Electron Pair Research Articles

Polyhedral and Macropolyhedral Metal-Rich Cobaltaboranes: A 25-Vertex Hourglass-Shaped Cluster.

In an effort to break the single-cage 16-vertex supraicosahedral barrier, we have explored the reaction of [Cp*CoCl2], 1 with [LiBH4·THF], followed by thermolysis with [BH3·SMe2] [Cp* = η5-C5Me5]. Although our objective to synthesize a high-nuclearity single-cage cluster was not achieved, we have isolated a 25-vertex macropolyhedral cluster [(Cp*Co)5Co2B18H17(CH3)S] (2). Cluster 2 is an exceptional fused hourglass-shaped macropolyhedral cluster composing two icosahedral cores ([Co3B9] and [Co4B8]) and three tetrahedral cores [Co2B2]. Although the fusion in cluster 2 is very complex, it follows Mingos fusion formalism, leading to an attractive hourglass-shaped cluster. Through subtle changes in reaction conditions, two new cobaltaborane clusters, nido-4,5,7-[(Cp*Co)3B7H11] (3) and nido-2,9-[(Cp*Co)2B8H12] (4), have been isolated. The observed core geometries of clusters 3 and 4 are similar to the parent deltahedra [B10H14] with (n + 2) SEP (SEP = skeletal electron pair, n = no. of vertices). All the synthesized cobaltaboranes have been characterized in solution by ESI-mass, nuclear magnetic resonance spectroscopy, infrared spectroscopy and structurally solved by single-crystal X-ray diffraction analysis.

Peptide‐Based Ammonium Halide with Inhibited Deprotonation Enabling Effective Interfacial Engineering for Highly Efficient and Stable FAPbI3 Perovskite Solar Cells

AbstractAmmonium iodides are intensively investigated as effective interfacial passivation agents in perovskite solar cells (PSCs) while facing a major challenge of their high reactivity with perovskites that undermines the operational stability of the PSCs. Exemplified by involving rationally designed/selected peptide into the widely adopted phenethylammonium iodide (PEAI), the present work demonstrates that the bespoke peptide‐PEAI can effectively inhibit the deprotonation of ammonium iodides and thus hinder the formation of 2D perovskite, facilitating the stability enhancement in perovskite films by multi hydrogen bonding. The additional lone pair electrons provided by peptide molecules can also enhance the passivation ability of the modified layer. Attributed to the stable co‐modifier peptide‐PEAI, the small‐area FAPbI3‐based PSCs yield a high efficiency of 25.02% with robust light and thermal stabilities. Moreover, the peptide‐PEAI‐based minimodules with an efficiency of 19.06% for a total area of 36 cm2 manifested the great application potential of this co‐modification strategy in the perovskite photovoltaics.

Conceptualized Fusion Reactor based on Gas Turbine with High Temperature CO2

Author discovered the mechanism of Cold fusion that covalent bond compression of D-D transition electron to deep orbit which distance is a few femto- meters from the nucleus, which electron density between d-d is so dense that it shields the coulomb repulsive force to cause Fusion, and discovered that nucleus is constituted only by proton and internal electron and neutron is a pair of proton and electron in deep orbit. Dr. Ohmasa claims that his transmutation reactor produce produces precious metal from base metal, which shows experimentally and author discovered that femto-H2 fusion to metal cause transmutation, which proves the existence of femto-H2, and femto-D2 therefore current nucleus model is probed to be incorrect. Dr. Ohmasa also claims that CO2 can be reduced by burning with fossil gas fuel mixed with H2 and O2, and author hypothesized the cause that compression of C-O bond cause fusion between C and O to be P and Si based on the correct nucleus model and based on author’s Cold fusion mechanism of bond compression. Developing this mechanism and hypothesis, I would like to propose the conceptualized fusion reactor based on gas turbine with high temperature CO2. D-D bond can be compressed by high temperature CO2 and by the collision of high-speed blades in gas turbine to cause D+D fusion and C+O fusion, which reduce the CO2 emission. Reactor needs to be cooling to generate power by steam turbine and high- speed blade rotation produce power and causes fusions.

