Search Results (99)

A synergistic approach to the photodegradation of polydimethylsiloxane-based composites upon photoaging was implemented by using La(III) complexes of Schiff base ligands with a silicon-containing spacer as fillers. The analysis methods were spectral, nanomechanical, and morphological. The results show that the accelerated oxidative degradation of the polydimethylsiloxane matrix is due to the combined actions of radicals, fragments, and photoproducts derived from the photolysis of the La(III) complexes and the water vapors in the photoaging chamber. Compared to the undoped polydimethylsiloxane, the photo-excited radical intermediates and photoproducts of the La(III) complexes, with aromatic or quinone structures, in ground or in excited state, have acted as photocatalysts and as new sources for reactive intermediates and for the generation of reactive oxygen species. Infrared, electron spin resonance, and nanomechanical investigations revealed that the chemistry of the photoaged surfaces comprises oxygen–containing species, photoreaction products, and an extended siloxane network with embedded ligand fragments. The key role of La(III) complexes in promoting the generation of reactive species is described. The study highlights the unexplored potential of La(III) complexes of Schiff base ligands bearing a silane/siloxane spacer as potential catalysts in the photodegradation of polymers and plastics. Full article

Self-healing materials have attracted increasing attention as a strategy to enhance durability, extend service life, and reduce maintenance in advanced material systems. Among these, cellulose-based self-healing materials represent a sophisticated intersection between sustainable macromolecular chemistry and adaptive materials science. This review provides a synthesis of recent advancements in the field, systematically categorizing materials derived from cellulose raw materials. We evaluate the fundamental chemical strategies employed to achieve autonomous repair, distinguishing between extrinsic mechanisms—utilizing cellulose-based micro/nano-capsules to sequester healing agents—and intrinsic mechanisms governed by dynamic covalent chemistry (Schiff-base, boronic ester, Diels–Alder) and supramolecular interactions (hydrogen bonding, metal–ligand coordination, and host–guest assemblies). The analysis highlights how cellulose’s hierarchical structure and abundant surface functionality are leveraged to overcome the traditional trade-off between mechanical toughness and healing efficiency. Particular emphasis is placed on the transition from simple structural hydrogels to sophisticated multifunctional systems. These include ultra-stretchable strain and pressure sensors for e-skin applications, biocompatible and injectable matrices for chronic wound management and stem cell delivery, and advanced anti-freezing eutectogels for performance in extreme environments. Furthermore, we explore the integration of cellulose into traditional sectors, such as self-healing concrete utilizing microbe-induced calcification and smart, eco-friendly coatings for corrosion protection. Finally, we discuss critical challenges, including environmental stability, scalability, and the development of standardized evaluation protocols, providing a roadmap for the next generation of bio-derived, sustainable and intelligent materials. Full article

The selective removal of beryllium from aqueous matrices remains a critical environmental and industrial challenge due to beryllium’s extreme toxicity, strong hydration chemistry, and the difficulty of separating Be²⁺ from chemically similar cations such as Al³⁺. In this study, a novel multidentate Schiff-base porous organic adsorbent, TFP-HEDA, was synthesized by condensation of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (TFP) with N-(2-hydroxyethyl)ethylenediamine (HEDA) followed by urethane post-functionalization and systematically characterized by FTIR, ¹H/¹³C NMR, MALDI-TOF MS, elemental analysis, BET surface area analysis (617 m² g⁻¹), PXRD, and XPS. Batch adsorption experiments demonstrated rapid Be²⁺ uptake, achieving 90% removal within 20 min and equilibrium within 30 min. Among the isotherm models evaluated, the Langmuir model yielded the highest statistical consistency (R² = 0.9835, RMSE = 5.15 mg g⁻¹, χ² = 1.137) with a predicted maximum adsorption capacity of 163.93 mg g⁻¹ agreeing closely with the experimental value of 163.67 ± 6.42 mg g⁻¹ (deviation < 0.2%); this mathematical adequacy is interpreted as compatibility with a finite, saturable set of inner-sphere coordination sites rather than confirmation of a flat, energetically uniform surface, with chemisorption independently and more rigorously established by Dubinin–Radushkevich analysis (E = 28.87 kJ mol⁻¹) and post-adsorption FTIR and XPS evidence. Dubinin–Radushkevich analysis confirmed a chemisorption mechanism with mean adsorption energy E = 28.87 kJ mol⁻¹, consistent with inner-sphere Be²⁺–O/N coordination. Process optimization using response surface methodology based on a central composite design achieved 99% Be²⁺ removal at pH 5, an adsorbent dose of 60 mg/20 mL, and a contact time of 30 min (R² = 0.9892). Post-adsorption FTIR, XPS, BET, and TGA characterization confirmed framework integrity and the inner-sphere multidentate coordination mechanism. TFP-HEDA retained 82.4% of its initial capacity after nine adsorption–desorption cycles, demonstrating practical regenerability for Be²⁺ recovery applications. Full article

