查找使用阿拉丁产品的科研文献

Electron-Phonon Interaction in Te-Doped (NH4)2SnCl6: Dual-Parameter Optical Thermometry (100–400 K)

Ting Geng,Yuhan Qin,Zhuo Chen,Yuhan Sun,Ao Zhang,Mengyuan Lu,Mengzhen Lu,Siying Zhou,Yongguang Li,Guanjun Xiao

Lead-free perovskite variants have emerged as promising candidates due to their self-trapped exciton emission. However, in ASnX3systems, facile oxidation of Sn(II) to Sn(IV) yields A2SnCl6vacancy-ordered derivatives. Paradoxically, despite possessing a direct bandgap, these variants exhibit diminished photoluminescence (PL). Doping engineering thus becomes essential for precise optical tailoring of A2SnX6materials. Herein, through integrated first-principles calculations and spectroscopic analysis, we elucidate the luminescence mechanism in Te4+-doped (NH4)2SnCl6lead-free perovskites. Density functional theory, X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) confirm Te4+substitution at Sn sites via favorable chemical potentials. Spectral interrogations, including absorption and emission profiles, reveal that the intense emission originates from the triplet STE recombination (3P1→1S0) of Te centers. Temperature-dependent PL spectra further demonstrate strong electron–phonon coupling that induces symmetry-breaking distortions to stabilize STEs. Complementary electronic band structure and molecular orbital calculations unveil the underlying photophysical pathway. Leveraging these distinct thermal responses of PL intensity and peak position, 0.5%Te:(NH4)2SnCl6emerges as a highly promising candidate for non-contact, dual-parameter optical thermometry over an ultra-broad range (100–400 K). This work provides fundamental insights into the exciton dynamics and thermal engineering of optical properties in this material system, establishing its significant potential for advanced temperature-sensing applications.

Tailoring MnO2 nanowire defects with K-doping for enhanced electrochemical energy storage in aqueous supercapacitors

Jianghua Wu,Faisal Faiz,Mashkoor Ahmad,Miao Zhengjie,Zha Qiang,Wei Xu,Xiaojin Zhao,Xiaofang Pan,Yasir Faiz

The fabrication of supercapacitors with outstanding performance is presented with a distinct defect-rich nanostructures. A one-pot, energy-efficient method for synthesizing defective manganese dioxide nanowires doped with potassium (K 0.35 MnO 2 ) was developed. The introduction of potassium ions at 35 % birnessite resulted in a significant increase in lattice defects and an improvement in conductivity. Addition of KOH induces a phase transition from α-MnO 2 to δ-MnO 2 . These imperfections result in a greater quantity of active sites, which are crucial for the process of energy storage. The K 0.35 MnO 2 structure demonstrates a 405F/g increased capacity at a current density of 1 A/g. The asymmetric supercapacitor (K 0.35 MnO 2 /AC) that was manufactured exhibits a capacitance of 106.4F/g when operating at 1 A/g, while maintaining a maximum energy density of 71.5 Wh kg −1 and a power density of 672 W kg −1 . Furthermore, 92.7 % of the initial capacitance of the device is retained even after 8,000 cycles at 20 A/g. This study presents novel insights into the production of defective materials for energy storage applications through the utilization of a one-pot process as opposed to the multi-step method. In order to produce high-performance supercapacitors for practical applications, the results indicate that defect engineering is a crucial factor.

Reconstructing Vanadium Oxide with Anisotropic Pathways for a Durable and Fast Aqueous K-Ion Battery

Guojin Liang,Zhongdong Gan,Xiaoqi Wang,Xu Jin,Bo Xiong,Xiankun Zhang,Shimou Chen,Yanlei Wang,Hongyan He,Chunyi Zhi

Aqueous potassium-ion batteries are long-term pursued, due to their excellent performance and intrinsic superiority in safe, low-cost storage for portable and grid-scale applications. However, the notorious issues of K-ion battery chemistry are the inferior cycling stability and poor rate performance, due to the inevitably destabilization of the crystal structure caused by K-ions with pronouncedly large ionic radius. Here, we resolve such issues by reconstructing commercial vanadium oxide (α-V2O5) into the bronze form, i.e., δ-K0.5V2O5 (KVO) nanobelts, as cathode materials with layered structure of enlarged space and anisotropic pathways for K-ion storage. Specifically, it can deliver a high capacity as 116 mAh g–1 at the 1 C-rate, an outstanding rate capacity of 65 mAh g–1 at 50 C, and a robust cyclic stability with 88.2% capacity retention after 1,000 cycles at 1 C. When coupled with organic anode in a full-cell configuration, the KVO electrodes can output 95 mAh g–1 at 1 C and cyclic stability with 77.3% capacity retention after 20,000 cycles at 10 C. According to experimental and calculational results, the ultradurable cyclic performance is assigned to the robust structural reversibility of the KVO electrode, and the ultrahigh-rate capability is attributed to the anisotropic pathways with improved electrical conductivity in KVO nanobelts. In addition, applying a 22 M KCF3SO3 water-in-salt electrolyte can impede the dissolving issues of the KVO electrode and further stabilize the battery cyclic performance. Lastly, the as-designed AKIBs can operate with superior low-temperature adaptivity even at −30 °C. Overall, the KVO electrode can serve as a paradigm toward developing more suitable electrode materials for high-performance AKIBs.

