Abstract
We describe the growth and characterization of a set of gold and silver nanoparticles (NPs) as well as fluorescent nanoclusters (NCs) using one-step reduction (in aqueous phase) of Au and Ag precursors in the presence of modular bifunctional ligands. These ligands are made of bidentate (lipoic acid) anchoring groups appended with poly(ethylene glycol) segment, LA-PEG. The particle size can be easily controlled by varying the metal-to-ligand molar ratio during growth. We found that while high metal-to-ligand molar ratios promote the formation of NPs, small size and highly fluorescent NCs are exclusively formed when molar excesses of ligands are used. Both sets of NCs emit in the red to near infrared (NIR) region of the optical spectrum, though the exact location of the emission depends on the material used. The growth strategy further permitted the in-situ functionalization of the NCs with reactive groups (e.g., carboxylic acid or amine), which opens up the opportunity to conjugate these materials to biomolecules using simple to implement coupling chemistries.