17 research outputs found
Single‐Crystalline Colloidal Quasi‐2D Tin Telluride
Tin telluride is a narrow‐gap semiconductor with promising properties for infrared (IR) optical applications and topological insulators. A convenient colloidal synthesis of quasi‐2D SnTe nanocrystals through the hot‐injection method in a nonpolar solvent is reported. By introducing the halide alkane 1‐bromotetradecane as well as oleic acid and trioctylphosphine, the thickness of 2D SnTe nanostripes can be tuned down to 30 nm, while the lateral dimensional can reach 6 µm. The obtained SnTe nanostripes are single crystalline with a rock‐salt crystal structure. The absorption spectra demonstrate pronounced absorption features in the IR range revealing the effect of quantum confinement in such structures
Enhanced Gas Sensing Performance of Electrospun Pt-Functionalized NiO Nanotubes with Chemical and Electronic Sensitization
Pt-functionalized
NiO composite nanotubes were synthesized by a simple electrospinning
method, and their morphology, chemistry, and crystal structure have
been characterized at the nanoscale. It was found that the Pt nanoparticles
were dispersed uniformly in the NiO nanotubes, and the Pt-functionalized
NiO composite nanotubes showed some dendritic structure in the body
of nanotubes just like thorns growing in the nanotubes. Compared with
the pristine NiO nanotube based gas sensor and other NiO-based gas
sensors reported previously, the Pt-functionalized NiO composite nanotube
based gas sensor showed substantially enhanced electrical responses
to target gas (methane, hydrogen, acetone, and ethanol), especially
ethanol. The NiO–Pt 0.7% composite nanotube based gas sensor
displayed a response value of 20.85 at 100 ppm at ethanol and 200
°C, whereas the pristine NiO nanotube based gas sensor only showed
a response of 2.06 under the same conditions. Moreover, the Pt-functionalized
NiO composite nanotube based gas sensor demonstrated outstanding gas
selectivity for ethanol against methane, hydrogen, and acetone. The
reason for which the Pt-functionalized NiO composite nanotube based
gas sensor obviously enhanced the gas sensing performance is attributed
to the role of Pt on the chemical sensitization (catalytic oxidation)
of target gases and the electronic sensitization (Fermi-level shifting)
of NiO
Direct observation of dynamical magnetization reversal process governed by shape anisotropy in single NiFe2O4 nanowire
Discovering how the magnetization reversal process is governed by the magnetic anisotropy in magnetic nanomaterials is essential and significant to understand the magnetic behaviour of micro-magnetics and to facilitate the design of magnetic nanostructures for diverse technological applications. In this study, we present a direct observation of a dynamical magnetization reversal process in single NiFe2O4 nanowire, thus clearly revealing the domination of shape anisotropy on its magnetic behaviour. Individual nanoparticles on the NiFe2O4 nanowire appear as single domain states in the remanence state, which is maintained until the magnetic field reaches 200 Oe. The magnetization reversal mechanism of the nanowire is observed to be a curling rotation mode. These observations are further verified by micromagnetic computational simulations. Our findings show that the modulation of shape anisotropy is an efficient way to tune the magnetic behaviours of cubic spinel nano-ferrites
Direct observation of dynamical magnetization reversal process governed by shape anisotropy in single NiFe2O4 nanowire
Discovering how the magnetization reversal process is governed by the magnetic anisotropy in magnetic nanomaterials is essential and significant to understand the magnetic behaviour of micro-magnetics and to facilitate the design of magnetic nanostructures for diverse technological applications. In this study, we present a direct observation of a dynamical magnetization reversal process in single NiFe2O4 nanowire, thus clearly revealing the domination of shape anisotropy on its magnetic behaviour. Individual nanoparticles on the NiFe2O4 nanowire appear as single domain states in the remanence state, which is maintained until the magnetic field reaches 200 Oe. The magnetization reversal mechanism of the nanowire is observed to be a curling rotation mode. These observations are further verified by micromagnetic computational simulations. Our findings show that the modulation of shape anisotropy is an efficient way to tune the magnetic behaviours of cubic spinel nano-ferrites
BaFe<sub>12</sub>O<sub>19</sub> Single-Particle-Chain Nanofibers: Preparation, Characterization, Formation Principle, and Magnetization Reversal Mechanism