Enhancement of luminescence and thermal stability of NaLi3SiO4: Eu phosphor by co-doping K+ ions

Jun Sun,Bei Zhang,Wei Zhu,Feifei Huang,Ruoshan Lei,Hongping Ma,Renguang Ye,Youjie Hua,Shiqing Xu

High-efficiency phosphor with excellent luminescence properties and thermal stabilities is essential for phosphor-converted white light-emitting diodes (w-LEDs). Compared with red and green phosphors, near-ultraviolet excited blue phosphors with high efficiency and excellent thermal stability are still scarce, and the development of efficient blue phosphors remains challenging. NaLi 3 SiO 4 : Eu 2+ (NLSO: Eu 2+ ) is a promising narrow-band blue phosphor. In this paper, a series of Na 1-y K y Li 3 SiO 4 : 5%Eu 2+ (0.05 ≤ y ≤ 0.2) phosphors were successfully synthesized by high-temperature solid-state reaction through co-doping a small amount of K + ions in the matrix, significantly improving their luminescence property and thermal stability. Because of the weaker electronegativity of K + ions, the emission peaks of Na 1-y K y Li 3 SiO 4 : 5%Eu 2+ were slightly blue-shifted from 467 to 463 nm compared with those of NLSO: Eu 2+ . With an increase in the number of K + ions, the luminescence intensity of the phosphors increased. When the content of the K + ion reached 0.2, the luminescence intensity of the Na 0.8 K 0.2 Li 3 SiO 4 : 5%Eu 2+ (NKLSO: 5%Eu 2+ ) phosphor reached its maximum. Compared to the NLSO: 5%Eu 2+ phosphor, the luminescence intensity increased by approximately 300 %. At 150 °C, the luminescence intensity of NLSO: 5%Eu 2+ phosphor was retained at 75.98 % compared with room temperature , while the NKLSO: 5%Eu 2+ phosphor maintained a luminescence intensity of 84.36 % relative to room temperature, demonstrating excellent thermal stability. The enhanced luminescence performance of the NKLSO: Eu 2+ phosphor makes it a promising high-efficiency blue phosphor for phosphor-converted w-LEDs.

A novel high pseudo-capacitive contribution anode in K-ion battery: Porous TiNbO4/C nanofibers

Die Su,Jianping Yang,Qingshui Hong,Min Yang,Jiaxing Wen,Qianfu Wang,Hai Hu,Li Liu,Xiukang Yang

Pseudo-capacitive materials show long cycling life as anode of K-ion battery (KIBs), yet low specific capacity and poor rate performance. Herein, the porous TiNbO 4 /C nanofibers (denoted as TNO/C) are synthesized via electro-spinning. Abundant oxygen vacancies and large specific surface area make the sample exudes high specific capacity and good rate performance. After optimizing the calcination temperature, it is found that the porous TiNbO 4 /C nanofibers at 700 °C (denoted as TNO/C-700) can deliver the specific discharge capacity of 250.4 mAh g −1 in K-ion half cell and demonstrate good cycle stability for 100 cycles in K-ion full cell in 100 mA g − 1 . Even in 5 A g − 1 , the discharge capacity of TNO/C-700 electrodes is still 116.7 mAh g − 1 at rate performance. Ex-situ XRD results show that this TNO/C-700 electrode is associated with pseudo-capacitive effect and insertion/de-insertion process. The TNO/C-700 electrode exhibits a high pseudo-capacitive contribution, which can reach to 85.0% at 3 mV s −1 . This novel high pseudo-capacitive contribution anode material provides more possibilities for the selection in KIBs.

