Highly Uniform Gd(OH)(3) and Gd2O3:Eu3+ Nanotubes: Facile Synthesis and Luminescence Properties

Uniform Gd(OH)(3) nanotubes have been prepared via a simple wet-chemical route at ambient pressure and low temperature, without any catalysts, templates, or substrates, in which Gd(NO3)(3) was used as the gallium source and ammonia as the alkali. SEM and TEM images indicate that the as-obtained Gd(OH)3 entirely consists of uniform nanotubes in high yield with diameters of about 40 nm and lengths of 200-300 nm. The temperature-dependent morphological evolution and the formation mechanism of the Gd(OH)(3) nanotubes were investigated in detail. Furthermore, the Gd2O3 and Eu3+-doped Gd2O3 nanotubes, which inherit their parents' morphology, were obtained during a direct annealing process in air. The corresponding Gd2O3:Eu3+ nanotubes exhibit the strong red emission corresponding to the D-5(0)-F-7(2), transition of the Eu3+ ions under UV light or low-voltage electron beam excitation, which might find potential applications in the fields such as light-emitting phosphors, advanced flat panel displays, or biological labeling.

Nanotubes of mixed-valence, transition metal compounds synthesized by solution phase approach

A solution-phase approach to synthesize four kinds of mixed-valence, transition metal compounds nanotube is described. The approach is based on the self-assembly of siloxane sol. The resulted production of mixed-valence, transition metal compounds share a common structural characteristic of tubular geometrical morphology, at least for the ones we studied. The results demonstrate that the synthesis strategy can be a general route for preparation of compound nanotubes. In addition, the size control of nanotubular materials can be easily achieved through varying the ionic strength of solution. Based on the strategy, the diameters of ultrathin Ru-Fe nanotubes can be easily tuned between 100 nm and 800 nm.

Synthesis of neodymium hydroxide nanotubes and nanorods by soft chemical process

A facile soft chemical approach using cetyltrimethylammoniurn bromide (CTAB) as template is successfully designed for synthesis of neodymium hydroxide nanotubes. These nanotubes have an average outer diameter around 20 nm, inner diameter around 2 nm, and length ranging from 100 to 120 nm, high BET surface area of 495.71 m(2) g(-1). We also find that neodymium hydroxide nanorods would be obtained when CTAB absented in reaction system. The Nd(OH)(3) nanorods might act as precursors that are converted into Nd2O3 nanorods through dehydration at 550 degrees C. The nanorods could exhibit upconversion emission characteristic under excitation of 591 nm at room temperature.

Reinforcement of silica with single-walled carbon nanotubes through covalent functionalization

Single-walled carbon nanotubes (SWCNTs) as reinforcing components were extended into silica monoliths and thin films via covalent functionalization for the first time. Silica materials have poor mechanical attributes, which limit their applications. Because of the extreme flexibility of SWCNTs and their large interfacial area, they may be very intriguing as reinforcing fillers for the silica matrix. To get more uniform dispersion and stronger interfacial interaction, SWCNTs were covalently functionalized with silane, and then integrated into silica via a sol - gel process, and their properties were also compared with those of pristine SWCNTs. Results show that the silane-functionalized nanotubes resulted in better mechanical properties ( for example, 33% increase in stress, and 53% increase in toughness), as well as higher electron-transfer kinetics.

Electrogenerated chemiluminescence sensing platform using Ru(bpy)(3)(2+) doped silica nanoparticles and carbon nanotubes

An effective electrogenerated chemiluminescence (ECL) sensor was developed by coimmobilization of the Ru(bpy)(2)(3+)-doped silica (RuDS) nanoparticles and carbon nanotubes (CNTs) on glassy carbon electrode through hydrophobic interaction. The uniform RuDS nanoparticles were prepared by a water-in-oil (W/O) microemulsion method and Ru(bpy)(3)(2+) doped inside could still maintain its high ECL efficiency. With such unique immobilization method, a great deal of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode , which could greatly enhance the ECL response and result in the increased sensitivity. On the other hand, CNTs played dual roles as matrix to immobilize RuDS nanoparticles and promoter to accelerate the electron transfer between Ru(bpy)(3)(2+) and the electrode. The as-prepared ECL sensor displayed good sensitivity and stability.

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified by Nafion and ordered mesoporous silica-SBA-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified by ordered mesoporous silica-SBA-15 and Nafion. The sorption behavior of GOD immobilized on SBA-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that SBA-15 can facilitate the electron exchange between the electroactive center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and SBA-15 matrices displays direct, nearly reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 3.89 s(-1) in 0.1 M phosphate buffer solution (PBS) (pH 7.12).

Nanoelectrocatalyst based on high-density Au/Pt hybrid nanoparticles supported on a silica nanosphere

A high-efficiency nanoelectrocatalyst based on high-density Au/Pt hybrid nanoparticles supported on a silica nanosphere (Au-Pt/SiO2) has been prepared by a facile wet chemical method. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy are employed to characterize the obtained Au-Pt/SiO2. It was found that each hybrid nanosphere is composed of high-density small Au/Pt hybrid nanoparticles with rough surfaces. These small Au/Pt hybrid nanoparticles interconnect and form a porous nanostructure, which provides highly accessible activity sites, as required for high electrocatalytic activity. We suggest that the particular morphology of the AuPt/SiO2 may be the reason for the high catalytic activity. Thus, this hybrid nanomaterial may find a potential application in fuel cells.

