Dalton Transactions最新文献

Transition metal-based oxides have been reported as an important family of electrocatalysts for water splitting owing to their possible large-scale applications that are highly desirable for the hydrogen generation industry. Herein, we report a facile method for the preparation of phosphate-decorated NiFe oxides on nickel foam as efficient oxygen evolution reaction (OER) electrocatalysts for water oxidation. The OER electrocatalysts were developed through the pyrolysis of MIL(Fe) metal–organic frameworks (MOFs), which were modified with Ni and P species. It was found that the formation of NiO on the Fe₂O₃ surface (NiO@Fe₂O₃) can enrich electrocatalytic active sites for the OER. Meanwhile, the incorporation of P into NiO@Fe₂O₃ (P_x-NiO@Fe₂O₃) creates abundant oxygen vacancies, which facilitates the surface charge transfer for OER electrocatalysis. Benefiting from the structure and composition advantages, P_2.0-NiO@Fe₂O₃/NF exhibits the best performance for OER electrocatalysis among other prepared electrocatalysts, with an overpotential of 208 mV at the OER current density of 10 mA cm⁻² and a small Tafel slope of 69.64 mV dec⁻¹ in 1 M KOH solution. Additionally, P_2.0-NiO@Fe₂O₃/NF shows an outstanding durability for the OER electrocatalysis, maintaining the OER current density above 20 mA cm⁻² for more than 100 h.

Pyridinium cesium cobalt nitrate, (PyH)CsCo₂(NO₃)₆, obtained from a nitric acid solution crystallizes in the orthorhombic space group Pnma with unit cell parameters a = 8.6905(14) Å, b = 11.9599(18) Å, c = 18.386(3) Å, V = 1911.0(5) ų, and Z = 4. It consists of [Co(NO₃)₃]⁻ layers, in which each Co²⁺ ion is connected with four monodentate bridging NO₃-groups and one bidentate terminal NO₃-group, forming a corrugated rectangular net. Magnetization and specific heat measurements show that (PyH)CsCo₂(NO₃)₆ undergoes a long-range canted antiferromagnetic ordering in two steps at T_C1 = 5.0 K and T_C2 = 2.6 K. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetization measured for (PyH)CsCo₂(NO₃)₆ show that it is an Ising antiferromagnet. In support of these observations, our DFT + U + SOC calculations show that the Co²⁺ ions of (PyH)CsCo₂(NO₃)₆ have an easy-axis magnetic anisotropy with preferred spin orientation along the b-axis. To a first approximation, the spin lattice of (PyH)CsCo₂(NO₃)₆ is a weakly alternating Ising antiferromagnetic chain (J₁/J₂ ∼ 0.85), and these chains interact weakly (J₃/J₂ ∼ 0.07) to form a rectangular Ising antiferromagnetic lattice. In agreement with the prediction for a rectangular Ising antiferromagnet by Onsager, (PyH)CsCo₂(NO₃)₆ undergoes a long-range antiferromagnetic ordering.

The rapid recombination of charge carriers in semiconductor-based photocatalysts results in a low photocatalytic activity. Co-catalysis is considered a promising strategy to improve the photocatalytic performance of semiconductors. In this study, a bimetallic phosphide was grown by a facile in situ growth method. Loading the cocatalyst (7 wt% NiCoP) leads to activity enhancement by a factor of approximately 27 times in the visible-light-driven hydrogen evolution relative to the pristine Zn_0.5Cd_0.5S. The photocatalysis shows a high hydrogen evolution rate of 19.5 mmol g⁻¹ h⁻¹, which is much higher than that of the single metal phosphide (Ni₂P: 7.0 mmol g⁻¹ h⁻¹; Co_xP: 8.1 mmol g⁻¹ h⁻¹) and 7 wt% Pt modified Zn_0.5Cd_0.5S (0.3 mmol g⁻¹ h⁻¹). Its apparent quantum efficiency reaches 41.6% at 420 nm. Moreover, the photocatalyst exhibits a remarkable photostability for five consecutive cycles of photocatalytic activity measurements with a total reaction time of 15 hours. The excellent photocatalytic activity of the photocatalyst was attributed to the in situ-formed NiCoP cocatalyst, which not only acts as a reactive site but also accelerates the separation of charge carriers.

