ISSN 0253-2778

CN 34-1054/N

Chemistry

Display Method:
Charge-balanced codoping enables exceeding doping limit and ultralow thermal conductivity
Long Chen, Chun Wang, Lin Wang, Minghao Wang, Yongchun Zhu, Changzheng Wu
2024, 54(6): 0601. doi: 10.52396/JUSTC-2024-0025
Abstract:
Materials with low thermal conductivity are applied extensively in energy management, and breaking the amorphous limits of thermal conductivity to solids has attracted widespread attention from scientists. Doping is a common strategy for achieving low thermal conductivity that can offer abundant scattering centers in which heavier dopants always result in lower phonon group velocities and lower thermal conductivities. However, the amount of equivalent heavy-atom single dopant available is limited. Unfortunately, nonequivalent heavy dopants have finite solubility because of charge imbalance. Here, we propose a charge balance strategy for SnS by substituting Sn2+ with Ag+ and heavy Bi3+, improving the doping limit of Ag from 2% to 3%. Ag and Bi codoping increases the point defect concentration and introduces abundant boundaries simultaneously, scattering the phonons at both the atomic scale and nanoscale. The thermal conductivity of Ag0.03Bi0.03Sn0.94S decreased to 0.535 W·m−1·K−1 at room temperature and 0.388 W·m−1·K−1 at 275 ℃, which is below the amorphous limit of 0.450 W·m−1·K−1 for SnS. This strategy offers a simple way to enhance the doping limit and achieve ultralow thermal conductivity in solids below the amorphous limit without precise structural modification. Materials with low thermal conductivity are applied extensively in energy management, and breaking the amorphous limits of thermal conductivity to solids has attracted widespread attention from scientists. Doping is a common strategy for achieving low thermal conductivity that can offer abundant scattering centers in which heavier dopants always result in lower phonon group velocities and lower thermal conductivities. However, the amount of equivalent heavy-atom single dopant available is limited. Unfortunately, nonequivalent heavy dopants have finite solubility because of charge imbalance. Here, we propose a charge balance strategy for SnS by substituting Sn2+ with Ag+ and heavy Bi3+, improving the doping limit of Ag from 2% to 3%. Ag and Bi codoping increases the point defect concentration and introduces abundant boundaries simultaneously, scattering the phonons at both the atomic scale and nanoscale. The thermal conductivity of Ag0.03Bi0.03Sn0.94S decreased to 0.535 W·m−1·K−1 at room temperature and 0.388 W·m−1·K−1 at 275 ℃, which is below the amorphous limit of 0.450 W·m−1·K−1 for SnS. This strategy offers a simple way to enhance the doping limit and achieve ultralow thermal conductivity in solids below the amorphous limit without precise structural modification.
Large and nonlinear electric field response in a two-dimensional ferroelectric Rashba material
Li Sheng, Xiaomin Fu, Chao Jia, Xingxing Li, Qunxiang Li
2024, 54(6): 0602. doi: 10.52396/JUSTC-2024-0004
Abstract:
The achievement of electrical spin control is highly desirable. One promising strategy involves electrically modulating the Rashba spin orbital coupling effect in materials. A semiconductor with high sensitivity in its Rashba constant to external electric fields holds great potential for short channel lengths in spin field-effect transistors, which is crucial for preserving spin coherence and enhancing integration density. Hence, two-dimensional (2D) Rashba semiconductors with large Rashba constants and significant electric field responses are highly desirable. Herein, by employing first-principles calculations, we design a thermodynamically stable 2D Rashba semiconductor, YSbTe3, which possesses an indirect band gap of 1.04 eV, a large Rashba constant of 1.54 eV·Å and a strong electric field response of up to 4.80 e·Å2. In particular, the Rashba constant dependence on the electric field shows an unusual nonlinear relationship. At the same time, YSbTe3 has been identified as a 2D ferroelectric material with a moderate polarization switching energy barrier (~ 0.33 eV per formula). By changing the electric polarization direction, the Rashba spin texture of YSbTe3 can be reversed. These outstanding properties make the ferroelectric Rashba semiconductor YSbTe3 quite promising for spintronic applications. The achievement of electrical spin control is highly desirable. One promising strategy involves electrically modulating the Rashba spin orbital coupling effect in materials. A semiconductor with high sensitivity in its Rashba constant to external electric fields holds great potential for short channel lengths in spin field-effect transistors, which is crucial for preserving spin coherence and enhancing integration density. Hence, two-dimensional (2D) Rashba semiconductors with large Rashba constants and significant electric field responses are highly desirable. Herein, by employing first-principles calculations, we design a thermodynamically stable 2D Rashba semiconductor, YSbTe3, which possesses an indirect band gap of 1.04 eV, a large Rashba constant of 1.54 eV·Å and a strong electric field response of up to 4.80 e·Å2. In particular, the Rashba constant dependence on the electric field shows an unusual nonlinear relationship. At the same time, YSbTe3 has been identified as a 2D ferroelectric material with a moderate polarization switching energy barrier (~ 0.33 eV per formula). By changing the electric polarization direction, the Rashba spin texture of YSbTe3 can be reversed. These outstanding properties make the ferroelectric Rashba semiconductor YSbTe3 quite promising for spintronic applications.
