Current-less photoreactivity catalyzed by functionalized AFM tips.

A spatially confined photocatalytic oxidation of a thin film of synthetic textile azo dye (Procion Red MX-5B) using TiO2-functionalized AFM probes is described.

Importance of aromatic content for peptide/single-walled carbon nanotube interactions.

We have previously demonstrated that a designed amphiphilic peptide helix, denoted nano-1, coats and debundles single-walled carbon nanotubes (SWNTs) and promotes the assembly of these coated SWNTs into novel hierarchical structures via peptide-peptide interactions. The purpose of this study is to better understand how aromatic content impacts interactions between peptides and SWNTs. We have designed a series of peptides, based on the nano-1 sequence, in which the aromatic content is systematically varied.

Diameter-selective solubilization of single-walled carbon nanotubes by reversible cyclic peptides.

We have utilized reversible cyclic peptides (RCPs)-peptides containing alternating l- and d-amino acids with N- and C-termini derivatized with thiol-containing groups allowing reversible peptide cyclization-to solubilize and noncovalently functionalize carbon single-walled nanotubes (SWNTs) in aqueous solution. Solubilization occurs through wrapping of RCPs around the circumference of a SWNT, followed by the formation of head-to-tail covalent bonds, yielding closed rings on the nanotubes. By controlling the length of the RCPs, we have demonstrated limited diameter-selective solubilization of the SWNTs as revealed by UV/vis/NIR and Raman spectroscopies, as well as atomic force microscopy.

Preparation and characterization of individual peptide-wrapped single-walled carbon nanotubes.

Two challenges for effectively exploiting the remarkable properties of single-walled carbon nanotubes (SWNTs) are the isolation of intact individual nanotubes from the raw material and the assembly of these isolated SWNTs into useful structures. In this study, we present atomic force microscopy (AFM) evidence that we can isolate individual peptide-wrapped SWNTs, possibly connected end-to-end into long fibrillar structures, using an amphiphilic alpha-helical peptide, termed nano-1. Transmission electron microscopy (TEM) and well-resolved absorption spectral features further corroborate nano-1's ability to debundle SWNTs in aqueous solution.