InN nanocrystals, nanowires, and nanotubes

On the Determination of Elastic Properties of Single-Walled Nitride Nanotubes Using Numerical Simulation

In recent years, tubular nanostructures have been related to immense advances in various fields of science and technology. Considerable research efforts have been centred on the theoretical prediction and manufacturing of non-carbon nanotubes (NTs), which meet modern requirements for the development of novel devices and systems. In this context, diatomic inorganic nanotubes formed by atoms of elements from the 13th group of the periodic table (B, Al, Ga, In, Tl) and nitrogen (N) have received much research attention. In this study, the elastic properties of single-walled boron nitride, aluminium nitride, gallium nitride, indium nitride, and thallium nitride nanotubes were assessed numerically using the nanoscale continuum modelling approach (also called molecular structural mechanics). The elastic properties (rigidities, surface Young's and shear moduli, and Poisson's ratio) of nitride nanotubes are discussed with respect to the bond length of the corresponding diatomic hexagonal lattice. The results obtained contribute to a better understanding of the mechanical response of nitride compound-based nanotubes, covering a broad range, from the well-studied boron nitride NTs to the hypothetical thallium nitride NTs.

A Facile Route for the Preparation of Monodisperse Iron nitride at Silica Core/shell Nanostructures

Uniform-sized iron oxide nanoparticles obtained from the solution phase thermal decomposition of the iron-oleate complex were encapsulated inside the silica shell by the reverse microemulsion technique, and then thermal treatment under NH₃ to transfer the iron oxide to iron nitride. The transmission electron microscopy images distinctly demonstrated that the as-prepared iron nitride at silica core/shell nanostructures were highly uniform in particle-size distribution. By using iron oxide nanoparticles of 6.1, 10.3, 16.2, and 21.8 nm as starting materials, iron nitride nanoparticles with average diameters of 5.6, 9.3, 11.6, and 16.7 nm were produced, respectively. The acid-resistant properties of the iron nitride at silica core/shell nanostructures were found to be much higher than the starting iron oxide at silica. A superconducting quantum interference device was used for the magnetic characterization of the nanostructure. Besides, magnetic resonance imaging (MRI) studies using iron nitride at silica nanocomposites as contrast agents demonstrated T ₂ enhanced effects that were dependent on the concentration. These core/shell nanostructures have enormous potential in magnetic nanodevice and biomedical applications. The current process is expected to be easy for large-scale and transfer other metal oxide nanoparticles.

Synthesis and morphology evolution of indium nitride (InN) nanotubes and nanobelts by chemical vapor deposition

InN can form ternary alloys with Ga or Al, which increases the versatility of group-III nitride optoelectronic devices.

Conversion Mechanism of Soluble Alkylamide Precursors for the Synthesis of Colloidal Nitride Nanomaterials

There are few molecular precursors that chemically convert to nitride nanomaterials, which severely limits the development of this important class of materials. Alkylamides are soluble and stable nitride precursors that can be based on the same primary amines that are often used in colloidal nanomaterial synthesis, but their conversion involves the breaking of stable C-N bonds through a mechanism that remained unknown up to now. A critical aspect of this conversion mechanism is uncovered here, involving a prelimary step whereby alkylamides are oxidized to N-alkylimines to yield NH₂^- amide species that are postulated to be the actual reactive precursors in the formation of indium nitride nanomaterials. Interestingly, this step also involves the concomitant reduction of indium(III) to In(0) nanodroplets, which consequently catalyze the growth of InN nanomaterials. The elucidation of the origin of the surprising reactivity of otherwise stable molecular precursors opens the door to the development of new solution-phase approaches for the synthesis of nitride materials.

Controllable Synthesis of [11-2-2] Faceted InN Nanopyramids on ZnO for Photoelectrochemical Water Splitting

Indium nitride (InN) is one of the promising narrow band gap semiconductors for utilizing solar energy in photoelectrochemical (PEC) water splitting. However, its widespread application is still hindered by the difficulties in growing high-quality InN samples. Here, high-quality InN nanopyramid arrays are synthesized via epitaxial growth on ZnO single-crystals. The as-prepared InN nanopyramids have well-defined exposed facets of [0001], [11-2-2], [1-212], and [-2112], which provide a possible routine for understanding water oxidation processes on the different facets of nanostructures in nanoscale. First-principles density functional calculations reveal that the nonpolar [11-2-2] face has the highest catalytic activity for water oxidation. PEC investigations demonstrate that the band positions of the InN nanopyramids are strongly altered by the ZnO substrate and a heterogeneous n-n junction is naturally formed at the InN/ZnO interface. The formation of the n-n junction and the built-in electric field is ascribed to the efficient separation of the photogenerated electron-hole pairs and the good PEC performance of the InN/ZnO. The InN/ZnO shows good photostability and the hydrogen evolution is about 0.56 µmol cm^-2 h^-1 , which is about 30 times higher than that of the ZnO substrate. This study demonstrates the potential application of the InN/ZnO photoanodes for PEC water splitting.