Machine learning molecular dynamics simulations of liquid methanol
Jie Qian, Junfan Xia, Bin Jiang
2024, 54(6): 0603. doi: 10.52396/JUSTC-2024-0031
Abstract:
As the simplest hydrogen-bonded alcohol, liquid methanol has attracted intensive experimental and theoretical interest. However, theoretical investigations on this system have primarily relied on empirical intermolecular force fields or ab initio molecular dynamics with semilocal density functionals. Inspired by recent studies on bulk water using increasingly accurate machine learning force fields, we report a new machine learning force field for liquid methanol with a hybrid functional revPBE0 plus dispersion correction. Molecular dynamics simulations on this machine learning force field are orders of magnitude faster than ab initio molecular dynamics simulations, yielding the radial distribution functions, self-diffusion coefficients, and hydrogen bond network properties with very small statistical errors. The resulting structural and dynamical properties are compared well with the experimental data, demonstrating the superior accuracy of this machine learning force field. This work represents a successful step toward a first-principles description of this benchmark system and showcases the general applicability of the machine learning force field in studying liquid systems. As the simplest hydrogen-bonded alcohol, liquid methanol has attracted intensive experimental and theoretical interest. However, theoretical investigations on this system have primarily relied on empirical intermolecular force fields or ab initio molecular dynamics with semilocal density functionals. Inspired by recent studies on bulk water using increasingly accurate machine learning force fields, we report a new machine learning force field for liquid methanol with a hybrid functional revPBE0 plus dispersion correction. Molecular dynamics simulations on this machine learning force field are orders of magnitude faster than ab initio molecular dynamics simulations, yielding the radial distribution functions, self-diffusion coefficients, and hydrogen bond network properties with very small statistical errors. The resulting structural and dynamical properties are compared well with the experimental data, demonstrating the superior accuracy of this machine learning force field. This work represents a successful step toward a first-principles description of this benchmark system and showcases the general applicability of the machine learning force field in studying liquid systems.
Effect of substrate temperature and oxygen plasma treatment on the properties of magnetron-sputtered CdS for solar cell applications
Runxuan Zang, Haolin Wang, Xiaoqi Peng, Ke Li, Yuehao Gu, Yizhe Dong, Zhihao Yan, Zhiyuan Cai, Huihui Gao, Shuwei Sheng, Rongfeng Tang, Tao Chen
2024, 54(6): 0604. doi: 10.52396/JUSTC-2024-0048
Abstract:
Cadmium sulfide (CdS) is an n-type semiconductor with excellent electrical conductivity that is widely used as an electron transport material (ETM) in solar cells. At present, numerous methods for preparing CdS thin films have emerged, among which magnetron sputtering (MS) is one of the most commonly used vacuum techniques. For this type of technique, the substrate temperature is one of the key deposition parameters that affects the interfacial properties between the target film and substrate, determining the specific growth habits of the films. Herein, the effect of substrate temperature on the microstructure and electrical properties of magnetron-sputtered CdS (MS-CdS) films was studied and applied for the first time in hydrothermally deposited antimony selenosulfide (Sb2(S,Se)3) solar cells. Adjusting the substrate temperature not only results in the design of the flat and dense film with enhanced crystallinity but also leads to the formation of an energy level arrangement with a Sb2(S,Se)3 layer that is more favorable for electron transfer. In addition, we developed an oxygen plasma treatment for CdS, reducing the parasitic absorption of the device and resulting in an increase in the short-circuit current density of the solar cell. This study demonstrates the feasibility of MS-CdS in the fabrication of hydrothermal Sb2(S,Se)3 solar cells and provides interface optimization strategies to improve device performance. Cadmium sulfide (CdS) is an n-type semiconductor with excellent electrical conductivity that is widely used as an electron transport material (ETM) in solar cells. At present, numerous methods for preparing CdS thin films have emerged, among which magnetron sputtering (MS) is one of the most commonly used vacuum techniques. For this type of technique, the substrate temperature is one of the key deposition parameters that affects the interfacial properties between the target film and substrate, determining the specific growth habits of the films. Herein, the effect of substrate temperature on the microstructure and electrical properties of magnetron-sputtered CdS (MS-CdS) films was studied and applied for the first time in hydrothermally deposited antimony selenosulfide (Sb2(S,Se)3) solar cells. Adjusting the substrate temperature not only results in the design of the flat and dense film with enhanced crystallinity but also leads to the formation of an energy level arrangement with a Sb2(S,Se)3 layer that is more favorable for electron transfer. In addition, we developed an oxygen plasma treatment for CdS, reducing the parasitic absorption of the device and resulting in an increase in the short-circuit current density of the solar cell. This study demonstrates the feasibility of MS-CdS in the fabrication of hydrothermal Sb2(S,Se)3 solar cells and provides interface optimization strategies to improve device performance.
