All authors read and approved the final manuscript.”
“Background Noble metal nanoparticles with localized surface plasmon resonance (LSPR) absorption in the visible wavelength region have a wide variety of beautiful colors. These noble metal nanoparticles have been applied in the field of nonlinear find more optics [1, 2], biological and chemical sensing, and surface-enhanced Raman scattering (SERS)

[3, 4]. Among the noble metal nanoparticles, silver (Ag) and gold (Au) nanoparticles are one of the most investigated SERS-active metal nanoparticles because of their clear LSPR absorption [5–8]. In recent years, a lot of studies have been carried out focusing on the preparation of SERS-active substrates with larger area, low cost, and high performance [3–14]. The LSPR of a noble metal nanoparticle is primarily responsible for the SERS effect [5–8] and the LSPR properties are strongly dependent on the size and shape of the nanoparticles. The surface nanostructures of the substrates affect the properties of the nanoparticles deposited Autophagy inhibitor manufacturer on the substrates. New types of SERS-active substrates have

been developed by using the nanostructures of butterfly and cicada wings [9–14]. It is known that the butterfly and cicada wings have a number of predominant optical effects such as antireflection and photonic bandgap [15, 16]. Especially, the wings of some kinds of cicadas have nanopillar array structures and they show OICR-9429 molecular weight excellent antireflection properties. Usually, nanopillar array structures with tunable gap size are fabricated by electron-beam lithography [11]. On the other hand, the cicada wings composed of chitin are a self-assembled natural nanocomposite material. In our previous studies [17, 18], we have reported that the photocatalytically prepared Ag and Au nanoparticles deposited on TiO2 films showed the excellent SPR-sensing properties. Photocatalytic deposition method seems to be a convenient Oxymatrine and desirable method to obtain stable and immobilized metal nanoparticles on the substrates. Thus, we have applied the photocatalytic deposition method

to fabricate Ag nanoparticles deposited on the cicada wings with nanopillar array structures as SERS-active substrates. In this paper, we have reported the preparation and SERS properties of the Ag nanoparticles deposited on TiO2-coated cicada wings with uniformly ordered nanopillar array structures. Methods The preparation of Ag/TiO2-coated wings, Ag/wings and Ag films The preparation processes of the Ag nanoparticles deposited on TiO2-coated cicada wings (Ag/TiO2-coated wings) and Ag nanoparticles deposited on cicada wings (Ag/wings) without TiO2 are outlined as follows. Cicada wing samples were collected from a Japanese endemic species Cryptotympana facialis (a black cicada with clear and transparent wings). The cicadas were captured locally in Osaka City, Japan.