Search for singly produced vectorlike top partners in multilepton final states with 139 fb−1 of pp collision data at s=13 TeV with the ATLAS detector

A search for the single production of a vectorlike top partner (T) with mass greater than 1 TeV decaying into a Z boson and a top quark is presented, using the full Run 2 dataset corresponding to 139 fb−1 of pp collisions at s=13 TeV, collected in 2015–2018 with the ATLAS detector at the Large Hadron Collider. The targeted final state is characterized by the presence of a pair of electrons or muons with opposite-sign charges which form a Z-boson candidate, as well as by the presence of b-tagged jets and forward jets. Events with exactly two or at least three leptons are categorized into two independently optimized analysis channels. No significant excess above the background expectation is observed and the results from the two channels are statistically combined to set exclusion limits at 95% confidence level on the masses and couplings of T. The results are interpreted in several benchmark scenarios to set limits on the mass and universal coupling strength (κ) of the vectorlike quark. For singlet T quarks, κ values between 0.22 and 0.64 are excluded for masses between 1000 and 1975 GeV. For T quarks in the doublet scenario, where the production cross section is much lower, κ values between 0.54 and 0.88 are excluded for masses between 1000 and 1425 GeV. © 2024 CERN, for the ATLAS Collaboration 2024 CERN

Frustrated Lewis pairs on Al-doped CeO2 for efficient reverse water–gas shift reaction

The reverse water–gas shift (RWGS) reaction holds promise for producing high value-added CO from CO2, serving as a crucial intermediate to feedstock for producing various hydrocarbons through Fischer-Tropsch synthesis reactions. Metallic catalysts often yield significant methane production as a by-product during operation, whereas non-metallic oxide catalysts offer potential for high CO selectivity. We prepare Al doped CeO2 nanorod by atomic layer deposition (ALD). The incorporation of Al creates more oxygen vacancies on the surface, resulting in increased Frustrated Lewis Pair (FLP) sites. Particularly, the CO yield of ALD-modified CeO2 was enhanced by 134 % compared to that of pristine CeO2 nanorods (CeO2-NR) at 500 °C, with CO selectivity reached 100 %. Density Functional Theory (DFT) calculations reveal a lower energy barrier for H2 dissociation facilitated by the formation of FLP sites, potentially leading to heightened activity in the Reverse Water Gas Shift (RWGS) reaction.

Highly Reversible Zn Metal Anode Securing by Functional Electrolyte Modulation

AbstractThe stability of the Zn metal anode is significantly affected by the various parasitic reactions during plating/stripping. Here, sodium 4‐aminobenzenesulfonate (SABS) is a functional electrolyte additive to modulate the electrode/electrolyte interface to protect the Zn metal. An electrical double layer (EDL) reconstruction of the interface is affected by providing hydrogen bond sites through nitrogen and oxygen elements with lone pair electrons in SABS molecules. These strong hydrogen bonds not only limit the corrosion of free H2O molecules on the surface of Zn anode but also promote the desolvation process. Besides, the SABS can be further in situ decomposed into a solid electrode/electrolyte interface (SEI) layer to regulate the plating/stripping behavior of Zn2+. As a result, based on the synergism of organic–inorganic hybrid SEI layer and the EDL reconstruction, the Zn//Zn symmetric cells exceptionally survive lasting for 6500 hours at 1 mA cm−2 and 1 mAh cm−2, and over 900 cycles even at 40 mA cm−2 and 10 mAh cm−2. The Zn‐I2 full cell maintains excellent cycle stability of 92.4% after 20000 cycles. Remarkably, the pouch cell maintains a capacity retention of over 99.1% (63 mAh) for 820 cycles at 5 mA cm−2.

