Search Results (5,389)

Copper ions (Cu²⁺), indispensable in physiological processes yet toxic at elevated concentrations, require sensitive on-site monitoring. Here, a portable fluorescent sensing film (Y-CDs@BCM) was fabricated by anchoring yellow-emitting carbon dots (Y-CDs) into bacterial cellulose films, which enables rapid and sensitive detection of Cu²⁺ in complex real-world samples. The yellow fluorescent carbon dots (Y-CDs) were synthesized with the aid of o-phenylenediamine and 1-octyl-3-methylimidazolium tetrafluoroborate as precursors, exhibiting excellent fluorescence stability. The fluorescence of Y-CDs was selectively quenched by Cu²⁺ via the inner filter effect (IFE), allowing quantitative analysis with superior sensitivity compared to existing methods. By adding bacterial cellulose (BC) as a solid support, aggregation-induced fluorescence quenching was effectively reduced, and sensor robustness and portability were improved. Through smartphone-based colorimetric analysis, the Y-CDs@BCM sensor enabled rapid, visual interpretation of Cu²⁺ detection (within 1 min). Furthermore, cell viability and in vivo assays confirmed the biocompatibility of Y-CDs, indicating their suitability for biological imaging. This work presents an environmentally friendly, reliable, and practical method for on-site Cu²⁺ monitoring, emphasizing its broad application potential in food safety control and environmental analysis. Full article

Addressing the challenge of sulfonated lignite (SL) removal from oilfield wastewater, this study introduces a novel hierarchical MgFe-layered double hydroxide (LDH) adsorbent. The material was fabricated via in situ co-precipitation, utilizing a template formed by the NaCl-induced co-assembly of oleylaminopropyl betaine (OAPB) and sodium dodecyl sulfate (SLS) into zwitterionic, anionic, shear-responsive viscoelastic gels. This gel-templating approach yielded an LDH structure featuring a hierarchical pore network spanning 1–80 nm and a notably high specific surface area of 199.82 m²/g, as characterized by SEM and BET. The resulting MgFe-LDH demonstrated exceptional efficacy, achieving a SL removal efficiency exceeding 96% and a maximum adsorption capacity of 90.68 mg/g at neutral pH. Adsorption kinetics were best described by a pseudo-second-order model (R² > 0.99), with intra-particle diffusion identified as the rate-determining step. Equilibrium adsorption data conformed to the Langmuir isotherm, signifying monolayer uptake. Thermodynamic analysis confirmed the process was spontaneous (ΔG < 0) and exothermic (ΔH = −20.09 kJ/mol), driven primarily by electrostatic interactions and ion exchange. The adsorbent exhibited robust recyclability, maintaining over 79% of its initial capacity after three adsorption–desorption cycles. This gel-directed synthesis presents a sustainable pathway for developing high-performance adsorbents targeting complex contaminants in oilfield effluents. Full article

The Long Interspersed Element-1 (L1) retrotransposon is an ancient genetic parasite that comprises a significant part of the human genome. ORF2p is a multifunctional enzyme with endonuclease (EN) and reverse transcriptase (RT) activities that mediate target-primed reverse transcription of RNA into DNA. Structural studies of LINE-1 ORF2p consistently show a single Mg²⁺ cation in the reverse transcriptase active site, conflicting with the common DNA polymerase mechanism which involves two divalent cations. We explored a reaction pathway of the DNA elongation based on the recent high-resolution ternary complex structure of the ORF2p. The combined quantum and molecular mechanics approach at the QM (PBE0-D3/6-31G**)/MM (CHARMM) level is employed for biased umbrella sampling molecular dynamics simulations followed by umbrella integration utilized to obtain the free energy profile. The nucleotidyl transfer reaction proceeds in a single step with a free energy barrier of 15.1 ± 0.8 kcal/mol, and 7.8 ± 1.2 kcal/mol product stabilization relative to reagents. Concerted nucleophilic attack by DNA O3′ and proton transfer to Asp703 occur without a second catalytic metal ion. Estimated rate constant ∼60 s⁻¹ aligns with RT kinetics, while analysis of the Laplacian of the electron density along the cleaving P-O bond identifies a dissociative mechanism. Full article

