▎ 摘　　要

Graphene quantum dots (GQDs) are one of the most attractive graphene nanostructures due to their potential optoelectronic device applications, but it is a challenge to accurately control the size and arrangement of GQDs. In this report, we fabricate well-aligned GQDs on a large area by polystyrene (PS)-nanosphere (NS) lithography and study their structural and optical properties. Single-layer graphene grown on a Cu foil by chemical vapour deposition is patterned by reactive ion etching employing aligned PS-NS arrays as an etching mask. The size (d) of the GQDs is controlled from 75 to 23 nm by varying the etching time, as proved by scanning electron microscopy and atomic force microscopy. This method is well valid for both rigid/flexible target substrates and even for multilayer graphene formed by piling up single layers. The absorption peak of the GQDs is blue-shifted with respect to that of a graphene sheet, and is sequentially shifted to higher energies by reducing d, consistent with the quantum confinement effect (QCE). The Raman D-to-G band intensity ratio shows an almost monotonic increase with decreasing d, resulting from the dominant contribution of the edge states at the periphery of smaller GQDs. The G-band frequency shows a three-step size-dependence: initial increase, interim saturation, and final decrease with decreasing d, thought to be caused by the competition between the QCE and edge-induced strain effect.