Construction of frustrated lewis pairs in ZnO surface for boosting electrocatalytic NO reduction to NH3: Theoretical prediction and experimental validation

Herein, we reported the design of unique FLPs for electrocatalytic reduction of nitric oxide (NOER) through anion doping on the ZnO (100) surface. The results demonstrated that the introduced dopant and its adjacent non−bonding Zn site function as a Lewis base and Lewis acid, respectively, to synergistically activate NO molecules. Using density functional theory for material screening, P−doped ZnO is predicted to exhibit rather high NOER activity with an ultralow limiting potential (−0.04 V), accompanied by the excellent suppression effect on the competitive side reactions to guarantee its high selectivity for NH3 production. Motivated by the theoretical prediction, the synthesized P−doped ZnO catalyst showed a high NH3 yield rate (218.2 μmol h−1cm−2 at −0.7 V) and a high Faradaic efficiency (91.4 %), as confirmed by our experimental measurements. This work not only suggests a high−performance catalyst for NO reduction but also expands upon the potential applications of FLPs in electrocatalysis.

Frustrated Lewis pair-mediated hydro-dehalogenation: crucial role of non-covalent interactions.

Organic halides stand as invaluable reagents with diverse applications in synthetic chemistry and various industrial processes. Despite their utility, concerns arise due to their inherent toxicity. Addressing these apprehensions, hydro-dehalogenation has emerged as a promising strategy involving the replacement of halogen atoms with hydrogen atoms to transform toxic organic halides into hydrocarbons. This study delves into the computational exploration of hydro-dehalogenation reactions of benzyl halide, mediated by frustrated Lewis pairs (FLPs), using density functional theory (DFT). The reactions entail the formation of FLP1 or FLP2 in the presence of TMP or lutidine with B(C6F5)3, respectively. This is followed by heterolytic cleavage of dihydrogen and subsequent reaction with benzyl halides. Non-covalent interaction analysis underscores the significance of π-π stacking and CH-π interactions in stabilizing transition states. Additionally, the activation strain model (ASM) dissects activation energies, revealing the substantial impact of strain energy on reaction barriers. Energy decomposition analysis (EDA) offers insights into the contributions of electrostatic, orbital, and dispersion energies to the overall attractive interaction energy. The investigation extends to hydro-dehalogenation reactions of ethyl halides, uncovering distinct mechanisms and activation barriers. This comprehensive analysis illuminates the intricacies of hydro-dehalogenation reactions, providing valuable insights into their mechanisms and paving the way for future studies in this field. Geometry optimizations were carried out at the M06-2X/def2-SVP level of theory, which was performed using the Gaussian 16 program. Solvent-corrected single-point energies were also calculated using the polarizable continuum model (PCM) at the PCM(chloroform)-M06-2X/def2-TZVP//M06-2X/def2-SVP level of theory. The Gibbs free energy correction was determined from computations performed at the M06-2X/def2-SVP level of theory. Principal interacting orbital (PIO) analysis was conducted using the NBO 6.0 software. The nature of bonding in the respective transition state (TS) structures was analyzed using atoms-in-molecules (AIM) analyses. Additionally, the presence of non-covalent interactions (NCI) was exemplified using Multiwfn software.

Potential of Molecular Catalysts with Electron-Rich Transition Metal Centers for Addressing Long-Standing Chemistry Enigmas.

Molecular complexes with electron-rich metal centers are highlighted as potential catalysts for the following five important chemical transformations: selective conversion of methane to methanol, capture and utilization of carbon dioxide, fixation of molecular nitrogen, water splitting, and recycling of perfluorochemicals. Our initial focus lies on negatively charged metal centers and ligands that can stabilize anionic metal atoms. Catalysts with electron-rich metal atoms (CERMAs) can sustain catalytic cycles with a "ping-pong" mechanism, where one or more electrons are transferred from the metal center to the substrate and back. The donated electrons can activate the chemical bonds of the substrate by populating its antibonding orbitals. At the last step of the catalytic cycle, the electrons return to the metal and the product interacts only weakly with the formed anion, which enables the solvent molecules to remove the product fast from the catalytic cycle and prevent subsequent unfavorable reactions. This process resembles electrocatalysis, but the metal serves as both an anode and a cathode (molecular electrocatalysis). We also analyze the usage of CERMAs as the base of Frustrated Lewis pairs proposing a new type of bimetallic catalysts. This Featured Article aspires to initiate systematic experimental and theoretical studies on CERMAs and their reactivity, the potential of which has probably been underestimated in the literature.