Drying is ubiquitous. However, its influence on surface speciation has been seldom studied. Through an in situ Attenuated Total Reflection–Infrared (ATR-IR) spectroscopy analysis of the drying of molybdate solutions on a lepidocrocite particle film, the change in surface speciation is followed. No formation polymolybdates nor precipitate are observed upon drying at pH 8. An in situ washing of the dried solid/solution interface unveils the existence of surface outer-sphere and inner-sphere complexes. Decreasing the molybdate concentration highlights a saturation effect of the surface upon drying. Moreover, the careful analysis of substrate IR bands showed non-uniform drying which is an important insight to understand dehydration chemistry. The remaining molybdate ions at the surface as inner-sphere complexes are present as binuclear monodentate complexes stabilized by sodium. Full article

Human population growth and increasing transportation demands have led to rising global tire consumption and associated waste. In response, various material and energy recovery strategies, such as pyrolysis, have been developed to produce high-value-added products such as pyrolysis oils, which can be reused as materials or fuels. However, these oils often contain heteroatom-containing compounds (e.g., nitrogen, oxygen, sulfur) that can hinder their valorization and must therefore be identified and removed. To characterize heteroatomic compounds present in distillation fractions of pyrolysis oils, GC×GC/TOFMS and GC/HRMS were employed. For non-target analysis, data processing parameters were optimized using a Central Composite Design (CCD). The most influential parameters for GC×GC/TOFMS were the minimum number of mass-to-charge ratio (m/z) signals kept in the deconvoluted spectra (minimum stick count) and peak signal-to-noise ratio (S/N), while for GC/HRMS, optimization focused on the m/z S/N threshold, peak S/N, and total ion current (TIC). Under optimal conditions, 129 and 92 heteroatomic compounds were identified via GC×GC/TOFMS and GC/HRMS, respectively, within a single distillation fraction, with 57 compounds identified using both techniques. Notably, GC×GC/TOFMS exclusively identified 72 compounds, while there were only 5 unique to GC/HRMS. These results highlight the effectiveness of GC×GC/TOFMS in characterizing heteroatomic compounds in complex mixtures, while also underlining the complementary value of GC/HRMS. Full article

Simulated (or measured) photoabsorption spectra often provide the first indication of how matter interacts with light when irradiated by some radiation source. In addition to the direct, often slowly varying photoabsorption cross-section as a function of the incident photon frequency, such spectra typically exhibit numerous resonances and edges arising from the interaction of the radiation field with the subvalence or even inner-shell electrons. Broadly speaking, these resonances reflect photoexcitation, with its subsequent fluorescence, or the autoionization of bound electrons. Here, a (relativistic) cascade model is developed for estimating the photoabsorption of (many) atoms and multiply charged ions with a complex shell structure across the periodic table. This model helps distinguish between level- and shell-resolved, as well as total photoabsorption, cross-sections, starting from admixtures of selected initial-level populations. Examples are shown for the photoabsorption of C${}^{+}$ ions near the $1s-2p$ excitation threshold and for Xe${}^{2+}$ ions in the photon energy range from 10 to 200 eV. While the accuracy and resolution of the predicted photoabsortion spectra remain limited due to the additive treatment of resonances and because of missing electronic correlations in the representation of the levels involved, the present implementation is suitable for ions with quite different open-shell structures and may support smart surveys of resonances along different isoelectronic sequences. Full article

