Single Laser Pulse Effects on Suspended-Au-Nanoparticle Size Distributions and Morphology

Abstract

Samples of suspended gold nanoparticles in the diameter range 10 to 100 nm were subjected to a single 7 ns pulse from a 532 nm laser to determine the effect of laser power on particle size distribution, mean size, and morphology. The experimental techniques used were dynamic light scattering (DLS), depolarized dynamic light scattering (DDLS), electrospray-differential mobility analysis (ES-DMA), ultraviolet−visible absorption spectroscopy, and transmission electron microscopy (TEM). For 60 nm particles, a laser pulse of fluence 10 mJ/cm 2 was sufficient to produce observable changes. In the range 10−72 mJ/cm 2 , DLS indicated little change in mean particle size but a more than three-fold reduction in the polydispersity index (significantly tightened distribution) and a decrease in scattering intensity. TEM showed that the particles became highly spherical and that there was a growing population of particles <10 nm in size that could not be detected by DLS and ES-DMA. Fused dimers were also observed, which suggest that heated particles can interact prior to cooling. DDLS showed a decrease in scattering due to shape anisotropy with a 20 mJ/cm 2 pulse and a decrease in the diffusion time constant. At higher power, the mean particle size decreased until all particles were <10 nm in size. The threshold for observable changes decreased with increasing particle size in the range 10 to 60 nm but increased for 100 nm particles. These results will be useful for potential therapeutic applications for pulse-heated nanoparticles and demonstrate the use of a simple laser treatment for modifying and improving nanoparticle properties.

Fluence Threshold for Photothermal Bubble Generation Using Plasmonic Nanoparticles

“…They do observe a minimum fluence threshold at a NP diameter of 60 nm, in agreement with our numerical predictions (see Fig.6 and Fig.9c). The occurrence of a non-monotonic shape of F s (a) with a minimum at 60 nm is also supported by the results of Cavicchi et al, 42 who investigated nanoparticle reshaping dependence on laser fluence.…”

Quantitative Evaluation of Nanosecond Pulsed Laser-Induced Photomodification of Plasmonic Gold Nanoparticles

“…investigated the effect of irradiation wavelength on 55 nm gold nanospheres and was mostly concerned with modeling the difference between interband and intraband excitation 22 . Another study used dynamic light scattering (DLS), electron microscopy and UV-Vis spectroscopy to examine the impact of a single laser pulse on particles of different sizes 26 . While results were presented for a range of energy levels, specific damage thresholds were not determined and comparison with theoretical results was not presented.…”

Surface nanobubbles and nanodroplets

“…Ongoing research issues in this context are the fabrication of highly effective nanoparticles, the durability of nanoparticles, and the mechanisms of nanoscale nucleation and enhanced (photo)catalytic reactions (Boulais, Lachaine, and Meunier, 2012;Carlson, Green, and Richardson, 2012;Cavicchi et al, 2013;. In particular, the plasmon enhanced solar to fuel conversion is extremely attractive (Thomann et al, 2011).…”