One-pot solution synthesis of shape-controlled copper selenide nanostructures and their potential applications in photocatalysis and photothermal therapy

Developing a facile and reliable method for the fabrication of transition metal chalcogenides is a vital and endless pursuit of scientific and technological disciplines. In this work, we develop a one-pot solution approach to obtain copper selenide nanostructures with different morphologies and crystal structures (Cu₂Se nanoparticles, CuSe nanoplates and CuSe₂ nanosheets). In comparison to previously reported methods, our method did not use expensive and very toxic raw materials. After detailed studies of reaction conditions, including temperature, reaction time, and feeding amount of surfactants and precursors, we found that the feeding ratio of precursors played a key role in the crystal structures and morphologies of the final products. Moreover, as a proof-of-concept study, the potential applications of the as-prepared copper selenide nanostructures in the photocatalytic discoloration of aqueous methylene blue (MB) under visible light irradiation and near-infrared (NIR) light induced photothermal therapy for cancer treatment were investigated. Encouraged by their strong photocatalytic activities and high photothermal conversion efficiencies (calculated to be 51.0%, 49.5% and 48.9% for Cu₂Se nanoparticles, CuSe nanoplates and CuSe₂ nanosheets, respectively), we believe that copper selenide nanostructures fabricated from the one-pot solution approach developed in this work would be promising candidates for a wide variety of emerging applications.

Growth, structure, and luminescence properties of novel silica nanowires and interconnected nanorings

Novel silica nanowires and interconnected nanorings were firstly synthesized on a graphite paper by typical thermal catalytic chemical vapor deposition method, using silicon and carbon black powders as raw materials. The field emission scanning electron microscopy, energy dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were used to investigate the composition and structure characterization, which indicates that the silica nanowires and interconnected nanorings were amorphous. The growth of the as-prepared silica nanowires and interconnected nanorings was related to the vapor-liquid-solid mechanism, but the nanowire-ring structure may be due to the polycentric nucleation and periodic stable growth with gradual direction changes. The room temperature photoluminescence emission spectrum showed that the silica nanostructures emitted strong blue light at 460 nm, resulting from the combination of neutral oxygen vacancy (≡Si-Si≡) and selftrapped excitons. The as-synthesized novel silica nanowires and interconnected nanorings could be a potential candidate for applications in future light-emitting diodes and optoelectronic nanodevices.

Terahertz detectors arrays based on orderly aligned InN nanowires

Nanostructured terahertz detectors employing a single semiconducting nanowire or graphene sheet have recently generated considerable interest as an alternative to existing THz technologies, for their merit on the ease of fabrication and above-room-temperature operation. However, the lack of alignment in nanostructure device hindered their potential toward practical applications. The present work reports ordered terahertz detectors arrays based on neatly aligned InN nanowires. The InN nanostructures (nanowires and nano-necklaces) were achieved by chemical vapor deposition growth, and then InN nanowires were successfully transferred and aligned into micrometer-sized groups by a “transfer-printing” method. Field effect transistors on aligned nanowires were fabricated and tested for terahertz detection purpose. The detector showed good photoresponse as well as low noise level. Besides, dense arrays of such detectors were also fabricated, which rendered a peak responsivity of 1.1 V/W from 7 detectors connected in series.

Synthesis, microstructure, growth mechanism and photoluminescence of high quality [0001]-oriented InN nanowires and nanonecklaces

Novel indium nitride (InN) nanowires and nanonecklaces were grown on a single substrate and characterised, and the growth mechanism and of the nanonecklaces was studied.

