Analysis of the structure, configuration, and sizing of Cu and Cu oxide nanoparticles generated by fs laser ablation of solid target in liquids

Abstract

We report on the analysis of structure, configuration, and sizing of Cu and Cu oxide nanoparticles (Nps) produced by femtosecond (fs) laser ablation of solid copper target in liquids. Laser pulse energy ranged between 500 lJ and 50 lJ. Water and acetone were used to produce the colloidal suspensions. The study was performed through optical extinction spectroscopy using Mie theory to fit the full experimental spectra, considering free and bound electrons size dependent contributions to the metal dielectric function. Raman spectroscopy and AFM technique were also used to characterize the sample. Considering the possible oxidation of copper during the fabrication process, two species (Cu and Cu 2 O) arranged in two structures (bare core or core-shell) and in two configuration types (Cu-Cu 2 O or Cu 2 O-Cu) were considered for the fitting depending on the laser pulse energy and the surrounding media. For water at high energy, it can be observed that a CuCu 2 O configuration fits the experimental spectra of the colloidal suspension, while for decreasing energy and below a certain threshold, a Cu 2 O-Cu configuration needs to be included for the optimum fit. Both species coexist for energies below 170 lJ for water. On the other hand, for acetone at high energy, optimum fit of the full spectrum suggests the presence a bimodal Cu-Cu 2 O core-shell Nps distribution while for decreasing energy and below a 70 lJ threshold energy value, Cu 2 O-Cu core-shell Nps must be included, together with the former configuration, for the fit of the full spectrum. We discuss possible reasons for the changes in the structural configuration of the core-shell Nps. V C 2013 American Institute of Physics. [http://dx

Determination of plasma frequency, damping constant, and size distribution from the complex dielectric function of noble metal nanoparticles

“…Since the metals studied in this work satisfy the Random Phase Approximation (RPA), [18][19][20][21]27 the expression for bound-electron contribution can be written as an integral over a continuum of interband transitions. So, expression (4) may be rewritten as…”

“…Values of c bound , x g , Fðx; TÞ, and K b for gold, copper, and silver were determined in our previous works. [18][19][20][21] For spherical Nps under 20 nm radius, 22 electron collisions with the particle boundary reduce the mean free path, increasing the collision frequency. In a "top-down" description of size effects, this fact may be taken into account by a modification of the free electron damping constant in the form c size ðRÞ ¼ c f ree þ C v F R , 22,28 where v F is the Fermi velocity and C is a constant that depends on the material and on the carrier scattering at the particle wall.…”

“…[18][19][20][21] In the second step, the full dielectric function is rewritten considering the size-dependent free-electron contribution as a power series expansion of radius and frequency and a size-dependent term for bound electrons. The final expression, obtained after regrouping, may be reinterpreted as the bulk dielectric function (which is usually measured experimentally as a function of frequency or wavelength) plus size corrective terms for free and bound electrons.…”

Liquid assisted ablation of zirconium for the growth of LIPSS at varying pulse durations and pulse energies by femtosecond laser irradiation

“…Greater pulse durations (50 and 100 fs) are responsible for enhancement of the energy deposition time of laser at the target-liquid interface and therefore chemical reactions support the growth of new bands by the combination of the elements of the target and the liquid [36]. The extreme pressure and temperature conditions in the focal volume during laser ablation, enhances the chemical reactivity of Zr with dissolved oxygen in ethanol and supports the formation of various kinds of oxides [56]. The shockwave that results from the laser breakdown generates high pressure-high temperature conditions at the liquid-plasma interface, which becomes an active chemical reaction zone that enhances the bonding of Zr species with ionized ethanol molecules to form Zr oxide nanostructures.…”

Picosecond laser induced fragmentation of coarse Cu2O particles into nanoparticles in liquid media

“…However, synthesis of Cu 2 O and especially nanosized Cu 2 O is not straight forward [1,6]. In this context, Cu 2 O nanoparticles are often produced by laser induced breakdown at solid Cu-liquid (such as water) interface [7][8][9]. However, the final product is often not Cu 2 A c c e p t e d M a n u s c r i p t greater is the oxidation of Cu).…”