Protein glycation is a nonenzymatic modification that links sugar chemistry to molecular aging and chronic disease. Sequential reactions involving Schiff bases, Amadori products, and reactive α dicarbonyl intermediates generate advanced glycation end products (AGEs) that irreversibly alter protein structure and function. AGEs also act as ligands for the receptor for advanced glycation end products (RAGE), initiating oxidative stress, inflammation, and tissue remodeling. This review synthesizes the molecular pathways of AGE formation, their structural diversity, and the biological factors influencing glycation kinetics. Advances in analytical detection methods—including fluorescence spectroscopy, LC–MS/MS, and immunochemical approaches—are highlighted for their role in monitoring AGE accumulation. Particular attention is given to the contribution of glycation to diabetes, cardiovascular disease, neurodegeneration, and cancer, alongside emerging therapeutic strategies to limit AGE formation or block AGE–RAGE signaling. Glycation thus represents a central mechanism in human disease pathogenesis and an emerging therapeutic frontier. Full article

The catalytic conversion of carbon dioxide to methanol is significantly important both practically and scientifically for the reduction in CO₂ emissions. Furthermore, it can partially address the issue of human reliance on non-renewable resources. The main motivation of this study is to use a melamine polymer network to support a copper-based catalyst for CO₂ hydrogenation to methanol. Based on Schiff base chemistry, a facile catalyst-free process, a novel porous polyaminal polymer (MGPN) was prepared with nitrogen contents as high as 38%. MGPN was used as a support for Cu-based catalyst and applied in CO₂ hydrogenation to CH₃OH under mild conditions. A deep characterization of the MGPN@CuO/ZnO/Al₂O₃ catalyst was made through FTIR, N₂ adsorption–desorption, SEM-EDS, TEM, TGA, XRD, CO₂-TPD, and H₂-TPR techniques. The CO₂ hydrogenation study was performed in a fixed bed reactor with a residence time of 1.104 s on varying parameters such as the metal loading, catalyst amount, flow rate, pressure, calcination temperatures, reduction temperatures, and catalytic reaction temperature profile. The space-time yield (STY) of 145.43 mg_methanol·g_catalyst⁻¹·h⁻¹, a selectivity of 98.36%, and CO₂ conversion of 11.76% were obtained under an economically and energetically sustainable low-pressure (1 MPa) and 260 °C hydrogenation process. Full article

