Quantification of mass-specific laser energy input converted into particle properties during picosecond pulsed laser fragmentation of zinc oxide and boron carbide in liquids

Pulsed laser fragmentation in liquids is an effective method to fabricate organic, metal or semiconductor nanoparticles by ablation of suspended particles. However, modelling and up-scaling of this process lacks quantification of the laser energy required for a specific product property like particle diameter of the colloid or bandgap energy of the fabricated nanoparticles. A novel set-up for defined laser energy dose in a free liquid jet enables mass-specific energy balancing and exact threshold determination for pulsed laser fragmentation. By this technique laser energy and material responses can be precisely correlated. Linear decrease of the particle diameter and linear increase of the bandgap energy with mass-specific laser energy input has been observed for the examples of ZnO and B4C particles. Trends are analysed by density gradient centrifugation, electron microscopy, UV-vis and X-ray diffraction analysis of the crystal structure. The study contributes to quantitative model parameters for up-scaling and provides insight into the mechanisms occurring when suspended particles are irradiated with pulsed laser sources. (C) 2014 Elsevier B.V. All rights reserved.