Halogen Bonding in Perfluoroalkyl Adsorption.

Adsorption is a promising technology to remove perfluoroalkyl substances (PFAS), including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), from contaminated water. Although a large number of materials have been evaluated for PFAS adsorption, guidelines that can facilitate the rational design and selection of adsorbents have not been established due to the lack of a mechanistic understanding on the molecular level. Using a novel interpretation of the Freundlich isotherm, this study identifies halogen bonding as the main mechanism controlling perfluoroalkyl adsorption by using a materiomic approach that compares the electrostatic polarities of a variety of carbon, polymer, and mineral-based materials reported in the literature. Comparisons show that both PFOS and PFOA are favorably adsorbed by materials containing high densities of π electrons, lone electron pairs, and negative charges, consistent with the formation of halogen bonding between the positive σ-hole of fluorine as a Lewis acid and a nucleophilic solid as a Lewis base. The identification of this previously unappreciated noncovalent bonding mechanism offers fresh insight into the search of suitable materials for perfluoroalkyl adsorption.

Electron Dynamics in Alkane C-H Activation Mediated by Transition Metal Complexes.

Alkanes, ideal raw materials for industrial chemical production, typically exhibit limited reactivity due to their robust and weakly polarized C-H bonds. The challenge lies in selectively activating these C-H bonds under mild conditions. To address this challenge, various C-H activation mechanisms have been developed. Yet, classifying these mechanisms depends on the overall stoichiometry, which can be ambiguous and sometimes problematic. In this study, we utilized density functional theory calculations combined with intrinsic bond orbital (IBO) analysis to examine electron flow in the four primary alkane C-H activation mechanisms: oxidative addition, σ-bond metathesis, 1,2-addition, and electrophilic activation. Methane was selected as the representative alkane molecule to undergo C-H heterolytic cleavage in these reactions. Across all mechanisms studied, we find that the CH3 moiety in methane consistently uses an electron pair from the cleaved C-H bond to form a σ-bond with the metal. Yet, the electron pair that accepts the proton differs with each mechanism: in oxidative addition, it is derived from the d-orbitals; in σ-bond metathesis, it resulted from the metal-ligand σ-bonds; in 1,2-addition, it arose from the π-orbital of the metal-ligand multiple bonds; and in electrophilic activation, it came from the lone pairs on ligands. This detailed analysis not only provides a clear visual understanding of these reactions but also showcases the ability of the IBO method to differentiate between mechanisms. The electron flow discerned from IBO analysis is further corroborated by results from absolutely localized molecular orbital energy decomposition analysis, which also helps to quantify the two predominant interactions in each process. Our findings offer profound insights into the electron dynamics at play in alkane C-H activation, enhancing our understanding of these critical reactions.

Assembly of 2D/2D Bi2WO6/Boron-doped g-C3N4 Z-type heterojunction photocatalysts for efficient antibiotic adsorption and degradation

The photocatalytic heterojunction systems have shown remarkable development in improving the efficiency of visible-light absorption and photocarriers separation. Herein, we successfully engineered efficient 2D/2D Bi2WO6/Boron-doped g-C3N4 (BiWO/BCN) architectures as Z-type heterojunction photocatalysts with different BiWO to BCN ratios for degradation of antimicrobial drug sulfamethoxazole (SMX) under visible illumination. The SMX degradation using the optimized 40%BWO/BCN sample was obviously enhanced, and the degradation rate was 99.3 % after 120 min of irradiation. Its degradation efficiency was 6.5-, 3.2-, and 2.9-times better than that of BiWO, CN, BCN, and, respectively. The significantly boosted performance of the BiWO/BCN photocatalyst was credited to the effective separation of photo-excited electron and hole pairs. The SMX photodegradation pathways have been explained with a complete assessment of the active species, which showed the major role of •O2− and electrons. The reusability tests proved the high photostability of 40%BiWO/BCN sample throughout 5 sequential cycles (only 3.8 % reduction was witnessed). Therefore, this work presents an innovative photocatalyst combination for green degradation of SMX antibiotic.

