Synthesis and surface characterization of yttrium doped boehmite nanofibers

Yttrium doped boehmite nanofibers with varying yttrium content have been synthesized at low temperatures using a soft-chemistry route in the presence of polyglycol ether surfactant. The effect of yttrium content, hydrothermal temperature on the growth of boehmite nanostructures was systematically studied. Nanofibers were formed in all samples with varying doped Y% treated at 100 °C; large Y(OH)₃ crystals were also formed at high yttrium doping. Treated at an elevated temperatures resulted in a remarkable changes in size and morphology for samples with the same doped Y content. The resultant nanofibers were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray analysis (EDX), N₂ adsorption and thermogravimetric analysis. The detailed characterization and discussion on the Y doped nanostructures are presented.     

Polyaniline nanofibers: facile synthesis and chemical sensors

Polyaniline nanofibers with uniform diameters between 30 and 50 nm can be made in bulk quantities through a facile aqueous/organic interfacial polymerization method at ambient conditions. The nanofibers have lengths varying from 500 nm to several micrometers and form interconnected networks. Thin films made of the nanofibers have superior performance in both sensitivity and time response to vapors of acid (HCl) and base (NH3).     

Polyaniline nanofibers: chemical synthesis using surfactants

Nanofibers of doped polyaniline.HCSA having diameters 1-2 nm are observed in TEM images of bath sonicated aqueous dispersions of larger nanofibers (30-50 nm diameter) synthesized by surfactant-assisted chemical oxidative polymerization of aniline in dilute aqueous organic acids.     

Growth and surface properties of boehmite nanofibers and nanotubes at low temperatures using a hydrothermal synthesis route

The growth of boehmite nanostructures at low temperature using a soft chemistry route with and without (PEO) surfactant is presented. Remarkably long boehmite 1D nanotubes/nanofibers were formed within a significantly short time by changing the reaction mechanism of aluminum hydroxide. By using the PEO surfactant as a templating agent, boehmite nanotubes up to 170 nm in length with internal and external diameters of 2-5 and 3-7 nm, respectively, were formed at 100 degrees C. A slightly higher temperature (120 degrees C) resulted in the formation of lath-like nanofibers with an average length of 250 nm. Using the cationic surfactant CTAB, nanotubes rather than nanofibers were formed at 120 degrees C. Without surfactant, nanotubes counted for around 20% of the entire sample. A regular interval supply of fresh boehmite precipitate resulted in a larger crystallite size distribution of nanotubes. The morphology of nanotubes was more uniform in samples without the regular addition of aluminum hydroxide. Moreover, for the same hydrothermal time, the final nanotubes for nanomaterials without a regular interval supply of fresh aluminum hydroxide precipitate were longer than those with a regular aluminum hydroxide precipitate supply, which is in contrast to previously published results. Higher Al/PEO concentrations resulted in the formation of shorter nanotubes. A detailed characterization and mechanism are presented.     

Thermal study of boehmite nanofibers with controlled particle size

Boehmite nanofiber materials with controlled particle size were synthesized without any surfactant by careful tuning of the hydrothermal temperatures, and followed by a series of characterizations. It was found that the boehmite nanofibers became shorter and coarser with the increase of temperature, and resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by in situ HT X-ray diffraction and thermogravimetry–differential scanning calorimetry. All materials showed the phase transition from γ-Al₂O₃ to other forms. Yet the transition temperature was increased with the increase of hydrothermal temperature. The boehmite nanofibers with the largest diameter showed the best thermal stability.     

Selective synthesis of CdWO4 short nanorods and nanofibers and their self-assembly

Single-crystalline CdWO₄ nanorods and nanofibers are selectively prepared based on hydrothermal treatment with cetyltrimethylammonium bromide (CTAB) as capping molecule and ordinary inorganic reactant as precursors through exactly controlling the pre-treated condition. With almost uniform breadth and pointed ends, the obtained short nanorods show a relatively thick nature along [010] direction and self-assemble to an ordered structure with (001) and (010) faces, respectively, while the as-prepared nanofibers are flexible and vertically self-assemble to form woven network. The mechanism of selective preparation and self-assembly was also discussed. Both obtained nanorods and nanofibers display a very strong blue-green luminescence property at room temperature.     

