Lina Nie

A crystalline Cu–Sn–S framework for high-performance lithium storage

In order to address the increasing demands for clean energy, it is highly desirable to explore new electrode materials to improve the efficiency of lithium ion batteries (LIBs). In this work, we report the successful synthesis of a crystalline (H3O)2(enH2)Cu8Sn3S12 material via a surfactant-thermal strategy. The crystal structure analysis shows that the as-prepared chalcogenide has 3D interconnected channels occupied by disordered H2en2+ and H3O+. Taking advantage of porous structures and H2en2+ and H3O+ as stabilizers, (H3O)2(enH2)Cu8Sn3S12 has been explored as an anode material for lithium ion batteries. Our results exhibit a high capacity of 563 mA h g−1 at a current density of 0.1 A g−1 after 100 cycles. In addition, outstanding cycling properties are demonstrated with only 7.2% capacity loss from the 5th to 100th cycle. Our research could provide insight into the exploration of crystalline ternary thiostannate for lithium ion batteries in the future.

Surfactant-thermal syntheses, structures, and magnetic properties of Mn-Ge-sulfides/selenides.

Although either surfactants or amines have been investigated to direct the crystal growth of metal chalcogenides, the synergic effect of organic amines and surfactants to control the crystal growth has not been explored. In this report, several organic bases (hydrazine monohydrate, ethylenediamine (en), 1,2-propanediamine (1,2-dap), and 1,3-propanediamine (1,3-dap)) have been employed as structure-directing agents (SDAs) to prepare four novel chalcogenides (Mn3Ge2S7(NH3)4 (1), [Mn(en)2(H2O)][Mn(en)2MnGe3Se9] (2), (1,2-dapH)2{[Mn(1,2-dap)2]Ge2Se7} (3), and (1,3-dapH)(puH)MnGeSe4(4) (pu = propyleneurea) under surfactant media (PEG-400). These as-prepared new crystalline materials provide diverse metal coordination geometries, including MnS3N tetrahedra, MnGe2Se7 trimer, and MnGe3Se10 T2 cluster. Compounds 1-3 have been fully characterized by single-crystal X-ray diffraction (XRD), powder XRD, UV-vis spectra, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Moreover, magnetic measurements for compound 1 showed an obvious antiferromagnetic transition at ~9 K. Our research not only enriches the structural chemistry of the transitional-metal/14/16 chalcogenides but also allows us to better understand the synergic effect of organic amines and surfactants on the crystallization of metal chalcogenides.

Self-Healing Behavior in a Thermo-Mechanically Responsive Cocrystal during a Reversible Phase Transition

The molecular-level motions of a coronene-based supramolecular rotator are amplified into macroscopic changes of crystals by co-assembly of coronene and TCNB (1,2,4,5-tetracyanobenzene) into a charge-transfer complex. The as-prepared cocrystals show remarkable self-healing behavior and thermo-mechanical responses during thermally-induced reversible single-crystal-to-single-crystal (SCSC) phase transitions. Comprehensive analysis of the microscopic observations as well as differential scanning calorimetry (DSC) measurements and crystal habits reveal that a thermally-reduced-rate-dependent dynamic character exists in the phase transition. The crystallographic studies show that the global similarity of the packing patterns of both phases with local differences, such as molecular stacking sequence and orientations, should be the origin of the self-healing behavior of these crystals.

Improving the Performance of Lithium-Sulfur Batteries by Employing Polyimide Particles as Hosting Matrixes.

Sulfur cathodes with four polyimide (PI) compounds as hosting matrixes have been prepared through a simple one-step approach. These four PIs-S composites exhibited higher sulfur utilization and better cycling stability than pure sulfur. At a current rate of 300 mA g(-1), the initial discharge capacities of PI-1S, PI-2S, PI-3S, and BBLS reached 1120, 1100, 1150, and 1040 mAh g(-1), respectively. After the 30th cycle, PI-1S, PI-2S, PI-3S, BBLS and pristine sulfur powder still remained discharge capacities of 715, 673, 729, 643, and 550 mAh g(-1). Especially, PI-1S and PI-3S cathodes exhibit excellent cycling stability with the discharge capacities of 522 and 574 mAh g(-1) at the 450th cycle, respectively.

A surfactant-thermal method to prepare crystalline thioantimonate for high-performance lithium-ion batteries

Rechargeable lithium-ion batteries (LIBs) have attracted great attention in various applications. However, high energy density is still a challenge for next-generation lithium ion batteries. Therefore, searching for novel electrode materials to address this issue is highly desirable. In this report, we employed a surfactant-thermal method to prepare a novel 1D crystalline thioantimonate [NH(CH3)2][Sb4S5(S3)]. After grinding for 10 min using a mortar, [NH(CH3)2][Sb4S5(S3)] presented an ultrathin nanosheet morphology (around 20 nm in thickness and several micrometers in lateral dimension). Employed as an anode material for lithium ion batteries, the nano-sized crystalline thioantimonate shows a high reversible specific capacity of 568 mA h g−1 over 50 cycles at a current density of 0.1 A g−1 and an excellent rate capability of 301 mA h g−1 at a current density of 5 A g−1. Our research suggests that crystalline thioantimonate could have great potential applications in high performance Li-ion batteries.

