title: Asymmetric free-standing 2-D photonic crystal films and their Janus particles.
abstract: We report the fabrication of large area, thin asymmetric free-standing two-dimensional (2-D) photonic crystals. We fabricate large area 2-D close-packed monodisperse polystyrene (PS) particle monolayers at air/water interfaces by using our needle tip flow method. We then layer tetraethyl orthosilicate (TEOS) onto the 2-D array to form a thin TEOS layer on the 2-D particle array on water. The hemispheres of PS particles located within the TEOS phase swell such that the adjacent particle hemispheres fuse. After TEOS evaporation, we obtain a free-standing connected photonic crystal film of hemispheres that efficiently diffracts light. The other side of the photonic crystal film consists of a fused connecting thin, flat sheet. Reactive ion etching (RIE) of the asymmetric films forms unusual, rough particle 2-D arrays and 2-D flower-like arrays. Mechanical abrasion allows one to separate the resulting novel Janus particles.
authors.affiliation: Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, USA.
authors.forename: Jian-Tao
authors.initials: JT
authors.lastname: Zhang
authors.forename: Xing
authors.initials: X
authors.lastname: Chao
authors.forename: Sanford A
authors.initials: SA
authors.lastname: Asher