Gold nanoparticles obtained by ns-pulsed laser ablation in liquids (ns-PLAL) are arranged in the form of fractal clusters

Abstract

Gold nanoparticles (AuNPs), synthesized by ns-pulsed laser ablation in liquid (ns-PLAL) in the absence of any capping agents, are potential model systems to study the interactions with biological structures unencumbered by interference from the presence of stabilizers and capping agents. However, several aspects of the physics behind these AuNPs solutions deserve a detailed investigation. The structure in solution of ns-PLAL-synthesized AuNPs was investigated in solution by means of small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS). Furthermore, the (dried) NPs have been examined using TEM. The analysis of the SAXS curve shows the presence of a large number of small aggregates with a fractal structure stabilized by strong long-range repulsive interactions. Fitting of the SAXS curve to a suitable “fractal model” allows the estimation of the features of the fractal including the fractal dimension d = 1.9. The latter allows to estimate the fraction of light scattered by fractals of different sizes and thus permits a fair comparison between the DLS and TEM data. Here, a stable abundant population of fractal clusters is reported reflecting a mechanism where primary AuNPs (size 7.6 nm) are forced to aggregate forming clusters during the collapse of the cavitation bubble. When these clusters are released in the aqueous phase, their large negative charge builds up repulsive interactions that prevent cluster-cluster aggregation imparting colloidal stability.

Quantitative evaluation of LAL productivity of colloidal nanomaterials: Which laser pulse width is more productive, ergonomic, and economic?

“…The observed NP abundances consistently represent the known general ablation features of these LAL regimes. [8][9][10][11][12][13][14][44][45][46] In addition, for the 0.3-ps duration a narrow distribution is observed within 70 nm-100 nm; there are no changes with the increasing energy, as in the case of ns-laser ablation. For the 10-ps pulse duration, the distribution is wide and the particle size varies from 20 nm to 500 nm.…”

“…Laser ablation in liquids (LAL) is the well-established high-throughput (g/hour) nanofabrication method of colloidal nanoparticles [1][2][3] and potentially promising, though well-understood yet approach for advanced surface micromachining. [4][5][6] Different -CW, [7] shortpulse (ns-ms durations) [8][9][10][11][12][13][14][15] and ultrashort-pulse (fs-ps durations) [1,2,8,[16][17][18][19][20][21] were extensively used for colloidal nanoparticle generation, but the optimal, potentially casedependent pulsewidth range was not identified, despite these numerous efforts. [1][2][3][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Specifically, absolute possible productivity in mass per time equivalent (in units g/s) and laserpower specific productivity (in units g/J) are o...…”

“…[4][5][6] Different -CW, [7] shortpulse (ns-ms durations) [8][9][10][11][12][13][14][15] and ultrashort-pulse (fs-ps durations) [1,2,8,[16][17][18][19][20][21] were extensively used for colloidal nanoparticle generation, but the optimal, potentially casedependent pulsewidth range was not identified, despite these numerous efforts. [1][2][3][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Specifically, absolute possible productivity in mass per time equivalent (in units g/s) and laserpower specific productivity (in units g/J) are of interest, enabling scalability of NP production as a function of laser power, while considering the economic aspects too. [8] The use of a liquid as a medium changes the position of the focus of the laser radiation due to the transition of the air-water interface.…”

“…Currently, nanosecond LAL is known to proceed via surface phase explosion and plasma formation, [3,[8][9][10][11][12][13][14] once confining fluid prevents intense surface vaporization during the laser pulse, while liquid vapor bubble emerges on microsecond timescale. [37,38] Dense vapor/droplet plume during threshold-like phase explosion facilitates its optical breakdown and plasma formation, [39] with the resulting opaque ablative plasma regulating the basic parameters of the lasertarget interaction [40] -plasma pressure, driving the vapor bubble…”

pH‑EGFET Sensor Based on the Surface Modification of MacroPSi with Au-NPs

“…A colloidal solution of metallic nanoparticles can be made by means of pulsed laser ablation in liquid (PLAL) technique. In PLAL, laser pulses are applied to a solid metallic target submerged in a liquid [26]. A colloidal nanoparticle can be deposited with various techniques.…”