Understanding the structure-determining solid fluorescence of an azaacene derivative

Tuning the solid-state light emission properties of a single azaacene derivative system to achieve a high emission efficiency without any further modification is highly desirable and probably has many potential applications. In this research, we prepared a new azaacene derivative (TBIDQ) without any aromatic rotors and found that it exhibited different fluorescence emission behaviors in its three different single crystal forms (Form I, Form II and Form III). The fluorescence quantum yields (ϕ) of Form I, Form II and Form III are 30.2%, 26.0% and 14.6%, respectively. From single-crystal structural analysis and optical experimental results, we found that the mean distance of the interlayers and the radiative decay rate decreased from Form I to Form III, while the π–π stacking interactions and the nonradiative decay rate increased. Our results strongly suggest that planar molecules can display the loose stacking mode with weak π–π stacking interactions through careful crystal-engineering.

Recent progress in crystalline metal chalcogenides as efficient photocatalysts for organic pollutant degradation

Photodegradation of aqueous organic pollutants is a very promising strategy to address environmental issues and energy problems. Among all the reported photocatalysts, crystalline metal chalcogenides not only possess diverse architectures that can be enriched by integrating different metal ions and templates, but also have narrower band gaps (visible light adsorption) and suitable band positions that can be tuned through composition regulation. Therefore, the application of crystalline metal chalcogenides as efficient photocatalysts has attracted much attention. However, the limited synthetic methods, low degradation efficiency, and poor chemical stability are the major challenges that impede their practical application. In this review, the recent progress in employing crystalline metal chalcogenides as visible-light-driven catalysts for the photodegradation of organic contaminants is summarized. Besides this, the synthetic methods to prepare crystalline chalcogenides are discussed and the perspectives in regard to the improvement of the degradation efficiency and the chemical stability of metal chalcogenides are proposed.

Syntheses, crystal structures, and photocatalytic properties of two ammonium-directed Ag–Sb–S complexes

With ammonium ions as structure-directing agents, two novel silver thioantimonates (NH4)AgSb4S7·H2O (1) and (NH4)AgSb2S4 (2) have been surfactant-thermally synthesized and fully characterized. Compound 1 features a three dimensional (3D) open framework while compound 2 possesses a two dimensional (2D) layer structure. The optical band gaps are estimated to be 1.70 eV for 1 and 1.84 eV for 2, exhibiting semiconductor properties for visible light absorption. The photocatalytic experiments demonstrated that both 1 and 2 were able to degrade crystal violet (CV) and rhodamine B (RhB) under visible light irradiation. Moreover, compounds 1 and 2 also displayed selective photocatalytic abilities in CV degradation.

A novel heteroacene 2-(perfluorophenyl)-1H-imidazo[4,5-b]phenazine for selective sensing of picric acid

A novel sensing probe, 2-(perfluorophenyl)-1H-imidazo[4,5-b]phenazine (PFIPZ) containing imidazole and phenazine units, has been successfully synthesized and can identify picric acid over other electron-deficient compounds or strong acids.

Structure engineering: extending the length of azaacene derivatives through quinone bridges

Increasing the length of azaacene derivatives through quinone bridges is very important because these materials could have deep LUMO energy levels and larger overlapping in the solid state, which would have great applications in organic semiconducting devices. Here, two fully characterized large quinone-fused azaacenes Hex-CO and Hept-CO prepared through a novel palladium-catalyzed coupling reaction are reported. Our research clearly proved that the quinone unit can be employed as a bridge to extend the molecular conjugation length, increase the molecular overlapping, and engineer the molecular stacking mode. Hex-CO shows lamellar 2-D π-stacking modes, while Hept-CO shows 1-D π-stacking and adopts a 3-D interlocked stacking mode with the adjacent molecular layers vertical to each other. With the deep LUMO energy levels (∼−4.27 eV), Hex-CO and Hept-CO were both demonstrated to be electron-transport layers. Their charge transport properties were investigated through OFETs and theoretical calculations. Due to the different stacking modes, Hex-CO shows a higher electron mobility of 0.22 cm2 V−1 s−1 than Hept-CO (7.5 × 10−3 cm2 V−1 s−1) in a single-crystal-based OFET. Our results provide a new route for structure engineering through extending the azaacene derivatives by quinone bridges, which can be of profound significance in organic electronics.