Anisotropic metal nanoparticles for surface enhanced Raman scattering

Abstract

The optimization of the enhancement of Raman scattering by plasmonic effects is largely determined by the properties of the enhancing substrates. The main parameters behind this effect are related to the morphology of plasmonic nanoparticles and their relative distribution within the substrate. We focus this tutorial review on the effects of nanoparticle morphology, for the particular case of anisotropic metal nanoparticles. Anisotropy in silver and gold nanoparticles offers the possibility to tailor their plasmonic properties and intrinsic electromagnetic "hotspots". We describe the effect of varying particle size and shape on the SERS signal, focusing on the most common anisotropic morphologies used for SERS. Especial emphasis is made on existing comparative studies that shed light on the effect of nanoparticle anisotropy on their enhancement capabilities. We aim at providing a general perspective toward understanding the general key factors and highlighting the difficulty in quantitatively determining SERS performance.

Plasmonic Nanoassemblies: Tentacles Beat Satellites for Boosting Broadband NIR Plasmon Coupling Providing a Novel Candidate for SERS and Photothermal Therapy

“…Another example reporting a complicated gold−SERS label−silver nanorattle structure deposited as films inside micropipettes for SERS detection of methyl parathion featured experimental LOD of 10 −6 m and calculated a theoretical LOD (from calibration curves) to be 68 × 10 −9 m (6.8 × 10 −8 m ) . A recent review suggests that most designed nanostructures allow detection of medium‐high Raman cross‐section molecules (labels) in the concentration range of 10 −5 to 10 −7 m , and detection of signal below that is quite challenging. Typically higher signal enhancement and potentially detection of below 10 −8 m is observed for nanostars (of sizes 50−200 nm) and lowest for spherical nanoparticles (especially < 30 nm), hence the core multitentacle nanoassemblies comprised of 5 and 15 nm NPs provides a dramatic boost to the SERS signals allowing detection of 47 × 10 −9 m concentrations, without compromising on the size restrictions for in vivo use.…”

Nanostructured Assemblies of Gold and Silver Nanoparticles for Plasmon Enhanced Spectroscopy Using Living Biotemplates

“…Raman spectroscopy is an analytical technique commonly used in biomedical applications. Over the years, a wide variety of molecular targets have been investigated by SERS using active nanoparticles, mainly gold and silver [2,3,11,12,[26][27][28][29][30][31][32][33][34]. The plasmonic origin of the phenomenon is fully understood [19,37], and nowadays the major effort focuses on the fabrication of new substrates for SERS [38].…”

“…Several techniques allow tuning the characteristics of surfaces for SERS, for instance through lithographic methods, precipitation from colloidal suspensions, or by the physical vapor deposition of metals on a nanostructured surface of silicon or ZnO [27]. Anisotropic metal nanoparticles, on the other hand, offer the possibility of creating "hotspots" of enhanced activity [26,[28][29][30][31][32][33].…”

Surface‐enhanced Raman spectroscopy solution and solid substrates with built‐in calibration for quantitative applications

“…The requirements of controlling the hot spots confine the selection of enhancing media to NPs with high monodisperse and regular shapes, such as cube, cuboid, and octahedron . Among these NPs, both Au and Ag nanocuboids (NCs) with high monodisperse can be synthesized through the Au nanorod (NR)‐mediated seed growth .…”