Search Results (160)

Graphitic carbon nitride (g-C₃N₄), an emerging metal-free semiconductor material, has attracted considerable attention in the field of photoelectrochemical (PEC) sensing due to its unique electronic structure, excellent chemical stability, and visible-light responsiveness. This article systematically reviews recent advances in research on g-C₃N₄-based PEC sensors applied to water environment monitoring. First, the fundamental physicochemical properties of g-C₃N₄ are introduced, along with its advantages and limitations in PEC sensing applications. Subsequently, four main performance enhancement strategies are outlined: heterojunction construction (including type II, Z-scheme, and S-scheme heterojunction), elemental doping and defect engineering, morphology control and nanostructure design, as well as various signal amplification approaches such as self-powered systems, dual-mode detection, and cyclic amplification. Furthermore, the current application status of these sensors in detecting typical water pollutants, including heavy metal ions (e.g., Pb²⁺, Cu²⁺, Cd²⁺, Hg²⁺), antibiotics (e.g., tobramycin, norfloxacin, kanamycin), pesticide residues (e.g., chlorpyrifos, atrazine, glyphosate), and pathogenic microorganisms (e.g., Salmonella, Candida albicans), is comprehensively reviewed, with particular emphasis on detection sensitivity, selectivity, and real-sample performance. Finally, the remaining challenges in terms of long-term stability, anti-interference capabilities in complex matrices, portability, and multifunctional integration are analyzed, and future development directions are proposed, including smartphone-based intelligent sensing, CRISPR/Cas12a-assisted signal amplification, and multi-target high-throughput detection. This review aims to provide a reference for the rational design and practical application of g-C₃N₄-based PEC sensors in the field of water environment monitoring. Full article

Mercury pollution from artisanal and small-scale gold mining remains one of the most persistent environmental threats due to the high toxicity, mobility, and bioaccumulation of Hg(II). In this work, Colombian banana pseudostem waste is valorized into a lignocellulosic carbocatalyst through pyrolysis at 500 °C followed by MnCO₃-derived MnOx functionalization, producing a sustainable material for Hg(II) remediation. The transformation of the biomass leads from a fibrous structure (~25 µm) to a pyrolyzed carbon matrix (9.56 µm), and finally to a heterogeneous Mn-modified system with bimodal particle distribution (~25 µm and ~0.85 µm), the latter being associated with highly dispersed MnOx redox-active domains. Structural and textural analyses reveal that Mn incorporation significantly enhances surface properties, increasing the BET surface area from 140.8 to 213 m² g⁻¹ while reducing pore size to the meso–microporous range (~1.9 nm). Importantly, the material retains intrinsic minerals such as Ca, Mg, K, and Si, which contribute to surface basicity and ion-exchange capacity, supporting additional Hg(II) interaction pathways. Optical and electronic characterization shows a wide band gap semiconductor behavior (≈3.4 eV) and a conduction band position at −0.892 V vs. NHE, sufficiently negative to thermodynamically drive Hg²⁺ reduction to Hg⁰ under UV-A irradiation. Hg(II) quantification was validated using a UV–Vis method based on the Hg²⁺–dipicolinic acid (DPA) complex, confirming stable complex formation with 1:2 stoichiometry (Hg²⁺:DPA) and high analytical reliability (R² = 0.948, LOD = 1.85 mg L⁻¹). Photocatalytic experiments demonstrated negligible Hg(II) reduction under UV-A light in the absence of catalyst, whereas the carbon-based materials enabled significant Hg transformation through adsorption-assisted photoinduced electron transfer. Electrochemical analyses (Rct ≈ 11 Ω) confirmed efficient charge transport, while cyclic voltammetry evidenced reversible Mn(IV)/Mn(III)/Mn(II) redox cycling, which sustains electron mediation during photocatalysis. Overall, pristine biochar acts primarily through adsorption driven by oxygenated functional groups and porous structure, whereas Mn-functionalized biochar operates via a synergistic adsorption–photocatalytic mechanism. In this system, MnOx species function as redox-active centers that facilitate electron transfer from the carbon matrix to Hg(II), while the conductive lignocellulosic-derived framework enhances charge mobility. The combination of structural carbon stability, dispersed Mn active sites, and inherent mineral functionality establishes a highly efficient and sustainable carbocatalyst, demonstrating a green and scalable approach for mercury remediation in mining-impacted regions. Full article

