Water-Wettable Open Plasmonic Nanocavities for Ultrasensitive Molecular Detections in Multiple Phases

Abstract

Plasmonic nanocavities between metal nanoparticles on metal films are either hydrophobic or fully occupied by nonmetallic spacers, preventing molecular diffusion into electromagnetic hotspots. Here we realize water-wettable open plasmonic cavities by devising gold nanoparticle with site-selectively grown ultrathin dielectric layer-on-gold film structures. We directly confirm that hydrophilic dielectric layers of SiO 2 or TiO 2 , which are formed only at the tips of gold nanorod via precise temperature control, render sub-10 nm cavities open to the surroundings and completely water-wettable. Simulations reveal that spontaneous wetting in our cavities is driven by the presence of tip-selective hydrophilic layer and tendency of minimizing high energy air/ water interface inside the cavities. Our plasmonic cavities show significant Raman enhancement of up to 4 orders of magnitude higher than those of conventional ones for molecules in various media. Our findings will offer new opportunities for sensing applications of plasmonic nanocavities and have huge impacts on cavity plasmonics.

Au@Ag Nanocube-Coated Polystyrene Microspheres as Hierarchical SERS Substrates for Trace Detection of As5+

“…As depicted in Figure 3e,f, for the curved arrangement of the Au@Ag NCs, the gap at the upper side is larger while the gap at the lower side is smaller. According to previous literature, 51 we suggest that the "V"shaped gap structure might be more favorable for the target molecules to diffusion into the nanogap. While the horizontally arranged Au@Ag NCs have uniform and narrow nanogaps in the vertical direction, the molecules cannot diffuse into the electromagnetic hotspots due to the spatial potential resistance effect.…”

Spectrum and size controllable synthesis of high-quality gold nanorods using 1,7-dihydroxynaphthalene as a reducing agent

“…Gold nanorods (AuNRs) have broad applications in the fields of biomedicine, 1,2 imaging, 3,4 sensing, 5 and catalysis 6 due to their tunable longitudinal surface plasmon resonance (LSPR). Because the LSPR frequency is directly related to the aspect ratio of AuNRs, 2,7 AuNRs with different aspect ratios and sizes have different application prospects, of which the small-sized AuNRs possessing a high absorption cross section are more attractive for photothermal applications, 8–10 whereas large-sized AuNRs have applications in scattering-related fields.…”

Capillarity‐Driven Enrichment and Hydrodynamic Trapping of Trace Nucleic Acids by Plasmonic Cavity Membrane for Rapid and Sensitive Detections

“…To realize the design of our plasmonic cavity membrane, the tips of the AuNR (110 nm in length and 45 nm in diameter) are selectively coated with SiO 2 according to the previous method with some modifications, [26,27] and the AuNR-SiO 2 are selfassembled into a monolayer at an air/water interface (Figure 3a). Next, the monolayer is transferred onto a 100 nm thick Au film (5 mm × 5 mm) using the Langmuir-Blodgett method [28,29] and a glass with identical size is placed on top of the monolayer.…”

“…The assynthesized AuNRs with SiO 2 tips were self-assembled at an air/water interface and transferred onto gold film (100 nm thick) by the Langmuir-Blodgett method. [26,27] Hexane (3 mL) was first added onto deionized (DI) water (4.5 mL) and nanoparticle (1.5 mL) solution was injected into the aqueous phase. After 10 h at room temperature, the self-assembled nanoparticles were transferred onto the gold film.…”