With the rapid development of flexible electronic skin materials, the demand for ion-conductive hydrogels is constantly growing. Specifically, these ion-conductive hydrogels are required to simultaneously exhibit excellent mechanical properties, high conductivity, and multifunctionality. Moreover, this performance requirement needs to be met in complex environments. However, the rapid production of hydrogels that combine high conductivity and photochromic properties remains a major challenge. In this study, a simple one-pot method was employed to successfully prepare multifunctional photochromic hydrogels by incorporating ammonium molybdate (Mo₇) and lithium chloride (LiCl) into a dual-network hydrogel composed of polyacrylamide (PAAm) and sodium alginate (SA). PAAm/SA/Mo₇/LiCl (PSML) hydrogels exhibit excellent comprehensive performance, including superior conductivity (average value of 164 S/cm), rapid UV response time (<20 s), good color-changing reversibility, outstanding high stretchability (peak value of 2800%), and high transparency (>70%). The design ingeniously combines two types of synergistic effects: the synergistic effect of the dual-network structure and that of the multifunctional component functional additives (Mo₇, LiCl). Specifically, the PSML hydrogel integrates photochromic properties, excellent mechanical properties, good anti-freezing properties, and 3D printability through this design. Due to these outstanding properties, the PSML hydrogel shows broad application prospects in fields such as flexible strain sensors, information storage, and encryption devices. Full article

This study evaluates the sorption behavior of natural zeolite (NZ) and Fe(III)-modified natural zeolite (FeZ) for Ni(II) ions, with the objective of assessing their potential for application in the remediation of nickel-contaminated environments. Optimization of sorption parameters, including pH_o, solid/liquid ratio (S/L), contact time, and initial Ni(II) concentration was performed to maximize both the sorption capacity of the zeolites and the removal efficiency of Ni(II) from suspension. The results demonstrated that both pH_o and S/L ratio exert a significant influence on Ni(II) sorption onto both zeolites, with a particularly pronounced effect observed for FeZ. Experimental results confirmed that FeZ exhibits a four-to-five times higher sorption capacity for Ni(II) than NZ, which was additionally verified by elemental analysis, SEM-EDS, and elemental mapping of Ni(II)-saturated zeolites. Intraparticle diffusion was identified as the rate-limiting step in the transfer of Ni(II) ions to the active sorption sites. Ion exchange was identified as the main sorption mechanism accompanied by outer-sphere complexation and electrostatic attraction. Leaching tests of Ni(II)-saturated zeolites, conducted in accordance with the standard DIN 38414 S4 method, demonstrated that both zeolites effectively retained Ni(II) within their structures over a wide pH range, 4.11 ≤ pH_o ≤ 12.02. These findings indicate the potential applicability of zeolites for remediation of nickel-contaminated environments, with FeZ being particularly promising due to its enhanced sorption capacity for Ni(II) ions. Full article

In this article, the binding interactions of lysozyme with hexacyanoferrate(III)/(II), i.e., [Fe(CN)₆]³⁻ and [Fe(CN)₆]⁴⁻ ions, have been characterised using steady-state fluorescence spectroscopy (SF), isothermal titration calorimetry (ITC), circular dichroism spectroscopy (CD), cyclic voltammetry (CV), and molecular-dynamics-based computational approaches. Studies have shown that under experimental conditions (10 mM cacodylate buffer, pH 7, 298.15 K), complexes with a 1:1 stoichiometry are formed. Four distinct regions on the lysozyme surface patches with the potential to bind hexacyanoferrate(III)/(II) were identified and described. Thermodynamic parameters revealed that the interactions are predominantly governed by electrostatic and van der Waals forces. These interactions enhance the electron transfer kinetics of the [Fe(CN)₆]^3−/4− system. The secondary structure of the protein is not affected by these interactions. Enzyme activity studies demonstrated that the affinity of lysozyme for the substrate remained unchanged regardless of whether free lysozyme or the lysozyme-[Fe(CN)₆]^3−/4− complex was present in the test sample. Finally, biological tests performed on both Gram-positive (B. subtilis, S. aureus) and Gram-negative (E. coli, P. aeruginosa) bacteria confirmed the results of the biochemical analysis, indicating that [Fe(CN)₆]^3−/4− ions do not block the active site of the enzyme and do not interfere with its activity. Full article

