Ag nanoparticle/ZnO hollow nanosphere arrays: large scale synthesis and surface plasmon resonance effect induced Raman scattering enhancement

Abstract

ZnO hollow nanosphere (HNS) arrays decorated with Ag nanoparticles (NPs) were fabricated on silicon substrates using self-assembled monolayer polystyrene (PS) nanospheres as the template. The O 2 plasma etching was introduced to manipulate the diameters of the ZnO HNSs. This fabrication method has the advantages of simplicity, large scale production, easy size and shape manipulations, low cost and bio-compatibility. Scanning electron microscopy (SEM) images show that the obtained Ag NP-ZnO HNS hybrid structures are hexagonally arranged, with the uniform size and shape, and the X-ray diffraction (XRD) pattern shows that the ZnO HNS arrays are of high crystal quality and have a dominant orientation of <0001> direction. Resonant Raman scattering spectra reveal the multiphonon A1 (LO) modes of ZnO hollow nanospheres at 574, 1147 and 1725 cm À1 . Enhanced resonant Raman scattering from the Ag NP modified ZnO HNSs was observed, indicating a strong energy coupling effect located at the metal/semiconductor interface. Surface enhanced Raman scattering (SERS) application for the Ag NP decorated ZnO HNS arrays was verified using a Rhodamine 6G (R6G) chromophore as a standard analyte, which is proved to be an effective SERS template for Raman signal detection. SERS substrates with different structures have been compared, and the Ag NP modified ZnO HNS system exhibits superior Raman scattering enhancements induced by the local surface plasmon resonance (LSPR) effect. The SERS mechanism was well explained by theoretical calculation results. This study is helpful to fabricate controllable Ag NP arrays using the ZnO HNS as the supporting structure and to understand the mechanism of bio-sensing enhancements due to the LSPR effect originated from the metal NPs and metal/semiconductor interface.

Ag-Decorated Localized Surface Plasmon-Enhanced Ultraviolet Electroluminescence from ZnO Quantum Dot-Based/GaN Heterojunction Diodes by Optimizing MgO Interlayer Thickness

“…Since the work function of ZnO is about 5.2 eV vs. NHE and its first electron affinity is about 4.3 eV vs. NHE, the work function of Ag is about 4.26 eV vs. NHE, as illustrated in Fig. 4a, this enables the electron transfer from the Ag to ZnO until the two systems achieve the uniform Fermi level, thus resulting in forming a strong polarization-induced local electromagnetic field due to the charge separation [36]. The oscillating electrons in the Ag-NPs can be excited to a high energy level by LSPR.…”

A sensitive SERS substrate based on Au/TiO2/Au nanosheets

“…The support materials were decorated with nanoparticles that induced ''hot spots'' in the gaps and provided several orders of magnitude enhancement [12]. Various materials have been used as support component such as nanoporous GaN [13,14], Si [15] and ZnO [16,17]. Being an important wide gap semiconductor with particular optical and chemical properties [18,19], TiO 2 is also a good candidates for support material [20,21].…”

ZnO/Ag heterostructured nanoassemblies: Wet-chemical preparation and improved visible-light photocatalytic performance

“…Especially, hybridized ZnO/Ag nanoarchitectures are of particular interest on account of their outstanding physical-chemical properties and their wide range of applications in such fields as photocatalysis [16,17], microelectronics [18], solar cells [19], sensors [20], and surface-enhanced Raman scattering (SERS) [21]. Therefore, in the past few years, a variety of ZnO/Ag hierarchical nanostructure, including ZnO nanorods/Ag nanowires [22,23], ZnO nanorods/Ag nanoparticles [24], ZnO nanoflowers/Ag nanoparticles [25], ZnO nanoparticles/Ag nanoparticles [26], and ZnO hollow nanospheres/Ag nanoparticles [27], have been prepared using different approaches and strategies. In spite of great achievements in the design and fabrication of ZnO/Ag hybrid nanoassemblies, further exploration of some facile, mild, low-cost, and high-yield synthetic routes to manufacture tailored nanostructured materials is still desired.…”