Background: Chronic diabetic wounds, particularly diabetic foot ulcers (DFUs), are prone to recurrent infection and delayed healing, resulting in substantial morbidity, mortality, and economic burden. Multifunctional wound dressings that combine antibacterial, antioxidant, conductive, and self-healing properties may help to address the complex microenvironment of chronic diabetic wounds. Methods: In this study, ε-poly-L-lysine and amino-terminated polyethylene glycol were grafted onto carboxylated single-walled carbon nanotubes (SWCNTs) via amide coupling to obtain ε-PL-CNT-PEG. Aminated chondroitin sulfate (CS-ADH) and a catechol–metal coordination complex of protocatechualdehyde and Fe³⁺ (PA@Fe) were then used to construct a dynamic covalently cross-linked hydrogel network through Schiff-base chemistry. The obtained hydrogels (Gel0–3, Gel4) were characterized for photothermal performance, rheological behavior, microstructure, swelling/degradation, adhesiveness, antioxidant capacity, electrical conductivity, cytocompatibility, hemocompatibility, and antibacterial activity in the presence and absence of near-infrared (NIR, 808 nm) irradiation. Results: ε-PL-CNT-PEG showed good aqueous dispersibility, NIR-induced photothermal conversion, and improved cytocompatibility after surface modification. Incorporation of ε-PL-CNT-PEG into the PA@Fe/CS-ADH network yielded conductive hydrogels with porous microstructures and storage modulus (G′) higher than loss modulus (G′′) over the tested frequency range, indicating stable gel-like behavior. The hydrogels exhibited self-healing under alternating strain and macroscopic rejoining after cutting. Swelling and degradation studies demonstrated pH-dependent degradation, with faster degradation in mildly acidic conditions (pH 5.0), mimicking infected chronic diabetic wounds. The hydrogels adhered to diverse substrates and tolerated joint movements. Gel4 showed notable DPPH• and H₂O₂ scavenging (≈65% and ≈60%, respectively, within several hours). The electrical conductivity was 0.19 ± 0.0X mS/cm for Gel0–3 and 0.21 ± 0.0Y mS/cm for Gel4 (mean ± SD, n = 3), falling within the range reported for human skin. In vitro, NIH3T3 cells maintained >90% viability in the presence of hydrogel extracts, and hemolysis ratios remained below 5%. Hydrogels containing ε-PL-CNT-PEG displayed enhanced antibacterial effects against Escherichia coli and Staphylococcus aureus, and NIR irradiation further reduced bacterial survival, with some formulations achieving near-complete inhibition under low-power (0.2–0.3 W/cm²) 808 nm irradiation. Conclusions: A dynamic, conductive hydrogel based on PA@Fe, CS-ADH, and ε-PL-CNT-PEG was successfully developed. The hydrogel combines photothermal antibacterial activity, antioxidant capacity, electrical conductivity, self-healing behavior, adhesiveness, cytocompatibility, and hemocompatibility. These properties suggest potential for application as a wound dressing for chronic diabetic wounds, including diabetic foot ulcers, although further in vivo studies are required to validate therapeutic efficacy. Full article

An inorganic–organic hybrid nano-adsorbent was prepared by chemical immobilisation of an organic Schiff base Cu (II) ion receptor, DHB ((E)-N-(1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl) ethylidene) benzohydrazide), a selective dehydroacetic acid-based chemosensor, onto a mesoporous silica support. In order to prepare the sorbent, the silylating agent was anchored onto the silica. During this procedure, 3-Chloropropyl trimethoxy silane (CPTS) was attached to the surface, increasing hydrophobicity. By immobilising DHB onto the CPTS platform, the silica surface was activated, and as a result the coordination chemistry of the Schiff base generated a hybrid adsorbent with the capability to rapidly sequestrate Cu (II) ions from wastewater, as an answer to combat growing Waste Electrical and Electronic Equipment (WEEE) contamination in water supplies, in the wake of a prolonged consumerism mentality and boom in cryptocurrency mining. The produced hybrid materials were characterised by FTIR, proximate and ultimate analysis, nitrogen physisorption, PXRD, SEM, and TEM. The parameters influencing the removal efficiency of the sorbent, including pH, initial metal ion concentration, contact time, and adsorbent dosage, were optimised to achieve enhanced removal efficiency. Under optimal conditions (pH 7.0, adsorbent dosage 3 mg, contact time of 70 min, and 25 °C), Cu (II) ions were quantitatively sequestered from the sample solution; 93.1% of Cu (II) was removed under these conditions. The adsorption was found to follow pseudo-second-order kinetics, and Langmuir model fitting affirmed the monolayer adsorption. Full article

Schiff bases are bioactive compounds that have been synthesized by many researchers in recent years. They may also exhibit strong antimicrobial activities against various pathogenic microorganisms in both medicine and veterinary applications. The synthesis of new Schiff base-derived compounds remains of interest due to the increasing problem of antibiotic-resistance in clinical practice. Seven new Schiff base derivatives were synthesized, and their chemical structures were characterized using FT-IR, ¹H/¹³C NMR, and LCMS-MS analyses. The antimicrobial activities of thesyntesized compounds against various pathogenic bacteria, yeasts, and fungi were evaluated using the disk-diffusion method, and their MIC values were also determined. In addition, one representative microorganisms from each class were selected for molecular docking studies. IFD analyses were performed for the 4f and 4g ligands using the dihydrofolate reductase enzyme. Spectroscopic analyses confirmed the structures of the synthesized compounds, revealing the presence of characteristic imine functionalities and validating the integrity of the molecular frameworks. Antimicrobial assays demonstrated that several derivatives exhibited measurable activity, with compounds 4f and 4g showing the most potent effects, displaying MIC values of 32 µg/mL against B. cereus and E. faecalis, respectively. Molecular docking studies further indicated that both 4f and 4g bind efficiently to the DHFR active site. These findings indicate that among the synthesized Schiff base derivatives, compounds 4f and 4g exhibit particularly promising antimicrobial activity, warranting further pharmacological evaluation and medicinal chemistry optimization. Full article