Octahedral molybdenum (Mo₆) clusters constitute suitable building blocks for the design of promising single crystal materials in the field of optoelectronics. Here, we prepared single crystals composed of hydroxo Mo₆X₈ (X = Br, Cl) cluster complexes interconnected by H-bonding interactions with water molecules and protons. The optoelectronic responses and the absorption and emission spectra of these cluster-based single crystals were acquired upon light irradiation, and they show dependency on the nature of the halogens, with the brominated cluster being the most conductive. A fast photoelectrical response was recorded and it showed remarkable stability after multiple illumination on/off cycles. The results obtained provide relevant information for the development of photonic and optoelectronic devices, sensors and photocatalysts.

By introducing enantiomerically pure mono-bidentate N-donor ligands (L_R/L_S) into Yb(btfa)₃(H₂O)₂ and Yb(dbm)₃(H₂O), respectively, two pairs of chiral Yb^III enantiomers, namely Yb(btfa)₃L_R/Yb(btfa)₃L_S (D-1/L-1) and [Yb(dbm)₃L_R]·[Yb(dbm)₃(C₂H₅OH)]/[Yb(dbm)₃L_S]·[Yb(dbm)₃(C₂H₅OH)] (D-2/L-2) were isolated, where btfa⁻ = 3-benzoyl-1,1,1-trifluoroacetonate, dbm⁻ = dibenzoylmethanate, and L_R/L_S = (−)/(+)-4,5-pinenepyridyl-2-pyrazine. D-1/L-1 possess mononuclear structures in which the Yb^III ions are eight-coordinated, while D-2/L-2 show cocrystal structures containing Yb(dbm)₃(L_R/L_S) and Yb(dbm)₃(C₂H₅OH) moieties in which the two Yb^III ions are eight and seven-coordinated, respectively. They not only feature different molecular structures but also present distinct linear and nonlinear optical performances. Chiral mononuclear D-1 has better near infrared photo-luminescence (NIR-PL) and circularly polarized luminescence (CPL) performances than chiral cocrystal D-2. More remarkably, D-1/L-1 show large second-harmonic generation (SHG) responses (up to 1.25/1.28 × KDP) 18/16 times those of D-2/L-2 (0.07/0.08 × KDP). In addition, D-2/L-2 represent the first examples of lanthanide cocrystal complexes with NIR-PL, NIR-CPL and SHG properties.

Seven heterometallic iodoantimonates with the general formula (Cat)₂{[Sb₂M₂I₁₀]} (M = Cu(I) (1–6), Ag(I) (7)) were prepared. X-ray diffraction data indicate that these compounds are the first Sb(III) representatives of the structural type previously known only for heterometallic iodobismuthates(III). In 3 and 4, halogen-substituted cations form halogen bonds with the heterometallic halometalate chain. 1–7 show prominent thermal stability. The estimated optical band gaps lie between 2.16 and 2.40 eV. As in heterometallic iodobismuthates, incorporation of Cu⁺ rather than Ag⁺ provides a much lower band gap.

CsPbBr₃ all-inorganic perovskite solar cells (PSCs) have been extensively investigated due to their remarkable stability. However, their limited film quality and wide bandgap result in a low photoelectric conversion efficiency (PCE). In this study, BiI₃ was incorporated into CsPbBr₃ films to synergistically enhance light absorption and film quality. It was found that the partial substitution of Pb²⁺ and Br⁻ with Bi³⁺ and I⁻ in CsPbBr₃ improved film quality, enhanced light absorption, and facilitated charge transfer and extraction. The device incorporating BiI₃-incorporated CsPbBr₃ as a light absorbing layer achieved an efficiency of 9.54%, exhibiting a significant enhancement of 19.4% compared to the undoped device. This work provides a new incorporating strategy that collaboratively improves light absorption and film quality.

