Hollow Gold Nanoparticles Produced by Femtosecond Laser Irradiation

Abstract

Metallic hollow nanoparticles exhibit interesting optical properties that can be controlled by geometrical parameters. Irradiation with femtosecond laser pulses has emerged recently as a valuable tool for reshaping and size modification of plasmonic metal nanoparticles, thereby enabling the synthesis of nanostructures with unique morphologies. In this letter, we use classical molecular dynamics simulations to investigate the solid-to-hollow conversion of gold nanoparticles upon femtosecond laser irradiation. Here, we suggest an efficient method to produce hollow nanoparticles under certain specific conditions, namely that the particles should be heated to a maximum temperature between 2500 and 3500 K, followed by a fast quenching to room temperature, with cooling rates below 120 ps. Therefore, we advance the experimental conditions to efficiently produce hollow nanoparticles, opening a broad range of possibilities for applications in key areas, such as energy storage and catalysis. TOC GRAPHICS

Controlled Alloying of Au@Ag Core–Shell Nanorods Induced by Femtosecond Laser Irradiation

“…[45] With the aim of determining the optimal conditions to trigger alloy formation, we explored the use of fs-laser pulses at different fluences, as this is the most relevant parameter to control energy deposition. [34,38,39,45,46] By varying the laser fluence, it is possible to reshape, melt, or even disintegrate plasmonic metal nanoparticles. Upon irradiation at a fluence of 3.2 J m −2 for 20 min (complete modification of the LSPRs), we observed a 60 nm blueshift of the Au@Ag NR longitudinal LSPR band www.advopticalmat.de (i.e., from 800 to 740 nm, Figure 1A).…”

“…This fact might also be explained by a partial loss of the Ag atoms due to oxidation (as hypothesized for hot-dog NRs), or due to a laser-induced fragmentation of the shell (an effect described for high-fluence fs-pulsed laser irradiation of plasmonic nanoparticles). [36][37][38][39]46,61] That could explain the presence of some irradiated Au@Ag NRs where the silver shell was partially degraded in the middle region (Figures S5 and S13, Supporting Information) or has been completely removed ("naked" NRs, Figures S4-S6, Supporting Information). Finally, at the highest investigated fluence (92 J m −2 ), the energy absorbed by Au@Ag NRs is sufficient to induce complete reshaping and mixing (interdiffusion) of Au and Ag atoms.…”

“…Plasmonic Au@Ag core-shell nanoparticles are excellent candidates to investigate this hypothesis, as they can actively interact with fs-laser pulses (owing to their ability to sustain tunable localized surface plasmon resonances, LSPRs) and thereby be heated and alloyed directly in solution. [34][35][36][37][38][39] Interestingly, this process should occur at the subnanosecond scale, without significant heating of the bulk solution, which would further help preserve the colloidal stability of the nanoparticles. [34] Hence, we first synthesized plasmonic Au@Ag nanorods (Au@Ag NRs) with a longitudinal LSPR band centered at 800 nm, in resonance with the wavelength of a 50-fs-pulsed Ti:Sapphire laser, used to investigate the proposed hypothesis.…”

Toward Programmable Moiré Computation

“…[19] The femtosecond laser has been widely used in the synthesis of nanoparticles. [20] These techniques enable programmable control and modifications of electronic properties for 2D materials, making these materials appropriate for programmable optical computation, explained in detail.…”

Especies ligeras en materiales de interés para aplicaciones energéticas

“…De entre las diferentes propuestas, el desarrollo de superficies modificadas en la micro y nanoescala, de elevada porosidad, supone una estrategia interesante y prometedora, ya que aúna la presencia de canales de migración (como GBs para átomos de H), caminos de migración cortos, elevada área superficial y la presencia de múltiples centros de recombinación. El máximo exponente de este tipo de materiales está representado por las hNPs, con una densidad disminuida gracias a su configuración (una delgada capa de material rodeando el núcleo vacío de la NP), y con una versatilidad inmensa tanto en materiales como formas gracias a los diversos procesos de síntesis existentes, en innovación continua, como el recientemente desarrollado por Gonzalez-Rubio et al, basado en la modificación de nanoestructuras de oro mediante irradiación láser para la obtención de hNPs [229,230]. Las propiedades mostradas por este tipo de materiales hace que la opción de emplear nanopartículas huecas de wolframio (W-hNPs) para la fabricación de la capa exterior de un PFM resulta interesante por las siguientes razones: (i) los defectos puntuales generados por las especies ligeras (He y H) en la cobertura de la W-hNP alcanzarán la superficie sin dificultad, aniquilándose; (ii) de igual manera, las especies ligeras serán capaces de llegar bien a la superficie exterior y desorberse, o bien a la superficie interior y acumularse en la cavidad; y (iii) la existencia de gas presurizado en la cavidad de las W-hNPs puede contribuir de forma efectiva a detener los iones incidentes sin efectos perjudiciales para la integridad de la partícula.…”