New Journal of Chemistry最新文献

This study reports a sensitive and rapid dual-mode (colorimetric/fluorescence) sensing platform for the detection of ascorbic acid (AA), which is based on bimetallic copper–cobalt-doped carbon dot nanozymes (CuCo–CQDs, Cu : Co molar ratio = 1 : 2). The material exhibits strong peroxidase-like catalytic activity and inherent fluorescence, attributed to synergistic effects between copper and cobalt, as well as the presence of catalytically active Cu(I)/Cu(II) redox pairs and Co–N coordination sites. Utilizing the peroxidase-mimetic properties, CuCo–CQDs catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) in the presence of H₂O₂. Concurrently, the fluorescence of the nanozymes is quenched via the inner filter effect (IFE) induced by oxTMB. Upon addition of AA, oxTMB is reduced to TMB, resulting in fluorescence recovery. The colorimetric mode exhibits a linear detection range of 0.1–30 µmol L⁻¹ with a limit of detection (LOD) of 2.039 µmol L⁻¹, while the fluorescence mode exhibits a linear range of 2–40 µmol L⁻¹ with an LOD of 1.59 µmol L⁻¹. The platform was successfully applied to determine AA in human serum, demonstrating satisfactory analytical performance.

In this study, ligands and tin(IV) complexes containing two non-conjugated redox-active fragments—a Schiff base and an imino-substituted ferrocene—were synthesized and characterized using techniques, including X-ray diffraction analysis. Complexation with tin(IV) was found to induce a dramatic increase (approximately 50-fold) in absorption intensity within the visible region. In the solid state, the complexes adopt a dimeric structure stabilized by Sn–O coordination bonds between adjacent molecules. Notably, a significant proportion of the corresponding dimer persists even in highly diluted solutions, irrespective of solvent polarity. The redox properties of the synthesized compounds were investigated in aprotic media (DMF and MeCN). Reduction processes in both ligands and their tin(IV) complexes involve the Schiff-base moiety, as anticipated, given the redox inertness of ferrocene at negative potentials. In contrast, electrochemical oxidation exhibits greater complexity, with both redox-active components—the Schiff base and ferrocene. The oxidation of ligands is chemically reversible, confirming that the ferrocene unit serves as the primary redox center. In turn, the oxidation of complexes (first stage) is chemically irreversible, proceeding via the Schiff-base moiety of the monomer. The monomeric cation radicals formed during the initial oxidation undergo rapid dimerization. The resulting dimers are further oxidized at more positive potentials, producing a reversible wave attributable to electron transfer from the ferrocene units. Density functional theory (DFT) calculations corroborate these findings, confirming electron transfer from the ferrocene moiety during ligand oxidation and electron transfer from the Schiff base during oxidation of the monomeric complexes.

Cobalt sulfide (CoS) has emerged as a promising electrode material for various energy-related applications, including dye-sensitized solar cells (DSSCs) and supercapacitors (SCs). Nevertheless, poor electrical conductivity, suboptimal microstructural features, and limited long-term stability often hinder its practical performance. These drawbacks can be effectively mitigated by gadolinium (Gd) doping, which induces lattice distortion and defect formation, thereby improving charge transport and enhancing structural stability. In this work, nitrogen-enriched gadolinium-doped Co/CoS (Gd–N–Co/CoS) materials with different gadolinium contents were prepared, coated onto fluorine-doped tin oxide (FTO) glass substrates, and employed as counter electrodes in dye-sensitized solar cells (DSSCs). The 4% Gd-doped-N–Co/CoS electrode exhibited the lowest charge-transfer resistance. It achieved a notable power conversion efficiency (PCE) of 7.3%, outperforming the conventional platinum (Pt) electrode (6.6%) under simulated solar irradiation (100 mW cm⁻²). When employed in a symmetric supercapacitor configuration, the same 4% Gd-doped-N–Co/CoS electrode delivered a wide operating potential window of 1.6 V, a specific capacitance of 92.1 F g⁻¹ at 1 A g⁻¹, a specific energy of 32.74 Wh kg⁻¹, and a specific power of 1687 W kg⁻¹. Moreover, it retained 94.6% of its initial capacitance and maintained a coulombic efficiency of 92.05% after 2000 charge–discharge cycles. Overall, this work demonstrates the potential of Gd–N–Co/CoS as a high-performance electrode material for next-generation energy-harvesting and storage devices.

