Rapid Biochemical Mixture Screening by Three-Dimensional Patterned Multifunctional Substrate with Ultra-Thin Layer Chromatography (UTLC) and Surface Enhanced Raman Scattering (SERS)

Abstract

We present a three-dimensional patterned (3DP) multifunctional substrate with the functions of ultra-thin layer chromatography (UTLC) and surface enhanced Raman scattering (SERS), which simultaneously enables mixture separation, target localization and label-free detection. This multifunctional substrate is comprised of a 3DP silicon nanowires array (3DP-SiNWA), decorated with silver nano-dendrites (AgNDs) atop. The 3DP-SiNWA is fabricated by a facile photolithographic process and low-cost metal assisted chemical etching (MaCE) process. Then, the AgNDs are decorated onto 3DP-SiNWA by a wet chemical reduction process, obtaining 3DP-AgNDs@SiNWA multifunctional substrates. With various patterns designed on the substrates, the signal intensity could be maximized by the excellent confinement and concentrated effects of patterns. By using this 3DP-AgNDs@SiNWA substrate to scrutinize the mixture of two visible dyes, the individual target could be recognized and further boosted the Raman signal of target 15.42 times comparing to the un-patterned AgNDs@SiNWA substrate. Therefore, such a three-dimensional patterned multifunctional substrate empowers rapid mixture screening, and can be readily employed in practical applications for biochemical assays, food safety and other fields.

Preparation of Surface-Enhanced Raman Scattering Substrates Based on Immobilized Silver-Capped Nanoparticles

“…Hence, the upgrade of metal films with controlled nanostructure and composition is of pivotal importance and is currently intensely investigated [6,7,37]. There is a variety of methods for the fabrication of SERS substrates, such as pulsed laser deposition (PLD) [38], metal evaporation [39,40], chemical or electrochemical etching or deposition on smooth surfaces [41][42][43][44], and deposition or assembly of metal nanoparticles from solution (dried droplet (DD) method) [45,46]. However, for a given excitation wavelength, SERS effect is nearly absent in isolated particles, while the coupling of transition dipoles in aggregates enhances relatively this effect in the nanoscopic scale [47].…”

Progress in the Development of SERS-Active Substrates Based on Metal-Coated Porous Silicon

“…Some additional methods have also been utilized to form a template of a nanoscaled silicon skeleton for the SERS-active substrates. Reactive ion plasma etching [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ], hydrothermal etching [ 46 , 47 , 48 ], and metal-assisted chemical etching (MACE) [ 49 , 50 , 51 , 52 , 53 , 54 ] are among these techniques. The common feature of the listed methods compared with electrochemical etching is in the formation of arrays of silicon nanowires.…”

“…The latter strongly depends on the shape and size of the metallic nanostructures and the gaps between them, while porous silicon template helps to manage these properties. The family of the SERS-active nanostructures formed by metal deposition on porous silicon is very rich and includes metallic nanoparticles [ 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ] or polydisperse particles [ 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ], dendrites [ 49 , 54 , 83 , 84 ], nanovoids [ 85 ], and metallic oval-shaped NPs [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. Figure 2 presents schematic views of plasmonic structures that can be formed with a dependence on porous silicon morphology, doping type, the level of silicon, and the method and conditions of metal deposition.…”

“…Following Table S1 , mesoporous silicon is the most popular template for the fabrication of the SERS-active substrates since it combines good mechanical strengths, nanoscale pores, and morphology reproducibility. The same benefits go from the silicon nanowires [ 50 , 51 , 53 , 73 , 86 , 87 ], nanotips [ 36 ], nanopillars [ 34 , 46 , 54 , 64 ], and so forth. Microporous silicon has not been used very often [ 88 , 89 ].…”

Detection of Permethrin pesticide using silver nano-dendrites SERS on optical fibre fabricated by laser-assisted photochemical method

“…The SERS substrates with many hot-spots and uniform distribution of nanostructures on the surface will have a large Raman enhancement and high repetition of measurement. The metal dendritic nanostructures are structures with many hot-spots which are formed from the tips and the sharp edges of the trunk and branches of the nano-dendrites, and the narrow gap between the branches 20,21 . The Ag nanostructure is considered to be one of the most excellent candidates for SERS application due to its highly desired plasmonic properties, low cost and easy fabrication/synthesis.…”