26 research outputs found
Charge-transfer with graphene and nanotubes
Charge-transfer between electron–donor and –acceptor molecules is a widely studied subject of great chemical interest. Some of the charge-transfer compounds in solid state exhibit novel electronic properties. In the last two to three years, occurrence of molecular charge-transfer involving single-walled carbon nanotubes (SWNTs) and graphene has been demonstrated. This interaction gives rise to significant changes in the electronic properties of these nanocarbons. We examine charge-transfer phenomenon in graphene and SWNTs in this article in view of its potential utility in device applications
Changes in the electronic structure and properties of graphene induced by molecular charge-transfer
Interaction with electron donor and acceptor molecules such as aniline and
nitrobenzene brings about marked changes in the Raman spectrum and the
electronic structure of graphene, prepared by the exfoliation of graphitic
oxide.Comment: 13 pages, 4 figure
Semiconductor to metal transition in SWNTs caused by interaction with gold and platinum nanoparticles
Single-walled carbon nanotubes (SWNTs) have been coated with gold and
platinum nanoparticles either by microwave treatment or by the click reaction
and the Raman spectra of these SWNT-metal nanoparticle composites have been
investigated. Analysis of the G bands in the Raman spectra shows an increase in
the proportion of metallic SWNTs on attachment with metal nanoparticles. This
conclusion is also supported by the changes observed in the RBM bands.
Ab-initio calculations reveal that semiconductor-metal transition occurs in
SWNTs due to Columbic charge transfer between the metal nanoparticles and the
semiconducting SWNTs.Comment: 16 pages, 5 figure
Selective synthesis of metallic and semiconducting single-walled carbon nanotubes
As-prepared single-walled carbon nanotubes (SWNTs) are generally mixtures of semiconducting and metallic species, the proportion of the former being around 67%. Since most applications of SWNTs are best served by semiconducting or metallic nanotubes, rather than by mixtures of the two, methods which would directly yield semiconducting and metallic SWNTs in pure form are desirable. In this article, we present the available methods for the direct synthesis of such SWNTs along with the methods available to separate semiconducting and metallic SWNTs from mixtures. We also discuss the synthesis of Y-junction carbon nanotubes
Dependence of the properties of magnetic nanoparticles on the interparticle separation
Dependence of the magnetic properties of FePt nanoparticles with an average diameter, D, of 5 nm on the interparticle separation, d, has been investigated by employing different spacer molecules. The observed decrease in the blocking temperature and Curie-Weiss temperature with increase in d as well as the increase in saturation magnetization with increase in d have been explained on the basis of a simple model for the case d«D where the magnetic nanoparticles are treated as finite dipoles coupled through anisotropic multipolar interactions
Assembling covalently linked nanocrystals and nanotubes through click chemistry
The click reaction involving the Huisgen 1,3-cycloaddition reaction between azide and ethynyl groups has been employed to obtain assemblies of nanostructures. The click reaction between gold nanorods capped with azidoalkane- and alkyne-thiols yields chains and complex assemblies, accompanied by a large red shift of the longitudinal surface plasmon band. A similar reaction between CdSe nanocrystals results in a splitting of the photoluminescence band, possibly due to exciton splitting. Carbon nanotubes decorated by covalently linked gold nanoparticles have been obtained through click chemistry
Use of Fluorous Chemistry in the Solubilization and Phase Transfer of Nanocrystals, Nanorods, and Nanotubes
Fluorous chemistry, involving the use of a fluorous label for the functionalization of a substrate and a fluorous solvent for extraction of the functionalized substrate, is shown to be effective in solubilizing gold and CdSe nanoparticles in a fluorous medium, through phase transfer from an aqueous or a hydrocarbon medium. While these nanoparticles were functionalized with a fluorous thiol, single-walled carbon nanotubes and ZnO nanorods could be solubilized in a fluorous medium by reacting them with a fluorous amine. Fluorous chemistry enables the solubilization of the nanostructures in the most nonpolar liquid medium possible
New Strategies for the Enrichment of Metallic Single-Walled Carbon Nanotubes
Enrichment of metallic single-walled carbon nanotubes (SWNTs) has been accomplished by several means, including new extraction and synthetic procedures and by interaction with metal nanoparticles as well as electron donor molecules. In the presence of Fe(CO)(5) the arc discharge method yields nearly pure metallic nanotubes. Fluorous chemistry involving the preferential diazotization of metallic SWNTs offers a good procedure of obtaining the pure metallic species. Interaction of gold or platinum nanoparticles as well as of electron-donor molecules such as aniline and tetrathiafulvalene (TTF) transform semiconducting SWNTs into metallic ones. Raman and electroni spectroscopies provide ideal means to monitor enrichment of metallic SWNTs