Tailored Single-Walled Carbon Nanotube−CdS Nanoparticle Hybrids for Tunable Optoelectronic Devices

The integration of organic and inorganic building blocks into novel nanohybrids is an important tool to exploit innovative materials with desirable functionalities. For this purpose, carbon nanotube−nanoparticle nanoarchitectures are intensively studied. We report here an efficient noncovalent chemical route to density-controllably and uniformly assemble single-walled carbon nanotubes with CdS nanoparticles. The methodology not only promises the resulting hybrids will be solution-processable but also endows the hybrids with distinct optoelectronic properties including tunable photoresponse mediated by amine molecules. On the basis of these merits, reliable thin-film photoswitches and light-driven chemical sensors are demonstrated, which highlights the potential of tailored hybrids in the development of new tunable optoelectronic devices and sensors

The formation mechanism and morphology of the nickel particles by the ultrasound-aided spark discharge in different liquid media

Spark discharge is widely applied in the fabrication process of the particles with very small sizes. The ultrasound-aided spark discharge process is based on the electrical discharge in the liquid media of the electrical discharge machining (EDM). In this paper, the morphology, element composition, and crystal structure of the Nickle particles produced by the ultrasound-aided spark discharge were observed and analyzed by SEM, EDS and XRD respectively. The EDS and XRD indicated that the purity of the nickel particles generated in pure water is higher than that in kerosene. Meanwhile the effects of dielectric media on the size distribution were also investigated. It was found that the size distribution of the particles in pure water is narrower than that in kerosene, but when the ultrasound was introduced into the generating process, the size distributions of the particles in both media have remarkable improvements (both became narrower). Based on the attaching and entrapping processes, the formation mechanism of different structural particles was also presented. Following the study on the changes of the effective densities and the ratios of the closed hollow particles in different experiments (with and without ultrasound), we found that, with the aid of ultrasound, the ratio of the closed hollow particles increased about 10–15%. In overall, the results in this paper provide a foundation for the some future research, such as the study on the control of the particle properties (in size and morphology) by improving the experimental conditions

Intrinsic Line Shape of the Raman 2D-Mode in Freestanding Graphene Monolayers

We report a comprehensive study of the two-phonon intervalley (2D) Raman mode in graphene monolayers, motivated by recent reports of asymmetric 2D-mode line shapes in freestanding graphene. For photon energies in the range 1.53–2.71 eV, the 2D-mode Raman response of freestanding samples appears as bimodal, in stark contrast with the Lorentzian approximation that is commonly used for supported monolayers. The transition between the freestanding and supported cases is mimicked by electrostatically doping freestanding graphene at carrier densities above 2 × 1011 cm–2. This result quantitatively demonstrates that low levels of charging can obscure the intrinsically bimodal 2D-mode line shape of monolayer graphene. In pristine freestanding graphene, we observe a broadening of the 2D-mode feature with decreasing photon energy that cannot be rationalized using a simple one-dimensional model based on resonant inner and outer processes. This indicates that phonon wavevectors away from the high-symmetry lines of the Brillouin zone must contribute to the 2D-mode, so that a full two-dimensional calculation is required to properly describe multiphonon-resonant Raman processes

A Magnetism-Assisted Chemical Vapor Deposition Method To Produce Branched or Iron-Encapsulated Carbon Nanotubes

A magnetism-assisted chemical vapor deposition method was developed to synthesize branched or iron-encapsulated carbon nanotubes. In the process, the external magnetic field can promote the coalescence or division of the catalyst particles, causing the formation of branched or encapsulated nanostructures. This finding will extend the understanding of the chemical vapor deposition method in a magnetic field and promote the applications of branched or encapsulated nanostructures

Nanofibers with an Adjustable Core-Sheath Structure Constructed from Hyperbranched Polyester for Efficient Loading of ZnO Nanoparticles