The accurate monitoring of metal ions is essential for applications that include environmental protection, food safety, and biomedical diagnostics. These areas depend on highly sensitive and selective methods for detecting both toxic and biologically relevant ions. Electrochemical sensors have emerged as promising devices due to their excellent sensitivity, cost-effectiveness, and ease of use. Within these sensor systems, ionophores, either synthetic or natural ligands that exhibit selective ion binding, are fundamental in boosting analytical performance. This review outlines the current progress of ionophore-based electrochemical sensors for metal-ion analysis, emphasizing material selection, architectural strategies, and practical applications. Key classes of ionophores, such as crown ethers, calixarenes, Schiff bases, porphyrins, and oxime derivatives, are discussed with an emphasis on their recognition mechanisms. We also examine strategies for incorporating ionophores into diverse electrochemical sensor configurations and explore recent advances in technologies, such as all-solid-state sensor construction and the development of portable analytical devices. This review bridges the chemistry of ionophores with sensor engineering and serves as a resource for the rational development of advanced platforms for metal-ion sensing. Full article

The application of microsphere molecularly imprinted materials for the targeted extraction and purification of flavonoids derived from agricultural waste has emerged as a prominent area of investigation. An innovative boronate affinity imprinted microsphere (MC-CD@BA-MIP) was successfully synthesized using the Pickering emulsion interfacial assembly strategy for the selective separation of naringin (NRG). The double-bond functionalized covalent organic framework (COF)-based microspheres were synthesized through Schiff–base reaction and secondary interfacial emulsion polymerization. Then, the synthetic mono-(6-mercapto-6-deoxy)-β-cyclodextrin (SH-β-CD) was grafted onto the surface of the microspheres (MC) using click chemistry. The 1-allylpyridine-3-boronic acid (APBA) as a functional monomer was grafted onto the initiator (ABIB) through atom transfer radical polymerization (ATRP). Ultimately, the synthesized boronic acid-imprinted ABIB-BA-MIPs were immobilized onto the COFs microsphere surface through host–guest interactions. As expected, under neutral conditions, the MC-CD@BA-MIPs still exhibited a significant adsorption capacity (38.78 μmol g⁻¹ at 308 K) for NRG. The regenerated MC-CD@BA-MIPs maintained 92.56% of their initial adsorption capacity through six consecutive cycles. Full article

The coordination chemistry of a hydrazinylpyrazine-derived Schiff base ligand (L1), formed in situ from salicylaldehyde and 2-hydrazinopyrazine, with Fe(III) salts has been systematically investigated under varied synthetic conditions. Six discrete Fe(III) complexes (1a–1e and 2) were isolated and structurally characterised via single-crystal X-ray diffraction, revealing diverse coordination geometries ranging from five-coordinate pseudo-trigonal bipyramidal to six-coordinate pseudo-octahedral environments. The supramolecular architectures are governed by a rich interplay of non-covalent interactions, including hydrogen bonding, halogen bonding, and π–π stacking, which significantly influence the crystallisation pathways and final solid-state structures. Continuous shape measure (CShM) analysis highlights substantial geometric distortion in the bis-tridentate complexes, attributed to the steric and electronic constraints imposed by the ligand. Powder X-ray diffraction and infrared spectroscopy confirm the presence of multiple phases in bulk samples, underscoring the kinetic competition between crystallisation and coordination. The results demonstrate that supramolecular stabilisation of monoligated species can kinetically inhibit bis-ligation, with ligand excess and solvent polarity serving as key parameters to direct complex speciation. These findings provide insight into the delicate balance between coordination geometry, ligand strain, and supramolecular assembly in Fe(III) Schiff base complexes. Full article

