Latest ArticlesCovalent organic frameworks (COFs) are a class of crystalline porous organic materials with variable structures and fascinating properties. The intrinsic low conductivity impedes their widely application in optoelectronic. Iodine doping is an effective way to enhance the electrical conductivity of COFs. Here, a novel 3D imine COF with lvt topology is synthesized from two different pentacene derivatives with the same core in the form of structural complementarity. DDHP-COF is a highly crystalline material featuring high surface area of 1679 m2/g and excellent thermal stability up to 490 ℃. Upon doping with iodine, the electrical conductivity can reach as high as 1.5 × 10−2 S/m which is significantly enhanced over 6 orders of magnitude compared with the pristine COF.
In this work, Ti3C2Tx MXene with -F, -Cl and -Br surface terminations are synthesized and the effect of these halogen terminations on the lithium storage properties is investigated. A maximum Li+ storage capacity of 189 mAh/g is achieved with Ti3C2Brx MXene much higher than Ti3C2Clx and Ti3C2Fx with 138 mAh/g and 123 mAh/g, respectively. Density functional theory (DFT) calculation shows that the adsorption formation energy of halogen atoms on Ti atoms follows the trend of Ti-F > Ti-Cl > Ti-Br, leading to the same trend in the content of terminations on corresponding MXenes. In addition, inevitable exposure of MXene to oxygen causes competition between halogen and oxygen. Theoretical results show Ti3C2Brx MXene has the highest Ti to O ratio and the lowest Ti to Br ratio, the high lithium affinity of O explains the maximum Li-ion storage capacity with Ti3C2Brx MXene. This work shed light on the opportunity for achieving improved lithium storage properties of MXene electrodes by regulating the surface chemistry.
Aqueous zinc-ion batteries (ZIBs) have attracted significant attentions because of low cost and high reliability. However, conventional ZIBs are severely limited by the development of high energy density cathode materials with reversible Zn2+ insertion/extraction. Herein, a conducting polymer intercalated MoO3 (PMO) with extensively extended interlayer spacing is developed as a high-performance ZIBs cathode material. The interlayer spacing of PMO is prominently increased which results in an improved Zn2+ mobility during charge and discharge process. More significantly, the electrochemical results reveals that the intercalation of PANI facilitates the charge storage and reinforces the layered structure of MoO3, leading to a high capacity and good cycling stability. DFT calculation further reveals the intercalation of PANI into MoO3 significantly lower Zn2+ diffusion barrier. Benefit from these advantages, the ZIBs based on PMO electrode delivers a considerable capacity of 157 mAh/g at 0.5 A/g and ameliorative stability with 63.4% capacity retention after 1000 cycles.
Antimony-based materials are considered as promising anodes for potassium ion batteries due to their high theoretical capacity and low electrode potential. However, the aggregation and bulk expansion of Sb particles in cycling will cause capacity attenuation and poor rate performance. In this paper, Sb nanoplates were designed to be embedded in flexible porous N-dopped carbon nanofibers (Sb@PCNFs) by a simple electrospinning deposition (ESD) method. In this structural design, Sb nanoplates of high capacity were employed as active materials, N-dopped carbon nanofibers were used to improve conductivity and structural stability. The introduction of pore-forming agent enables the nanofibers to possess porous structure, thus buffering the huge volume change and promoting the transfer of electrolyte/ions. More importantly, the freestanding film can be directly used as a working electrode, reducing the redundancy in the battery and the cost. Benefitting from the favorable structure, the freestanding flexible Sb@PCNFs electrode shows excellent potassium storage performance with a capacity of 314 mAh/g after 2000 cycles at 500 mA/g. This strategy of employing active material with high capacity in porous and conductive flexible nanofibers represents an effective method of achieving binder-free electrode with good electrochemical performance towards wearable energy storage devices.
The morphology regulation of hollow silica microspheres is significant for their properties and applications. In this paper, hollow silica microspheres were formed through the hydrolysis and condensation reaction of tetraethyl orthosilicate (TEOS) at the interface of the emulsion droplet templates composed of liquid paraffin and TEOS, followed by dissolving paraffin with ethanol. The effects of various factors including the emulsifier structure and content, TEOS content, catalyst type, and the ethanol content in the continuous water phase on the particle size, shell thickness and morphology of the prepared hollow silica microspheres were studied in detail. The results show that the diffusion and contact of TEOS and water molecules as well as the hydrolysis condensation reaction of TEOS at the oil-water interface are two critical processes for the synthesis and morphological regulation of hollow silica microspheres. Cationic emulsifier with a hydrophobic chain of appropriate length is the prerequisite for the successful synthesis of hollow silica microspheres. The ethanol content in water phase is the dominant factor to determine the average diameter of hollow microspheres, which can vary from 96 nm to 660 nm with the increase of the volume ratio of alcohol-water from 0 to 0.7. The silica wall thickness varies with the content and the hydrophobic chain length of the emulsifier, TEOS content, and the activity of the catalyst. The component of the soft template will affect the morphology of the silica wall. When the liquid paraffin is replaced by cyclohexane, hollow microspheres with fibrous mesoporous silica wall are fabricated. This work not only enriches the basic theory of interfacial polymerization in the emulsion system, but also provides ideas and methods for expanding the morphology and application of hollow silica microspheres.
