Chemistry of Materials最新文献

Chemiluminescence microreactors (CLMR) integrate catalytic centers, luminescent centers, and open channels into an atomic-scale platform, which can provide significantly enhanced light emission compared with usual homogeneous solvent systems. Herein, we report a novel metal–organic framework (MOF), UPC-88, which is constructed by a lophinyl-functionalized H₄L^IM-2H ligand (4,4′,4″,4‴-((naphthalene-1,4-diylbis(4,1-phenylene))bis(1H-imidazole-2,4,5-triyl))tetrabenzoic acid) with the first double (metal/organic) H₂O₂ catalytic center for CLMR. Due to the fixed chromophore and integrated dual catalytic sites, the relaxation phenomenon is greatly reduced and the energy transfer efficiency is significantly improved, resulting in the outstanding light emission performance of UPC-88. The visible luminous time of the UPC-88 system up to 1100 min was recorded as one of the highest ever reported for MOF systems. We linearly fitted the fluorescence intensity and fluorescence power for the first time, and the results show that UPC-88 is the MOF chemiluminescent material with the highest fluorescence power reported so far. The exploration of the CL reaction mechanism reveals the key role of the lophine base center in the decomposition of hydrogen peroxide, enabling the efficient conversion of chemical energy to light energy. This platform will provide a theoretical and experimental basis for next-generation CLMR systems and improved CL performance.

Li₆PS₅Cl has attracted significant attention due to its high Li-ion conductivity and processability, facilitating large-scale solid-state battery applications. However, when paired with high-voltage cathodes, it experiences adverse side reactions. Li₃InCl₆ (LIC), known for its higher stability at high voltages and moderate Li-ion conductivity, is considered a catholyte to address the limitations of Li₆PS₅Cl. To extend the stability of Li₆PS₅Cl toward LiNi_0.8Co_0.15Al_0.05O₂ (NCA), we applied nanocrystalline LIC as a 180 nm-thick protective coating in a core–shell-like fashion (LIC@NCA) via mechanofusion. Solid-state batteries with LIC@NCA allow an initial discharge specific capacity of 148 mA h/g at 0.1C and 80% capacity retention for 200 cycles at 0.2C with a cutoff voltage of 4.2 V (vs Li/Li⁺), while cells without LIC coating suffers from low initial discharge capacity and poor retention. Using a wide spectrum of advanced characterization techniques, such as operando XRD, XPS, FIB-SEM, and TOF-SIMS, we reveal that the superior performance of solid-state batteries employing LIC@NCA is related to the suppression of detrimental interfacial reactions of NCA with Li₆PS₅Cl, delamination, and particle cracking compared to uncoated NCA.

By combining experimental and computational studies, the orthorhombic stannide CeMgSn with a TiNiSi-type structure has been characterized as a potential hydrogen storage material. Experimental studies of the formed monohydride CeMgSnH including hydrogen absorption–desorption, thermal desorption spectroscopy, synchrotron and neutron powder diffraction (298 and 2 K), magnetization, and ¹¹⁹Sn Mössbauer spectroscopic measurements are discussed in parallel with ab initio electronic structure calculations. A small, 1.27 vol %, expansion of the unit cell of CeMgSn during its transformation into a thermally stable CeMgSnH monohydride is caused by an ordered insertion of H atoms into half of the available Ce₃Mg tetrahedral interstices leaving the CeMg₃ tetrahedra unoccupied. The bonding in CeMgSnH is dominated by strong Ce–Sn and Mg–Sn interactions which are almost not altered by hydrogenation, whereas the H atoms carry a small negative charge and show bonding interactions with Ce and Mg. Hydrogenation causes a conversion of the antiferromagnetic CeMgSn into ferromagnetic CeMgSnH with the Ce moments aligned along [001] with a magnetic moment of 1.4(3) μ_B. The ¹¹⁹Sn isomer shifts and the values of quadrupole splitting in the Mössbauer spectra suggest a similar s-electron density distribution for the Ce- and La-containing REMgSnH monohydrides.

We present findings from an electron diffraction and high-resolution transmission electron microscopy (HRTEM) study of composites mPbS + NaSbS₂ (m = 10, 18). The study reveals that these materials exhibit a nanostructured nature. The dominant observed structure corresponds to the NaCl type, characterized by numerous inhomogeneities. Interestingly, nanocrystals with a cubic structure, but possessing distinct lattice parameters (i.e., different compositions) compared to their surroundings, were observed. Additionally, some nanocrystals exhibited an orthorhombic structure distortion and some nanocrystals with a modulated structure resulting from long-range ordering effects were observed. All types of nanocrystals were observed to grow endotaxially within the matrix. Evidence was also found, suggesting a remarkable phenomenon where, in some areas, S atoms migrate from octahedral to tetrahedral sites, thereby validating previous predictions. These findings significantly contribute to our understanding of these semiconductors and motivate future studies of the thermoelectric properties in PbS-NaSbS₂ materials.

Zero thermal expansion (ZTE) materials with the advantage of an invariable length with varying temperatures are in high demand for modern industry but are relatively rare for metals. Fe-based Laves phases attract significant attention due to the rich and intriguing physical properties resulting from the coupling between crystal, electric, and magnetic structures. In this work, the structural, magnetic transition, thermal expansion, and magnetocaloric effect of single-phase Fe_2–xHf_0.80Nb_0.20 Laves phase alloys were investigated by means of macroscopic magnetic measurements, Mössbauer spectroscopy, and X-ray diffraction at the temperature range of 4.2–400 K. With the introduction of Fe vacancies, the ZTE coefficient of −1.2 ppm/K is smaller than that (1.7 ppm/K) of stoichiometric Fe₂Hf_0.80Nb_0.20 alloy. Meanwhile, the magnetic entropy change experiences an enhancement from 0.39 to 0.50 J/kg K at a magnetic field change of 2 T. These improved properties are attributed to the vacancy-induced coexistence of ferromagnetic and antiferromagnetic phases, as evidenced by variable-temperature X-ray diffraction and Mössbauer spectroscopy. This work unveils a promising avenue for new zero thermal expansion materials by controlling the vacancies at magnetic atom positions in Fe-based Laves phase alloys.

The structurally related compounds NiI₂ and CoI₂ are multiferroic van der Waals materials in which helimagnetic orders exist simultaneously with electric polarization. Here, we report on the evolution of the crystal structure and of the magnetic properties across solid solution Co_1–xNi_xI₂. We have successfully grown crystals of the whole range of the solid solution, i.e., x = 0–1, by employing the self-selecting vapor growth (SSVG) technique and by carefully tuning the synthesis conditions according to the chemical composition. Our structural investigations show that the crystal symmetry changes from P3̅m1 to R3̅m when Ni substitutes for Co beyond x = 0.2. Both the lattice parameters and magnetic properties evolve continuously and smoothly from one end member to the other, showing that they can be finely tuned by the chemical composition. We also observe that the degree of Ni substitution in the solid solution affects the metamagnetic transition typical for CoI₂ at high magnetic fields. In particular, we find the existence of a metamagnetic transition similar to that for CoI₂ in the NiI₂ structure. Based on magnetic measurements, we construct the phase diagram of the Co_1–xNi_xI₂ system. Controlling the magnetic properties by the chemical composition may open new pathways for the fabrication of electronic devices made of two-dimensional (2D) flakes of multiferroic van der Waals materials.