Using orange peels as a biowaste, fluorescent N-CDs were prepared simply and rapidly through a one-step microwave-assisted method and urea as a nitrogen source. The synthesized N-CDs exhibited a high QY value of 47.12% compared to CDs prepared using different methods. Moreover, the N-CDs have good pH and thermal stability. N-CDs exhibited high sensitivity toward Fe(III), Hg(I), and Hg(II) ions with low LOD values of about 0.0555, 0.15379, and 0.02505 μM, respectively. This approach is hopeful for the large-scale formation of N-CDs and could encourage their utilization as fluorescent chemosensors due to their affordability, simplicity, high efficiency, and environmental friendliness. Full article

A continued interest in developing a low-cost, rapid screening method for quantifying Hg (II) and As (III) in biological samples stems from the toxic effects of human exposure to these heavy metal ions. This study reports the use of cysteine-capped gold nanoparticles (CysAuNPs) for chemical sensing, colorimetric detection, and quantification of As (III) and Hg (II) ions in human serum albumin (HSA) under physiological conditions. Zeta potential measurements indicated that the CysAuNPs have a negative surface charge, which was decreased in the presence of HSA and reversed to a positive value upon binding of As (III) and Hg (II) metal ions. Circular dichroism (CD) spectroscopy revealed changes in HSA conformation upon binding to As (III) and Hg (II) ions. X-ray fluorescence enables rapid qualitative screening for As (III) and Hg (II) ions before colorimetric quantification. The figures of merit (R² ≥ 0.940) and the low detection limits (0.05 ppm for As (III) ions and 0.02 ppm for Hg (II)) in serum albumin demonstrate the high sensitivity of the method. The developed calibration curves correctly quantified the concentration of As (III) and Hg (II) ions of independently prepared test validation samples in HSA with an accuracy of ≥95% over a period of seven months without recalibrations, demonstrating the stability of CysAuNPs in solution and the robustness of the method for analysis of As (III) and Hg (II) ions in serum albumin. Full article

A previously unexplored magnetic biocomposite (CMC-HSDs/Fe₃O₄) was developed through the valorization of hydrophobic scleroprotein discards (HSDs). The synthesized material was evaluated for its efficacy in the adsorption of Cr(VI) and Hg(II) ions from contaminated aqueous systems. The physicochemical properties of the synthesized CMC-HSDs/Fe₃O₄ nanocomposite were characterized using XRD, FTIR, BET, TG/DTG, FESEM, EDX, and elemental mapping. Subsequently, a Box–Behnken experimental design was employed to model and optimize the adsorption process for Cr(VI) and Hg(II), focusing on the critical parameters of solution pH, adsorbent dosage, and interaction time. Kinetic data were best fitted to the pseudo-first-order (PFO) model. Equilibrium isotherm analysis revealed that Cr(VI) adsorption followed the Langmuir model, while Hg(II) adsorption was better fitted by the Freundlich model. Advanced ionic calculations elucidated a consistent multimolecular adsorption mechanism for both ions, characterized by temperature invariance and a preferential vertical geometry of the adsorbed species. Through a production cost of 25.56 USD/kg, the biosorbent demonstrates excellent reusability, retaining 88.60% efficiency for Cr(VI) and 85.69% for Hg(II) after five adsorption–desorption cycles. Based on a 50 mg/L influent concentration, projected treatment costs are ~$3.50/100 L for Cr(VI) and ~$1.22/100 L for Hg(II), underscoring the nanocomposite’s economic feasibility for industrial deployment in advanced tertiary wastewater remediation. Full article