Synergistic effect of heterogeneous single atoms and clusters for improved catalytic performance
Long Liu, Wenting Gao, Yiling Ma, Kainan Mei, Wenlong Wu, Hongliang Li, Zhirong Zhang, Jie Zeng
2024, 54(6): 0605. doi: 10.52396/JUSTC-2024-0046
Abstract:
Electrocatalytic water splitting provides an efficient method for the production of hydrogen. In electrocatalytic water splitting, the oxygen evolution reaction (OER) involves a kinetically sluggish four-electron transfer process, which limits the efficiency of electrocatalytic water splitting. Therefore, it is urgent to develop highly active OER catalysts to accelerate reaction kinetics. Coupling single atoms and clusters in one system is an innovative approach for developing efficient catalysts that can synergistically optimize the adsorption and configuration of intermediates and improve catalytic activity. However, research in this area is still scarce. Herein, we constructed a heterogeneous single-atom cluster system by anchoring Ir single atoms and Co clusters on the surface of Ni(OH)2 nanosheets. Ir single atoms and Co clusters synergistically improved the catalytic activity toward the OER. Specifically, ConIr1/Ni(OH)2 required an overpotential of 255 mV at a current density of 10 mA·cm−2, which was 60 mV and 67 mV lower than those of Con/Ni(OH)2 and Ir1/Ni(OH)2, respectively. The turnover frequency of ConIr1/Ni(OH)2 was 0.49 s−1, which was 4.9 times greater than that of Con/Ni(OH)2 at an overpotential of 300 mV. Electrocatalytic water splitting provides an efficient method for the production of hydrogen. In electrocatalytic water splitting, the oxygen evolution reaction (OER) involves a kinetically sluggish four-electron transfer process, which limits the efficiency of electrocatalytic water splitting. Therefore, it is urgent to develop highly active OER catalysts to accelerate reaction kinetics. Coupling single atoms and clusters in one system is an innovative approach for developing efficient catalysts that can synergistically optimize the adsorption and configuration of intermediates and improve catalytic activity. However, research in this area is still scarce. Herein, we constructed a heterogeneous single-atom cluster system by anchoring Ir single atoms and Co clusters on the surface of Ni(OH)2 nanosheets. Ir single atoms and Co clusters synergistically improved the catalytic activity toward the OER. Specifically, ConIr1/Ni(OH)2 required an overpotential of 255 mV at a current density of 10 mA·cm−2, which was 60 mV and 67 mV lower than those of Con/Ni(OH)2 and Ir1/Ni(OH)2, respectively. The turnover frequency of ConIr1/Ni(OH)2 was 0.49 s−1, which was 4.9 times greater than that of Con/Ni(OH)2 at an overpotential of 300 mV.
