Hierarchical silver nanostructures, consisting of dendritic (symmetric branched) and fractal patterns (randomly ramified), were synthesized very easily by dropping a droplet of AgNO
3-HF solution on ...silicon wafers. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and open circuit potential-time (Ocp-t) measurement demonstrated that the two nanostructures converted with the reaction composition. The structural evolution was tentatively explained with the theory that oriented growth was determined by the anisotropy of the solid–liquid interfacial energy and the oriented attachment-based aggregation mechanism. Results on surface-enhanced Raman scattering (SERS) signals of the silver films with hierarchical nanostructures demonstrate that SERS is sensitive to silver nanostructures.
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Vapor–liquid–solid processing of boron nanowires (BNWs) can be carried out either using a bottom‐up or top‐down growth mode, which results in different contact modes between the nanowire and the ...substrate. The contact mode may strongly affect the electrical transport and field‐emission performance of the individual boron nanowires grown on a Si substrate. The electrical transport and field‐emission characteristics of individual boron nanowires of different contact modes are investigated in situ using a scanning electron microscope. The contact barriers are very distinct for the different contact modes. Moreover, the transition from a “contact‐limited” to a “bulk‐limited” field‐emission (FE) process is demonstrated in nanoemitters for the first time, and the proposed improved metal–insulator–vacuum (MIV) model may better illustrate the nonlinear behavior of the Fowler‐Nordheim (FN) plots in these nanoscale systems. Individual BNWs with different contact modes have a discrepancy in their emission stability and vacuum breakdown characteristics though they have similar aspect ratios, which suggests that their electrical transport and field‐emission performance are closely related to their contact mode. Boron nanowires grown in the base‐up mode have better field‐emission performances and are more beneficial than those grown in the top‐down mode for various device applications.
Growing nanowires from the base up is essential for assuring better device performances. The contact mode between nanostructures and their substrate strongly affects the electrical transport and field‐emission behavior of boron nanowires. The in situ physical properties of individual boron nanowires with different contact modes are elaborated on and nanowires grown from the base up exhibit much better performances than those grown from the top down.
Monodisperse CoPh nanocrystals （NCs） have been synthesized in oleylamine solution by an organic solvothermal method. The NCs were ellipsoidal particles with a diameter around 6.6 nm and length around ...10 nm with a good single crystal structure. Using CoPt3 NCs as catalysts, large-area boron nanowires with diameters ranging from 30 to 50 nm were successfully prepared by chemical vapor deposition using a C/B/B203 mixture as the precursor. Structural analysis indicated that these nanowires were single crystalline with a fl-rhombohedral structure. Measurement of the field emission properties of boron nanowire films showed that the boron nanowires have good field emission characteristics.
Nanomaterials play an important role in modern science and engineering. The ability to fabricate nanomaterials with high quality and low cost is a primary stage for further discovering their ...applications. This research article presents a facile fabrication of Cu
2
O nanowires on Cu substrate. It was found that simply heating Cu in air leads to the growth of Cu
2
O nanowires. The Cu
2
O nanowires are aligned in one direction and vertically grown on the Cu substrate. The growth process of nanowires was tracked by SEM and the root at the initial stage was observed by HRTEM. The access to oxygen is critical to the growth of Cu
2
O nanowires and the patterned nanowire arrays can be readily fabricated by using a mask. The method reported here offers a great potential route toward a large scale manufacture of Cu
2
O nanowires.
How nature uses water molecules to create fascinating patterns ranging from snowflakes to ice cubes has intrigued mankind for centuries. Here we use ZnO to mimic nature's versatility in creating ...microscopic patterns with tunable morphology. During growth of ZnO on Zn-dominant spheres
via
chemical vapor deposition, highly regular and symmetric dendritic snowflake patterns and smooth compact islands can be obtained at different growth conditions. We reproduce the dendritic patterns using atomistic Monte Carlo simulations. These findings not only improve understanding of how water molecules form various patterns, but may also be instrumental in tailoring ZnOnanostructures for desirable functionality.
ZnO patterns grown on the surface of Zn microspheres mimic natural snowflakes well, and the dendritic patterns are reproduced using atomistic Monte Carlo simulations.
Single‐crystalline transition metal films are ideal playing fields for the epitaxial growth of graphene and graphene‐based materials. Graphene–silicon layered structures are successfully constructed ...on Ir(111) thin films on Si substrates with an yttria‐stabilized zirconia buffer layer via intercalation approach. Such heterolayered structures are compatible with the current Si‐based microelectronic technique, showing high promise for applications in future micro‐ and nanoelectronic devices.
Indium selenide (InSe) has a high electron mobility and tunable direct band gap, enabling its potential applications to electronic and optoelectronic devices. Here, we report the fabrication of InSe ...photodetectors with high on/off ratios and ultrahigh photoresponsivity, using ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer films as the top-gate dielectric. Benefiting from the successful suppression of the dark current down to ∼10–14A in the InSe channel by tuning the three different polarization states in ferroelectric P(VDF-TrFE) and improved interface properties using h-BN as a substrate, the ferroelectric-gated InSe photodetectors show a high on/off ratio of over 108, a high photoresponsivity up to 14 250 AW–1, a high detectivity up to 1.63 × 1013 Jones, and a fast response time of 600 μs even at zero-gate voltage. The present results highlight the role of ferroelectric P(VDF-TrFE) in tuning the carrier transport of InSe and may provide an avenue for the development of InSe-based photodetectors.
Silica coated magnetite (Fe3O4@SiO2) core-shell nanoparticles (NPs) with controlled silica shell thicknesses were prepared by a modified Stöber method using 20 nm hydrophilic Fe3O4 NPs as seeds. The ...core-shell NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), and UV-Vis adsorption spectra (UV-Vis). The results imply that NPs consist of a crystalline magnetite core and an amorphous silica shell. The silica shell thickness can be controlled from 12.5 nm to 45 nm by varying the experimental parameters. The reaction time, the ratio of TEOS/Fe3O4, and the concentration of hydrophilic Fe3O4 seeds were found to be very influential in the control of silica shell thickness. These well-dispersed core-shell Fe3O4@SiO2 NPs show superparamagnetic properties at room temperature.
Monolayer and bilayer graphene sheets have been produced by a solvothermal-assisted exfoliation process in a highly polar organic solvent, acetonitrile, using expanded graphite (EG) as the starting ...material. It is proposed that the dipole-induced dipole interactions between graphene and acetonitrile facilitate the exfoliation and dispersion of graphene. The facile and effective solvothermal-assisted exfoliation process raises the low yield of graphene reported in previous syntheses to 10 wt%–12 wt%. By means of centrifugation at 2000 rpm for 90 min, monolayer and bilayer graphene were separated effectively without the need to add a stabilizer or modifier. Electron diffraction and Raman spectroscopy indicate that the resulting graphene sheets are high quality products without any significant structural defects.
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