Self-Assembled Au Nanoparticle Monolayers on Silicon in Two- and Three-Dimensions for Surface-Enhanced Raman Scattering Sensing

Abstract

Gold nanoparticle/silicon composites are canonical substrates for sensing applications because of their geometry-dependent physicochemical properties and high sensing activity via surface-enhanced Raman spectroscopy (SERS). The self-assembly of gold nanoparticles (AuNPs) synthesized via wet-chemistry on functionalized flat silicon (Si) and vertically aligned Si nanowire (VA-SiNW) arrays is a simple and cost-effective approach to prepare such substrates. Herein, we report on the critical parameters that influence nanoparticle coverage, aggregation, and assembly sites in two- and three-dimensions to prepare substrates with homogeneous optical properties and SERS activity. We show that the degree of AuNP aggregation on flat Si depends on the silane used for the Si functionalization, while the AuNP coverage can be adjusted by the incubation time in the AuNP solution, both of which directly affect the substrate properties. In particular, we report the reproducible synthesis of nearly touching AuNP chain monolayers where the AuNPs are separated by nanoscale gaps, likely to be formed due to the capillary forces generated during the drying process. Such substrates, when used for SERS sensing, produce a uniform and large enhancement of the Raman signal due to the high density of hot spots that they provide. We also report the controlled self-assembly of AuNPs on VA-SiNW arrays, which can provide even higher Raman signal enhancement. The directed assembly of the AuNPs in specific regions of the SiNWs with a control over NP density and monolayer morphology (i.e., isolated vs nearly touching NPs) is demonstrated, together with its influence on the resulting SERS activity.

Carbon Dots Embedded in Nanoporous SiO2 Nanoparticles for Enhancing Photosynthesis in Agricultural Crops

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Rh in the gap: maximizing E-field enhancement within nanorod heterodimers

“…While every single measurement on the AuRh_Au NR dimers shows two strong peaks which can be attributed to aromatic ring vibrations of 4-MBA at 1584 cm −1 and at 1073 cm −1 , 65,66 these peaks were not observed in any of the Raman spectra measured on the AuRhAu NRs and the other reference samples (Fig. S10, ESI†).…”

Surface-Enhanced Raman Spectroscopy on Selectively Adsorbed Plasmonic Nanostructures Using Polar Surface Arrays

“…Attractive interactions among each AuNP dimer might encourage aggregation. Bartschmid et al have observed similar cluster formation of AuNPs on silicon substrates . Compared to pure DNA origami, the presence of gold nanoparticles impairs the adsorption behavior of AuNP dimers.…”

“…Bartschmid et al have observed similar cluster formation of AuNPs on silicon substrates. 44 Compared to pure DNA origami, the presence of gold nanoparticles impairs the adsorption behavior of AuNP dimers. Nonetheless, PSA clearly demonstrates the ability to isolate single nanostructures for single-molecule experiments.…”