Self-propulsion of flapping bodies in viscous fluids: Recent advances and perspectives

Flapping-powered propulsion is used by many animals to locomote through air or water. Here we review recent experimental and numerical studies on self-propelled mechanical systems powered by a flapping motion. These studies improve our understanding of the mutual interaction between actively flapping bodies and surrounding fluids. The results obtained in these works provide not only new insights into biolocomotion but also useful information for the bio-mimetic design of artificial flyers and swimmers.     

Promoting the Phosphidation Process using an Oxygen Vacancy Precursor for Efficient Hydrogen Evolution Reaction

Based on previous works, most of the transition metal phosphides (TMPs) were directly prepared by decomposing NaH₂PO₂ with the precursors at high temperatures, which resulted in different degrees of phosphidation in the final product. Therefore, it is necessary to design an innovative approach to enhance the degree of phosphidation in the material using crystal defects. Here, oxygen-vacancy iron oxide/iron foam (Ov-Fe₂O₃/IF) was firstly prepared by generating oxygen vacancy in situ in an iron foam through heating in vacuum conditions. Subsequently, FeP/IF was formed by phosphating Ov-Fe₂O₃/IF. Under the effects of oxygen vacancies, oxygen-vacancy iron oxide could be completely phosphatized to produce more active sites on the surface of the material. This, in turn, could result in a catalyst with exceptional hydrogen evolution activity. Thus, the successful fabrication of FeP/IF demonstrated in this work provides an effective and feasible way for the preparation of other high-efficiency catalysts.     

Two-Dimensional Germanium Sulfide Nanosheets as an Ultra-Stable and High Capacity Anode for Lithium Ion Batteries

Lithium ion batteries (LIBs) at present still suffer from low rate capability and poor cycle life during fast ion insertion/extraction processes. Searching for high-capacity and stable anode materials is still an ongoing challenge. Herein, a facile strategy for the synthesis of ultrathin GeS₂ nanosheets with the thickness of 1.1 nm is reported. When used as anodes for LIBs, the two-dimensional (2D) structure can effectively increase the electrode/electrolyte interface area, facilitate the ion transport, and buffer the volume expansion. Benefiting from these merits, the as-synthesized GeS₂ nanosheets deliver high specific capacity (1335 mAh g⁻¹ at 0.15 A g⁻¹), extraordinary rate performance (337 mAh g⁻¹ at 15 A g⁻¹) and stable cycling performance (974 mAh g⁻¹ after 200 cycles at 0.5 A g⁻¹). Importantly, our fabricated Li-ion full cells manifest an impressive specific capacity of 577 mAh g⁻¹ after 50 cycles at 0.1 A g⁻¹ and a high energy density of 361 Wh kg⁻¹ at a power density of 346 W kg⁻¹. Furthermore, the electrochemical reaction mechanism is investigated by the means of ex-situ high-resolution transmission electron microscopy. These results suggest that GeS₂ can use to be an alternative anode material and encourage more efforts to develop other high-performance LIBs anodes.     

Daphnane Diterpenoids of Trigonostemon thyrsoideus

Chemistry of Natural Compounds -     

Two novel d10 transition metal complexes based on 1H‐benzimidazole‐5,6‐dicarboxylic acid: Synthesis,structure and multifunctional luminescence detection

Two new coordination complexes based on benzimidazole dicarboxylic acid, Zn(Hbidc)?H₂O ( 1 ) and Cd(Hbidc)(H₂O) ( 2 ), have been synthesized under hydrothermal conditions. The complexes were characterized using elemental analysis, infrared and UV–visible spectroscopies, powder X‐ray diffraction, thermogravimetry and single‐crystal X‐ray diffraction. Structural analyses showed that the crystal structures of 1 and 2 are different, due to the various modes of linking of the benzimidazole dicarboxylic acid. Complex 1 has a two‐dimensional network structure and 2 has a three‐dimensional network structure. In addition, we studied the performance of the fluorescence response of two complexes. Results showed that the complexes can be used as chemical sensors for multifunctional testing, such as for UO₂²⁺, xanthine and Fe³⁺ ions. Even if the concentration is very low, they could also be detected, showing that coordination complexes 1 and 2 have very high fluorescence sensitivity. The detection limit for UO₂²⁺ is 5.42 nM ( 1 ) and 0.02 nM ( 2 ), that for xanthine is 1.37 nM ( 1 ) and 0.28 nM ( 2 ), and that for Fe³⁺ ions is 0.76 nM ( 1 ) and 0.62 nM ( 2 ).     