Europium mononuclear complexes are able to form organic molecular crystals by aggregation of molecules through non-covalent bonding interactions. These crystals have many unique optical properties. However, this kind of crystal still faces some difficulties and challenges in the process of research and application, such as the high difficulty of synthesis and purification, and the difficulty of spectral property modulation. In this work, an europium-containing rare-earth molecular crystal material [Eu(BA)₄(pip)], was prepared via a solvothermal method. It is characterized by low melting point, low polarity, stable structure, high luminescence intensity, and has the potential for the preparation of quantum optical devices. After that, optimized the structure of the molecular crystals by petroleum ether solvent. Through the recrystallization process, a uniform and continuous film was formed, which resulted with a more regular surface morphology, and the changes in the optimized crystal structure had an effect on the europium ion electron-leap energy level, the fluorescence emission spectra also showed higher fluorescence resolving ratio. This study particular emphasis on enhancing the quality of [Eu(BA)₄(pip)] molecular crystals and investigating their impact on their spectral properties. Full article

Nitrate leaching from agricultural soils is a major contributor to groundwater contamination and non-point source pollution. Controlling this loss remains challenging due to the complexity of soil–water–nutrient interactions under intensive farming practices. Biochar, a porous, carbon-rich material derived from biomass pyrolysis, has emerged as a promising amendment for nitrate mitigation. This review summarizes recent advances in understanding the roles of biochar in nitrate retention and transformation in soils, including both direct mechanisms—such as surface adsorption, ion exchange, and pore entrapment—and indirect mechanisms—such as enhanced microbial activity, soil structure improvement, and root system development. Field and laboratory evidence shows that biochar can reduce NO₃⁻-N leaching by 15–70%, depending on its properties, soil conditions, and application context. However, inconsistencies in performance due to differences in biochar types, soil conditions, and environmental factors remain a major barrier to widespread adoption. This review also suggests current knowledge gaps and research needs, including long-term field validation, biochar material optimization, and integration of biochar into precision nutrient management. Overall, biochar presents a multifunctional strategy for reducing nitrate leaching and promoting sustainable nitrogen management in agroecosystems. Full article

The oxalic acid leachate of vanadium-bearing shale (OALS) is a complex system in which the ion states and coordination mechanisms of the primary metallic elements—vanadium, iron, and aluminum—are not fully understood. This study investigated the ionic speciation and coordination mechanisms of vanadium, iron, and aluminum in OALS. The results indicate that vanadium predominantly existed as VO(C₂O₄)₂²⁻ anions, iron as Fe(C₂O₄)₂⁻ and Fe(C₂O₄)₃³⁻ anions, and aluminum as Al(C₂O₄)₂⁻ and Al(C₂O₄)₃³⁻ anions. The coordination reaction processes and equations of various oxalate complexes were examined. Regardless of whether the molar ratio was 1:1 or 1:2, the iron–oxalate complex exhibited the lowest reaction Gibbs free energy (ΔG), with values of −5343.69 and −1470.72 kJ/mol, respectively. The aluminum–oxalate complex followed, with ΔG values of −5169.23 and −1318.87 kJ/mol, respectively. The vanadium–oxalate complex displayed the highest reaction ΔG, at −2760.65 and −714.12 kJ/mol, respectively. Therefore, the coordination mechanism of vanadium, iron, and aluminum with oxalate ions in OALS is such that iron coordinated with oxalate first, followed by aluminum, and finally vanadium. The research results have important guiding significance for the purification, enrichment, and coordination mechanisms of complex solutions. Full article