Sb2O2SeO3 and Sb2O(SeO3)2: Two-Layered Antimony(III) Selenites with Enhanced Birefringence.

Two antimony selenites, Sb2O2SeO3 and Sb2O(SeO3)2, were synthesized by simultaneously incorporating stereochemically active lone pair electrons containing SeO32- and Sb3+. These compounds are structured with [SbOx] polyhedra and [SeO3] units within a two-dimensional framework. Both of them exhibit cutoffs at 300 and 330 nm within the ultraviolet (UV) range and demonstrate significant birefringence, with indices of 0.069 and 0.126 at 546 nm, respectively. These properties highlight their potential as UV birefringent materials. Structural analyses and theoretical calculations reveal that their exceptional birefringence results from the synergistic interactions between SeO32- anions and Sb3+ cations.

LnSb2O4Br (Ln=Nd and Er) and Sb4O5Br2: Lanthanoid‐Bearing and ‐Free Antimony(III) Oxide Bromides

AbstractSb4O5Br2 crystallizes plate‐shaped in the monoclinic space group P21/c with the lattice parameters a=660.82(5) pm, b=513.71(4) pm, c=1346.35(9) pm and β=97.876(3)° for Z=2. Its crystal structure contains {[Sb4O5]2+} layers with connected [(Sb1)O3+1]5− ψ1‐units and undisturbed pyramidal [(Sb2)O3]3− ψ1‐units, where the free electron pair is counted as a pseudo‐ligand (ψ). The bromide anions required for charge compensation of these cationic {[Sb4O5]2+} layers form single sheets and are only bonded via van‐der‐Waals interactions in this crystal structure, as the nearest distance to antimony cations is at least 300 pm. NdSb2O4Br crystallizes plate‐shaped in the monoclinic space group P21/c as well, but with the lattice parameters a=896.24(6) pm, b=801.16(5) pm, c=799.27(5) pm and β=92.129(3)° for Z=4. The [NdO8]13− polyhedra are linked to each other via four edges and thus form fluorite‐related layers {[NdO ]5−}, which run parallel to the (100) plane. The [SbO3]3− anions share vertices to build chains {[SbO O ]−} along [001], which align parallel within the (100) plane. The isolated Br− anions arrange in layers and show a minimum distance of 319 pm to the next Sb3+ cation. ErSb2O4Br crystallizes plate‐shaped in the non‐centrosymmetric tetragonal space group P4212 with the lattice parameters a=774.76(4) pm, c=899.53(6) pm and c/a=1.161 for Z=4. The erbium‐oxygen environment appears to be roughly the same as in NdSb2O4Br, so the main difference is the linkage of the ψ1‐[SbO3]3− units. Four of these [SbO3]3− anions assemble in a ring structure {[Sb4O8]4−} by sharing corners. Layers of rings are located in the (001) plane and almost planar bromide‐anion slabs assemble between the antimony‐oxygen layers. In this article, all three crystal structures are compared with each other and single‐crystal Raman spectra were recorded and analyzed for NdSb2O4Br and ErSb2O4Br.

