Fabrication of poly(methyl methacrylate) colloidal monolayer on chemically modified silicon surface and hemispherical platinum nanoshell

A dip-coating technique was used to deposit self-assembled monolayer arrays of PMMA colloidal particles with a diameter of 125 nm onto a silicon surface coated with (3-aminopropyl)-triethoxysilane (APTES), exploiting the electrostatic interaction between the negative particle and the positive substrate. The PMMA colloidal arrangement was controlled efficiently by the dipping time and temperature, concentration and pH of the colloidal solutions. A non-close-packed monolayer assembly was prepared without the need for pre-patterned templates. The deposition of platinum metal on the 2D PMMA arrays and subsequent thermal treatment produced ordered hemispherical Pt nanoshells, 74 nm in height, as soft-lithographic templates and biological sensor materials.