Latest ArticlesPlant polyphenol-based coordination polymers (CPs) with ultra-small particle size and tailorable compositions are highly desired in biomedical applications, but their synthesis is still challenging due to the sophisticated coordination assembly process and unavoidable self-oxidation polymerization of polyphenol. Herein, a general ligand covalent-modification mediated coordination assembly strategy is proposed for the synthesis of water-dispersible CPs with tunable metal species (e.g., Gd, Cu, Ni, Zn, Fe) and ultra-small diameter (8.6–37.8 nm) using nontoxic plant polyphenol (e.g., tannic acid, gallic acid) as a polymerizable ligand. Polyphenol molecules react with formaldehyde firstly, which can effectively retard the oxidation induced self-polymerization of polyphenol and lead to the formation of metal ions containing CPs colloidal nanoparticles. These ultrafine nanoparticles with stably chelated metal ions are highly water dispersible and thus advantageous for bioimaging. As an example, ultra-small Gd contained CPs exhibit higher longitudinal relaxivity (r1 = 25.5 L mmol-1 s-1) value with low r2/r1 (1.19) than clinically used Magnevist (Gd-DTPA, r1 = 3.7 L mmol-1 s-1). Due to the enhanced permeability and retention effect, they can be further used as a positive contrast agent for T1-weighted MR imaging of tumour.
The P2-type manganese-based Na0.7MnO2 cathode materials attract great interest due to their high theoretical capacity. However, these materials suffer from rapid capacity fading, poor rate performance and severe voltage decay resulting from phase transition and sluggish reaction kinetics. In this work we report a novel Nb-doped Na0.7[Ni0.3Co0.1Mn0.6]1-xNbxO2 with significantly suppressed voltage decay and enhanced cycling stability. The strong Nb-O bond can efficiently stabilize the TMO framework, and the as prepared material demonstrates much lower discharge midpoint voltage decay (0.132 V) than that of pristine one (0.319 V) after 200 cycles. Consequently, a remarkably improved cycling performance with a capacity retention of 87.9% after 200 cycle at 0.5 C is achieved, showing a 2.4 fold improvement as compared to the control sample Na0.7Ni0.3Co0.1Mn0.6O2 (~37% rotation). Even at 2 C, a capacity retention of 68.4% is retained after 500 cycles. Remarkably, the as prepared material can be applied at low temperature of −20 ℃, showing a capacity retention of 81% as compared to that at room temperature.
The series of heterodinuclear metal oxide carbonyls in the form of TaNiO(CO) n- (n = 5–8) are generated in the pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy. During the consecutive CO adsorption, the μ2-O-bent structure initially is the most favorable for TaNiO(CO)5-, and subsequently both μ2-O-bent and μ2-O-linear structures are degenerate for TaNiO(CO)6-, then the μ2-O-linear structure is most preferential for TaNiO(CO)7-, and finally the η2-CO2-tagged structure is the most energetically competitive one for TaNiO(CO)8-, i.e., the CO oxidation occurs at n = 8. In contrast to the literature reported CO oxidation on heteronuclear metal oxide complexes generally proceeding via Langmuir–Hinshelwood-like mechanism, complementary theoretical calculations suggest that both Langmuir–Hinshelwood-like and Eley–Rideal-like mechanisms prevail for the CO oxidation reaction on TaNiO(CO)8- complex. Our findings provide new insight into the composition-selective mechanism of CO oxidation on heteronuclear metal complexes, of which the composition be tailored to fulfill the desired chemical behaviors.
Long-emission carbon dots (CDs) is triggering immense enthusiasm on account of their intrinsic merits of high chemical stability and excellent optical properties. In this study, a facile and rapid approach was developed for the preparation of barium-doped carbon dots (Ba-CDs) with yellow fluorescence emission and high quantum yields. Surface chemistry and the chemical architecture of the Ba-CDs was revealed under various spectroscopic methods. This work provides more insights into the effects of charge transfer caused by Ba heteroatoms, which is considered as the most challenging step in the investigation on luminescence mechanism. Remarkably, the prepared Ba-CDs were successfully applied as fluorescent probes in the detection of trace water in organic solvents (ethanol, isopropanol, acetone, tetrahydrofuran). Comparing with traditional fluorescent probes for water detection in organic solvents, Ba-CDs detection provides a more sensitive, much faster and more economical approach.
The design of pore structure is the key factor for the performance of porous carbon spheres. In this work, novel micron-sized colloidal crystal microspheres consisting of fibrous silica (F-SiO2) nanoparticles are firstly prepared by water-evaporation-induced self-assembly of F-SiO2 nanoparticles in the droplets of an inverse emulsion system to be used as sacrificial templates. Acrylonitrile (AN) was infiltrated in the voids of the F-SiO2 colloidal crystal microspheres, and in-situ induced by 60Co γ-ray to polymerize into polyacrylonitrile (PAN). After the PAN-infiltrated F-SiO2 colloidal crystal microspheres were carbonized and etched with HF solution, novel micron-sized inverse-opal N-doped carbon (IO-NC) microspheres consisting of hollow carbon nanoparticles with a hierarchical macro/meso-porous inner surface were obtained. The IO-NC microspheres have a specific surface area as high as 266.4 m2/g and a molar ratio of C/N of 5. They have a good dispersibility in water, and show a high adsorption capacity towards rhodamine B (RhB) up to 137.28 mg/(g microsphere). This work offers a way to obtain novel micron-sized hierarchical macro/meso-porous N-doped carbon microspheres, which opens a new idea to prepare high-performance hierarchical porous carbon materials.