An efficient strategy for the preparation of a MIL-53(Al)-NH2 membranes with high ion selectivity and desalination performance
Wenmin Li, Zheng Liu, Xingya Li, Rongqiang Fu, Zhaoming Liu, Tingting Xu, Tongwen Xu
2024, 54(6): 0606. doi: 10.52396/JUSTC-2024-0016
Abstract:
The efficient extraction of sodium (Na+) and lithium (Li+) from seawater and salt lakes is increasingly demanding due to their great application value in chemical industries. However, coexisting cations such as divalent calcium (Ca2+) and magnesium (Mg2+) ions are at the subnanometer scale in diameter, similar to target monovalent ions, making ion separation a great challenge. Here, we propose a simple and fast secondary growth method for the preparation of MIL-53(Al)-NH2 membranes on the surface of anodic aluminum oxide. Such membranes contain angstrom-scale (~7 Å) channels for the entrance of small monovalent ions and water molecules, endowing the selectivities for monovalent cations over divalent cations and water over salt molecules. The resulting high-connectivity MIL-53(Al)-NH2 membranes exhibit excellent ion separation performance (a selectivity of 121.42 for Na+/Ca2+ and 93.81 for Li+/Mg2+) and desalination performance (a water/salt selectivity of up to 5196). This work highlights metal-organic framework membranes as potential candidates for realizing ion separation and desalination in liquid treatment. The efficient extraction of sodium (Na+) and lithium (Li+) from seawater and salt lakes is increasingly demanding due to their great application value in chemical industries. However, coexisting cations such as divalent calcium (Ca2+) and magnesium (Mg2+) ions are at the subnanometer scale in diameter, similar to target monovalent ions, making ion separation a great challenge. Here, we propose a simple and fast secondary growth method for the preparation of MIL-53(Al)-NH2 membranes on the surface of anodic aluminum oxide. Such membranes contain angstrom-scale (~7 Å) channels for the entrance of small monovalent ions and water molecules, endowing the selectivities for monovalent cations over divalent cations and water over salt molecules. The resulting high-connectivity MIL-53(Al)-NH2 membranes exhibit excellent ion separation performance (a selectivity of 121.42 for Na+/Ca2+ and 93.81 for Li+/Mg2+) and desalination performance (a water/salt selectivity of up to 5196). This work highlights metal-organic framework membranes as potential candidates for realizing ion separation and desalination in liquid treatment.
Nickel catalysts with asymmetric steric hindrance for ethylene polymerization
Wanlu Tian, Fuzhou Wang, Chen Zou
2024, 54(6): 0607. doi: 10.52396/JUSTC-2024-0001
Abstract:
α-Diimide catalysts have attracted widespread attention due to their unique chain walking characteristics. A series of α-diimide nickel/palladium catalysts with different electronic effects and steric hindrances were designed and synthesized for olefin polymerization. In this work, we synthesized a series of asymmetric α-diimide nickel complexes with different steric hindrances and used them for ethylene polymerization. These nickel catalysts have high ethylene polymerization activity, up to 6.51×106 g·mol−1·h−1, and the prepared polyethylene has a moderate melting point and high molecular weight (up to 38.2 × 104 g·mol−1), with a branching density distribution between 7 and 94 branches per 1000 carbons. More importantly, the polyethylene prepared by these catalysts exhibits excellent tensile properties, with strain and stress reaching 800% and 30 MPa, respectively. α-Diimide catalysts have attracted widespread attention due to their unique chain walking characteristics. A series of α-diimide nickel/palladium catalysts with different electronic effects and steric hindrances were designed and synthesized for olefin polymerization. In this work, we synthesized a series of asymmetric α-diimide nickel complexes with different steric hindrances and used them for ethylene polymerization. These nickel catalysts have high ethylene polymerization activity, up to 6.51×106 g·mol−1·h−1, and the prepared polyethylene has a moderate melting point and high molecular weight (up to 38.2 × 104 g·mol−1), with a branching density distribution between 7 and 94 branches per 1000 carbons. More importantly, the polyethylene prepared by these catalysts exhibits excellent tensile properties, with strain and stress reaching 800% and 30 MPa, respectively.
Temperature-feedback two-photon-responsive metal-organic frameworks for efficient photothermal therapy
Xianshun Sun, Xin Lu, Wenyao Duan, Bo Li, Yupeng Tian, Dandan Li, Hongping Zhou
2024, 54(6): 0608. doi: 10.52396/JUSTC-2024-0005
Abstract:
The realization of real-time thermal feedback for monitoring photothermal therapy (PTT) under near-infrared (NIR) light irradiation is of great interest and challenge for antitumor therapy. Herein, by assembling highly efficient photothermal conversion gold nanorods and a temperature-responsive probe ((E)-4-(4-(diethylamino)styryl)-1-methylpyridin-1-ium, PyS) within MOF-199, an intelligent nanoplatform (AMPP) was fabricated for simultaneous chemodynamic therapy and NIR light-induced temperature-feedback PTT. The fluorescence intensity and temperature of the PyS probe are linearly related due to the restriction of the rotation of the characteristic monomethine bridge. Moreover, the copper ions resulting from the degradation of MOF-199 in an acidic microenvironment can convert H2O2 into •OH, resulting in tumor ablation through a Fenton-like reaction, and this process can be accelerated by increasing the temperature. This study establishes a feasible platform for fabricating highly sensitive temperature sensors for efficient temperature-feedback PTT. The realization of real-time thermal feedback for monitoring photothermal therapy (PTT) under near-infrared (NIR) light irradiation is of great interest and challenge for antitumor therapy. Herein, by assembling highly efficient photothermal conversion gold nanorods and a temperature-responsive probe ((E)-4-(4-(diethylamino)styryl)-1-methylpyridin-1-ium, PyS) within MOF-199, an intelligent nanoplatform (AMPP) was fabricated for simultaneous chemodynamic therapy and NIR light-induced temperature-feedback PTT. The fluorescence intensity and temperature of the PyS probe are linearly related due to the restriction of the rotation of the characteristic monomethine bridge. Moreover, the copper ions resulting from the degradation of MOF-199 in an acidic microenvironment can convert H2O2 into •OH, resulting in tumor ablation through a Fenton-like reaction, and this process can be accelerated by increasing the temperature. This study establishes a feasible platform for fabricating highly sensitive temperature sensors for efficient temperature-feedback PTT.
