Low-Cost Fabrication of Pt Thin Films with ... - IngentaConnect

716 Plasmonics (2011) 6:715–723achieve this is to construct nanostructured films withcontrolled morphologies. For example, Abdelsalam et al.fabricated Pt films by replicating close-packed polymerspheres to produce regular patterns with repeating distancesof a few hundreds of nanometers, and showed some ofthem have good matching with visible light enabling SERSon them [14]. The other possibility is to form regularnanostructured films in which constituting nanoparticlesand/or nanorods interact to broaden the SPR peak and shiftthe SPR band to longer wavelengths. This method also mayhave the advantage of producing narrow gaps betweennanoparticles or nanorods with strongly localized electromagneticfields, which are believed to serve as hot spots forSERS effects. However, there has been quite a few worksdone in this direction.In fact, the importance of the morphology control ofnanostructured films is not limited to Pt. The morphologyeffects of coinage metals have been widely studied. Typically,electron beam lithography [20–22] andLangmuir–Blodgett(LB) technique of colloidal nanoparticles [23–27] have beenexplored toward this end. These methods have beensuccessful in increasing the SERS effects, but also revealsome limitations. As for the electron beam lithography, thefabrication is time-consuming and expensive, prohibitingsubstrates in large areas [28]. Although the LB techniquecan produce nanostructured films with large areas atmuch lower cost, it is difficult to make films with highdensities and regular inter-particle distances.Template-assisted synthesis can produce thin films withregularly ordered nanostructures over large areas at lowcost [29]. However, such possibilities have been exploredfor SERS only in a few cases. Although there have been anumber of cases in which anodized aluminum oxidetemplates are used to synthesize nanorods, the main focushas been on the control of the shape and size of thenanorods, not on the formation of the array structure ofnanorods [30–33]. In this regard, mesoporous thin filmtemplates appear to be advantageous because nanostructuredfilms with very fine features