Specific topographic Ni anchoring on reduced graphene oxide (rGO) composites show an astronomical potential as effective wave absorbers due to the synergistic electromagnetic loss effects. Herein, Ni/rGO composites with different topography were successfully prepared via hydrothermal in-situ reduction method. The structure and morphology characteristics revealed that particle-like, chain-like, coin-like and flower-like Ni were closely anchored onto rGO, respectively. The electromagnetic wave absorption (EMA) performance revealed that chain-like Ni/rGO exhibited the optimal reflection loss of -43.7 dB with a thickness of 1.8 mm as well as the EAB of 6.1 GHz at 2.0 mm among all samples due to the good impedance match and the synergistic dielectric and magnetic losses. Besides, one conclusion can be drawn that excellent magnetic coupling effect and impedance matching were the main reasons for significantly improving the EMA performance. Considering the systematic dependence of morphology on EMA, this work provides a perspective for designing high-performance absorbing materials.
A novel kind of fully bio-based PSAs were obtained through the curing reaction between two components derived from the plant oils: carboxyl-terminated polyricinoleate (PRA) from the castor oil and epoxidized soybean oil (ESO). The gel content, glass transition temperature (Tg), rheological behavior, tensile strength, creep resistance and 180° peel strength of the PSAs were feasibly tailored by adjusting the component ratio of ESO to PRA. At low cross-linking level, the PSAs behaved like a viscous liquid and did not possess enough cohesiveness to sustain the mechanical stress during peeling. The PSAs cross-linked at or near the optimal stoichiometric conditions displayed an adhesive (interfacial) failure between the substrate and the adhesive layer, which were associated with the lowest adhesion levels. The PSAs with the dosage amount of ESO ranging from 10~20 wt% were tacky and flexible, which exhibited 180° peel strength ranging from 0.4~2.3 N/cm; and could be easily removed without any residues on the adherend. The process for the preparation of the fully bio-based PSAs was environmentally friendly without using any organic solvent or other toxic chemical, herein showing the great potential as sustainable materials.
Ion diffusion kinetics, depending on the size, tortuosity, connectivity of the channels, greatly affects the rate performance of the electrodes. Two-dimensional materials (2DMs) has emerged as promising electrode materials in the past decades. However, the applications of 2DMs electrodes are limited by the strong restacking problem, which leads to a poor rate capability. In this work, we for the first time mediated the morphology of molybdenum disulfide (MoS2) nanosheets via a facile coagulation method; abundant sheet crumples were induced, which greatly enhance their surface accessibility and thus benefit the ion diffusion kinetics. Consequently, the crumpled-MoS2 electrodes follow a capacitive Na-ion charge-storage mechanism to a large extent. Importantly, we demonstrate the special role of organic cations in the inter-sheet assembly configuration, in sharp contrast with that of alkali/alkaline-earth ones. We propose that organic cations cause edge/face contact of the sheets, instead of the face/face contact, thus affording a house-of-cards structure.
Fe-based phosphates with excellent physical and chemical features are potential electrode materials for supercapacitors. In this work, we successfully synthesized Fe-based phosphates with different dimensions, morphologies, and compositions by one-step hydrothermal method. Influence factors on the chemical composition and morphology of the as-prepared materials were explored and the energy storage performance of the as-prepared samples were tested under the traditional three electrode system. Two-dimensional (2D) iron metaphosphate (Fe(PO3)3) showed the best electrochemical performance. For Fe(PO3)3 electrode materials, the layered structure can provide a larger specific surface area than the bulk structure, which is conducive to the diffusion and transport of electrolyte ions during charging-discharging and further improves the rate performance and cycle stability of supercapacitor. 2D Fe(PO3)3 and activated carbon were used as electrode materials to construct a 2D Fe(PO3)3//AC supercapacitor. The supercapacitor showed high energy density, high power density, and excellent cycling stability, which indicates 2D Fe(PO3)3 is a promising electrode material for supercapacitors.
Lithium polymer batteries (LPBs) rely on a high ion transport to gain improved cell performance. Thermostable and porous gel polymer electrolytes (GPEs) have attracted much attention due to their excellent properties in electrolyte wettability and ionic conductivity. In this work, iron-nickel-cobalt trimetal Prussian blue analogue (PBA) nanocubes are filled into the electrospun polyacrylonitrile (PAN)-based membranes to generate GPE composites with morphological superiority consisting of fine fibers and interconnected pores. The thus obtained PBA@PAN fibrous membrane showcases good thermal stability, high porosity and electrolyte uptake, as well as a peak ionic conductivity of 2.7 mS/cm with the addition of 10% PBA. Consequently, the assembled lithium iron phosphate (LiFePO4) battery using PBA@PAN-10 as the GPE delivers a high capacity of 152.2 mAh/g at 0.2 C and an ultralow capacity decay of 0.09% per cycle in a long-term cycle life of 350 cycles at 1 C, endorsing its promising applications in LPBs.
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