We report a comprehensive kinetic and product study of the oxidation of mandelic acid (MA) by permanganate in the pH range of 1–13, including a full account of total oxidizing equivalents (five and three-electron change in acidic and basic media, respectively). In the entire pH range, the reaction shows a primary kinetic deuterium isotope effect (k_H/k_D ≥8–9), indicating rate-limiting hydride transfer. The deuterium label in α-deutero-mandelic acid is retained in benzaldehyde. Benzaldehyde (BZ) is formed in post-rate limiting steps due to reactions involving manganese intermediates. In alkaline pH (≥13), in the presence of barium acetate, Mn(VI) is removed as insoluble blue barium manganate; the stoichiometry of the first step of reduction was found to be: MA + 2Mn(VII) → PGA + 2Mn(VI). Manganate, MnO₄²⁻, is directly reduced to MnO₂ giving an additional mole of phenylglyoxylic acid (PGA). The experimentally observed ratio of benzaldehyde to phenylglyoxylic (BZ/PGA) provides a basis for discrimination between mechanistic choices that include direct reduction of Mn(V) to Mn(III) (in an acidic medium), disproportionation to Mn(IV) and Mn(VI) or oxidation to Mn(VI) by a second mole of permanganate. Interestingly, at pH 4, a stoichiometric, soluble Mn(IV) is observed for the first time for hydroxy-acid oxidation, reminiscent of the Guyard reaction. Because of the widespread use of permanganate as an environmentally green oxidant, results from mandelic acid oxidation have implications for the remediation of dissolved organic matter (DOM) including hydrocarbons and nitroaromatics in waste and groundwater.

The synthesis of barium and strontium stannates in the process of decomposition of hydrothermally obtained precursors has been investigated. It was found that endothermic weight loss during the synthesis of barium stannate occurs in two stages, whereas during the synthesis of strontium stannate it occurs in one stage. From the summary of the results of thermogravimetric analysis, X-ray diffraction, and Mössbauer spectroscopy, the composition and local structure of X-ray amorphous phases are proposed. It is shown that the improvement of the crystal structure of the perovskite phases of MSnO₃ (M = Ba, Sr) and the symmetry of the local environment of ¹¹⁹Sn continues up to high temperatures (1250–1500 °C) and is associated with the elimination of defects in the anion sublattice. The photocatalytic activity of hydrothermal phases MSn(OH)₆ and their thermolysis products has been studied and was found not to be directly related to the specific surface area of the photocatalysts. The degradation of rhodamine B (RhB) occurs during the “dark” stages of catalysis due to the interaction of the dye with reactive oxygen species (mainly singlet oxygen). At the first stage, the decomposition of the RhB photochromic system is observed, whereas at the final stage of bleaching the dye is deethylated.

As an important biomarker, microRNAs (miRNAs) play an important role in gene expression, and their detection has attracted increasing attention. In this study, a DNAzyme walker that could provide power to perform autonomous movement was designed. Based on the continuous mechanical motion characteristics of DNAzyme walker, a miRNA detection strategy for the self-assembly of AuNPs induced by the hairpin probe-guided DNAzyme walker “enzyme cleavage and walk” was established. In this strategy, DNAzyme walker continuously cleaved and walked on the hairpin probe on the surface of AuNPs to induce the continuous shedding of some segments of the hairpin probe. The remaining hairpin sequences on the surface of the AuNP pair with each other, causing the nanoparticles to self-assemble. This strategy uses the autonomous movement mechanism of DNAzyme walker to improve reaction efficiency and avoid the problem of using expensive and easily degradable proteases. Secondly, using dynamic light scattering technology as the signal output system, ultra-sensitive detection with a detection limit of 3.6 fM is achieved. In addition, this strategy has been successfully used to analyze target miRNAs in cancer cell samples.