A facile method of synthesizing Fe3O4-Au hybrid nanoparticles is reported utilizing the multifunctional nature of polyethyleneimine (PEI). An abundance of 5 nm
gold nanoparticles were attached to 50 nm Fe3O4 nanoparticles via the covalent binding between the -NH2 groups of the PEI and Au nanoparticles, as well as the electrostatic interaction between the negatively charged citrate-coated
Au nanoparticles and the positively charged PEI-coated Fe3O4 nanoparticles. The as-prepared Fe3O4-Au hybrid nanoparticles, which combine the merits of magnetic materials and gold, were successfully employed for the first
time in the dual-mode detection of carcinoembryonic antigen (CEA) via electrochemical and surface-enhanced Raman scattering
(SERS) methods. Both methods make clever use of Fe3O4-Au nanoparticles and can accurately verify the presence of antigens. In particular, the electrochemical immunosensor detection
displays a wide linear range (0.01–10 ng/mL) of response with a low detection limit (10 pg/mL), while the SERS method responds
to even lower antigen concentrations with a wider detection range. The Fe3O4-Au hybrid nanoparticles therefore exhibit great potential for biomedical applications.
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Magnetically recyclable Au/Co/Fe core-shell nanoparticles (NPs) have been successfully synthesized via a one-step in situ procedure. Transmission electron microscope (TEM), energy dispersive X-ray spectroscopic (EDS), and electron energy-loss
spectroscopic (EELS) measurements revealed that the trimetallic Au/Co/Fe NPs have a triple-layered core-shell structure composed
of a Au core, a Co-rich inter-layer, and a Fe-rich shell. The Au/Co/Fe core-shell NPs exhibit much higher catalytic activities
for hydrolytic dehydrogenation of ammonia borane (NH3BH3, AB) than the monometallic (Au, Co, Fe) or bimetallic (AuCo, AuFe, CoFe) counterparts.
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We have demonstrated the improved performance of oxygen evolution reactions (OER) using Au/nickel phosphide (Ni12P5) core/shell nanoparticles (NPs) under basic conditions. NPs with a Ni12P5 shell and a Au core, both of which have well-defined crystal structures, have been prepared using solution-based synthetic routes. Compared with pure Ni12P5 NPs and Au-Ni12P5 oligomer-like NPs, the core/shell crystalline structure with Au shows an improved OER activity. It affords a current density of 10 mA/cm2 at a small overpotential of 0.34 V, in 1 M KOH aqueous solution at room temperature. This enhanced OER activity may relate to the strong structural and effective electronic coupling between the single-crystal core and the shell.
A novel pure cubic-phase pyrochlore structure tin(II) antimonate nanophotocatalyst, stoichiometric Sn2Sb2O7, has been prepared by a modified ion-exchange process using an antimonic acid precursor, and employed in visible-light-driven photocatalytic H2 evolution for the first time. The physicochemical properties (crystal phase, chemical composition and state, textural properties, and optical properties) of the material were investigated by different instrumental techniques. Compared with the antimonic acid precursor, the as-prepared Sn2Sb2O7 had a narrower bandgap, smaller crystal size, and larger BET surface area. The as-prepared Sn2Sb2O7 was validated as a promising candidate for visible-light-driven photocatalytic H2 evolution with a constant rate of 40.10 μmol·h−1·gcat−1. 相似文献
Uniform colloidal Bi2S3 nanodots and nanorods with different sizes have been prepared in a controllable manner via a hot injection method. X-ray
diffraction (XRD) results show that the resulting nanocrystals have an orthorhombic structure. Both the diameter and length
of the nanorods increase with increasing concentration of the precursors. All of the prepared Bi2S3 nanostructures show high efficiency in the photodegradation of rhodamine B, especially in the case of small sized nanodots—which
is possibly due to their high surface area. The dynamics of the photocatalysis is also discussed.
