An Efficient Method for Covalent Surface Functionalization of Ultrasmall Metallic Nanoparticles by Surface Azidation Followed by Copper‐Catalyzed Azide‐Alkyne Cycloaddition (Click Chemistry)

The azidation of glutathione (GSH)-functionalized ultrasmall gold nanoparticles (2 nm) by the azide transfer reagent imidazole-1-sulfonyl hydrogen sulfate leads to azide-terminated with high yield. A subsequent copper-catalyzed azide-alkyne cycloaddition (CuAAC), i. e. a click reaction, covalently functionalized nanoparticles. This was demonstrated two alkyne-functionalized dyes, FAM-alkyne and AlexaFluor-647-alkyne, that were coupled integrity ligand successful surface one-dimensional two-dimensional NMR spectroscopy. composition determined quantitative spectroscopy UV/vis Each nanoparticle carries 125 molecules which 118 substituted an group. After dye conjugation, either 6 FAM or 11 AlexaFluor-647 present on each nanoparticle, respectively. dye-clicked highly fluorescent due absence plasmon resonance. post-functionalization GSH avoids chemical reaction functional during reduction gives yield (up 50 mg per batch), is based water as solvent, applicable for metallic in general.