Reaction of Terminal Phosphinidene Complexes with Acetylenic Alcohols: Intramolecular Hydrophosphination of a Phosphirene Ring

The transient phosphinidene complex [PhP−Mo(CO)5], as generated from the appropriate 7-phosphanorbornadiene complex at 110 °C in toluene, selectively reacts with the C⋮C triple bond of 4-phenyl-3-butyn-1-ol to give the corresponding phosphirene complex 4. Upon further heating, this phosphirene evolves via two pathways. The minor pathway involves the formal addition of the OH bond of the alcohol function onto the phosphirene P−C ring bond to give the 3-benzylidene-1,2-oxaphospholane complex 5. The major pathway involves the reaction of a second molecule of [PhP−Mo(CO)5] with the OH group of 4, giving an intermediate phosphirene with an additional secondary alkoxyphosphine functionality (7). An intramolecular hydrophosphination of one P−C bond of the phosphirene ring then immediately takes place to give the cis-1,2-bis(phosphino)ethene [Mo(CO)4] complex 8 as a mixture of two diastereomers. After methylation of the PH group of 8, decomplexation can be efficiently achieved by reaction with sulfur. Structures have been ascertained by X-ray analysis for 5, 8, and the disulfide 10

Functionalization and Dissolution of Nitric Acid Treated Single-Walled Carbon Nanotubes

We report an investigation of the nature and chemical functionalization of nitric acid treated single-walled carbon nanotubes (SWNTs). SWNTs washed with diluted sodium hydroxide solutions were characterized by near-IR, mid-IR, and Raman spectroscopy as well as TEM, and the remaining carboxylic acid content was determined to assess the effect of base washing on the removal of carboxylated carbon fractions, which are generated by the nitric acid treatment. It was found that even after exhaustive washing with aqueous base the purified SWNTs contain carboxylic acid groups in sufficient quantity to prepare high quality soluble SWNT materials by covalent functionalization with octadecylamine

Chemically Functionalized Water-Soluble Single-Walled Carbon Nanotubes Modulate Morpho-Functional Characteristics of Astrocytes

We report the use of chemically functionalized water-soluble single-walled carbon nanotubes (ws-SWCNTs) for the modulation of morpho-functional characteristics of astrocytes. When added to the culturing medium, ws-SWCNTs were able to make astrocytes larger and stellate/mature, changes associated with the increase in glial fibrillary acidic protein immunoreactivity. Thus, ws-SWCNTs could have more beneficial effects at the injury site than previously thought; by affecting astrocytes, they could provide for a more comprehensive re-establishment of the brain computational power

Synthesis, Dispersion, and Viscosity of Poly(ethylene glycol)-Functionalized Water-Soluble Single-Walled Carbon Nanotubes

The carbon nanotube−polyethylene glycol (PEG) graft copolymer was synthesized by covalent functionalization of electric arc single-walled carbon nanotubes (SWNTs) with the monofunctional, tetrahydrofurfuryl-terminated polyethylene glycol PEG-THFF (MW∼200), to give a material composed of 80 wt % SWNTs. We show that the sequential processing of the resulting material by ultrasonication and high-shear mixing provides a means to disperse the SWNT-PEG-THFF macromolecules on two different length scales and leads to highly viscous solutions; at a concentration of 10 mg/mL the kinematic viscosity (ν) of an aqueous SWNT-PEG-THFF dispersion reaches a value of ν > 1000 cSt (for water ν ∼ 1 cSt). Analysis of this procedure by means of viscosity measurements and atomic force microscopy (AFM), shows that ultrasonication is effective in disrupting the SWNT bundles, while the high shear mixing disperses the individual SWNTs. The kinematic viscosity of aqueous dispersions of SWNT-PEG-THFF was measured as a function of nanotube concentration and compared to that of SWNT-PEG dispersions. The viscosity and AFM measurements show that the SWNT-PEG-THFF and SWNT-PEG graft copolymers form aqueous dispersions with distinct viscous characteristics; the use of monofunctional PEG-THFF for covalent functionalization of the SWNTs prevents cross-linking of the SWNTs in the final product, and this allows the production of more completely dispersed SWNTs than in the case of the SWNT-PEG graft copolymer, which is synthesized from a bifunctional glycol

Mechanism of Ammonia Detection by Chemically Functionalized Single-Walled Carbon Nanotubes: <i>In </i><i>Situ</i> Electrical and Optical Study of Gas Analyte Detection

We provide definitive evidence for the mechanism of electronic detection of ammonia by monitoring in situ changes in the electrical resistance and optical spectra of films of poly(m-aminobenzenesulfonic acid)-functionalized SWNTs (SWNT-PABS). The increase of resistance during exposure to ammonia is associated with deprotonation of the PABS side chain that in turn induces electron transfer between the oligomer and the valence band of the semiconducting SWNTs. Near IR spectroscopy is used to demonstrate that the charge transfer is a weakly driven process, and this accounts for the high reversibility of the sensor. We show that the sensitivity of the chemiresistors increases as the film thickness is reduced to the percolation threshold and that the SWNT-PABS film thickness provides a simple means to enhance the electronic response

Chemically Functionalized Single-Walled Carbon Nanotube Films Modulate the Morpho-Functional and Proliferative Characteristics of Astrocytes

We used single-walled carbon nanotube (CNT) films to modulate the morpho-functional and proliferative characteristics of astrocytes. When plated on the CNT films of various thicknesses, astrocytes grow bigger and rounder in shape with a decrease in the immunoreactivity of glial fibrillary acidic protein along with an increase in their proliferation, changes associated with the dedifferentiation of astrocytes in culture. Thus, CNT films, as a coating material for electrodes used in brain machine interface, could reduce astrogliosis around the site of implantation