Dimensional Gradient Structure of CoSe2@CNTs-MXene Anode Assisted by Ether for High-Capacity, Stable Sodium Storage.

Recently, abundant resources, low-cost sodium-ion batteries are deemed to the new-generation battery in the field of large-scale energy storage. Nevertheless, poor active reaction dynamics, dissolution of intermediates and electrolyte matching problems are significant challenges that need to be solved. Herein, dimensional gradient structure of sheet-tube-dots is constructed with CoSe2@CNTs-MXene. Gradient structure is conducive to fast migration of electrons and ions with the association of ether electrolyte. For half-cell, CoSe2@CNTs-MXene exhibits high initial coulomb efficiency (81.7%) and excellent cycling performance (400 mAh g-1 cycling for 200 times in 2 A g-1). Phase transformation pathway from crystalline CoSe2-Na2Se with Co and then amorphous CoSe2 in the discharge/charge process is also explored by in situ X-ray diffraction. Density functional theory study discloses the CoSe2@CNTs-MXene in ether electrolyte system which contributes to stable sodium storage performance owing to the strong adsorption force from hierarchical structure and weak interaction between electrolyte and electrode interface. For full cell, CoSe2@CNTs-MXene//Na3V2 (PO4)3/C full battery can also afford a competitively reversible capacity of 280 mAh g-1 over 50 cycles. Concisely, profiting from dimensional gradient structure and matched electrolyte of CoSe2@CNTs-MXene hold great application potential for stable sodium storage.

Interface Engineering of a Sandwich Flexible Electrode PAn@CoHCF Rooted in Carbon Cloth for Enhanced Sodium-Ion Storage.

With the growth of demand for flexible devices, the development of flexible electrodes used in energy storage devices has attracted much attention of researchers. In this work, a thin flexible cathode of Prussian blue analogue@polyaniline rooted in carbon cloth has been fabricated. The Prussian blue analogue (PBA) is an electrochemically active material grafted on flexible carbon cloth substrates, which had been precoated with polyaniline. Polyaniline as an intermediate layer can not only improve the overall electronic conductivity of the electrode but also enhance the adhesion and load of the PBAs. The electrochemical properties of the flexible cathode with a "sandwich" structure were determined in half-cells, with a superior capacity of 151 mA h·g-1 and a striking cyclability with 96% capacity retention over 100 cycles at 100 mA h·g-1. This work proposes a novel perspective for the structural construction and material synthesis of flexible positive electrodes and gives new options for the practical application of flexible batteries.

A Ni-doping-induced phase transition and electron evolution in cobalt hexacyanoferrate as a stable cathode for sodium-ion batteries.

Prussian blue analogues are potential competitive energy storage materials due to their diverse metal combinations and wide three-dimensional ion channels. Here, we prepared a new highly crystalline monoclinic nickel-doped cobalt hexacyanoferrate via a feasible and simple one-step co-precipitation method. In the process of sodium-ion de-intercalation, three stable charge and discharge platforms, which are consistent with the cyclic voltammetry performance, are seen for the first time, showing the function of nickel ions in Prussian blue. Furthermore, the charge transfer and structural evolution caused by the transmission of sodium ions were well revealed via ex situ XRD, ex situ XPS, and in situ EIS studies. Simulation calculations are performed relating to the energy band structure and the highest-occupied bonding orbitals of the system in different charge states, revealing the charge and discharge mechanism of the nickel-doped material and the reason for the emergence of the new platform at low voltages. In addition, NaNi0.17Co0.83Fe(CN)6 also delivers a striking capacity of 146 mA h g-1 and superior cyclability, with 93% capacity retention over 100 cycles; it can be considered as a promising alternative cathode material for use in sodium-ion batteries.

Highly efficient and blue-emitting CsPbBr3 quantum dots synthesized by two-step supersaturated recrystallization.

Highly efficient and blue-emitting CsPbBr3 quantum dots were successfully synthesized by two-step supersaturated recrystallization under ambient condition. This method could control the particle size within 2.8 nm, thus resulting in strong quantum confinement effect of the products. The as-synthesized CsPbBr3 quantum dots presented outstanding optical properties with highest photo-luminescence quantum yield of 87.20% and longest PL lifetime of 12.24 ns. The blue light-emitting diode made from the CsPbBr3 quantum dots exhibited a CIE coordinate (0.14, 0.10), in good agreement with the standard blue CIE coordinate (0.14, 0.08) of National Television System Committee (NTSC).

Pulsed laser assisted synthesis of gadolinium carbide/carbon shell dots with enhanced magnetic resonance properties.

There is now the opportunity for nanomaterials to be utilized in bioapplications with low toxicity, good stability and fine dissolvability. Herein, we present a pulsed laser assisted carbon coating method for nanocrystals, and gadolinium carbide/carbon shell (GC/CS) dots with a face-centered cubic structured gadolinium carbide core that have been synthesized in toluene. Good stability of the GC/CS dots was observed, not only in ethanol but also in the immunoconjugates. The MTT assay revealed immunoconjugates with non/low cytotoxicities. As a type of paramagnetic species, the GC/CS dots revealed excellent enhancement in magnetic resonance imaging at a high magnetic field of 14.1 T at ultra-low concentrations. In terms of the relaxivity values of the 1-3 nm GC/CS sample, both [Formula: see text] and [Formula: see text] have been dramatically increased to 86.5 mM-1 s-1 and 107.3 mM-1 s-1, respectively, thereby demonstrating the great potential for GC/CS dots to be utilized as advanced magnetic resonance agents for the diagnosis of cancers.