β-Sialon nanowires, nanobelts and hierarchical nanostructures: morphology control, growth mechanism and cathodoluminescence properties

Morphology control of one dimension (1D) nanomaterials is a pivotal issue in the field of nanoscience research to exploit their novel properties. Herein, we report the morphology controlled synthesis of 1D β-Sialon nanowires, nanobelts and hierarchical nanostructures via a thermal-chemical vapour deposition process using an appropriately selected catalyst and optimized temperature schedule. Vapour-solid (VS), a combination of vapour-liquid-solid (VLS)-based and VS-tip, and a combination of VS for one-generation nanowires with nucleation, growth and coalescence of two-generation nanobranches (NGCB) are used to explain the growth of β-Sialon nanowires, nanobelts and hierarchical nanostructures, respectively. Cathodoluminescence measurements show that the individual β-Sialon 1D nanostructures with different morphologies have different luminescent properties. All nanostructures exhibit two distinct emission peaks, the violet/blue emission centered at ~390 nm (3.18 eV), attributable to the near band edge (NBE) emission, and the red emission centered at ~728 nm (1.70 eV), assigned to the deep level (DL) emission. However, the DL emission is the ruling emission in the case of an individual β-Sialon nanowire, whereas the NBE emission becomes dominant in the case of an individual nanobelt as well as a hierarchical nanostructure due to the size and surface effects. The as-synthesized β-Sialon with controlled nanostructures and various morphologies can find potential applications in future nanodevices with tailorable or tunable photoelectric properties.

Fe-catalyzed growth of one-dimensional α-Si3N4 nanostructures and their cathodoluminescence properties

Preparation of nanomaterials with various morphologies and exploiting their novel physical properties are of vital importance in nanoscientific field. Similarly to the III-N compound semiconductors, Si₃N₄ nanostructures also could be potentially used for making optoelectronic devices. In this paper, we report on an improved Fe-catalyzed chemical vapour deposition method for synthesizing ultra-long α-Si₃N₄ nanobelts along with a few nanowires and nanobranches on a carbon felt substrate. The ultra-long α-Si₃N₄ nanobelts grew via a combined VLS-base and nanobranches via a combined double-stage VLS-base and VS-tip mechanism, as well as nanowires via VLS-tip mechanism. The three individual nanostructures showed variant optical properties as revealed by a cathodoluminescence spectroscopy. A single α-Si₃N₄ nanobelt or nanobranch gave a strong UV-blue emission band as well as a broad red emission, whereas a single α-Si₃N₄ nanowire exhibited only a broad UV-blue emission. The results reported would be useful in developing new photoelectric nanodevices with tailorable or tunable properties.

Synthesis of InN@SiO₂ nanostructures and fabrication of blue LED devices

We synthesized InN@SiO(2) nanostructures (i.e., nanoparticles and nanowires) by varying the annealing temperature and nitridation conditions of In(2)O(3)@SiO(2) nanoparticles in the presence of ammonia. The In(2)O(3)@SiO(2) nanoparticles were synthesized using a urea-based homogeneous precipitation of indium hydroxide on the surface of the SiO(2) (15 nm) nanoparticles, followed by annealing at 600 °C in air. Subsequently, nitridation of In(2)O(3)@SiO(2) nanoparticles in ammonia at 600 °C for 2 h resulted in InN@SiO(2) nanoparticles. The sizes of InN nanoparticles are ∼5 nm on the silica surface. Nitridation at the same temperature for 3-5 h gave InN nanoparticles of size ∼20 nm. Furthermore, on annealing above 650 °C the InN nanoparticles grew in the form of nanowires. The nanowires are 4-5 μm in length and have a diameter of 100 nm. The photoluminescence peak of both InN@SiO(2) nanoparticles and nanowires is centered at 442 nm (λ(exi) = 325 nm). Subsequently, the surface of InN@SiO(2) nanoparticles was modified by reacting with dodecyltriethoxysilane at 80 °C, which enabled them to be dispersible in toluene. The surface-modified InN@SiO(2) nanoparticles were used to fabricate blue electroluminescence devices which showed blue electroluminescence peak centered at 442 nm. The Commission Internationale de I'Eclairage (CIE) coordinates of InN@SiO(2) nanoparticles are X = 0.15 and Y = 0.13, which is well within the blue region and commercially appropriate.

Recent progress in the synthesis of inorganic nanoparticles

Nanoparticles probably constitute the largest class of nanomaterials. Nanoparticles of several inorganic materials have been prepared by employing a variety of synthetic strategies. Besides synthesizing nanoparticles, there has been considerable effort to selectively prepare nanoparticles of different shapes. In view of the great interest in inorganic nanoparticles evinced in the last few years, we have prepared this perspective on the present status of the synthesis of inorganic nanoparticles. This article includes a brief discussion of methods followed by reports on the synthesis of nanoparticles of various classes of inorganic materials such as metals, alloys, oxides chalcogenides and pnictides. A brief section on core-shell nanoparticles is also included.