Ion-imprinting technology based on biosorbents via sorption demonstrates potential for the selective removal of metal ions from water and wastewater. This offers both high sorption capacity and selectivity for specific metals. Current research trends are toward the development of sorbents with minimal environmental impact. Among the most rapidly evolving classes of sorbents are those derived from biopolymers, such as chitosan—a natural derivative of chitin that can be readily functionalized. Due to the growing interest in this topic, it is necessary to summarize the current knowledge. In this article, we provide a comprehensive overview of the latest advances in ion-imprinted chitosan-based materials designed for the purification of metal-contaminated aqueous systems. We conduct a bibliographic analysis and describe a variety of chitosan-based materials exhibiting selectivity toward heavy metals, including chromium Cr(III/VI), cobalt Co(II), nickel Ni(II), copper Cu(II), zinc Zn(II), arsenic As(III/V), cadmium Cd(II), mercury Hg(II), and lead Pb(II). Finally, we discuss future prospects and highlight current research gaps, aiming to guide further scientific exploration and innovation in this promising field. Full article

A metal-free multicomponent polymerization (MCP) method was developed for synthesizing sulfur-containing polythioamides, using elemental sulfur, dicarboxylic acids, and diamines as monomers. This approach offers a versatile strategy for producing polythioamides with excellent thermal stability and high mechanical strength. The synthesized polymers demonstrated a maximum Hg(II) adsorption capacity of 187 mg·g⁻¹, with adsorption efficiencies exceeding 90% for most polymers. Both aliphatic and aromatic polythioamides showed similar high adsorption performance, indicating the universal applicability of this synthesis method. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) confirmed the strong interaction between Hg(II) ions and the sulfur-containing thioamide groups. These results highlight the potential of MCP-based polythioamides as efficient adsorbents for mercury removal, with promising applications in environmental remediation. Full article

This paper introduces a novel Lithium-Ion Battery (LIB) State-of-Charge (SOC) estimation approach that integrates Akima–Savitzky–Golay curve reconstruction with a Bayesian-optimized, adaptive Extended Kalman Filter (EKF). The method addresses crucial SOC estimation challenges by means of three foundational advancements: (i) a refined open-circuit voltage (OCV)-SOC curve reconstruction grounded in Akima interpolation coupled with Savitzky–Golay filtering, (ii) an adaptive EKF weighting strategy, and (iii) systematic hyperparameter value optimization executed through Bayesian optimization. Comprehensive performance validation utilizes an extensive dataset collected from LG HG2 18650 cells across temperatures of −20 °C to 40 °C, incorporating multiple standard driving cycles—namely HPPC, UDDS, HWFET, LA92, and US06 cycles. The proposed method achieves an improved estimation accuracy with an average Root Mean Square Error (RMSE) of 2.65% over the different operating conditions and temperature variations. Notably, the method markedly enhances SOC estimation reliability in the critical mid-SOC range (20–80%), while preserving the computational overhead necessary for real-time integration into Battery Management Systems (BMSs). The adaptive weighting successfully compensates for the present physical limitations, thereby delivering a resilient SOC estimation tailored for Electric Vehicle (EV) battery applications. Full article

Mercury (Hg) contamination in water and soil poses severe ecological and human health risks, yet conventional sorbents often suffer from limited capacity, selectivity, and stability. Here, we report a bifunctional porous organic polymer (AMTD-TCT) rationally constructed by covalently crosslinking 2-amino-5-mercapto-1,3,4-thiadiazole with trichlorotriazine, thereby integrating abundant sulfur and nitrogen coordination sites within a stable mesoporous framework. AMTD-TCT exhibits an ultrahigh Hg(II) adsorption capacity of 1257.7 mg g⁻¹, far exceeding most reported porous sorbents. Adsorption follows monolayer chemisorption, governed by strong S–Hg and N–Hg coordination and Na⁺/Hg²⁺ ion exchange, while hierarchical porosity ensures rapid diffusion and efficient utilization of active sites. The polymer maintains robust performance over a wide pH range and demonstrates strong retention with minimal desorption, underscoring its environmental durability. These findings highlight AMTD-TCT as a highly effective and scalable platform for Hg(II) remediation in complex aqueous–soil systems and illustrate a generalizable molecular design strategy for developing multifunctional porous polymers in advanced separation and purification technologies. Full article

