Fabrication of two-dimensional structures of metal oxide nanocrystals using Si substrate modified with 3,4-Dihydroxyhydrocinnamic acid

Sufficiently high-coverage monolayer structures of cerium oxide nanocrystals modified with decanoic acid, with sizes of ∼9 nm, were fabricated on the surface using a silicon substrate modified with 3,4-dihydroxyhydrocinnamic acid where catechol group lied at the top. By doing this, no further pretreatment for the modified nanocrystals is required to fix them chemically on the substrate. Selective adhesion between nanocyrstals and the substrate for the two-dimensional assembly can be attributed to the chemical bonding formed by on-site ligand exchange on the catechol-terminated substrate. Catechol-carboxyl group ligand exchange results in high-efficient due to higher affinity of catechol to metal oxide surfaces. This affinity difference enabled to perform this on-site ligand exchange even at room temperature.