New alkali-metal and 1,2-Diaminopropane intercalated superconductor Lix(C3H10N2)yFe2Se2 with Tc = 45 K

H.S. Xu,X.X. Wang,Z. Gao,H.L. Huang,Y.Z. Long,Y.L. Lu,K.B. Tang

A new iron-based superconductor Li x (C 3 H 10 N 2 ) y Fe 2 Se 2 was successfully synthesized via the novel ammonothermal technique. After post-annealing, the superconducting transition temperature T c changes from 36 K to 45 K, which is confirmed by measurements of the magnetic susceptibility and the electrical resistivity. The powder X-ray diffraction (XRD) measurements have revealed that the crystal structure keeps the same after post-annealing at 130 °C for 10 h. Hall coefficient and magnetoresistance (MR) have been measured on the annealed samples, indicating the role of electrons as the dominant charge carriers.

Influence of calcination temperature on the fluorescence and magnetic properties of Gd2O3:Tb3+, K+ nanoparticles

Hao Zhou,Hao Zhou,Rong Fu,Rong Fu,Chunlin Yang,Meigui Ou,Meigui Ou,Chengjie Xue,Chengjie Xue

High-purity KCl prepared with K(cl, Br) solid solution via controlled-coordination of glycerol

Yali Wang,Hongbao Ren,Ruizhi Cui,Bo Zhang,Qiuye Yang,Wu Li

A glycerol-water coordination method was developed to prepare high-pure KCl from K(Cl, Br) solid solutions. • Glycerol inhibits Br − from entering the KCl lattice. 30 wt% mixed solvent shows better separation performance. • KCl with 99.994% purity and 97.30% yield was obtained, while bromide was concentrated in the liquid phase. High-purity KCl is essential for semiconductors and laser crystals, yet even trace bromine severely compromises its performance. During the preparation of KCl via underground brine crystallization, Br − readily enters the KCl lattice to replace Cl − , forming crystals with a single-salt structure rather than a simple mixture. This makes it difficult to use conventional separation methods to produce high-purity KCl. To address this issue, this study proposes a separation strategy that involves intervening in the recrystallization process by regulating coordination interactions within the solvent system, thereby yielding ultra-pure potassium chloride. Systematic studies involving phase equilibrium experiments, solid-liquid phase characterization and molecular simulations indicate that as the number of hydroxyl groups in the alcohol molecule increases, the solvent's separation capacity increases accordingly, with glycerol exhibiting the best performance. As the simplest trihydric alcohol, glycerol's three hydroxyl groups create distinct solvation environments for Cl − and Br − , thereby inhibiting Br − from occupying the KCl lattice during the concentration and crystallization processes. Furthermore, the introduction of 30 wt% mass water inhibits intermolecular hydrogen bonding and self-aggregation of glycerol, releasing free coordination sites and significantly increasing the solubility of KCl in the system (from 1.7 wt% to 9.63 wt%), thereby further optimizing separation efficiency. The separation process, designed based on the phase diagram of the KCl − KBr − Gly(30 wt%) − H₂O system at 298.15 K, enables the efficient recovery of high-purity KCl (purity up to 99.9940%, recovery rate of 97.30%) and the simultaneous enrichment of bromine resources in the liquid phase (bromine content increased from 3.36 wt% to 44.30 wt%).

Pressure-driven reconstruction of single-atom Ni-O-K interface for near-equilibrium CO2 hydrogenation

Wendong Wang,Fangsong Guo,Longmei Shang,Kang Sun,Dandan Song,Jianchun Jiang,Guowu Zhan

Pressure-driven reconstruction forms Ni-O-K single-atom interfaces. • Near-equilibrium CO 2 conversion (∼58%) with ∼100% CO selectivity. • Exceptional stability over 200 h without sintering or deactivation. • Ni-O-K sites lower E a and suppress methanation. • Carboxyl pathway dominates over formate route. Achieving simultaneous high activity, selectivity, and stability in single-atom catalysts (SACs) under high-temperature conditions remains a significant challenge, primarily due to the difficulty in precisely controlling the coordination environment of metal centers. Here, we demonstrate that alkali ion (e.g., K + ) modification of both Ni single atoms and their carbon nitride (CN) support enables exceptional performance in the reverse water-gas shift (RWGS) reaction. The resulting Ni@K-CN catalyst achieves near-equilibrium CO 2 conversion with nearly 100% CO selectivity across a broad temperature range (400–600 ℃), alongside remarkable long-term stability. This performance substantially surpasses that of the K-free analogue and ranks among the best-reported non-noble metal RWGS catalysts. Operando studies reveal that the catalyst undergoes a thermodynamically driven in-situ reconstruction under high pressure reaction conditions, forming atomically dispersed Ni-O-K interfacial sites within a restructured carbon nitride matrix. Density functional theory calculations reveal that these sites markedly lower the apparent activation energy ( E a = 41.5 vs. 131.4 kJ·mol −1 ), modulate the electronic structure of Ni and surface-adsorbate interactions, and thereby promote a low-energy-barrier carboxyl pathway while kinetically suppressing methanation. This work establishes a design strategy based on alkali-mediated dynamic reconstruction to create highly stable and selective SACs for demanding high-temperature catalytic processes. Download: Download high-res image (174KB) Download: Download full-size image

