Facile fabrication of well-aligned Li4Ti5O12 (LTO) nanosheet arrays grown directly on conductive Ti foil was achieved by hydrothermal growth in LiOH solution. The reaction between Ti foil and LiOH led to the growth of vertically aligned, rectangular lithium titanate oxide hydrate (H-LTO) nanosheet arrays, which could be converted into LTO nanosheet arrays through topotactic transformation via thermal decomposition. An appropriate LiOH concentration was essential for the formation of densely aligned H-LTO nanosheet arrays on the substrate. It was proposed that the formation of the H-LTO nanosheet arrays was through kinetics-controlled growth during the hydrothermal metal corrosion process. When used as a binder-free anode for LIBs, the self-supported LTO nanosheet arrays standing on Ti foil exhibited an excellent rate capability (a reversible capacity of 163 mA h g−1 and 78 mA h g−1 at 20 C and 200 C, respectively) and an outstanding cycling performance (a capacity retention of 124 mA h g−1 after 3000 cycles at 50 C). Furthermore, a flexible lithium ion battery, which could be fully recharged within 30 s and was able to light an LED, was assembled by using the LTO nanosheet arrays as the anode.
Controlled synthesis of Au nanoparticles with adjustable sizes (10−50 nm) and narrow size distributions (<10% in standard deviation) was realized by reducing hydrochloroauric acid with α-cyclodextrin (α-CD) in an alkaline aqueous solution, which was very simple and "green". It was revealed that a proper pH was essential to the formation of stable dispersions of nonaggregated Au nanoparticles and a higher pH would lead to the welding of the Au nanoparticles into one-dimensional (1D) wires or three-dimensional (3D) aggregates. Moreover, 1D assembly of α-CD-capped Au nanoparticles into nanochains was readily induced by partial removal of the organic stabilization shell, which resulted from the host−guest interactions between α-CDs capped on Au nanoparticle surfaces and toluene molecules. Finally, the as-prepared Au nanoparticles were found to serve as effective catalyst to activate the reduction of 4-nitrophenol in the presence of NaBH4, and the application of the assembled Au nanoparticle thin film as a substrate for surface-enhanced Raman scattering (SERS) was also demonstrated.
A condensed benzothiophene peripherally carrying rich sulfur atoms favoring π−π stacking is developed through facile approaches. The 1H NMR and the absorption spectra strongly indicate that this molecule easily forms the self-assembled structures in solutions. Microwires directly precipitate from solution, and such 1D self-assembled nano- and microstructures can be controlled and tuned by changing solvents and casting on various substrates. Single microwire transistor based on such condensed benzothiophene is easily fabricated through solution process with carrier mobility as high as 0.01 cm2 V-1 s-1.
Uniform PbS–Au nanostar–nanoparticle heterodimers consisting of one Au nanoparticle grown on one horn of a well-defined six-horn PbS nanostar were prepared using the PbS nanostars as growth substrates for the selective deposition of Au nanoparticles. The size of the Au nanoparticles on the horns of the PbS nanostars could be readily adjusted by changing the PbS concentration for the deposition of Au nanoparticles. An optimum cetyltrimethylammonium bromide concentration and temperature were essential for the selective deposition of uniform Au nanoparticles on single horns of the PbS nanostars. Unusual PbS–Au nanoframe–nanoparticle heterodimers were obtained by etching the PbS–Au nanostar–nanoparticle heterodimers with oxalic acid while novel cap-like Au nanoparticles were obtained by etching with hydrochloric acid. The obtained heterodimeric nanostructures and cap-like nanoparticles are promising candidates for anisotropic nanoscale building blocks for the controllable assembly of useful, complex architectures.
Novel silver nanowire thin films, which consist of interwoven bundles of single-crystalline silver nanowires about 30−40 nm in diameter, have been successfully synthesized on glass wall by mild chemical reduction in aqueous solutions of poly(methacrylic acid) at room temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and UV−vis absorption spectroscopy have been used to characterize the obtained silver products. It was found that there existed a competition between precipitation of spherical particles, precipitation of individual nanowires, and formation of silver nanowire films. It was revealed that the negatively charged glass surface provided heterogeneous nucleation sites for the growth of bundles of silver nanowires. Appropriate pH values and polymer concentrations were crucial for the growth of dense silver nanowire films on the glass wall. A polymer-mediated heterogeneous nucleation and growth process has been proposed for the formation of the unique metal nanowire thin films.
Controllable self-assembly of uniform star-shaped PbS nanocrystals with six symmetric ⟨100⟩-oriented horns into highly ordered structures including close-packed arrays and patterned arrays was realized by evaporation-induced assembly routes. First, large-area three-dimensional (3D) and two-dimensional (2D) hexagonal close-packed (hcp) arrays of PbS nanostars were assembled on clean Si substrate by drop coating and vertical deposition, respectively. Then, by using monolayer colloidal crystals (MCC) and inverted MCC (IMCC) as the template, a variety of non-close-packed (ncp) arrays of PbS nanostars with controllable patterns were fabricated through the vertical deposition method. With the MCC template, an ncp array of [111]-oriented PbS nanostars with three horns stably standing on the template plane was prepared, leading to the formation of novel star−sphere binary colloidal crystals with a stoichiometric star/sphere ratio of 1. The reflectance spectrum of the resultant MCC−PbS composite array was measured, which exhibited a considerable red shift in the reflectance peak compared with the original MCC template. Alternatively, with the IMCC template, an ncp array of [001]-oriented PbS nanostars with a single horn stretched vertically upward was obtained. Furthermore, some novel patterns for PbS ncp arrays were readily fabricated using MCC/IMCC templates with larger periodic spacings. For the template-assisted assembly of PbS nanostars, the obtained PbS ncp arrays generally inherited the long-range hexagonal order from the initial MCC template. This assembly strategy is a versatile approach and may open a new route for the controlled assembly of anisotropic nanostructured materials into large-scale ordered arrays with desirable patterns.
Hierarchical, core−shell structured microspheres of bismuth chalcogenides (Bi2E3, E = S, Se, Te) have been synthesized by chemical transformation of reactive precursor templates, which involves the formation of intermediate BiOCl mircrospheres and their subsequent hydrothermal transformation into Bi2E3 core−shell microspheres. The uniform precursor microspheres consisting of BiOCl nanoplates were obtained by the hydrolysis of BiCl3 under the direction of dextran sulfate. It was proposed that the core−shell structured Bi2E3 microspheres were produced by the chemical transformation of the BiOCl microspheres through the microscale Kirkendall effect. It was found that the obtained core−shell Bi2S3 microspheres could electrochemically charge and discharge with a capacity of 110 mA h g−1 at room temperature. Furthermore, the photoresponsive properties of the hierarchical Bi2S3 core−shell microspheres were investigated, which showed better sensitivity than normal Bi2S3 nanorods, probably owing to multiple reflections of light within the sphere interior voids, indicating their potential applications in photodetectors and photoelectronic switches.
In this work, twinned anhydrous guanine β microplatelets were synthesized for the first time in the presence of a polyvinylpyrrolidone. The twinning angle of the two c axes for the synthetic and biogenic twinned guanine crystals is 84°, very similar to each other.
A new method of mass spectra analysis for organic peroxides has been intro duced in this paper.Several organic peroxides have been split at appropr iate conditions by which mass spectr a graph with molecular ion has been ma de.Their molecular splitting rule illustrated in this paper has been discussed an d verified by META' s technique.It provides value reference for analysing easily decomposed org anic peroxides.
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