Laser ablation of a platinum target in water. II. Ablation rate and nanoparticle size distributions

Abstract

This is the second in a series of three papers examining nanomaterial formation in laser ablation in liquids (LAL). Here we study the effect of the laser wavelength and fluence on the mass yield and size distribution of nanoparticles prepared by laser ablation of a platinum target immersed in water. For all wavelengths tested, laser fluences in the range of 10–70J∕cm2 resulted in spheroidal, nonagglomerated platinum nanoparticles with sizes ranging from 1to30nm. Nanoparticle size distributions are found to be composed of two modes that are attributed to thermal vaporization and explosive boiling mechanisms. The peak of the smaller size mode remains nearly constant at 3nm for all laser conditions, which is suggested to be due to the strong confinement of the vapor plume by the liquid. The larger size mode peaks in the range of 5–15nm with a population that is strongly dependent on the laser parameters. It is concluded that changes in the mean size reported in many earlier studies on LAL of metal targets are a result of the relative quantity of nanoparticles from each mechanism rather than direct control over the ablation process. Additionally, it was observed that the yield of platinum nanoparticles was significantly larger for 1064nm wavelength at fluences greater than 10J∕cm2. The maximum ablation rate was approximately 4.4mg∕h, with an estimated ablation and collection efficiency of 0.9μg∕J. Dependence of the mass yield on wavelength and fluence is seen to be dependent primarily on the extent of the explosive mechanism.

Platinum Nanoparticles as Photoactive Substrates for Mass Spectrometry and Spectroscopy Sensors

“…The NP size distributions described above are in consonance with previous studies of laser ablation of platinum in water using the wavelengths of 1064, 532 and 355 nm, although the laser fluences (11-65 J cm -2 ) used were significantly greater than those applied here. 36 In those studies, similarly broad and bimodal NP size distributions were observed, also narrowing down and shifting to smaller sizes with decreasing wavelength. The two components of the NP size distribution were plausibly traced back to a thermal vaporization mechanism (small NP component) and to an explosive ablation mechanism (large NP component) taking place in different time scales.…”

“…Hence, the shoulder observed around 250 nm in the UV absorption spectra could be attributed to plasmonic excitation, possibly partially overlapping with interband transitions. 36,38 We did not observe potential plasmonic bands better defined than those shown in Figure 1 for any of the samples. This is not surprising given the small size and appreciable polydispersity of the NPs produced by the ablation method, as discussed below.…”

“…The two components of the NP size distribution were plausibly traced back to a thermal vaporization mechanism (small NP component) and to an explosive ablation mechanism (large NP component) taking place in different time scales. 36 These mechanisms presumably also apply in our experiments and are briefly discussed below in Sect. 3.2.…”

“…The pioneering work on PLAL for materials processing on the stabilizing agent. [35][36][37][38][39][40] Nichols et al 36 prepared platinum colloidal solutions at 1064, 532 and 355 nm using a nanosecond pulsed Q-switched Nd:YAG laser with high fluences (greater than 11 J cm -2 ), well above the ablation threshold. It was found that the nanoparticle size distribution has a qualitatively similar bimodal shape at the three wavelengths, although a greater yield of large NPs was observed with increasing laser fluence and wavelength.…”

Influence of processing time on nanoparticle generation during picosecond-pulsed fundamental and second harmonic laser ablation of metals in tetrahydrofuran

“…The use of high-power picosecond pulses was successfully demonstrated by Bärsch et al for the ablation of various materials in liquids [25]. (iii) Several research groups have found that for nanosecond pulses the yield of nanoparticles was significantly higher for ablation using the fundamental wavelength (λ = 1064 nm) than for second or third harmonic wavelength (λ = 532 nm or 355 nm) [26][27][28]. Procházka et al demonstrated that an increasing number of irradiating nanosecond laser pulses using a laser wavelength of 1064 nm results in a decrease of the particle size in silver colloids [8].…”