Carbon nanotube–polymer composites: Chemistry, processing, mechanical and electrical properties

The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology. A good example of the synergism between scientific discovery and technological development is the electronics industry, where discoveries of new semiconducting materials resulted in the evolution from vacuum tubes to diodes and transistors, and eventually to miniature chips. The progression of this technology led to the development * To whom correspondence should be addressed. B.L.C.: (504) 2801385 (phone); (504) 280-3185 (fax); bcushing@uno.edu (e-mail). C.J.O.: (504)280-6846(phone);(504)280-3185(fax);coconnor@uno.edu (e-mail). 3893 Chem. Rev. 2004, 104, 3893−3946

http://depa.fquim.unam.mx/amyd//archivero/FidelmarLechugaSanabria_4940.pdf

Recent advances in the liquid-phase syntheses of inorganic nanoparticles.

Isolated graphene, a nanometer-thick two-dimensional analog of fullerenes and carbon nanotubes, has recently sparked great excitement in the scientific community given its excellent mechanical and electronic properties. Particularly attractive is the availability of bulk quantities of graphene as both colloidal dispersions and powders, which enables the facile fabrication of many carbon-based materials. The fact that such large amounts of graphene are most easily produced via the reduction of graphene oxide--oxygenated graphene sheets covered with epoxy, hydroxyl, and carboxyl groups--offers tremendous opportunities for access to functionalized graphene-based materials. Both graphene oxide and graphene can be processed into a wide variety of novel materials with distinctly different morphological features, where the carbonaceous nanosheets can serve as either the sole component, as in papers and thin films, or as fillers in polymer and/or inorganic nanocomposites. This Review summarizes techniques for preparing such advanced materials via stable graphene oxide, highly reduced graphene oxide, and graphene dispersions in aqueous and organic media. The excellent mechanical and electronic properties of the resulting materials are highlighted with a forward outlook on their applications.

Graphene oxide, highly reduced graphene oxide, and graphene: versatile building blocks for carbon-based materials.

The increasing energy demand in the near future will force us to seek environmentally clean alternative energy resources. The emergence of nanomaterials as the new building blocks to construct light energy harvesting assemblies has opened up new ways to utilize renewable energy sources. This article discusses three major ways to utilize nanostructures for the design of solar energy conversion devices:  (i) Mimicking photosynthesis with donor−acceptor molecular assemblies or clusters, (ii) semiconductor assisted photocatalysis to produce fuels such as hydrogen, and (iii) nanostructure semiconductor based solar cells. This account further highlights some of the recent developments in these areas and points out the factors that limit the efficiency optimization. Strategies to employ ordered assemblies of semiconductor and metal nanoparticles, inorganic-organic hybrid assemblies, and carbon nanostructures in the energy conversion schemes are also discussed. Directing the future research efforts toward utiliza...

Meeting the Clean Energy Demand: Nanostructure Architectures for Solar Energy Conversion

Biological synthesis of metallic nanoparticles.

Gold and platinum nanoparticles were synthesized by the reduction of their salts with potassium bitartrate as the reductant and poly(N-vinyl-2-pyrrolidone)
(PVP), polyethylene glycol (PEG)
(for Pt nanoparticles) or 3,3′-thiodipropionic acid (TDPC) as the protective agent. In the presence of PVP or TDPC, the preparation of palladium and silver nanoparticles were also realized by the reduction of their salts with potassium bitartrate under alkaline conditions. The effect of the concentration of the protective agents on the particle size and morphology were investigated in detail. At a constant concentration of Au and Pt ions, the average diameter of Au or Pt nanoparticles tends to decrease with an increase in the concentration ratios of the protective agents to AuCl4− or PtCl62−. Except for PVP passivated Au nanoparticles, smaller Au and Pt particles with a sharp size distribution could be obtained at higher concentration ratios of the protective agents to the metal ions, as determined by TEM measurements. All the noble metal colloidal particles have very high stability.

Preparation of gold, platinum, palladium and silver nanoparticles by the reduction of their salts with a weak reductant–potassium bitartrate

Segmented polyether−polyurethane (PU)/montmorillonite nanocomposites have been synthesized with poly(tetramethylene glycol), 4,4-diphenylmethane diisocyanate, propylenediamine, and montmorillonite. The nanoscale silicate layers are intercalated or exfoliated in the PU matrix, which are characterized by X-ray diffraction pattern and transmission electron microscopy. The PU/montmorillonite composites have been investigated by FT-IR dichroism during the stretching process in order to study the hard and soft chain orientation, hydrogen bonding, and strain induced by crystallization of the soft segment chains in PU. DSC experiment indicates that the soft phase Tg increases with the montmorillonite content. The mechanical analysis showed that tensile strength,Young's modulus, and elongation at break increase markedly, 1700% elongation at break for the composite containing 2.0 wt % montmorillonite.

Study on Structure and Orientation Action of Polyurethane Nanocomposites

Foaming of polyurethane (PU) films using supercritical CO 2 as a blowing agent, a “green” and high-efficient approach, has been studied. Microcellular foam material was prepared by saturating the polymer with CO 2 and its morphology was characterized by scanning election microscopy (SEM). The influence of processing parameters, such as pressure, temperature and soaking time, on the foam morphology was investigated. It was found that the size and distribution of the micro-cell could be controlled conveniently by changing the processing conditions. The results of dynamic mechanical temperature analysis (DMTA) showed that the damping property of the foamed materials was greatly improved and had a maximum value, tan  δ = 3.88 at 63 Hz due to the properties of the storage and loss moduli compared with the original PU. Reduction of the mass density led to a decline in the mechanical properties of the foamed materials.

Xinhua Dai

Papers

Preparation of gold, platinum, palladium and silver nanoparticles by the reduction of their salts with a weak reductant–potassium bitartrate

Study on Structure and Orientation Action of Polyurethane Nanocomposites

High damping property of microcellular polymer prepared by friendly environmental approach

Encapsulation of polystyrene within carbon nanotubes with the aid of supercritical CO2

Grafting of methyl methylacrylate onto isotactic polypropylene film using supercritical CO2 as a swelling agent