In this work, Sr-doped Ruddlesden–Popper nickelates, La2-ySryNiO4-δ (y = 0.25, 0.5, and 1.0), are investigated for microwave absorption applications. Tetragonal layered structures are confirmed by X-ray diffraction, while electron paramagnetic resonance and magnetic hysteresis measurements reveal that moderate Sr substitution induces weak ferromagnetic behavior, whereas higher Sr contents suppress magnetic ordering, leading to paramagnetic- or diamagnetic-like characteristics. Among the investigated compositions, the y = 0.25 sample exhibits the best impedance matching (|Zin/Z0| ≈ 1), delivering an ultralow RLmin of − 89 dB at a matching thickness of 0.9 mm and an effective absorption bandwidth of 2.1 GHz in the X-band. In contrast, higher Sr concentrations are associated with reduced dielectric loss and weaker absorption, likely due to changes in defect structure and charge-transport pathways. These results demonstrate that controlled Sr doping effectively tunes electromagnetic dissipation in layered nickelates, highlighting La2-ySryNiO4-δ as a promising candidate for microwave absorption applications.
In present work, a dye-integrated composite material, FS@ZrT-1-NH2, was fabricated through a one-pot solvothermal method. The fabrication process involved the effective combination of fluorescein sodium (FS) with an amino-functionalized metal-organic cage (ZrT-1-NH2) matrix. Subsequently, the as-prepared composite was employed as a dual-emission fluorescent probe for the targeted detection of sunset yellow (SY). Interaction energy and reduced density gradient (RDG) analyses revealed that hydrogen bonding interactions played a pivotal role in the stabilization of the composite. The unique dual-emission signal originated from efficient energy transfer between the cage and the embedded FS. This sensor exhibited a wide linear response to SY from 9.945 to 16.575 nM with a low detection limit of 0.980 nM, alongside remarkable selectivity. The fluorescence quenching mechanism was attributed to the synergistic effect of the inner filter effect (IFE) and static quenching. Notably, the proposed FS@ZrT-1-NH2 ratiometric fluorescent probe achieved high recovery rates (102.02%- 106.10%) and low relative standard deviations (RSD <3.1%) for SY detection in orange-flavored carbonated beverages, verifying its feasibility and practical applicability. These findings demonstrate that the dual-emission FS@ZrT-1-NH2 composite can function as a highly promising platform for the sensitive and selective detection of SY.
This study systematically investigated the synthesis optimization, structural features, and optical properties of lignin carbon dots (LCDs), along with their use in Fe3+ fluorescence sensing. Acid hydrolysis (1.0 M H2SO4) cleaved and rearranged alkali lignin from papermaking black liquor, reducing its molecular weight from 8301 to 497 and polydispersity from 1.50 to 1.19. This process also caused a decrease in the phenolic hydroxyl IR band intensity at 3401 cm(-1). The appropriate introduction of N and S heteroatoms enhanced the fluorescence quantum efficiency. The formed LCDs showed monodisperse nanoparticles (similar to 2.90 nm) with lattice fringes (0.233 nm) corresponding to those of the (100) plane of graphite. LCDs emitted cyan fluorescence (441 nm) with a quantum yield (QY) of 11.92% and a lifetime of 6.06 ns (lambda(ex) = 365 nm). The fluorescence sensor demonstrated high Fe3+ sensitivity (LOD: 1.0 mu M; linear range: 1.0 similar to 1000 mu M), with Fe3+-induced electron transfer as the dominant quenching mechanism (2.9 similar to 3.8% Fe3+ reduced to Fe2+ as proved by 1,10-Phenanthroline (phen) spectrophotometric method). Fluorescence recovery was achieved using reducing (ascorbic acid, NH2OH & centerdot;HCl, Glutathione(GSH)) or complexing agents (EDTA, F-), enabling reversible "on-off-on" sensing. Instrumental analysis methods, including XPS, fluorescence lifetime measurements, and TEM, were employed to prove the electron transfer mechanism between Fe3+ and LCDs. i.e., the main N1s XPS peak of pristine LCDs, located at 401.6 eV (attributed to -NH2 species), decreases in relative atomic concentration from 49.5% to 7.4% after Fe3+ treatment. An LCD-HDAB (4 '-hydroxyl-2,4-diaminoazobenzene, HDAB) test strip employs a dual-mode method combining colorimetric and fluorescence quenching for semi-quantitative visual Fe3+ detection (10 mu M similar to 20 mM) and smartphone-assisted measurement, thereby overcoming interference from Cr2O72-/MnO4-. This study presents a new strategy for functionalizing industrial product LCDs to enable selective and sensitive detection of Fe3+ ions in environmental and biological samples, with the underlying electron transfer mechanism induced by Fe3+ investigated.
This study developed a novel composite polymer flocculant, polyaluminum zinc silicate-cationic guar gum (PSAZ-CGG) and investigated the effects of preparation conditions and flocculation parameters on the removal of Congo Red (CR) and Reactive Blue 19 (RB-19). The synthesized flocculant and flocs were characterized using techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy–energy dispersive spectroscopy (SEM/EDX), elemental analyzer (EA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). These findings suggest the successful fabrication of the composite flocculant and its favorable flocculation performance. Single-factor flocculation experiments revealed maximum removal rates of 97.7
Pumpkin polysaccharides (PP) possess valuable bioactivities, yet conventional extraction suffers from low efficiency and structural degradation. In this study, dual-frequency ultrasound-assisted extraction (DF-UAE, 20/40 kHz) was applied to enhance PP extraction efficiency and to elucidate frequency-dependent extraction mechanisms. Compared with hot-water extraction (HWE), DF-UAE achieved a 1.78-fold higher extraction yield (21.55 vs. 12.11 g center dot 100 g- 1) and a 1.54-fold greater total sugar content. Response surface optimization yielded 40.51 +/- 0.35 g center dot 100 g- 1. DF-UAE reduced specific energy consumption by a factor of 0.9 and CO2 emissions by 0.9, with an estimated industrial payback period of 8 months. Structural analysis showed DF-UAE preserved higher molecular weight polysaccharides (Mw 219.3 vs. 32.4 Da), enriched high-molecular-weight fractions (25.36% vs. 3.26%), and maintained uronic acid content and narrow polydispersity. The purified fraction PPs2 was identified as a branched rhamnogalacturonan-I-type pectic heteropolysaccharide by methylation and NMR analyses. DFUAE-derived polysaccharides exhibited stronger antioxidant activity, correlated with molecular weight, uronic acid and protein content. Mechanistic evidence indicated that synergistic cavitation at a 2:1 frequency ratio balanced efficient cell disruption with reduced chain degradation. DF-UAE provides an efficient and sustainable strategy for producing structurally preserved bioactive pumpkin polysaccharides for functional food applications.