Upon reacting with cellular components, Hg(II) ions elicit the production of reactive oxygen species (ROS). While the ROS-promoted cytotoxic and genotoxic effects induced by Hg(II) have been widely described in eukaryotes, such effects have been less studied in bacteria. In this work, the prokaryotic environmental model Bacillus subtilis was employed to evaluate the cytotoxic and genotoxic impact of Hg(II) over strains proficient or deficient in SOS, general stress and antioxidant responses, as well as the global transcriptional response elicited by this ion. The exposure to HgCl₂ significantly increased the mutation frequency to rifampicin resistance (Rif^R) in WT and mutant strains, suggesting a major contribution of these pathways in counteracting the genotoxic effects of Hg(II). Detection of A → T and C → G transversion mutations in the rpoB gene of Hg(II)-exposed cells suggested the generation of 8-oxo-guanines (8-OxoGs) and other oxidized DNA bases. The RNA-seq study revealed upregulation of genes involved in efflux and/or reduction of metal ions, synthesis of sulfur-containing molecules, and downregulation of genes implicated in iron metabolism and cell envelope stress. Therefore, our results indicate that metal extrusion and scavenging of Hg(II) by thiol-rich molecules may constitute a line of defense of B. subtilis that counteracts the noxious effects of ROS resulting from an imbalance in iron metabolism elicited by this ion. Full article

This work introduces 2-(azulen-1-yldiazenyl)-5-(thiophen-2-yl)-1,3,4-thiadiazole (L) as a functional monomer capable of forming stable, redox-active films with high affinity for lead in aqueous solutions. L was synthesized and characterized using physical chemical methods and electrochemistry. Polymer films of L were prepared through oxidative electro polymerization on glassy carbon electrodes in L solutions in 0.1 M TBAP in acetonitrile. They were characterized through electrochemistry. The surface of chemically modified electrodes (CMEs) prepared through controlled potential electrolysis (CPE) at variable concentrations, potentials, and electric charges was characterized through scanning electron spectroscopy, atomic force microscopy, and Raman spectroscopy, which confirmed the films’ formation. Electrochemical sensing of the films deposited on these CMEs was tested with respect to heavy metal (HM) ion analysis in aqueous solutions to obtain sensors for HMs. The obtained CMEs presented the best characteristics for the recognition of Pb among the investigated HMs (Cd, Pb, Cu, and Hg). Calibration curves were obtained for the analysis of Pb(II) in aqueous solutions, which allowed for the estimation of a good detection limit of this cation (<10⁻⁸ M) for non-optimized CMEs. The resulting CMEs show promise for deployment in portable environmental monitoring systems, with implications for public health protection and environmental safety. Full article

Three new complexes of Hg(II), with the general formulas [Hg₂(ox)₂(NA)₄]_n·3nH₂O (1), [Hg(NO₃)₂(NA)₂(H₂O)₂]·2NA (2), and [Hg₂(SO₄)₂(H₂O)₂(NA)₄]·6H₂O (3), where ox = oxalate and NA = nicotinamide, were synthesized and characterized by single crystal X-ray diffraction, elemental analysis, FT-IR, and fluorescence spectra. For complex (2), ¹³C and ¹H NMR spectra were recorded. Thermogravimetric analysis was also performed for complexes (1) and (2). Single crystal X-ray diffraction shows that in the polymeric complex (1) and the binuclear complex (3), the Hg(II) ions are hexacoordinated, whereas in the mononuclear complex (2), Hg(II) is octacoordinated. In complex (1), each oxalate group acts in a µ₄ coordination manner, the basal plan being made up by four oxygen atoms belonging to the two oxalate ligands, while the nicotinamide molecules occupy the axial positions. In complex (2), the nitrate groups coordinate in a bidentate chelating mode, whereas in complex (3), each sulphate ligand acts in a bidentate chelating–bis monodentate bridging manner. Full article

