Enhanced photoabsorption efficiency of incomplete nanoshells

Abstract

The rather low scattering or extinction efficiency of small nanoparticles, metallic and otherwise, is significantly enhanced when they are adsorbed on a larger core particle. But the photoabsorption by particles with varying surface area fractions on a larger core particle is found to be limited by saturation. It is found that the core-shell particle can have a lower absorption efficiency than a dielectric core with its surface partially nucleated with absorbing particles-an "incomplete nanoshell" particle. We have both numerically and experimentally studied the optical efficiencies of titania (TiO2) nucleated in various degrees on silica (SiO2) nanospheres. We show that optimal surface nucleation over cores of appropriate sizes and optical properties will have a direct impact on the applications exploiting the absorption and scattering properties of such composite particles.

Fabrication of Si/Au Core/Shell Nanoplasmonic Structures with Ultrasensitive Surface-Enhanced Raman Scattering for Monolayer Molecule Detection

“…[17][18][19] Therefore, a suitable material with a high refractive index and small absorption coefficient together with a fabrication technology is urgent.…”

“…That is, advancing a novel concept and prototypes into real, practical techniques is needed from materials technology. Nowadays, the fabrication of dielectric-based noble metal-modified nanostructures still remains a challenge. − Therefore, a suitable material with a high refractive index and small absorption coefficient together with a fabrication technology is urgent. This technology should allow the generation of spherical NPs with electric and magnetic Mie resonances in the visible spectral range as well as precise control over their sizes, morphologies, and composition. − …”

Fano-type spectra and other interference effects in an all-dielectric nanoshell

“…The 180 nm dia particles (represented in Figure 2a) are unremarkable as they show a Rayleigh scattering type 1 λ 4 behavior for λ > 450 nm as expected, followed by an indication of interference structure around the optical efficiency of 2 for 400 nm < λ < 450 nm. The higher energies (λ < 350 nm) are strongly absorbed by titania and the extinction spectra show a saturation behavior based on thickness of the shells 40 . The 360 nm dia particles (represented in Figure 2b) exhibits a similar unremarkable Mie-Rayleigh behavior for wave-lengths larger than 500 nm based on its larger size.…”