Highly efficient copper-catalyzed benzylic C–H alkoxylation with NFSI
Cheng Zhang, Pu-Sheng Wang
2023, 53(12): 1202. doi: 10.52396/JUSTC-2023-0080
Abstract:
A sacrificial reductant-free copper-catalyzed benzylic C–H alkoxylation with N-Fluorobenzenesulfonimide (NFSI) was reported. Mechanistic studies suggested a novel pathway for the generation of active CuI species from Cu(OAc)2, NFSI and MeOH. A proper loading amount of copper catalyst was found to balance the reaction rates of benzylic C–H alkoxylation and overoxidation of benzyl ether to exhibit the best performance. A sacrificial reductant-free copper-catalyzed benzylic C–H alkoxylation with N-Fluorobenzenesulfonimide (NFSI) was reported. Mechanistic studies suggested a novel pathway for the generation of active CuI species from Cu(OAc)2, NFSI and MeOH. A proper loading amount of copper catalyst was found to balance the reaction rates of benzylic C–H alkoxylation and overoxidation of benzyl ether to exhibit the best performance.
Tuning the photoluminescence of MoS2/TiO2 by molecular self-assembly films
Hechenyu Zha, Yue Xing, Miaomiao Xiang, Xiang Shao
2023, 53(12): 1206. doi: 10.52396/JUSTC-2023-0078
Abstract:
Self-assembly films have demonstrated an efficient method to functionalize the surfaces of variously different materials. In this work, we preliminarily explored the modification effect of 10,12-pentacosadiynoic acid (PCDA) on the optical properties of monolayer molybdenum disulfide (MoS2) grown on a rutile titanium dioxide (r-TiO2) (110) single crystal surface. Atomic force microscopy (AFM) characterizations directly revealed that the PCDA molecules self-assemble into the same lamella structure as on pure MoS2, which can be further polymerized into conductive polydiacetylene (PDA) chains under ultraviolet light (UV) irradiation. Detailed photoluminescence (PL) measurements observed clearly increased luminescence of negative trions (A) yet decreased total intensities for MoS2 upon adding the PCDA assembly, which is further enhanced after stimulating its polymerization. These results indicate that the PCDA assembly and its polymerization have different electron donability to MoS2, which hence provides a deepened understanding of the interfacial interactions within a multicomponent system. Our work also demonstrates the self-assembly of films as a versatile strategy to tune the electronic/optical properties of hybridized two-dimensional materials. Self-assembly films have demonstrated an efficient method to functionalize the surfaces of variously different materials. In this work, we preliminarily explored the modification effect of 10,12-pentacosadiynoic acid (PCDA) on the optical properties of monolayer molybdenum disulfide (MoS2) grown on a rutile titanium dioxide (r-TiO2) (110) single crystal surface. Atomic force microscopy (AFM) characterizations directly revealed that the PCDA molecules self-assemble into the same lamella structure as on pure MoS2, which can be further polymerized into conductive polydiacetylene (PDA) chains under ultraviolet light (UV) irradiation. Detailed photoluminescence (PL) measurements observed clearly increased luminescence of negative trions (A) yet decreased total intensities for MoS2 upon adding the PCDA assembly, which is further enhanced after stimulating its polymerization. These results indicate that the PCDA assembly and its polymerization have different electron donability to MoS2, which hence provides a deepened understanding of the interfacial interactions within a multicomponent system. Our work also demonstrates the self-assembly of films as a versatile strategy to tune the electronic/optical properties of hybridized two-dimensional materials.
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