Silver-incorporated charge-transfer complex nanoparticles (CTAg) were synthesized and evaluated as a highly sensitive chemosensor for the rapid detection of aflatoxin B1 (AFB1). The parent charge-transfer complex (CTC) was constructed via N⁺–H⋯O⁻ hydrogen bonding among 1,3,5-tri(m-pyridin-3-ylphenyl)benzene (BTy), chloranilic acid (ChA), and 6-hydroxypyridine-3-carboxylic acid (FA), followed by Ag⁺ incorporation to yield CTAg nanoparticles. Structural, morphological, and thermal characteristics were determined by FTIR, PXRD, UV-vis spectroscopy, fluorescence spectroscopy, SEM, TEM, TGA-DTA, ¹H NMR, and DFT/TD-DFT calculations. TEM and SEM confirmed the nanoscale granular morphology of CTAg with high surface area for interaction with the analyte. Fluorescence titration experiments showed significant quenching of CTAg by interaction with AFB1 through synergistic static and dynamic modes involving Förster resonance energy transfer (FRET) and Dexter electron transfer (DET). The chemosensor has a 0.1407 ppb detection limit and a fast response and is highly effective. Practical applicability was shown by monitoring AFB1 in Aspergillus flavus contaminated peanut samples with efficiency similar to pure AFB1 standards. Moreover, CTAg nanoparticles were inscribed into plain paper strips, allowing for naked-eye colorimetric fluorescence-based detection in daylight and UV light. The facile synthesis, strong sensitivity, and portability of CTAg demonstrate its potential as an effective on-site sensing platform for food safety monitoring.

A photocatalyst-free strategy has been developed for the cross-dehydrogenative sulfenylation of aminocoumarins with thiols. A library of sulfenylated aminocoumarins has been synthesized using this protocol under the irradiation of blue LED light. This protocol is also useful for the sulfenylation of aminopyranones and amino-1,4-naphthoquinones. The photocatalytic activation of persulfate is the key step in this transformation. Simple and easy execution, excellent yields, practical applicability, photocatalyst-free conditions and column chromatography-free purification of sulfenylated aminocoumarins are the attractive features of this methodology.

Oxabicyclic scaffolds are increasingly coveted for their distinctive bioactivities. Herein, we report a BF₃·OEt₂-catalyzed Michael addition/ketalization sequence to access structurally fascinating 2,8-dioxabicyclo[3.3.1]nonanes from easily accessible 4-hydroxy-6-methyl-2H-pyran-2-one and ortho-hydroxychalcones. Simply by modulating the catalyst into CuCl, the same manifold can be steered to furnish benzo[c]chromen-6-ones, that are difficult to access by traditional methods.

A sulphonamide-based boranil probe (BS-1) is rationally designed and synthesized to demonstrate the formation of a reversible supramolecular self-assembly via a deprotonation-protonation strategy. Upon the formation of this self-assembly in the presence of sodium hypochlorite in DMSO, the probe exhibits a significant redshift in the UV absorption (406 to 422 nm) and emission (472 to 592 nm) spectra. BS-1 demonstrates a high sensitivity (LOD = 110 nM), rapid response (< 10 s), and fluorescence switching. The SEM observations collectively demonstrate a clear morphological transformation of BS-1 from linear microsheets to cubic J-aggregates, driven by deprotonation-induced self-assembly through charge-assisted hydrogen bonding.

A facile divergent construction of sulfur-containing heterocycles via a skeletal reorganization strategy is presented herein, in which the versatile and readily available rongalite was utilized as the C1 synthon. This organic-phosphine facilitated divergent transformations of benzo[c][1,2]dithiol-3-ones via S atom swapping reaction, enabling the streamlined construction of a sequence of 2,3-dihydrobenzothiazin-4-ones and benzo[d][1,3]oxathiin-4-ones under mild conditions. This newly-discovered skeletal reorganization strategy is transition-metal-free, insensitive to moisture and air, and characterized by convenient operation, good yields and broad substrate scope.

Retraction of ‘PEDOT/NiFe₂O₄ nanocomposites on biochar as a free-standing anode for high-performance and durable microbial fuel cells’ by N. Senthilkumar et al., New J. Chem., 2019, 43, 7743–7750, https://doi.org/10.1039/C9NJ00638A.

Various metal sulfides have been investigated as electrode materials for supercapacitors. NiCo₂S₄ is a popular material in this field due to its high electrical conductivity and theoretical capacity. Various approaches are used to improve its performance. We provide a hydrothermal approach for synthesizing a Mn–NiCo₂S₄/g-C₃N₄ composite material. The addition of Mn provides more electroactive sites, resulting in improved specific capacitance and improved cycling stability. The g-C₃N₄ has a 2D π-conjugated planar layer structure similar to graphene, which allows for more active sites for faradaic reactions, increases the surface area, improves electrical conductivity, and prevents NiCo₂S₄ aggregation. The Mn–NiCo₂S₄/g-C₃N₄ composites have a high specific capacitance of 940.2 F g⁻¹ at 1 A g⁻¹. The asymmetric supercapacitor (ASC) using Mn–NiCo₂S₄/g-C₃N₄ as the positive electrode and activated carbon as the negative electrode achieves a high energy density (ED) of 36.36 Wh kg⁻¹ and a power density (PD) of 749.8 W kg⁻¹. It also has excellent cycling stability, with 88.33% retention after 10 000 cycles. These findings show that Mn–NiCo₂S₄/g-C₃N₄ has significant promise for developing high-performance electrode materials for supercapacitors.