Due to its conjugated structure, 1,4,6,8-tetrakis((E)-2-(thiophen-2-yl)vinyl)azulene (L) has a high potential for nonlinear optics and coloring. This compound was studied electrochemically using cyclic voltammetry, pulse differential voltammetry and rotating disk voltammetry in organic electrolytes. The main processes occurring during oxidation and reduction scans were highlighted and characterized. Density functional theory (DFT) calculations were conducted to assess the chemical reactivity of this compound. UV-Vis studies of L were performed in acetonitrile to establish the optical parameters in this solvent and its complexing power towards heavy metal (HM) ions. Chemically modified electrodes (CMEs) based on L were prepared by electrooxidation of L in organic electrolytes. To evaluate the electrochemical behavior of the CMEs, they were characterized with a ferrocene redox probe. They were also tested for the analysis of synthetic samples of heavy metal ions (HM): Cd(II), Pb(II), Cu(II) and Hg(II) by anodic stripping. Specific responses were obtained for Pb(II) and Cd(II) ions. The preparation conditions have an influence on the electrochemical responses. This study is relevant for the design and further development of advanced materials based on this azulene for the analysis of HMs in water samples. Electrochemical experiments and DFT calculations recommended L as a new ligand for modifying the electrode surface for the analysis of HMs. Full article

Environmental contamination is a critical global concern, primarily due to detrimental greenhouse gas (GHG) emissions, especially carbon dioxide (CO₂), which significantly contribute to climate change. Moreover, the presence of harmful heavy metals like Ni, Cd, Cu, Hg, and Pb in soil and water ecosystems has led to poor water quality. Noble metal nanoparticles (MNPs), for instance, Pd, Ag, Pt, and Au, have emerged as promising solutions for addressing environmental pollution. However, the practical utilization of MNPs faces challenges as they tend to aggregate and lose stability. To overcome this issue, the reverse double-solvent method (RDSM) was utilized to synthesis melamine-based porous polyaminals (POPs) as a supportive material for the in situ growing of silver nanoparticles (Ag NPs). The porous structure of melamine-based porous polyaminals, featuring aminal-linked (-HN-C-NH-) and triazine groups, provides excellent binding sites for capturing Ag⁺ ions, thereby improving the dispersion and stability of the nanoparticles. The resulting material exhibited ultrafine particle sizes for Ag NPs, and the incorporation of Ag NPs within the porous polyaminals demonstrated a high surface area (~279 m²/g) and total pore volume (1.21 cm³/g), encompassing micropores and mesopores. Additionally, the Ag NPs@POPs showcased significant capacity for CO₂ capture (2.99 mmol/g at 273 K and 1 bar) and effectively removed Cu (II), with a remarkable removal efficiency of 99.04%. The nitrogen-rich porous polyaminals offer promising prospects for immobilizing and encapsulating Ag nanoparticles, making them outstanding adsorbents for selectively capturing carbon dioxide and removing metal ions. Pursuing this approach holds immense potential for various environmental applications. Full article

Waste drilling fluids represent a complex gel–colloidal system containing structurally stable polymeric networks and heavy-metal ions that can cause tremendous damage to the ecosystem. The current disposal methods, like solidification/landfills, formation reinjection, and chemical treatment, commonly suffer from high secondary pollution risks, poor resource recovery, and incomplete detoxification. This paper developed a photocatalytic approach to complex gel system treatment by hydrothermally synthesizing a novel sulfur-doped, oxygen-vacancy-modified 3D flower-like xS-BiOBr_0.5Cl_0.5 structure which effectively narrowed the bandgap of BiOX and thus significantly enhanced its catalytic activity. The chemical composition, morphology, specific surface areas, and bandgaps of the materials were characterized. The photocatalytic performance and cyclic stability of the materials were measured, and 0.5S-BiOBr_0.5Cl_0.5 showed the best photocatalytic performance. The rhodamine B(RhB) degradation and polymer degradation efficiencies of 0.5S-BiOBr_0.5Cl_0.5 were up to 91% and 79%, respectively, while the Hg(II), Cr(VI), and Cr(III) reduction efficiencies of the material were up to 48.10%, 96.58%, and 96.41%, respectively. The photocatalytic mechanism of the xS-BiOBr_0.5Cl_0.5 materials was evaluated through an oxygen vacancy analysis, active species capture experiments, and density functional theory (DFT) computations. Overall, the xS-BiOBr_0.5Cl_0.5 materials can provide a low-cost and harmless treatment method for waste drilling fluids and promote the “green” development of oil and gas. Full article