Electrochemiluminescence sensor based on partial sulfonation of polystyrene with carbon nanotubes

Herein, homogenously partial sulfonation of polystyrene (PSP) was performed. An effective electrochemiluminescence (ECL) sensor based on PSP with carbon nanotube (CNTs) composite film was developed. Cyclic voltammetry and electrochemical impendence spectroscopy were applied to characterize this composite film. The PSP was used as an immobilization matrix to entrap the ECL reagent Ru(bpy)(3)(2+) due to the electrostatic interactions between sulfonic acid groups and Ru(bpy)(3)(2+) cations. The introduction of CNTs into PSP acted not only as a conducting pathway to accelerate the electron transfer but also as a proper matrix to immobilize Ru(bpy)(3)(2+) on the electrode by hydrophobic interaction. Furthermore, the results indicated the ECL intensity produced at this composite film was over 3-fold compared with that of the pure PSP film due to the electrocatalytic activity of the CNTs. Such a sensor was verified by the sensitive determinations of 2-(dibutylamino)ethanol and tripropylamine.

In situ synthesis of silica gel nanowire/Na+-montmorillonite nanocomposites by the sol-gel route

Silica-gel nanowire/Na+-montmorillonite (Na+-MMT) nanocomposites were prepared by the in situ sol-gel process of tetraethyl orthosilicate (TEOS) in the presence of Na+-MMT and ammonia as catalyst. Microstructure characterization of the nanocomposites was done by SEM, , EDX, XRD and FTIR. It was found that a lot of silica-gel nanowires grew along the edges of Na+-MMT. The combination between the nanowires and Na+-MMT was accomplished via polycondensation of the hydrolyzed TEOS and the edge-OH groups of Na+-MMT.

Preparation of highly conductive, self-assembled gold/polyaniline nanocables and polyaniline nanotubes

One-dimensional gold/polyaniline (Au/PANI-CSA) coaxial nanocables with an average diameter of 5060 nm and lengths of more than 1 mu m were successfully synthesized by reacting aniline monomer with chlorauric acid (HAuCl4) through a self-assembly process in the presence Of D-camphor-10-sulfonic acid (CSA), which acts as both a dopant and surfactant. It was found that the formation probability and the size of the Au/PANI-CSA nanocables depends on the molar ratio of aniline to HAuCl4 and the concentration of CSA, respectively. A synergistic growth mechanism was proposed to interpret the formation of the Au/PANI-CSA nanocables. The directly measured conductivity of a single gold/polyaniline nanocable was found to be high (approximate to 77.2S cm(-1)). Hollow PANI-CSA nanotubes, with an average diameter of 50-60 nm, were also obtained successfully by dissolving the Au nanowire core of the Au/PANI-CSA nanocables.

Macroporous fluoropolymeric films templated by silica colloidal assembly: A possible route to super-hydrophobic surfaces

A super-hydrophobic surface was obtained on a three-dimensional (313) polyvinylidene fluoride (PVDF) macroporous film. The porous films were fabricated through self-assembled silica colloidal templates. The apparent water contact angle of the surface can be tuned from 106 degrees to 153 degrees through altering the sintering temperature and the diameter of the colloidal templates. A composite structure of micro-cavities and nanoholes on the PVDF surface was responsible for the super-hydrophobicity. The wettability of the porous surfaces was described by the use of the Cassie-Baxter model and Wenzel's equation.

Synthesis of ordered mesoporous carbons composed of nanotubes via catalytic chemical vapor deposition

Ordered mesoporous carbons composed of arrays of nanotubes have been synthesized using ordered mesoporous silica templates via catalytic chemical vapor deposition. The ordered carbons possess bimodal pores, namely, the pores arise from the "replica" of frameworks of the template and the pores correspond to carbon nanotubes formed in the channels of the template (see Figure).

Laser-surface-alloyed carbon nanotubes reinforced hydroxyapatite composite coatings

Carbon-nanotube sCNTd-reinforced hydroxyapatite composite coatings have been fabricated by laser surface alloying. Microstructural observation using high-resolution transmission electron microscopy showed that a large amount of CNTs remained with their or

Wear Studies of Hydroxyapatite Composite Coating Reinforced by Carbon Nanotubes

Multi-walled carbon nanotubes (CNTs) have been successfully introduced into hydroxyapatite (HA) coatings using laser surface alloying. It is evident from transmission electron microscopy (TEM) observations that the CNTs present in the matrix still keep their multi-walled cylinder graphic structure, although they undergo the laser irradiation. Scratching test results indicated that the as-alloyed HA composite coatings exhibit improved wear resistance and lower friction coefficient with increasing the amount of CNTs in the precursor material powders. These composites have potential applications in the field of coating materials for metal implants under high-load-bearing conditions. (c) 2006 Elsevier Ltd. All rights reserved.