Water Activity Measurement and Thermodynamic Modeling for the System Na2CO3–Cs2CO3–H2O at 308.15 K

Jia Xu,Xun Wang,Tongqing Wang,Ziwei Hu,Ruyi Lin,Dan Li,Yong Ma,Lingzong Meng,Yafei Guo,Guangli Zhou,Tianlong Deng

The isopiestic equilibria in the system Na2CO3–Cs2CO3–H2O at 308.15 K were investigated with an improved isopiestic method with a modified gravimetric isopiestic apparatus. The water activities and osmotic coefficients were determined based on the calcium chloride standard reference solution. The equilibrium vapor pressure was calculated with the water activity. Combining the Pitzer binary parameters of Na2CO3, the Pitzer binary parameters β(0), β(1), and Cφ of Cs2CO3 and Pitzer mixing parameters θNa+, Cs+ and ψNa+, Cs+, CO32– were fitted with the experimental osmotic coefficients on the basis of the Pitzer model. The water activities were then calculated by the Pitzer parameters, and the good agreement between the calculated water activities and experimental results of this ternary system indicated that the Pitzer parameters obtained in this work were reliable. The thermodynamic data and Pitzer parameters obtained in this work can provide fundamental thermodynamic data for development of universal chemical models for brine systems containing cesium carbonate.

Sulfur-induced nitrogen vacancy modulation in K/S-Codoped g-C3N4 for efficient CO2 photoreduction

Jingce Bi,Nianzhu Yang,Huichun Xue,Ningning Liu,Yi Wang,Xia Zhang,Zhuopeng Wang,Lin Zhu,Yide Han

Molten salt-assisted pyrolysis has emerged as an effective strategy for engineering defective/doped g-C 3 N 4 photocatalysts for CO 2 reduction. While K + incorporation enhances interlayer charge transport, excessive K + generates detrimental nitrogen vacancies that destabilize the heptazine framework and compromise carrier mobility. Herein, we developed S/K co-doped graphitic carbon nitride (g-C 3 N 4 ) with tunable nitrogen vacancies (denoted SWCN-M) via molten salt (KCl-LiCl) pyrolysis of sulfur-containing supramolecular precursors (melamine with thiourea or thioacetamide). The nitrogen vacancy concentration is precisely modulated by the choice of sulfur precursor (thiourea vs. thioacetamide) to optimize the synergy effect of K + -N-vacancy, and eventually boosting photocatalytic performance. The thiourea-derived SWCN-M TU achieves a CO evolution rate of 165.7 μmol g −1 h −1 , outperforming its thioacetamide analogue (SWCN-M TAA , 90.4 μmol g −1 h −1 ), pristine WCN (53.8 μmol g −1 h −1 ), and K-doped WCN-M (64.3 μmol g −1 h −1 ) by factors of 1.8, 3.1, and 2.6, respectively. DFT calculation results reveal that S-doping induces charge localization, elevating the N-vacancy formation energy via Coulombic repulsion with K + . This work advances the rational design of vacancy-engineered carbon nitride for photocatalytic CO 2 reduction

Solvothermal syntheses, characterization and photoluminescence properties of layered quaternary sulfides ACuZnS2 (A = K, Rb, Cs)

Hai Li,Jiahao Huang,Xin Tan,Xiaofang Lai,Jun Deng,Duan Zhao,Shaoming Zeng,Jikang Jian

Three layered quaternary sulfides, A CuZnS 2 ( A  = K, Rb, Cs) have been synthesized by a facile solvothermal method using ethylenediamine as solvent and characterized by a combination of structural, magnetic, and optical measurements . They adopt the ThCr 2 Si 2 -type structure (space group I 4/ mmm ) and are composed of alternating two-dimensional [CuZnS 2 ] −1 layers and alkali metal layers. Based on magnetization and optical measurements, these three compounds are found to be paramagnetic semiconductors. The optical band gap is around 2.75 eV and for the first time two photoluminescence bands are observed for each compound. The green luminescence can be ascribed to a localized Cu + emitting level and the red one to an excitonic state.