Ultraviolet and Infrared luminescent Au-rich nanostructure growth in SiO2 by burrowing and inverse Oswald ripening process

Abstract

We study the evolution of nanoparticle morphology through successive stages when Au-Si bilayer on SiO2 is irradiated with 500 keV Xe-ions and resulting luminescence in the UV, Visible and infrared range. An array of nanoscale island morphology is developed on the silica surface in the initial stage of evolution which undergoes gradual burrowing in the silica matrix accompanied by elongation of large ones in the direction of incident ions under cumulative ion irradiation. Burrowing is found to occur in order to minimize the surface free energy of the nanoparticles. Numerical simulation based on the unified thermal spike model shows formation of molten latent tracks due to ions energy release which drive the dewetting of the metal layer and further give mobility to nanoparticle atoms leading to burrowing in the later stage of evolution and elongation of large nanoparticles. Satellite nanoparticles are observed to grow around Au nanoparticles embedded in silica through nucleation of Au atoms dissolved in the matrix by incident ions. The varying diameters of the Au satellite nanoparticles seem to result in luminescence in the UV and infrared range. The observed structure may find application in surface enhanced Raman scattering, catalysis, and LEDs.

Structural and chemical evolution of Au-silica core–shell nanoparticles during 20 keV helium ion irradiation: a comparison between experiment and simulation

“…It is worth noting that an additional possible mechanism which could be happening is a burrowing effect, similar to what has been seen for ion irradiation of Pt particles on SiO 2 59 and Au particles on SiO 2 21 . In addition, the alternative process of SiO 2 particles burrowing onto a composite metal surface has been shown to occur after laser irradiation 60 .…”

“…1, column iv too. Similar satellites are known to form after MeV heavy ion irradiation of Au particles 21,61 , and satellites have also been seen during the 10 keV He irradiation of Pt particles on silica 59 . This effect has previously been explained by "inverse" Ostwald ripening which occurs under ion bombardment 18,62 .…”

“…Previous studies have investigated the effect of radiation on similar nanoparticle systems. However these have mostly been at MeV energies and with ions heavier than helium 18 – 21 . The size of the particle has been shown to determine what the beam shaping effect will be, either shaping into nanorods, faceting or no major change 22 .…”

Valence State Tuning of Gold Nanoparticles in the Dewetting Process: An X-ray Photoelectron Spectroscopy Study

“…Several experimental approaches have been carried out on the effect caused by ion beam irradiation on AuNPs on top of various substrates. The thermodynamic driving force resulting from the interaction between the AuNPs and the substrate when it is under Ar + /Xe + ion bombardment produces effects such as burrowing and dewetting, which are explained by the minimization of the surface free energy. , Although the burrowing on AuNPs has been studied, the effects produced by Ar 1+ ion bombardment on the changes in the valence states of AuNPs are still scarce. This contribution investigates the controlled modification in the valence states, which will allow expanding the previously reported approaches and increasing the possible number of technological applications of AuNPs.…”