the hydration states and particular hydration heterogeneities. The Cd (II), Pb (II), and Ba cations were most affected by these alterations, which resulted in a constrained and inhibited CEC performance. The theoretical decomposition of the observed XRD profiles was used to show the existence of multiple layer type populations and their stacking mode, with most of the studied samples showing a tendency toward segregated stacking configuration. Moreover, as a function of the applied stress, the CEC of the stress samples gradually dropped.

Unveiling the Superior Optical Properties of Novel Melamine-Based Nonlinear Optical Material with Strong Second-Harmonic Generation and Giant Optical Anisotropy.

Two melamine-based metal halides, (C3 N6 H7 )(C3 N6 H6 )HgCl3 (I) and (C3 N6 H7 )3 HgCl5 (II), are synthesized by incorporating the heavy d10 cation, Hg2+ , and the halide anion, Cl- . The noncentrosymmetric structure of I results from two unique attributes: large asymmetric secondary building units produced by direct covalent coordination of melamine to Hg2+ and a small dihedral angle between melamine molecules. The former makes inorganic modules locally acentric, while the latter prevents planar organic groups from forming deleterious antiparallel arrangement. The unique coordination in I results in an enlarged band gap of 4.40eV. Due to the large polarizability of the heavy Hg2+ cation and the π-conjugated system of melamine, I exhibits a strong second-harmonic generation efficiency of 5 × KH2 PO4 , larger than any reported melamine-based nonlinear optical materials to date. Density functional theory calculations indicate that I possesses giant optical anisotropy, with a birefringence of 0.246@1064nm.

Theoretical Study of Pressure-Induced Phase Transitions in Sb2S3, Bi2S3, and Sb2Se3

We report an ab initio study of Sb2S3, Sb2Se3, and Bi2S3 sesquichalcogenides at hydrostatic pressures of up to 60 GPa. We explore the possibility that the C2/m, C2/c, the disordered Im-3m, and the I4/mmm phases observed in sesquichalcogenides with heavier cations, viz. Bi2Se3, Bi2Te3, and Sb2Te3, could also be formed in Sb2S3, Sb2Se3, and Bi2S3, as suggested from recent experiments. Our calculations show that the C2/c phase is not energetically favorable in any of the three compounds, up to 60 GPa. The C2/m system is also unfavorable for Sb2S3 and Bi2S3; however, it is energetically favorable with respect to the Pnma phase of Sb2Se3 above 10 GPa. Finally, the I4/mmm and the disordered body-centered cubic-type Im-3m structures are competitive in energy and are energetically more stable than the C2/m phase at pressures beyond 30 GPa. The dynamical stabilities of the Pnma, Im-3m, C2/m, and I4/mmm structural phases at high pressures are discussed for the three compounds.

FACTORS FAVORING PREFERENCE OF ARTERIOGRAPHY OVER CT ANGIOGRAPHY FOR PERIPHERAL ARTERIAL DISEASE EVALUATION

Despite many advances in the quality and availability of less invasive arterial imaging modalities, arteriography remains the “gold standard.” This is a Prospective study which analyzes the factors favoring the preference of DSA over CTA in patients with peripheral vascular disease. Those patients with peripheral vascular disease undergoing DSA, who were initially planned for CTA and could not undergo CTA for various reasons were included. This study consists of 38 patients with most of them were males 29 (76%). In our study common factor for referral over CTA was renal dysfunction patients 18 out of 38 ( 47%), as contrast required in standard CTA for lower limb runoff is around 100ml and in our DSA average volume required is only 30ml because of target lesion arteriography with magnication. Next common factor was presence of heavy calcications in tibial vessel walls which hampers the evaluation of the CTA who were 37% of our study patients (14). Other factors were severe congestive Cardiac Failure, Previous Bone Plating/Nailing in leg bones and limb Contracture. With increasing incidences of diabetic patients with their associated diabetic nephropathy and heavy calcicated arteries, makes these patients more preferred for DSA than CTA due to its low contrast dose requirements and images free of calcication artefacts

Characteristics of Water Pollution and Evaluation of Water Quality in Subsidence Water Bodies in Huainan Coal Mining Areas, China

