Plasmonic-heating-induced nanofabrication on glass substrates

Abstract

Fabricating nano-sized through-holes on a coverslip approximately 100 μm thick is challenging but rewarding when applied to ultrafine filters that separate proteins and DNA of various sizes and isolate viruses from cells. Toward this end, we developed an in situ etching-assisted laser processing technique exploiting gold nanoparticles. Plasmonic heating of a single gold nanoparticle through focused illumination of a continuous-wave laser beam enables structural modifications to be localized to the contact area on the glass surface. This results in the embedding of the particle forming nanocavities caused by chemical etching with aqueous tetrabutylammonium hydroxide. Depending on the shape of the nanoparticle, a highly flexible face geometry design such as a disk and triangle was achieved. The etching was monitored in situ through measurements of spectral red shifts in single-particle scattering, indicating an increasing medium refractive index consistent with embedding. The embedding process is unexpectedly fast, at 0.8 μm with 5 minutes of illumination. Besides nanoholes, we fabricated nanodomes around a single gold nanoparticle supported on a glass substrate through laser-heating-induced encapsulation. Overall, we were able to demonstrate true nano-laser processing free from diffraction-limited optics, with potential benefits of simple low-cost fabrication.

Insight into plasmonic hot-electron transfer and plasmon molecular drive: new dimensions in energy conversion and nanofabrication

“…87 They demonstrated the fabrication of nanoholes on glass surfaces by embedding Au NPs under photoillumination. As illustrated in Figure 20 (left), single Au NPs supported on a borosilicate glass substrate submerged in aqueous alkaline solution, such as tetrabutylammonium hydroxide (TBAOH), were subjected to illumination with a focused laser beam that excites the LSPR band of the NPs.…”

“…The scale bars represent 2 μm. Reprinted with permission from Osaka et al 87 (Copyright 2016, The Royal Society of Chemistry). Figure 21 Upper left: AFM images showing the effects of electric field alignment (with respect to the long axis of nanoparticle multimers) on excitation transfer along DNA (height scale: 15 nm).…”

Dry Etching with Nanoparticles: Formation of High Aspect‐Ratio Pores and Channels Using Magnetic Gold Nanoclusters

“…For a given etching condition, substrates with high CTEs such as PVDF and PTFE yield sub‐micrometer to micrometer‐sized pores and channels with a significant taper ( Figure a,b), whereas a low‐CTE substrate such as borosilicate glass yield channel widths corresponding to the size of the MGNC etchants (Figure c,d). Examples of Au nanoparticles as etchants of high‐aspect ratio pores in glass or ceramic substrates have only recently been reported, and suggest interesting opportunities for using MGNCs to etch nanopores in other materials with high deflection temperatures.…”

The photothermal nonlinearity in plasmon-assisted photocatalysis

“…Those include, in particular, high intensity illumination which invokes nonlinear thermo-optic and photothermal effects, [32][33][34][35][36] which are usually simply ignored (without any justification). Already in the context of thin metal layers [37][38][39] and single NPs, [33][34][35][36]40,41 this effect was shown to cause deviations of several tens to hundreds of percent in the permittivity, and hence the field and temperature distributions compared with the purely uniform linear thermal response. Note that such a nonlinear effect is far greater than conventional nonlinear optical effects.…”