Catalytic self-assembled monolayers on gold nanoparticles

This review describes the attractiveness of catalytic self-assembled monolayers (SAMs) on gold nanoparticles as catalytic systems. The hybrid inorganic–organic catalytic systems combine the advantages of homogeneous and heterogeneous catalysis (higher activity and catalyst recycling, respectively). The high fidelity process of SAM formation on gold nanoparticles, together with the possibility of making mixed SAMs composed of different thiols, provides an unprecedented route to stable, complex catalytic systems. Insertion of catalysts in a mixed monolayer can improve the catalytic performances, due to catalyst orientation, changes in the local chemical environment, or through the steering effect of neighbouring thiols. Alternatively, insertion of catalytic units in a monolayer may be an essential prerequisite in the case when catalysis requires cooperation between two catalytic units (for instance two metal ions). Finally, the multivalent nature of these systems is an important feature especially in the case when the substrate contains multiple reactive sites. Catalytic SAMs on gold nanoparticles also find applications beyond the field of catalysis, for instance in diagnostics and nanotechnology.