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Binary transition metal oxides are considered as promising anode materials for lithium-ion batteries (LIB), because they can effectively overcome the drawbacks of simple oxides. Here, a one-step hydrothermal method is described for the synthesis of regular ZnFe2O4 octahedrons about 200 nm in size at a low temperature without further annealing being required. The ZnFe2O4 octahedrons were characterized by powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The electrochemical performance of the ZnFe2O4 octahedrons was examined in terms of cyclic voltammetry and discharge/charge profiles. The ZnFe2O4 octahedrons exhibit a high capacity of 910 mA·h/g at 60 mA/g between 0.01 and 3.0 V after 80 cycles. They also deliver a reversible specific capacity of 730 mA·h/g even after 300 cycles at 1000 mA/g, a much better performance than those in previous reports. A set of reactions involved in the discharge/charge processes are proposed on the basis of ex situ high-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns of the electrode materials. The insights obtained will be of benefit in the design of future anode materials for lithium ion batteries. 相似文献
In-plane symmetry is an important contributor to the physical properties of two-dimensional layered materials, as well as atomically thin heterojunctions. Here, we demonstrate anisotropic/isotropic van der Waals (vdW) heterostructures of ReS2 and MoS2 monolayers, where interlayer coupling interactions and charge separation were observed by in situ Raman-photoluminescence spectroscopy, electrical, and photoelectrical measurements. We believe that these results could be helpful for understanding the fundamental physics of atomically thin vdW heterostructures and creating novel electronic and optoelectronic devices.
The size and density of Ag nanoparticles on n-layer MoS2 exhibit thicknessdependent behavior. The size and density of these particles increased and decreased, respectively, with increasing layer number (n) of n-layer MoS2. Furthermore, the surface-enhanced Raman scattering (SERS) of Ag on this substrate was observed. The enhancement factor of this scattering varied with the thickness of MoS2. The mechanisms governing the aforementioned thickness dependences are proposed and discussed.
Nanomaterials with electrochemical activity are always suffering from aggregations, particularly during the high-temperature synthesis processes, which will lead to decreased energy-storage performance. Here, hierarchically structured lithium titanate/nitrogen-doped porous graphene fiber nanocomposites were synthesized by using confined growth of Li4Ti5O12 (LTO) nanoparticles in nitrogen-doped mesoporous graphene fibers (NPGF). NPGFs with uniform pore structure are used as templates for hosting LTO precursors, followed by high-temperature treatment at 800 °C under argon (Ar). LTO nanoparticles with size of several nanometers are successfully synthesized in the mesopores of NPGFs, forming nanostructured LTO/NPGF composite fibers. As an anode material for lithium-ion batteries, such nanocomposite architecture offers effective electron and ion transport, and robust structure. Such nanocomposites in the electrodes delivered a high reversible capacity (164 mAh·g–1 at 0.3 C), excellent rate capability (102 mAh·g–1 at 10 C), and long cycling stability.
Approximately 15 nm thick nitrogen-doped lanthanum titanate (La2Ti2O7) nanosheets with a single-crystalline perovskite structure have been prepared by hydrothermal processing and subsequent heat
treatment in NH3 at 600 °C. Doping nitrogen into the La2Ti2O7 nanosheets results in the narrowing of the band gap, extending the light absorption into the visible light region (∼495 nm).
The nitrogen-doped La2Ti2O7 nanosheets not only show significant visible light photocatalytic activity toward the decomposition of methyl orange but
also exhibit enhanced the ultraviolet light photocatalytic activity. The enhancement of photocatalytic activity originates
from the narrowing of the band gap of La2Ti2O7 nanosheets. The results obtained show that the desirable route to extend the photocatalytic activity of a semiconductor from
the ultraviolet to the visible light region is to narrow the band gap rather than to create localized mid-gap states.
