**2. Nanosphere lithography (NSL)**

Enormous efforts have been devoted to investigate alternative nanolithography approaches. One of promising methods is nanosphere lithography (NSL) (Fuhrmann et al., 2005; Haynes & Van Duyne, 2001; Hulteen & Van Duyne, 1995; Kosiorek et al., 2004; Sinitskii et al., 2007), which is a highly accessible, low cost, parallel fabrication process capable of producing nanostructured surfaces over large areas and with high resolution. In NSL, self-assembled nanospheres can be served directly as ordered nanostructures (Park et al., 1998) or a mask for the subsequent fabrication of nanostructures, which can be realized by deposition of desired materials, or by etching on desired substrates. A rich varieties of ordered nanostructures have been achieved by NSL, such as triangular structures (Winzer et al., 1996), metallic rings (Boneberg et al., 1997), nanopillars (Weeks et al., 2004), and multilayer with modified topography (Albrecht et al., 2005), nanodots (Chen et al., 2009; Weekes et al., 2007), 3D nanostructure (Zhang et al., 2007), discs (Hanarp et al., 2003) and nanoscale crescents (Gwinner et al., 2009; Retsch et al., 2009; Vogel et al, 2011). The shape, the size and the arrangement of ordered nanostructures can be readily controlled in combination of NSL and the subsequent deposition of desired materials (Haynes & Van Duyne, 2001; Zhang et al., 2007; Vogel et al, 2011).