The intercalation behavior of spiro-(1,1′)-bipyrrolidinium cation (SBP+) into graphite electrode from spiro-(1,1′)-bipyrrolidinium tetrafluoroborate-ethylene carbonate (SBPBF4-EC) solutions is investigated by conventional electrochemical tests and in situ X-ray diffraction measurements. Two kinds of graphite intercalation compounds (GICs) with discrete characteristic intercalated gallery heights (IGHs) (ca. 0.95 and 0.75 nm) can be obtained with varying the salt concentration. The effect of graphite type is also addressed.
To explore the lead-free key scientific issue in perovskite, double perovskite based on AgBi and CuBi was naturally selected as a competitive candidate due to its fascinating functional features, such as self-powered circularly polarized light detection, X-ray detection, photoluminescence and so on. However, the most challenging point is to simulate the structure and function of traditional lead-based perovskite in new double perovskite. At the same time, there are few suitable double perovskite systems with optical and electrical potential. The above two points greatly limit the competitiveness of double perovskite. In order to solve this problem, firstly, by analyzing and comparing previous studies, we used 2,2-dimethylpropan-1-aminium (abbreviated as 2,2-DPA) as the organic template to assemble materials. Solid-to-solid phase transition materials (2,2-DPA)3Bi2I9 1 and (2,2-DPA)3Pb2I7 2 were constructed. Along the path of lead-free and two-dimensional maintenance, we successfully synthesized (2,2-DPA)4AgBiI8·H2O 3 and (2,2-DPA)4CuBiI8·H2O 4. As two typical semiconductors, 3 and 4 with narrower optical band gaps of 1.98 and 1.76 eV show obvious photo-response when the xenon lamp with intensity of 20 mW/cm2 is on or off, implying that they may be applied to light-harvesting and light-detecting devices. By referring to the phase transition mechanism of 1 and 2, 3 may be caused by ordered-disordered transition of the organic part, which was proven to be the first solid-to-solid phase transition material with <100> -oriented layered double perovskites with n = 1 by systematic characterization methods after dehydration for all we know. We believed that this work can provide meaningful guidance for the development of lead-free double perovskites.
Fluorescent dyes with fluorescence emission above 700 nm are favorable for bio-imaging due to the higher tissue transparency and lower background fluorescence. In this study, we present a meso-benzimidazole-pyronin platform (SiBMs) with fluorescence emission maxima above 700 nm, which possess good cell permeability, photostability, and lysosomal localization. The great photophysical properties of the SiBMs encouraged us to further exploit their application toward bio-imaging. We synthesized the reduced 'dihydro' derivative HSiBM3 for sensing ONOO−, with high selectivity and sensitivity and a fast fluorescence "off-on" response (within 2 s). Then, we confirmed the potential of HSiBM3 for visualizing exogenous and endogenous ONOO− in cells and mice. More importantly, HSiBM3 was successfully employed for visualizing acute-liver-injury-induced peroxynitrite.
T4 polynucleotide kinase (T4 PNK) is a pivotal enzyme for DNA replication, recombination, and DNA damage repair. Herein, a robust single particle counting-based assay has been developed for the high-sensitive determination of T4 PNK activity through only a simple one-step reaction. Taking benefit of the exceptional space-confined enzymatic property of T4 PNK towards DNA substrates on a single nanoparticle, the T4 PNK activity can be precisely determined by counting the fluorescence-positive nanoparticles in a digital manner with a total internal reflection fluorescent microscope (TIRFM). Due to the featured spatial-confined enzymatic property of T4 PNK and the single particle counting-based signal readout, T4 PNK can be effectively differentiated from other interfering enzymes. This facile strategy has been also successfully applied to screen T4 PNK inhibitor and accurately determine T4 PNK activity in complex biological samples, paving a potential avenue for the digital analysis of biomarkers.
Pyrylium salts are a type of representative and convincing example of versatility and variety not only as a nodal point in organic transformations but also as an attractive building block in functional organic materials. Herein, we report an effective synthetic protocol to fabricate a new pyrylium-containing porous organic polymers (POPs), named TMP-P, via Knoevenagel condensation with 2,4,6-trimethylpyrylium salt (TMP) as the key building block and 1,4-phthalaldehyde as the linker. The resulting ionic polymer TMP-P exhibited efficient visible-light-driven heterogeneous photodegradation of Rhodamine B, owing to the presence of wide visible light absorption and a narrow optical band gap triggered pyrylium core in the framework.
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