Highly sensitive and selective detect of p‐arsanilic acid with a new water‐stable europium metal–organic framework

The p‐arsanilic acid (p‐ASA), as an aromatic organoarsenic compounds, had received considerable concerns for their potential toxicity and carcinogenic properties. It was essential to detect p‐ASA with a facile method. In this paper, an europium based fluorescent metal–organic framework (MOF) [Eu₂(clhex)·2H₂O)]·H₂O ( BUC‐69 ) was successfully prepared under hydrothermal conditions with 1,2,3,4,5,6‐cyclohexanehexacarboxylic acid (H₆clhex) as organic linker. BUC‐69 displayed superior fluorescence capability to achieve selective and sensitive detection toward p‐ASA in water, which presented the first example of a MOF‐based sensor to detect p‐ASA. BUC‐69 showed excellent chemical stability in solutions under pH ranging from 4 to 12, which makes it be a potential sensor both in acidity and alkalinity condition. Significantly, BUC‐69 performed well in fluorescent sensing of p‐ASA at a low concentration (10^?6 M) in the simulated wastewater prepared with real lake water, and the results were comparable to the values detected by Inductively Coupled Plasma Optical Emission Spectrometer (ICP‐OES). The corresponding mechanism of fluorescent sensing toward p‐ASA with BUC‐69 was proposed and affirmed.     

Gold-Catalyzed Oxidative Aminocyclizations of Propargyl Alcohols and Propargyl Amines to Form Two Distinct Azacyclic Products: Carbene Formation versus a 3,3-Sigmatropic Shift of an Initial Intermediate

Gold-catalyzed oxidations of propargyl alcohols with nitrones by using a P(tBu)₂(o-biphenyl)Au⁺ catalyst, afforded bicyclic annulation products from the Mannich reactions of gold enolates. The same reactions of propargyl amines with nitrones by using the same gold catalyst gave distinct oxoarylation products. Our DFT calculations indicate that oxidation of propargyl alcohols with nitrones by using electron-rich gold catalysts lead only to gold carbenes, which can generate gold enolates or oxoarylation intermediates with enolate species having a barrier smaller than that of oxoarylation species.     

1,2-Diketones as photoinitiators of both cationic and free-radical photopolymerization under UV (392 nm) or Blue (455 nm) LEDs

The photoinitiation abilities of three 1,2-diketones [i.e., acenaphthenequinone ( ANPQ ), aceanthrenequinone ( AATQ ), and 9,10-phenanthrenequinone ( PANQ )]-based photoinitiating systems [PISs, with additives such as iodonium salt, N-vinylcarbazole (NVK), tertiary amine, and phenacyl bromide (R-Br)] for cationic photopolymerization and free-radical photopolymerization under the irradiation of ultraviolet (UV; 392 nm) or blue (455 nm) light-emitting diode (LED) bulb are investigated. All 1,2-diketones studied exhibit ground state absorption that match with the emission spectra of UV (392 nm) or blue LED (455 nm) better than that of the well-known blue-light-sensitive photoinitiator camphorquinone (CQ). In particular, AATQ /iodonium salt/NVK can show high photoinitiating ability (with epoxide conversion yield >70%) under the UV light irradiation due to the effect of NVK. In addition, 1,2-diketone/iodonium salt (and optional NVK) systems are capable of initiating free-radical photopolymerization of methacrylates, with conversions of 50–58%. Furthermore, some 1,2-diketone/tertiary amine (and optional R-Br) combinations are found to demonstrate high efficiency to initiate free-radical photopolymerization, and 71% of methacrylate conversion can be achieved with PANQ /tertiary amine/R-Br PIS. Some 1,2-ketone-based PISs can even exhibit higher efficiency than the CQ-based systems. The photochemical mechanism of the radical generation from the 1,2-diketone-based PISs is investigated and found to be consistent with the related photopolymerization efficiency. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 792–802     

金色梦想，一触即发——化学专业校外实践教学基地建设与思考

高等教育要适应世界潮流和时代变化,本科教育须进一步提高实践教学的比重,加强理论教学与实践教学相结合,完善协同育人机制。结合学科发展和企业发展需求,中山大学化学学院与金发科技股份有限公司(简称金发科技)共同建设大学生实践教学基地。本文以中山大学-金发科技本科实践教学基地为例,探讨大学生校外实践基地建设过程中遇到的问题以及实践基地的建设内容与成果体会。