BaFe<sub>12</sub>O<sub>19</sub> single-particle-chain nanofibers have been successfully prepared by an electrospinning method and calcination process, and their morphology, chemistry, and crystal structure have been characterized at the nanoscale. It is found that individual BaFe<sub>12</sub>O<sub>19</sub> nanofibers consist of single nanoparticles which are found to stack along the nanofiber axis. The chemical analysis shows that the atomic ratio of Ba/Fe is 1:12, suggesting a BaFe<sub>12</sub>O<sub>19</sub> composition. The crystal structure of the BaFe<sub>12</sub>O<sub>19</sub> single-particle-chain nanofibers is proved to be M-type hexagonal. The single crystallites on each BaFe<sub>12</sub>O<sub>19</sub> single-particle-chain nanofibers have random orientations. A formation mechanism is proposed based on thermogravimetry/differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and transmission electron microscopy (TEM) at six temperatures, 250, 400, 500, 600, 650, and 800 °C. The magnetic measurement of the BaFe<sub>12</sub>O<sub>19</sub> single-particle-chain nanofibers reveals that the coercivity reaches a maximum of 5943 Oe and the saturated magnetization is 71.5 emu/g at room temperature. Theoretical analysis at the micromagnetism level is adapted to describe the magnetic behavior of the BaFe<sub>12</sub>O<sub>19</sub> single-particle-chain nanofibers
Constructed Uninterrupted Charge-Transfer Pathways in Three-Dimensional Micro/Nanointerconnected Carbon-Based Electrodes for High Energy-Density Ultralight Flexible Supercapacitors
A type of freestanding three-dimensional
(3D) micro/nanointerconnected structure, with a conjunction of microsized
3D graphene networks, nanosized 3D carbon nanofiber (CNF) forests,
and consequently loaded MnO<sub>2</sub> nanosheets, has been designed
as the electrodes of an ultralight flexible supercapacitor. The resulting
3D graphene/CNFs/MnO<sub>2</sub> composite networks exhibit remarkable
flexibility and highly mechanical properties due to good and intimate
contacts among them, without current collectors and binders. Simultaneously,
this designed 3D micro/nanointerconnected structure can provide an
uninterrupted double charges freeway network for both electron and
electrolyte ion to minimize electron accumulation and ion-diffusing
resistance, leading to an excellent electrochemical performance. The
ultrahigh specific capacitance of 946 F/g from cyclic voltammetry
(CV) (or 920 F/g from galvanostatic charging/discharging (GCD)) were
obtained, which is superior to that of the present electrode materials
based on 3D graphene/MnO<sub>2</sub> hybrid structure (482 F/g). Furthermore,
we have also investigated the superior electrochemical performances
of an asymmetric supercapacitor device (weight of less than 12 mg/cm<sup>2</sup> and thickness of ∼0.8 mm), showing a total capacitance
of 0.33 F/cm<sup>2</sup> at a window voltage of 1.8 V and a maximum
energy density of 53.4 W h/kg for driving a digital clock for 42 min.
These inspiring performances would make our designed supercapacitors
become one of the most promising candidates for the future flexible
and lightweight energy storage systems
Direct Observation of Magnetocrystalline Anisotropy Tuning Magnetization Configurations in Uniaxial Magnetic Nanomaterials
Discovering
the effect of magnetic anisotropy on the magnetization
configurations of magnetic nanomaterials is essential and significant
for not only enriching the fundamental knowledge of magnetics but
also facilitating the designs of desired magnetic nanostructures for
diverse technological applications, such as data storage devices,
spintronic devices, and magnetic nanosensors. Herein, we present a
direct observation of magnetocrystalline anisotropy tuning magnetization
configurations in uniaxial magnetic nanomaterials with hexagonal structure
by means of three modeled samples. The magnetic configuration in polycrystalline
BaFe<sub>12</sub>O<sub>19</sub> nanoslice is a curling structure,
revealing that the effect of magnetocrystalline anisotropy in uniaxial
magnetic nanomaterials can be broken by forming an amorphous structure
or polycrystalline structure with tiny grains. Both single crystalline
BaFe<sub>12</sub>O<sub>19</sub> nanoslice and individual particles
of single-particle-chain BaFe<sub>12</sub>O<sub>19</sub> nanowire
appear in a single domain state, revealing a dominant role of magnetocrystalline
anisotropy in the magnetization configuration of uniaxial magnetic
nanomaterials. These observations are further verified by micromagnetic
computational simulations