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Shape control of nanocrystals has become a significant subject in materials science. In this work, we describe a convenient
way to achieve morphology-controllable synthesis of CoO nanocrystals including octahedrons and spheres as well as LiCoO2 polyhedrons and spheres. In particular, we explain the formation of CoO octahedrons exposing only high-energy (111) facets
using theoretical calculations; these should also be a useful tool for directing future face-controlled preparation of other
nanocrystals. More importantly, the as-obtained LiCoO2 nanocrystals showed different electrochemical performance depending on their morphology, indicating that Li-insertion/deintercalation
dynamics might be crystal face-sensitive.
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Novel gold-supporting silicate nanotubes are synthesized via a hydrothermal method followed by colloid deposition. Their catalytic performance for the selective oxidation of ethanol to acetaldehyde is assessed. The results show that Au/CuSiO3 nanotubes exhibit both high activity and selectivity at high gas hourly space velocity (GHSV). Ethanol conversion can reach up to ~98%, and the selectivity for acetaldehyde is ~93% at 250 °C and ~100,000 mL·gcat–1·h–1. In comparison, the catalytic activity of Au/MgSiO3 nanotubes is relatively low, and ethanol conversion reaches only ~25% at 250 °C. However, when Cu species are added to Au/MgSiO3, the catalytic activity improves significantly, indicating that the interactions between Au nanoparticles and Cu species are responsible for the high performance for selective oxidation of ethanol to acetaldehyde.
Polyol synthesis route, which is a popular and effective way of synthesizing noble metal nanocrystals, has been employed for
the fabrication of Cu2O nanospheres. With this method, the particle size of the product can be readily tailored by tuning the concentration of Cu(NO3)2 and/or poly(vinyl pyrrolidone). It has been demonstrated that the main driving force of this reaction is the difference in
redox potentials between ethylene glycol (EG) and NO3−, and not that between those of EG and Cu2+. The resulting Cu2O nanospheres were used as a solid precursor for generating hollow nanospheres of copper sulfide with different sulfiding
degrees, as well as CuO, via suitable chemical conversions. The Kirkendall effect determined the final hollow structure. The
results in this paper provide a good example of the broadening of the scope of application of polyol synthesis route and may
supply a thinking clue for the synthesis of other oxide materials.
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Artificial photosynthesis uses a catalyst to convert CO2 into valuable hydrocarbon products by cleaving the C=O bond. However, this technology is strongly limited by two issues, namely insufficient catalytic efficiency and complicated catalyst-fabrication processes. Herein, we report the development of a novel spray-drying photocatalyst-engineering process that addresses these two issues. Through one-step spray drying, with a residence time of 1.5 s, nanocomposites composed of tin oxide (SnO2) nanoparticles and edge-oxidized graphene oxide (eo-GO) sheets were fabricated without post-treatment. These nanocomposites exhibited 28-fold and five-fold enhancements in photocatalytic efficiency during CO2 reduction compared to SnO2 and commercialized TiO2 (P25), respectively, after irradiation with simulated sunlight for 4 h. This scalable approach, based on short residence times and facile equipment setup, promotes the practical application of artificial photosynthesis through the potential mass production of efficient photocatalysts.
In this study, high-performance multilayer WSe2 field-effect transistor (FET) devices with carrier type control are demonstrated via thickness modulation and a remote oxygen plasma surface treatment. Carrier type control in multilayer WSe2 FET devices with Cr/Au contacts is initially demonstrated by modulating the WSe2 thickness. The carrier type evolves with increasing WSe2 channel thickness, being p-type, ambipolar, and n-type at thicknesses <3, ~4, and >5 nm, respectively. The thickness-dependent carrier type is attributed to changes in the bandgap of WSe2 as a function of the thickness and the carrier band offsets relative to the metal contacts. Furthermore, we present a strong hole carrier doping effect via remote oxygen plasma treatment. It non-degenerately converts n-type characteristics into p-type and enhances field-effect hole mobility by three orders of magnitude. This work demonstrates progress towards the realization of high-performance multilayer WSe2 FETs with carrier type control, potentially extendable to other transition metal dichalcogenides, for future electronic and optoelectronic applications.
