Electrochemical and optical characterization of triarylamine functionalized gold nanoparticles.

This paper describes the synthesis, structural analysis, and investigations of the optical and electrochemical properties of some gold nanoparticles (AuNPs) which consist of a triarylamine ligand shell attached to small gold cores (Au-Tara). The triarylamine chromophores were attached to small 4-bromobenzenethiol covered gold nanoparticles (ca. 2 nm in diameter) by Sonogashira reaction. This procedure yields triarylamine redox centers attached via π-conjugated bridging units of different length to the gold core. The AuNPs were analyzed with (1)H NMR spectroscopy, diffusion ordered NMR spectroscopy (DOSY), thermogravimetric analysis (TGA), and scanning transmission electron microscopy (STEM). Cyclic voltammetry (CV) technique was used to determine the composition of the redox active particles via the Randles-Sevcik equation. The optical and electrochemical properties of the Au-Tara nanoparticles and of their corresponding unbound ligands (Ref) were investigated with UV/vis/NIR absorption spectroscopy, Osteryoung square wave voltammetry (OSWV), and spectroelectrochemistry (SEC). These data show that the assembling of triarylamines in the vicinity of a gold nanoparticle can change the optical and electrochemical properties of the triarylamine redox chromophores depending on the kind and length of the bridging unit. This is due to gold core-chromophore and chromophore-chromophore interactions.

Design and synthesis of Raman reporter molecules for tissue imaging by immuno-SERS microscopy.

The design and synthesis of Raman reporter molecules comprising olefin or alkyne moieties with strong and characteristic vibrational Raman bands is presented. Chemisorption onto the surface of colloidal Au/Ag shells yields a self-assembled monolayer. Hydrophilic stabilization of such SERS labels can be achieved by short terminal ethylene glycol units attached to the Raman reporter. Encapsulation by silica with subsequent functionalization of the glass surface allows the conjugation to biomolecules such as antibodies. We demonstrate the use of SERS-labeled antibodies for tissue imaging of the tumor suppressor p63 in prostate biopsies.

Mixed-valence interactions in triarylamine-gold-nanoparticle conjugates.

Optical and electrochemical investigations of triarylamine redox centres attached to gold nanoparticles via a pi-conjugated bridge show intervalence charge-transfer bands which prove to be surprisingly strong interchromophore interactions.