N-doped carbon dots from phenol derivatives for excellent colour rendering WLEDs.

To achieve competitive fluorescence carbon dots (CDs), studies on regulating fluorescence of CDs under controlled, comparable conditions are in great demand. Herein, by changing the functional groups and nitrogenous existence forms in the precursors, three efficient yellow-green emissive N-doped CDs which have the same fluorescence peak wavelength but different photoluminescence quantum yields were realized through a facile hydrothermal method. The as-prepared CDs exhibit not only excited-independent emissions but also similar surface states. The best-performing CDs among the three products exhibits photoluminescence quantum yields of up to 24.4% in water and 53.3% in ethanol, abundant surface functional groups and its high N-doping degree would be the reason for its excellent performances. By washing and reduction processes, the emission evolution of the CDs was studied linking the changes of surface states. The fluorescence can certainly be attributed to the surface of the carbon dots, and the surface states control the photoluminescence features. Serving as a yellow-green colour conversion layer, the best CDs in the three products was used to fabricate a white light-emitting diode. The white light-emitting diode shows an excellent colour rendering index up to 93.3, suggesting broad application prospects of the CDs in lighting and display fields.

Ammonium hydroxide modulated synthesis of high-quality fluorescent carbon dots for white LEDs with excellent color rendering properties.

A novel type of aqueous fluorescent carbon dot (CD) was synthesized using citric acid as the only carbon source via an ammonium hydroxide modulated method, providing a blue color gamut. The amino group is considered to be the key factor in the high fluorescence of CDs and a model is established to investigate the mechanism of fluorescence. In addition, white light-emitting diodes (WLEDs) are fabricated by utilizing the prepared CDs and rare earth luminescent materials (SrSi2O2N2:Eu and Sr2Si5N8:Eu) as color conversion layers and UV-LED chips as the excitation light source. The WLEDs produce bright white light with attractive color rendering properties including a color rendering index of up to 95.1, a CIE coordinate of (0.33, 0.37), and a T c of 5447 K under a 100 mA driven current, indicating that the CDs are promising in the field of optoelectronic devices.

Oriented assembly of Fe3O4 nanoparticles into monodisperse hollow single-crystal microspheres.

Magnetite nanoparticles of Fe3O4 were found to assemble into monodisperse hollow Fe3O4 microspheres with tunable diameters ranging from 200 to 400 nm and open pores on the shells in ethylene glycol in the presence of dodecylamine (DDA). The oriented assembly of nanoparticles conferred the individual hollow Fe3O4 microspheres a remarkable feature of single crystals. The morphologies of the products could be easily manipulated by varying the synthesis parameters. Increasing the concentration of DDA led to an obvious shape evolution of the products from rhombic nanoparticles to hollow microspheres, solid microspheres, and finally irregular nanoparticles, which were mainly attributed to the special self-assembly phenomenon of Fe3O4 nanoparticles in the solvothermal process.

Hydrothermal-induced assembly of colloidal silver spheres into various nanoparticles on the basis of HTAB-modified silver mirror reaction.

Small colloidal silver spheres (diameter < 10 nm) were found to assemble into various silver nanoparticles including cubes, triangles, wires, and rods in water in the presence of HTAB (n-hexadecyltrimethylammonium bromide) at 120 degrees C, while the colloids were generated in situ on the basis of a HTAB-modified silver mirror reaction during the synthesis process. Adjustment of the synthesis parameters, in particular the concentrations of HTAB and [Ag(NH3)2]+, led to an obvious shape evolution of silver nanoparticles, thus resulting in the shape-selective formation of the silver nanoparticles. The monodisperse nanocubes with a well-defined crystallographical structure (a single crystal bounded by six {200} facets) have a strong tendency to assemble into two-dimensional arrays on substrates. The nanowires with uniform diameter usually existed in the form of two-dimensional alignments. The findings suggested that hydrothermal-induced assembly of small silver colloidal particles should be a convenient and effective approach to the preparation of various silver nanoparticles.

Controlled synthesis of monodisperse silver nanocubes in water.

Monodisperse silver nanocubes with edge length of 55 +/- 5 nm were, for the first time, synthesized in water on the basis of HTAB-modified silver mirror reaction at 120 degrees C (HTAB, n-hexadecyltrimethylammonium bromide). The individual nanocube was crystallographically well defined with a single crystal bonded by six {200} facets. The nanocubes were soluble to form stable aqueous solutions and had a strong tendency to assemble into two-dimensional arrays with regular checked pattern on substrate.

Seed-mediated growth approach to shape-controlled synthesis of Cu2O particles.

With glucose as reducing agent, Cu2O particles with different size and morphology were synthesized selectively by a seed-mediated growth approach. The major advantage of this process is that Cu(II) cannot be reduced to Cu metal. The size of the Cu2O particles can be controlled by changing the Cu(II) concentration in colloid solution. Square-shaped Cu2O particles (20-700 nm in diameter) were obtained in the presence of PEG 400, and polygonal-shaped Cu2O particles (approximately 1000 nm) were observed upon using triblock copolymer as modifier, while sphere-shaped Cu2O particles with a diameter of 400-700 nm were obtained in the absence of a modifier.