The sustainable recycling of valuable metals from spent lithium-ion batteries (LIBs) is critical for resource conservation and environmental protection but remains challenging due to the complex coexistence of target and impurity metals. This study systematically investigates the selective leaching behaviors of metals (Co, Li, Cu, Fe, Al) in phosphoric acid media, revealing that lithium could be preferentially extracted in mild acidic conditions (0.8 mol/L H₃PO₄), while complete dissolution of both Li and Co was achieved in concentrated acid (2.0 mol/L H₃PO₄). Kinetic analysis demonstrated that metal leaching followed a chemically controlled mechanism, with distinct extraction sequences: Li > Cu~Co > Fe > Al in dilute acid and Cu > Al~Li > Fe > Co in concentrated acid. Furthermore, we developed a closed-loop process wherein oxalic acid simultaneously precipitates Co/Li while regenerating H₃PO₄, enabling acid reuse with minimal efficiency loss during cyclic leaching. These findings establish a single-step phosphoric acid leaching strategy for selective metal recovery, governed by tunable acid concentration and reaction kinetics, offering a sustainable pathway for LIBs recycling. Full article

The synergistic effect of using D2EHPA and TOPO together to enhance the extraction of samarium(III) from aqueous media via emulsion liquid membrane (ELM) technology was explored. D2EHPA in binary mixtures with TBP and in ternary mixtures with TOPO and TBP was also tested. Among the tested extractants, a binary mixture of 0.1% (w/w) D2EHPA and 0.025% (w/w) TOPO achieved 100% samarium(III) extraction at a low loading. This mixture outperformed D2EHPA-TBP and other systems because D2EHPA strongly binds to Sm(III) ions, while TOPO increases the solubility and transport efficiency of metal complexes. Additionally, process factors that optimize performance and minimize emulsion breakage were examined. Key insights for successfully implementing the process include the following: 5 min emulsification with 0.75% Span 80 in kerosene at pH 6.7 (natural), 250 rpm stirring, a 1:1 internal/membrane phase volume ratio, a 20:200 treatment ratio, and a 0.2 N HNO₃ stripping agent. These insights produced stable, fine droplets, enabling complete recovery and rapid carrier regeneration without emulsion breakdown. Extraction kinetics accelerate with temperature up to 35 °C but declined above this limit due to emulsion rupture. The activation energy was calculated to be 33.13 kJ/mol using pseudo-first-order rate constants. This suggests that the process is diffusion-controlled rather than chemically controlled. Performance decreases with Sm(III) feed concentrations greater than 200 mg/L and in high-salt matrices (Na₂SO₄ > NaCl > KNO₃). Integrating these parameters yields a scalable, low-loading ELM framework capable of achieving complete Sm(III) separation with minimal breakage. Full article

The efficient purification of Pb(II)-containing wastewater is essential for safeguarding public health and maintaining the aquatic environment. In this study, novel hydrous ferric oxide (HFO) nanoparticle-embedded poly(vinylidene fluoride) (PVDF) composite adsorption membranes were developed through a simple blending method for efficient Pb(II) removal. This composite membrane (denoted as HFO-PVDF) combines the excellent selectivity of HFO nanoparticles for Pb(II) with the membrane’s advantage of easy scalability. The optimized HFO-PVDF_(1.5) membrane achieved adsorption equilibrium within 20 h and exhibited excellent adsorption capacity. Moreover, adsorption capacity markedly enhanced with increasing temperature, confirming the endothermic nature of the process. The developed HFO-PVDF membranes demonstrate significant potential for real-world wastewater treatment applications, exhibiting exceptional selectivity for Pb(II) in complex ionic matrices and could be effectively regenerated via a relatively straightforward process. Furthermore, filtration and dynamic regeneration tests demonstrated that at an initial Pb(II) concentration of 5 mg/L, the membrane operated continuously for 10–13 h before regeneration, treating up to 200 L/m² of wastewater before breakthrough, highlighting potential for cost-effective industrial wastewater treatment. This study not only demonstrates the high efficiency of the HFO-PVDF membrane for heavy metal ion removal but also provides a theoretical foundation and technical support for its practical application in water treatment. Full article