Adsorption of single walled carbon nanotubes onto silicon oxide surface gradients of 3-aminopropyltri(ethoxysilane) described by polymer adsorption theory.

Integration of single-walled carbon nanotubes (SWNT) into complex sensing and electronic devices can necessitate the selective placement of individual nanotubes from solution onto custom-prepared surfaces. Existing studies indicate carbon nanotube adsorption can be controlled by creating hydrophilic and/or hydrophobic surfaces, depending on the nanotube surface chemistry and solvent. Various recipes exist for specific conditions, but no quantitative theoretical model describing experimental observations has been developed.

Controlling the electrophoretic mobility of single-walled carbon nanotubes: a comparison of theory and experiment.

The electrophoretic mobilities of single-walled carbon nanotubes (SWNTs) in agarose gels subjected to negatively charged covalent functionalization and noncovalent anionic surfactant adsorption are compared using a simplified hydrodynamic model. Net charges are calculated on the basis of estimated friction coefficients for cylindrical rodlike particles. The effects of functionalization with negatively charged 4-hydroxybenzene diazonium and anionic sodium cholate are quantified and compared with model predictions.

A structure-reactivity relationship for single walled carbon nanotubes reacting with 4-hydroxybenzene diazonium salt.

The first structure-reactivity relationship for electron-transfer reactions of single walled carbon nanotubes (SWNTs) has been derived and experimentally validated using 4-hydroxybenzene diazonium as a model electron acceptor. The model describes steady-state reaction data using an adsorption-controlled scheme, and electron transfer theories are used to explain the difference in reactivities between different nanotube chiralities. The formalism provides a mechanistic insight into electronically selective reactions.

Estimation of the (n,m) concentration distribution of single-walled carbon nanotubes from photoabsorption spectra.

Deconvolution of the absorption spectrum of single-walled carbon nanotubes (SWNTs) into distinct (n,m) contributions is complicated because transition energies are closely spaced. The algorithm presented in this work attempts to simplify the problem by grouping nanotubes with similar transition energies and assigning weights to their spectral contributions. Voigt line shapes were used to fit absorption spectra of sodium dodecyl sulfate suspended HiPco SWNT and CoMoCat SWNT.

Evidence for a two-step mechanism in electronically selective single-walled carbon nanotube reactions.

Covalent and noncovalent chemistries that are selective to single-walled carbon nanotubes of a particular electronic type have become increasingly important for electronic structure separation and on-chip modification of nanoelectronic devices. By monitoring transient Raman spectroscopy and photoluminescence (PL) during a reaction with 4-chlorobenzene diazonium in aqueous solution, evidence for a characteristic two-step mechanism with two distinct time constants is uncovered. A long-lived intermediate selectively and noncovalently binds and partially dopes the nanotube surface (tau = 2.

Concomitant length and diameter separation of single-walled carbon nanotubes.

Gel electrophoresis and column chromatography conducted on individually dispersed, ultrasonicated single-walled carbon nanotubes yield simultaneous separation by tube length and diameter. Electroelution after electrophoresis is shown to produce highly resolved fractions of nanotubes with average lengths between 92 and 435 nm. Separation by diameter is concomitant with length fractionation, and nanotubes that have been cut shortest also possess the greatest relative enrichments of large-diameter species.

Electronic structure control of single-walled carbon nanotube functionalization.

Diazonium reagents functionalize single-walled carbon nanotubes suspended in aqueous solution with high selectivity and enable manipulation according to electronic structure. For example, metallic species are shown to react to the near exclusion of semiconducting nanotubes under controlled conditions. Selectivity is dictated by the availability of electrons near the Fermi level to stabilize a charge-transfer transition state preceding bond formation.