Abstract
Two-dimensional (2D) periodic micro/nanostructured arrays as SERS substrates have attracted intense attention due to their excellent uniformity and good stability. In this work, periodic hierarchical SiO2 nanopillar arrays decorated with Ag nanoparticles (NPs) with clean surface were prepared on a wafer-scale using monolayer Au NP arrays as masks, followed by reactive ion etching (RIE), depositing Ag layer and annealing. For the prepared SiO2 nanopillar arrays decorated with Ag NPs, the size of Ag NPs was tuned from ca. 24 to 126 nanometers by controlling the deposition thickness of Ag film. Importantly, the SiO2 nanopillar arrays decorated with Ag NPs could be used as highly sensitive SERS substrate for the detection of 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) due to the high loading of Ag NPs and a very uniform morphology. With a deposition thickness of Ag layer of 30 nm, the SiO2 nanopillar arrays decorated with Ag NPs exhibited the best sensitive SERS activity. The excellent SERS performance of this substrate is mainly attributed to high-density “hotspots” derived from nanogaps between Ag NPs. Furthermore, this strategy might be extended to synthesize other nanostructured arrays with a large area, which are difficult to be prepared only via conventional wet-chemical or physical methods.
Highlights
Surface enhanced Raman scattering (SERS) has been considered as a promising spectroscopic technique for label-free and nondestructive trace detection for biological and chemical analytes at super low concentration with ultra-sensitivity [1,2,3,4,5,6,7]
When the deposition thickness of Ag layer is 30 nm, the SiO2 nanopillar arrays decorated with Ag NPs possess highly sensitive SERS activity
2018, 11, periodic theMaterials hierarchical arrays composed of SiO2 nanopillar arrays decorated with Ag NPs with deposition thickness of 20 nm, 30 nm, 60 nm and 90 nm were selected for further SERS investigation
Summary
Surface enhanced Raman scattering (SERS) has been considered as a promising spectroscopic technique for label-free and nondestructive trace detection for biological and chemical analytes at super low concentration with ultra-sensitivity [1,2,3,4,5,6,7]. Noble metal (Au and Ag) nanoparticles (NPs) can generate intense electromagnetic field due to localized surface plasmon resonance (LSPR), resulting in excellent activity as a SERS substrate [9]. The places where the electromagnetic field is extremely strong for enhancing Raman scattering are called “hotspots”, which mainly depend on the nanogap, morphology, size and nature of the metal materials [12]. Significant efforts have been raised to construct SERS substrates by synthesizing Au, Ag and Au–Ag alloyed NPs with different size and morphologies, such as concave trisoctahedral and calyptriform Au nanocrystal [13], porous Au NPs [14], porous Au–Ag alloyed nanocubes [15], Ag–Au hybrid nanosponges [16] and AuAg bimetallic nanoparticles [17]. Gao and co-workers fabricated porous Au–Ag alloy NPs with clean surface via a dealloying process
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