Conjugated polymers/semiconductor nanocrystals hybrid materials--preparation, electrical transport properties and applications

This critical review discusses specific preparation and characterization methods applied to hybrid materials consisting of π-conjugated polymers (or oligomers) and semiconductor nanocrystals. These materials are of great importance in the quickly growing field of hybrid organic/inorganic electronics since they can serve as active components of photovoltaic cells, light emitting diodes, photodetectors and other devices. The electronic energy levels of the organic and inorganic components of the hybrid can be tuned individually and thin hybrid films can be processed using low cost solution based techniques. However, the interface between the hybrid components and the morphology of the hybrid directly influences the generation, separation and transport of charge carriers and those parameters are not easy to control. Therefore a large variety of different approaches for assembling the building blocks--conjugated polymers and semiconductor nanocrystals--has been developed. They range from their simple blending through various grafting procedures to methods exploiting specific non-covalent interactions between both components, induced by their tailor-made functionalization. In the first part of this review, we discuss the preparation of the building blocks (nanocrystals and polymers) and the strategies for their assembly into hybrid materials' thin films. In the second part, we focus on the charge carriers' generation and their transport within the hybrids. Finally, we summarize the performances of solar cells using conjugated polymer/semiconductor nanocrystals hybrids and give perspectives for future developments.

Phase mapping of aging process in InN nanostructures: oxygen incorporation and the role of the zinc blende phase

Uncapped InN nanostructures undergo a deleterious natural aging process at ambient conditions by oxygen incorporation. The phases involved in this process and their localization is mapped by transmission electron microscopy (TEM)-related techniques. The parent wurtzite InN (InN-w) phase disappears from the surface and gradually forms a highly textured cubic layer that completely wraps up a InN-w nucleus which still remains from the original single-crystalline quantum dots. The good reticular relationships between the different crystals generate low misfit strains and explain the apparent easiness for phase transformations at room temperature and pressure conditions, but also disable the classical methods to identify phases and grains from TEM images. The application of the geometrical phase algorithm in order to form numerical moiré mappings and RGB multilayered image reconstructions allows us to discern among the different phases and grains formed inside these nanostructures. Samples aged for shorter times reveal the presence of metastable InN:O zinc blende (zb) volumes, which act as the intermediate phase between the initial InN-w and the most stable cubic In(2)O(3) end phase. These cubic phases are highly twinned with a proportion of 50:50 between both orientations. We suggest that the existence of the intermediate InN:O-zb phase should be seriously considered to understand the reason for the widely scattered reported fundamental properties of thought to be InN-w, as its bandgap or superconductivity.

Synthesis of inorganic nanomaterials

Synthesis forms a vital aspect of the science of nanomaterials. In this context, chemical methods have proved to be more effective and versatile than physical methods and have therefore, been employed widely to synthesize a variety of nanomaterials, including zero-dimensional nanocrystals, one-dimensional nanowires and nanotubes as well as two-dimensional nanofilms and nanowalls. Chemical synthesis of inorganic nanomaterials has been pursued vigorously in the last few years and in this article we provide a perspective on the present status of the subject. The article includes a discussion of nanocrystals and nanowires of metals, oxides, chalcogenides and pnictides. In addition, inorganic nanotubes and nanowalls have been reviewed. Some aspects of core-shell particles, oriented attachment and the use of liquid-liquid interfaces are also presented.

Synthesis of long indium nitride nanowires with uniform diameters in large quantities

Large quantities of indium nitride (InN) nanowires are synthesized by the in situ nitriding of indium oxide (In(2)O(3)) powders in an ammonia (NH(3)) flux. Tens of milligrams of nanowires are obtained in one batch. Every 100 mg of In(2)O(3) starting powder can produce up to 65 mg of InN nanowires under the optimized conditions. The synthesized nanowires grow along the [001] direction with excellent crystallinity. They are of high purity and are 30-50 microm in length with an almost uniform diameter of about 100 nm. Photoluminescence measurements of the nanowires exhibit a strong peak at 707 nm. An optical bandgap of about 1.7 eV is estimated based on the absorption spectrum. The experimental results also demonstrate that the approach of nitriding In(2)O(3) powders in situ is feasible for the synthesis of high-purity InN nanowires in large quantities, with good reproducibility and without catalyst materials. The synthesis of InN nanowires in large quantities would be of benefit to the further study and understanding of their intrinsic properties, as well as being advantageous for their potential application in nanodevices.