Cu inanchored MnO/carbonaceous frameworks trigger peroxymonosulfate activation for enrofloxacin degradation: ROS generation and pollutant attacking processes

Despite Fluoroquinolone antibiotics (FQs) removal in peroxymonosulfate (PMS) activation have been widely researched and the outstanding degradation performance have been gained, the detailed processes by which reactive oxygen species attack pollutants have not been adequately studied. In this study, a Cu/MnO catalyst is anchored onto carbonaceous frameworks using a one-step calcination method for investigation. Benefiting from the sp2 unsaturated carbon as well as the synergistic effect between Cu2+/Cu+/Cu and Mn3+/Mn2+ bimetallic redox electron pairs, the prepared Cu/MnO anchored on carbonaceous frameworks catalyst (4CuMn/C-800) material possesses excellent enrofloxacin (ENR) removal performance, where 85.52 % of ENR is degraded in 80 mins, and maintains relatively high catalysis performance even in the various reaction conditions (reaction pH, reaction temperature, existing anions etc.). The analysis reveals the 1O2 and •O2-, as the dominate ROS, continuously attack the specific active sites of ENR molecules until they are mineralized. In detail, the generated •O2- mainly attacks the piperazine ring, while the formed 1O2 assaults the quinolone group of ENR. By combining density functional theory (DFT) calculations with LC-MS analysis, we propose four distinct pathways for ENR degradation in the 4CuMn/C-800/PMS system. In summary, this study offers a novel and practical approach to design metal/metal oxide/carbon catalysts and enhances our understanding of the mechanisms behind ROS-driven PMS activation.

Evidence for electron-hole crystals in a Mott insulator.

The coexistence of correlated electron and hole crystals enables the realization of quantum excitonic states, capable of hosting counterflow superfluidity and topological orders with long-range quantum entanglement. Here we report evidence for imbalanced electron-hole crystals in a doped Mott insulator, namely, α-RuCl3, through gate-tunable non-invasive van der Waals doping from graphene. Real-space imaging via scanning tunnelling microscopy reveals two distinct charge orderings at the lower and upper Hubbard band energies, whose origin is attributed to the correlation-driven honeycomb hole crystal composed of hole-rich Ru sites and rotational-symmetry-breaking paired electron crystal composed of electron-rich Ru-Ru bonds, respectively. Moreover, a gate-induced transition of electron-hole crystals is directly visualized, further corroborating their nature as correlation-driven charge crystals. The realization and atom-resolved visualization of imbalanced electron-hole crystals in a doped Mott insulator opens new doors in the search for correlated bosonic states within strongly correlated materials.

Constructing frustrated Lewis pairs on porous Ce-based metal-organic frameworks with improved dicyclopentadiene hydrogenation activity

Constructing frustrated Lewis pairs on porous Ce-based metal-organic frameworks with improved dicyclopentadiene hydrogenation activity

Electronic structure modulation in quinoline derivatives through substituent-mediated effects: Development of AIE fluorescent probes for Fe3+ detection in water samples

Iron (Fe3+) is an essential trace element in biological organisms. Abnormal concentrations of Fe3+ in aquatic possess the potential to disrupt normal physiological and metabolic processes in living organisms. Consequently, the pursuit of developing fluorescent probes for detecting Fe3+ concentrations in water samples is highly significant. The lone electron pair on the nitrogen atom of quinoline demonstrates outstanding coordination capabilities, enabling the selective detection of metal ions through coordination. Nevertheless, the interaction between metal ions and quinoline-based fluorescent probes tends to lead to nanoparticle aggregation, causing aggregation-caused quenching (ACQ) phenomena. This severely restricts the practical application of these probes. To address this challenge, the study utilizes quinoline as the foundational framework and modulates the excited-state electronic structure of quinoline derivatives through substituent effects. This facilitates the transition from ACQ to aggregation-induced emission (AIE). By integrating theoretical calculations, the paper proposes a comprehensive strategy for designing AIE molecules based on quinoline. This contribution provides innovative perspectives on AIE molecule design. Ultimately, the AIE property of the 8-MQB molecule is harnessed to develop a fluorescent probe capable of detecting Fe3+ in water samples. The fluorescence intensity exhibits a robust linear correlation with Fe3+ concentrations within the range of 5.0 μM to 0.3 mM. Moreover, the probe demonstrates exceptional resistance to interference from other metal ions. In conclusion, this research presents a universal strategy for designing AIE molecules and introduces an AIE probe for the rapid detection of Fe3+ concentrations in water samples.