Graphoepitaxial directed self-assembly (DSA) of block copolymers (BCPs) has emerged as a promising strategy for sub-30 nm line spacing patterning in semiconductor nanofabrication. Among the available BCP systems, polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) has been extensively utilized due to its well-characterized phase behavior and compatibility with standard lithographic processes. However, achieving a high-fidelity pattern with PS-b-PMMA remains challenging, owing to its limited etch contrast and reliance on UV-assisted degradation for PMMA removal. In this study, we report the synthesis of an acid-cleavable lamellar BCP, PS-N=CH-PMMA, incorporating a dynamic Schiff base (-N=CH-) linkage at the junction. This functional design enables UV-free wet etching, allowing selective removal of PMMA domains using glacial acetic acid. The synthesized copolymers retain the self-assembly characteristics of PS-b-PMMA and form vertically aligned lamellar nanostructures, with domain spacings tunable from 36.1 to 40.2 nm by varying the PMMA block length. When confined within 193i-defined trench templates with a critical dimension (CD) of 55 nm (trench width), these materials produced well-ordered one-space-per-trench patterns with interline spacings tunable from 15 to 25 nm, demonstrating significant line spacing shrinkage relative to the original template CD. SEM and FIB-TEM analyses confirmed that PS-N=CH-PMMA exhibits markedly improved vertical etch profiles and reduced PMMA residue compared to PS-b-PMMA, even without UV exposure. Furthermore, Ohta–Kawasaki simulations revealed that trench sidewall angle critically influences PS distribution and residual morphology. Collectively, this work demonstrates the potential of dynamic covalent chemistry to enhance the wet development fidelity of BCP lithography and offers a thermally compatible, UV-free strategy for sub-30 nm nanopatterning. Full article

This review provides a comprehensive overview of recent advances in the synthesis, structural characterization, and applications of Ru(II), Ru(III), and Ru(VI) complexes, which bear tetradentate Schiff bases of salen type. Ruthenium complexes exhibit catalytic, electrochemical, and biological properties, serving as multifunctional platforms that integrate fundamental aspects of coordination chemistry with potential practical applications. Full article

This study synthesized two eco-friendly inhibitors—a chitosan–copper metal–organic framework (CS@Cu MOF) and chitosan–Schiff base–Cu complex (Schiff–CS@Cu)—for Q345 steel protection in 3.5% NaCl/1M HCl. Electrochemical and weight loss analyses demonstrated exceptional corrosion inhibition: untreated specimens showed a 25.889 g/(m²·h) corrosion rate, while 100 mg/L of CS@Cu MOF and Schiff–CS@Cu reduced rates to 2.50 g/(m²·h) (90.34% efficiency) and 1.67 g/(m²·h) (93.56%), respectively. Schiff–CS@Cu’s superiority stemmed from its pyridine–Cu²⁺ chelation forming a dense coordination barrier that impeded Cl⁻/H⁺ penetration, whereas CS@Cu MOF relied on physical adsorption and micro-galvanic interactions. Surface characterization revealed that Schiff–CS@Cu suppressed pitting nucleation through chemical coordination, contrasting with CS@Cu MOF’s porous film delaying uniform corrosion. Both inhibitors achieved optimal performance at 100 mg/L concentration. This work establishes a molecular design strategy for green inhibitors, combining metal–organic coordination chemistry with biopolymer modification, offering practical solutions for marine infrastructure and acid-processing equipment protection. Full article

Polyimine-based composites have emerged as a promising class of dynamic covalent thermosets, combining high mechanical strength, thermal stability, self-healing, recyclability, and reprocessability. This review systematically summarizes recent advances in polyimine synthesis, highlighting dynamic covalent chemistry (DCC) strategies such as imine exchange and reversible Schiff base reactions. Structural customization can be achieved by incorporating reinforcing phases such as carbon nanotubes, graphene, and bio-based fibers. Advanced fabrication methods—including solution casting, hot pressing, and interfacial polymerization—enable precise integration of these components while preserving structural integrity and adaptability. Mechanical performance analysis emphasizes the interplay between dynamic bonds, interfacial engineering, and multiscale design strategies. Polyimine composites exhibit outstanding performance characteristics, including a self-healing efficiency exceeding 90%, a tensile strength reaching 96.2 MPa, and remarkable chemical recyclability. Emerging engineering applications encompass sustainable green materials, flexible electronics, energy storage devices, and flame-retardant systems. Key challenges include balancing multifunctionality, enhancing large-scale processability, and developing low-energy recycling strategies. Future efforts should focus on interfacial optimization and network adaptivity to accelerate the industrial translation of polyimine composites, advancing next-generation sustainable materials. Full article