Patterning of organic monolayers on silver via surface-induced photoreaction

4-Nitrobenzenethiol (4-NBT) is readily converted on silver to 4-aminobenzenethiol by irradiation with a visible laser. This is clearly evidenced from the surface-enhanced Raman scattering and the X-ray photoelectron spectroscopy measurements as well as from a coupling reaction to form amide bonds. The source of hydrogen atoms in the surface-induced photoreduction is presumed to be water or solvent molecules trapped inside the 4-NBT monolayer. The present surface-induced photoreaction allows us to readily prepare patterned binary monolayers on Ag that will show different chemical reactivities. Using the binary monolayers as a lithographic template, we can conduct site-specific chemical reactions. We also demonstrate that a typical biomineral, that is, calcite, can be grown selectively on either the nitro group terminated regions or the amine group terminated regions by adjusting the crystal growth conditions. Since the amine group can be derivatized further to give, for instance, a thiol terminus, the present surface modification method must be as beneficial as the hitherto known methods specifically for the construction of two-dimensional heterostructures consisting of different kinds of nanoparticles.