DEVELOPMENT AND VALIDATION OF METHODS FOR THE SPECTROPHOTOMETRIC DETERMINATION OF PROSPIDIUM CHLORIDE FOR IDENTIFICATION AND ASSAY ANALYSIS

Objective. The work is devoted to the development and validation of UV-spectrophotometric analysis of propidium chloride, an antitumour drug of the dyspyropiperazine group. The relevance of the study is due to the need to introduce into the practice of quality control of prospidium chloride analysis method characterised by high sensitivity, accuracy, rapidity and availability. Material and methods. The object of the study was a medicinal substance-powder Prospidin (Prospidium chloride, series 271222, expiry date until 12.2027g, produced by «Unitehprom BSU», Minsk). Solutions with working concentration range from 0.05 mol/l to 0.2 mol/l for spectrophotometric analysis were prepared using purified water. Absorption spectra with determination of analytical wavelength (λmax, nm) and value of molar absorption coefficient ε, (l mol-1cm-1) in the range from 200 nm to 400 nm were obtained and analysed on Agilent Cary 60 equipment. Validation parameters were determined in accordance with the regulations of the General Pharmacopoeial Article 1.1.0012.15. Results. Validation evaluation of the developed analytical techniques for the determination of authenticity and active ingredient content by UV spectro-photometry included tests for specificity (in the presence of NaCl 0.9% solution), analytical range (0.05−0.2 mol/L), linearity (r=0.9997), accuracy, preci-sion in terms of repeatability 3.89±0.24 ( ±SD) and intra-laboratory reproducibility (ε=2.1%) and stability. Conclusion. The analysis of electronic spectra of aqueous solutions of propidium chloride demonstrated the presence of R-band absorption (German radikalartig − radical, for systems with unshared electron pairs) with a characteristic wavelength in the far-UV region at λmax=282±0.4 nm, and λmin=255±0.4 nm. It was found that the absorption at λmax in the concentration range from 0.05 mol/L to 0.2 mol/L of a solution of propidine chloride containing nitrogen heteroatoms with unshared electron pairs is due to the implementation of the so-called formally forbidden n→σ* electronic transition involving molecular orbitals. The characteristic appearance of the electronic spectrum with λmax and λmin, compliance with the Beer–Lambert law in the given concentration range, the calculated value of the molar extinction coefficient ε (l mol1cm1) − allow to use the above described spectral characteristics to determine the authenticity and content of the active substance in quality control of prospidium chloride.

Mechanism of polyaspartic acid as acid-base regulation depressant in reverse flotation separation of molybdenite and talc

The separation of talc and molybdenite through flotation has become a significant issue. The current inorganic and organic depressants demonstrate inadequate selectivity and limited efficacy in both positive flotation and reverse flotation of molybdenite. In this study, the utilization of the highly efficient green agent polyaspartic acid (PASP) as a molybdenite depressant was explored to investigate its pH-dependent acid-base depression mechanism. In the case of pH 4.0, molybdenite exhibited effective depression, talc was floated, PASP was desorbed at pH 10.0, and molybdenite was activated. In this study, the impact of electrostatic force on the adsorption process of PASP and examined the mechanism of PASP on molybdenite surface were studied by means of micro-flotation experiments, zeta potential measurements, analysis of solution chemistry, Fourier Transform Infrared Spectrometer (FT-IR) analysis, Ultraviolet–visible spectroscopy (UV–Vis) study, and X-ray photoelectron spectroscopy (XPS) detections. PASP produced chemisorption through the coordination of O or N atoms lone pair electrons with Mo2+ on the molybdenite surface. In this process, electrostatic repulsion determines whether the mineral can come into contact with PASP.