Y. Shi, M. Osada, Y. Ebina, T. Sasaki: “Single droplet assembly for 2D nanosheet tiling”, ACS Nano, 14, 15216-15226 (2020).
Recent advances in two-dimensional (2D) materials offer an opportunity for atomic layer engineering of functional thin films and superlattices. For future applications of 2D materials, there is an urgent need to develop convenient deposition processes that enable precise control of thin-film architectures while reducing the time, cost, and energy/sample consumption. Here, we demonstrate a strategy for nanosheet assembly using a simple drop casting with a pipet and a hot plate. By controlled thermal convection of a single droplet on a hot plate, a range of 2D nanosheets, such as Ti0.87O20.52–, Ca2Nb3O10–, Ru0.95O20.2–, and graphene oxide, can be neatly tiled to form an ideal monolayer on various substrates in ∼30 s over a wide area (i.e., a 50 mmϕ substrate). The mechanism and control strategies are discussed. We also demonstrate the production of various functional coatings such as conducting, semiconducting, insulating, magnetic, and photochromic coatings in multilayer, superlattice, and submicrometer-thick forms, offering the potential for a convenient way to produce high-quality 2D nanosheet films.