Hydrothermal preparation of boehmite nanorods by selective adsorption of sulfate

A facile hydrothermal method was developed to synthesize boehmite nanorods with a length of 50-2000 nm, a diameter of 6-20 nm, and a preferential growth along [100] by treating the Al(OH)(3) gel in acidified sulfate solutions at 240 degrees C. Studies on the hydrothermal treatment of Al(OH)(3) gel in sulfate solutions showed that the morphology and the composition of the hydrothermal products were connected with the sulfate concentration and the pH of the hydrothermal solution. The aspect ratio of the boehmite nanorods increased to 300 as the initial H(2)SO(4) concentration increased to 0.043 mol x L(-1), whereas boehmite nanorods and (H(3)O)Al(3)(SO(4))(2)(OH)(6) cubic particles coexisted in the case of the initial H(2)SO(4) concentration > or = 0.054 mol x L (-1). Sole boehmite nanoflakes with a diameter of about 50 nm were formed under alkaline conditions (pH 10.5) despite the existence of the sulfate. The chemical and Raman analyses indicated that SO(4)(2-) in acidified solutions adsorbed on the boehmite surface via H-bonds. On the basis of the above results, the growth of boehmite along the [100] direction was attributed to the selective adsorption of SO(4) (2-) on the (010) and (001) planes of boehmite.     

Synthesis, characterization, and surface properties of iron-doped boehmite nanofibers

Iron-doped boehmite nanofibers with varying iron contents have been prepared at low temperatures using hydrothermal treatment in the presence of poly(ethylene oxide) surfactant. The resulting nanofibers were characterized by transmission electron microscopy (TEM), X-ray diffraction, energy-dispersive X-ray analysis, and N2 adsorption. TEM images showed that the resulting nanostructures are predominantly nanofibers when the doped iron content is less than 5% (mol/mol); in contrast, nanosheets were formed when iron doping was above 4%. Nanotubes instead of nanofibers and iron-rich particles were observed in samples with 20% added iron. A detailed characterization and discussion on the iron-doped nanofibers is presented.     

General method for the synthesis of crystalline organic nanorods using porous alumina templates

Nanorods composed of a variety of conjugated organic molecules were synthesized using an anodized alumina template and solvent annealing; detailed study of 200 nm thick 2,7-di-t-butylpyrene rods showed they are crystalline, with single domains extending over several microns.     

An inorganic route for controlled synthesis of W18O49 nanorods and nanofibers in solution

In this work, we describe a simple inorganic route for synthesis of monodispersed W(18)O(49) nanorods with dimensional control in the quantum confinement regime. The single-crystalline W(18)O(49) nanorods can be prepared into stable colloidal solutions, or assembled into fibrous and/or paper forms by tuning process parameters. The important role of Na(2)SO(4) salt in the synthesis has been demonstrated. This inorganic route should be feasible for large-scale production of low-dimensional nanostructured W(18)O(49).     

Thermal and morphological study of Al2O3 nanofibers derived from boehmite precursor

The boehmite nanofibers were prepared by using NaAlO₂ and Al₂(SO₄)₃ as the starting materials without any surfactant. The phase transitions of the boehmite nanofibres against different temperature were studied and various phases were derived from well-crystallized boehmite nanofibers. All these phases had the same morphology even after high temperature calcination. In addition, the retention of specific surface area of the samples were very high because of the limited aggregation occurred in calcinations for each sample. For instance, the ??-Al₂O₃ obtained at 500?°C had the specific surface area (208.56?m²/g) with an average pore diameter of 6.0?nm. With the further increase of the calcination temperature, the nanofibers became shorter and coarsening, which resulted in the decrease of the specific surface area. It is worthwhile to notice that the BET surface areas (40.97?m²/g) and the pore volume (0.27?cm³/g) of the fibrous structures obtained after 1200?°C calcination are substantially higher than that of the non-fibrous alumina because of the morphology maintenance.     

