Mapping Organic Functional Groups at Nanosurfaces Using Colloidal Gold Conjugation

The functionalization of nanomaterials surface is key to improve their stability, reactivity and confer specific properties. However, mapping functional groups at the nanoscale remains difficult, i.e. identifying chemical nature but also spatial distribution. It is particularly challenging for organic groups and non-planar objects such as nanoparticles. Here we report a strategy for mapping amine groups on the surface of silica particles using chemically-modified gold colloids, which are used as tags to specifically and spatially identify these organic groups under electron microscopy. A complete understanding of the correlation between spatial distribution of gold colloids and chemical state of the silica particle surface (by XPS) is presented. The range of reliability of this strategy for mapping organic groups at nanointerfaces is assessed and its implications for biofunctional nanoobjects where interdistance of biomolecules are of paramount importance are discussed.