Close-Packed Colloidal Monolayers of Ultra-Smooth Gold Nanospheres by Controlled Trapping onto Polymer Thin Films

Ultra-smooth and highly-spherical gold nanoparticles can form uniform colloidal film from evaporating sessile droplets on substrates at relatively high temperature, in which gold nanospheres are assembled at the air-liquid interface due to fast evaporation and further form multilayers on polystyrene-coated silicon wafer. Then, gold nanospheres at bottom layer are wetted by polystyrene upon thermal annealing around 80 °C and securely trapped in polymer solid film during cooling step. Finally, additionally stacked nanospheres in multilayer film are washed out by simple sonication leaving high-quality colloidal monolayers of gold nanospheres.