Pulse Laser Ablation in Water Fragmentation of Amorphous Silica in Water with Optional NaCl Spiking

Abstract

Amorphous SiO2 powders having two kinds of medium range order (MRO) were subjected to pulse laser ablation in water (PLAL) for X-ray diffraction, transmission electron microscopy and spectroscopy characterization. The powders fragmented down to 10-20 nm in size are mainly hydrogenated amorphous phase retaining Si-2nd O but not Si-2nd Si MRO. There are minor co-existing crystallites of beta-cristobalite, H2Si2O5 as well as additional alpha-tridymite and Na2SiO3 when water is spiked with NaCI for PLAL. Na-signature also caused lower vibration frequency of the hydrogenated silica network. The opal-like hydrogenated phase assemblage of amorphous phase, cristobalite and tridymite thus formed have a minimum band gap at ca. 5 eV for potential optoelectronic and catalytic applications in UV range and shed light on natural occurrence in dynamic settings such as meteorite impact and lightening strike on silicate-enrich crustal rocks.

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

“…Furthermore, higher seed concentrations favor the chemistry of seed-growth and ripening, resulting in high variation and large particles composed of ultrasmall building blocks. Accordingly, NPs generated by LFL are spherical, unless dissolution, subsequent chemical reactions (e.g., resulting from surface adsorbates), or external fields cause morphological or geometrical changes , during the ripening of the supersaturated colloids. For microparticle or submicroparticle educt, the irradiated material is often not entirely vaporized, and, as a result, the size of the solid educt gradually decreases in a linear fashion, depending on the educt mass-specific laser energy input (kJ/g) .…”