Loading nanoparticles is a valuable way to construct functional fiber materials, yet the lack of homogeneity and easy agglomeration hinder its functional effect. Hyper-branched polyester (HBPE) has been identified as the ideal delivery vehicle for nanoparticles. Its application in nanofibers can be a promising approach to enhancing the loading efficiency. In this study, adjustable core-sheath structured polyacrylonitrile (PAN)/HBPE nanofibers were fabricated owing to the phase separation of two components during centrifugal spinning, and zinc oxide nanoparticles (ZnO NPs) were further introduced into the sheath. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, and so forth were utilized to characterize the morphology of the obtained nanofibers. Results indicated that the thickness of sheath in PAN/HBPE nanofibers could expand from 33.33 to 57.14% as the mass ratio of PAN/HBPE decreased from 8:2 to 5:5. Additionally, the ZnO NPs were encapsulated and dispersed by HBPE and successfully delivered to the sheath layer of the nanofibers. Therefore, the Zn content on the surface of PAN/HBPE/ZnO NP nanofibers can reach 17.86 wt % with only 6 wt % ZnO NPs doped, representing a 90% increase compared with HBPE-free nanofibers. Besides, the PAN/HBPE/ZnO NP nanofibers exhibited excellent air permeability and qualified biocompatibility, as well as outstanding functional release. The antibacterial rates against Escherichia coli and Staphylococcus aureus reached 96.62 ± 0.34 and 99.55 ± 0.78%, respectively. This facile processing strategy subtly combines the advantages of material and structure, providing insights to better achieve efficient loading of nanoparticles on nanofibers, enabling more researchers to customize functional materials

A New Method to Synthesize Complicated Multibranched Carbon Nanotubes with Controlled Architecture and Composition

Here we develop a simple method by using flow fluctuation to synthesize arrays of multibranched carbon nanotubes (CNTs) that are far more complex than those previously reported. The architectures and compositions can be well controlled, thus avoiding any template or additive. A branching mechanism of fluctuation-promoted coalescence of catalyst particles is proposed. This finding will provide a hopeful approach to the goal of CNT-based integrated circuits and be valuable for applying branched junctions in nanoelectronics and producing branched junctions of other materials

Scalable Fabrication of Carbon-Networked Size-Tunable V₂O₃ for Lithium Storage

Vanadium sesquioxide (V2O3) is a promising electrode material for lithium-ion batteries and beyond, yet it encounters structural and cyclic instability issues. Although advances have been made with diverse material combination prototypes, the capacity or role of V2O3 is complicated, limiting rational design and performance enhancement. Herein, we demonstrate a simple, scalable intercalation and annealing strategy for synthesizing carbon-knitted V2O3, impressively in a V2O3 size-tunable manner. While holding similar morphology, composition, and pore structure, the hybrid with ∼3 nm V2O3 delivers stable cycling simultaneously with greatly improved capacity (∼450 mAh g–1) and initial Coulombic efficiency (∼87%) compared with its counterparts. This enhancement is verified by correlating it to the change in capacitive contribution. The study provides a smart and tailorable material model for understanding the lithium storage behavior of V2O3 and opens an avenue to combinedly improve stability, capacity, and initial Coulombic efficiency of V2O3 and other high-capacity intercalatable electrode materials

Intertwined Network of Si/C Nanocables and Carbon Nanotubes as Lithium-Ion Battery Anodes

We demonstrate a new kind of Si-based anode architectures consisting of silicon nanowire/overlapped graphene sheet core–sheath nanocables (SiNW@G) intertwined with carbon nanotubes (CNTs). In such a hybrid structure, the CNTs, mechanically binding SiNW@G nanocables together, act as a buffer matrix to accommodate the volume change of SiNW@G, and overlapped graphene sheets (that is, G sheaths) effectively prevent the direct contact of silicon with the electrolyte during cycling, both of which enable the structural integrity and interfacial stabilization of such hybrid electrodes. Furthermore, the one-dimensional nature of both components affords the creation of a three-dimensional interpenetrating network of lithium ion and electron pathways in the resultant hybrids, thereby enabling efficient transport of both electrons and lithium ions upon charging/discharging. As a result, the hybrids exhibit much-improved lithium storage performance

Basic static parameters of marble.

To study the effects that the perennial freeze–thaw environment exerts on the dynamic mechanical properties of marble, which characterizes the Qinghai-Tibet Plateau, impact tests were conducted, and saturated marble was utilized; thus, we analyzed the effect of different loading rates on its dynamic compressive strength, fragmentation pattern, and energy-absorbing density. The results indicate the following: (1) When 42.02s-1 ≤≤ 49.20s-1, the degree of fragmentation and the fractal dimension of saturated state marble is greater than that of the dry state marble; when -1 or >49.20s-1, the dry state marble exhibits greater fragmentation than the saturated marble; (2) When the saturated state marble is subjected to a specific fractal dimension, the energy-absorbing density of the marble that characterizes the saturated state is great compared with the dry state, and when the fractal dimension increases, the energy-absorbing densities that characterize the two states gradually converge. (3) The effect of water on the mechanical properties of marble has an obvious rate dependence, showing a weakening effect at low strain rates and a strengthening effect at high strain rates. In regard to the analysis pertaining to the dynamic fracture mechanism of marble under the influence of the freeze-thaw environment that characterizes the plateau, the aforementioned experimental results exhibit considerable significance.</div