Influence of peptization on the properties of alumina produced from boehmite sols

Formation of boehmite sols from aluminium alkoxides was studied by X-ray diffraction, IR-spectroscopy, DLS (Dynamic Light Scattering) and other methods. It was found that the distortion of the boehmite crystal lattice occurs under the electrolyte sol formation processes. The surface charges were evaluated to explain the observed changes in X-ray patterns and IR-spectra of the boehmite samples and the causes that bring about these changes. The influence of the peptizing process on -Al₂O₃ specific surface was also studied.     

Effect of boehmite nanorods on the properties of glycidoxypropyl-trimethoxysilane (GPTS) hybrid coatings

AlOOH boehmite nanorods, synthesized by a solid-based process, were incorporated into a sol–gel coating in which GPTS was used as a precursor. Transparent composite coatings with nanorod content up to 40 wt% were obtained by spin coating the sol–gel mixture on glass substrates. Nanorods in the coating were found be aligned parallel to the substrate surface. Mechanical properties, such as modulus and hardness of the nanorod filled coating, were slightly lower than coatings of the same composition but filled with commercially available nanosized boehmite particles. However, crack toughness was greatly improved, as supported by nanoindentation test results. The improvement in crack toughness was attributed to the high aspect ratio of the rigid nanorods, in addition to the fact that the nanorods were aligned within the composite parallel to the surface.     

Formation of organometallic polymer nanorods using a nanoporous alumina template and the conversion to magnetic ceramic nanorods

Polyferrocenylsilane nanorods were prepared using a porous anodic aluminium oxide template followed by chemical etching; pyrolysis was used to obtain magnetic iron oxide-containing ceramic nanorods.     

Solution-based synthesis of quaternary Cu-In-Zn-S nanobelts with tunable composition and band gap

We have demonstrated that quaternary Cu(x)In(x)Zn(2(1-x))S(2) nanobelts could be synthesized through a facile solution-based method. The composition and band gap of quaternary nanobelts can be tuned within the broad range by changing the relative ratio of precursors. The growth mechanism of quaternary nanobelts was deduced to be catalyst-assisted growth.     

Photochemical synthesis of gold nanorods

Gold nanorods have been synthesized by photochemically reducing gold ions within a micellar solution. The aspect ratio of the rods can be controlled with the addition of silver ions. This process reported here is highly promising for producing uniform nanorods, and more importantly it will be useful in resolving the growth mechanism of anisotropic metal nanoparticles due to its simplicity and the relatively slow growth rate of the nanorods.     

Chemical synthesis of PEDOT nanofibers

A one-step, room-temperature method is described to chemically synthesize bulk quantities of microns long, 100-180 nm diameter nanofibers of electrically conducting poly(3,4-ethylenedioxythiophene)(PEDOT) in the form of powders, or as optically transparent, substrate-supported films using a V2O5 seeding approach.     

Controlled synthesis and luminescence of semiconductor nanorods

A variety of nearly monodisperse semiconductor nanocrystals, such as CdS, ZnS, and ZnS:Mn, with controllable aspect ratios have been successfully prepared through a facile synthetic process. These as-prepared nanocrystals were obtained from the reactions between metal ions and thioacetamide by employing octadecylamine or oleylamine as the surfactants. The effects of reaction temperature and time, ratios of thioacetamide to inorganic precursors, and the reactant content on the size and crystal purity of the nanorods, have been systematically investigated. The optical properties and the formation mechanism of the nanorods have also been discussed. For the next biolabel applications, these hydrophobic nanocrystals have also been transferred into hydrophilic colloidal spheres by means of an emulsion-based bottom-up self-assembly approach.     

Rhodium nanoparticles entrapped in boehmite nanofibers: recyclable catalyst for arene hydrogenation under mild conditions

A new recyclable rhodium catalyst was synthesized by a simple procedure from readily available reagents, which showed high activities in the hydrogenation of various arenes under 1 atm H2 at room temperature.