We report a method using in situ etching to decouple the axial from the radial nanowire growth pathway, independent of other growth parameters. Thereby a
wide range of growth parameters can be explored to improve the nanowire properties without concern of tapering or excess structural
defects formed during radial growth. We demonstrate the method using etching by HCl during InP nanowire growth. The improved
crystal quality of etched nanowires is indicated by strongly enhanced photoluminescence as compared to reference nanowires
obtained without etching.
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Catalytic hydrogenation is an important process in the chemical industry. Traditional catalysts require the effective cleavage of hydrogen molecules on the metal-catalyst surface, which is difficult to achieve with non-noble metal catalysts. In this work, we report a new hydrogenation method based on water/proton reduction, which is completely different from the catalytic cleavage of hydrogen molecules. Active hydrogen species and photo-generated electrons can be directly applied to the hydrogenation process with Cu1.94S-Zn0.23Cd0.77S semiconductor heterojunction nanorods. Nitrobenzene, with a variety of substituent groups, can be efficiently reduced to the corresponding aniline without the addition of hydrogen gas. This is a novel and direct pathway for hydrogenation using non-noble metal catalysts.
The development of simple techniques for the separation and purification of recombinant proteins plays an important role in many of the advancements made in biotechnology and nanotechnology. Herein, we report an easy method for the efficient purification of polyhistidine affinity-tagged (His-tagged) proteins by using Ni2+-decorated superparamagnetic particles. Monodisperse Ni0.3Fe0.7Fe2O4 nanoparticles were prepared via a facile and economical one-pot hydrothermal process. Owing to the characteristic molecular recognition ability between nickel(II) ions and the polyhistidine affinity tag, the nanoparticles could be successfully employed to selectively bind and separate His-tagged cyan fluorescent protein (CFP) from an E. coli cell lysate in a recyclable process. Moreover, by changing the divalent metal precursors, various other metal-decorated magnetic nanoparticles can be obtained. This approach offers the possibility of constructing metal-decorated nanoparticles through a simple method and will be highly beneficial in further applications of nanoparticle-based technologies. 相似文献
This paper describes the synthesis of new upconverting luminescent nanoparticles that consist of YF3:Yb3+/Er3+ functionalized with poly(acrylic acid) (PAA). Unlike the upconverting nanocrystals previously reported in the literature
that emit visible (blue-green-red) upconversion fluorescence, these as-prepared nanoparticles emit strong near-infrared (NIR,
831 nm) upconversion luminescence under 980 nm excitation. Scanning electron microscopy, transmission electron microscopy,
and powder X-ray diffraction were used to characterize the size and composition of the luminescent nanocrystals. Their average
diameter was about 50 nm. The presence of the PAA coating was confirmed by infrared spectroscopy. The particles are highly
dispersible in aqueous solution due to the presence of carboxylate groups in the PAA coating. By carrying out the synthesis
in the absence of PAA, YF3:Yb3+/Er3+ nanorice materials were obtained. These nanorice particles are larger (∼700 nm in length) than the PAA-functionalized nanoparticles
and show strong typical visible red (668 nm), rather than NIR (831 nm), upconversion fluorescence. The new PAA-coated luminescent
nanoparticles have the pottential be used in a variety of bioanalytical and medical assays involving luminescence detection
and fluorescence imaging, especially in vivo fluorescence imaging, due to the deep penetration of NIR radiation.
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Bismuth telluride (Bi2Te3) is one of the most important commercial thermoelectric materials. In recent years, the discovery of topologically protected surface states in Bi chalcogenides has paved the way for their application in nanoelectronics. Determination of the fracture toughness plays a crucial role for the potential application of topological insulators in flexible electronics and nanoelectromechanical devices. Using depth-sensing nanoindentation tests, we investigated for the first time the fracture toughness of bulk single crystals of Bi2Te3 topological insulators, grown using the Bridgman-Stockbarger method. Our results highlight one of the possible pitfalls of the technology based on topological insulators.