An Invisible Template Method toward Gold Regular Arrays of Nanoflowers by Electrodeposition Jingjing Wang, Guotao Duan,* Yue Li, Guangqiang Liu, Zhengfei Dai, Hongwen Zhang, and Weiping Cai* Key Lab of Materials Physics, Anhui Key Lab of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, Anhui, PR China * S Supporting Information ABSTRACT: A new approach, an invisible template method that is realized through controlling the interface electroconductivity of an electrode surface, is presented to synthesize gold regular arrays of nanoflowers with variable separations through further electrochemical deposition. Using polystyrene monolayer colloidal crystals as the first template, a hexagonally packed 1-hexadecanethiol pattern was self-assembled and used as an invisible template to control the interface electroconductivity. Further electrochemical deposition under appropriate conditions can easily lead to gold regular arrays of nanoflowers. This new approach demonstrates a simple route to the fabrication of novel gold micro/nanostructured arrays that may find applications as SERS active substrates, superhydrophobic materials, and so forth. 1. INTRODUCTION Micro/nanostructured arrays, having microscale periodicity and nanostructured building blocks, are of great interest because of their possible applications as surface-enhanced Raman scatter- ing (SERS) active substrates, 1-4 as superhydrophobic surfa- ces, 5-9 and in gas sensors. 10-12 Many methods are developed to fabricate the micro/nanostructured array structures, such as photolithographic techniques, 13,14 electron-beam lithogra- phy, 15-17 and various hard-template methods. 18-21 Among them, the hard-template methods were most widely used because of their simple, effective, low-cost merits. Generally, hard templates are used as the mold and have a spatial confinement effect on the formation of the final structures. Typically, polystyrene (PS) spheres or SiO 2 sphere monolayer colloidal crystals have been the most commonly used hard templates in past decades. 22-26 Besides hard-template methods, soft-template methods are also developed in nanofabrication techniques. Usually, the surfactant used as a soft template mainly plays the role of a structure-directing effect and mask. Different from cells of PS or SiO 2 spheres in a hard template, the surfactant molecule cells in soft template seem to be invisible by scanning electron microscopy. Thus, we also called it an invisible template. Such an invisible template method can also be used for the fabrication of patterned arrays if combined with hard-template methods. For example, Xia et al. fabricated gold and silver ring arrays on solid substrates using alkanethiol as the mask and self- assembled silica beads as the hard template. 27 Liu et al. made use of octadecanethiol as a corrosion protection layer for fabricating gold particle patterns to grow vertically aligned ZnO nanorod arrays with the aid of PS monolayer colloidal crystals. 28 Compared to a hard template, invisible template methods have three main advantages in the fabrication of micro/nanostructures: (1) First, the invisible template has a weak spatial confinement effect on the formation of materials, which is advantageous to the control of crystallization. (2) Second, the hard template also plays a supporting skeleton role for the as-prepared micro/nanostructures whereas the soft template does not play this role, which leads to greater structural stability after the removal of the template as for the invisible template method. (3) Third, the removal of the invisible template is easily realized and has a greater effect on the as-fabricated materials, and even in many applications, the existence of an invisible template has no effect on the final functional applications. Although these advantages exist, reports of the invisible template method for the fabrication of micro/nanostructured arrays are quite limited in the literature. Here, we proposed an invisible template method that is realized through controlling the interfacial electroconductivity of an electrode surface. In this case, gold regular arrays of nanoflowers were prepared on the basis of this template combined with further electro- deposition. The key to this method is realizing a pattern of self- assembled 1-hexadecanethiol (HDT) on a gold electrode based on a PS monolayer colloidal crystal. The whole procedure is schematically shown in Figure 1. First, the well-cleaned ITO substrate was coated with a layer of gold via ion-sputtering deposition. Then an as-formed uniform monolayer colloidal Received: January 31, 2013 Revised: February 25, 2013 Published: March 1, 2013 Letter pubs.acs.org/Langmuir © 2013 American Chemical Society 3512 dx.doi.org/10.1021/la400433z | Langmuir 2013, 29, 3512-3517