The subsidence water bodies in coal mining areas are vulnerable to being polluted by the surrounding mining production wastewater, domestic sewage, and agricultural return flow. Therefore, it is important to grasp the water quality condition of the above water bodies. A total of 16 surface water samples from 7 different subsidence water bodies in the Huainan mining area were collected and focused on the selection of 22 water quality indicators for water pollution characteristics analysis. The result of correlation analysis showed that Cr and Zn came from the same source of pollution. Three principal factors were selected by factor analysis, which could explain 82.294% of the total variance. Principal factor 1 indicated a mixture of pollution related to nitrogen and phosphorus nutrients, organic pollutants, and heavy metals; principal factor 2 showed heavy metal pollution; and principal factor 3 presented the pollution from heavy metals and cations. Results of cluster analysis showed that the water quality status of 16 sampling points could be divided into 4 clusters. The results of the heavy metal pollution index method showed that the heavy metal pollution was most serious in sample 9 (S9), S15, and S16, and the main elements of pollution were Ni, Fe, and Mn. Single-factor evaluation, comprehensive pollution index, the universal exponential formula of logarithmic power function, and membership degree method were used to evaluate the five important water quality indicators, namely total nitrogen, ammonia nitrogen, total phosphorus, dissolved oxygen, and chemical oxygen demand. The results showed that the total nitrogen pollution in the study area was more serious, most of the sites exceed class V standards of the surface water, S14 and S16 were heavily polluted. Based on the comparison of the different methods, the surface water quality in the study area can be reflected more comprehensively.

Sol-gel matrices for the separation of uranyl and other heavy metals

The development of simple, cheap, and efficient techniques for separating and recycling heavy metal cations, including radioactive species, motivated this study of the feasibility of using sol-gel matrices as ion exchange columns. The goal of this study was to elucidate the selectivity of a sol-gel matrix for heavy and radionuclide cations to separate heavy metal cations from a solution of heavy and radioactive metals. The effect of ligand incorporation in the host matrix on adsorption capacity was determined by measuring matrix capacities to adsorb the metal cations. Analysis of the results obtained by DFT calculations showed a good fit to the relative capacity values measured by the wet experiments, and they lead to some important conclusions:The higher capacity observed for the matrices prepared at pH 13 for all of the studied cations, indicates that this method could be applicable in the durable entrapment of cations. The sol-gel matrices were found to be selective for the uranyl, and the entrapment of nitrilotris(methylene)]tris(phosphonic acid) in these matrices increases the capacity and selectivity for cerium and accelerates the cation adsorption process (the measured capacities are 25.3 μmol/g sol-gel and 28.4 μmol/g sol-gel for the TMOS-Blank and TMOS-NTPH, respectively). Since uranyl and chromium reached their maximum capacities at different times, which also differed from the times for the other cations, these matrices can be used as ion exchange columns for the separation of chromium and uranyl from other cations and for the recycling of heavy and radioactive metals.

Ion Correlation in Choline Chloride-Urea Deep Eutectic Solvent (Reline) from Polarizable Molecular Dynamics Simulations.

In recent years, deep eutectic solvents (DESs) emerged as highly tunable and environmentally friendly alternatives to common ionic liquids and organic solvents. In this work, a polarizable model based on the CHARMM Drude polarizable force field is developed for a 1:2 ratio mixture of choline chloride/urea (reline) DES. To successfully reproduce the structure of the liquid as compared to first-principles molecular dynamics simulations, a damping factor was introduced to correct the observed over-binding between the chloride and the hydrogen bonding site of choline. Investigated radial distributions reveal the formation of hydrogen bonds between all the constituents of reline and similar interactions for chloride and urea's oxygen atoms, which could contribute to the melting point depression of the mixture. Predicted dynamic properties from our polarizable force field are in good agreement with experiments, showing significant improvements over nonpolarizable models. Similar to some ionic liquids, an oscillatory behavior in the velocity autocorrelation function of the anion is visible, which can be interpreted as a rattling motion of the lighter anion surrounded by the heavier cations. The obtained results for ionic conductivity of reline show some degree of correlated ion motion in this DES. However, a joint diffusion of ion pairs cannot be observed during the simulations.

Mixed Chalcogenide‐Halides for Stable, Lead‐Free and Defect‐Tolerant Photovoltaics: Computational Screening and Experimental Validation of CuBiSCl2 with Ideal Band Gap

AbstractLead halide perovskites have emerged as promising photovoltaic (PV) materials owing to their superior optoelectronic properties. However, they suffer from poor stability and potential toxicity. Here, computational screening with experimental synthesis is combined to explore stable, lead‐free, and defect‐tolerant PV materials. Heavy cations with lone‐pair electrons and mixed anions of chalcogens and halogens as a descriptor for simultaneous realization of defect tolerance and high stability are adopted. Together with the criteria of possessing direct band gap and optimal gap value, the inorganic material database is screened and CuBiSCl2 in the post‐perovskite structure is identified with an ideal band gap of 1.37 eV. The electronic structure and defect calculations suggest its defect‐tolerant characteristics. By optical absorption measurement, its band gap is confirmed to be ≈1.44 eV, with strong absorption near the band edge. The material is stable against thermal decomposition up to 300 °C and can survive from 25 days of storage at ambient conditions with 60% relative humidity. Prototype solar cells are fabricated and demonstrate an open circuit voltage of 1.09 V and a power conversion efficiency of 1.00%. With the excellent properties above, CuBiSCl2 is proposed to be a promising candidate for PV application.