Novel perspectives of laser ablation in liquids: the formation of a high-pressure orthorhombic FeS phase and absorption of FeS-derived colloids on a porous surface for solar-light photocatalytic wastewater cleaning

A novel route of colloidal chemistry: room temperature reactive interactions between titanium monoxide and silicon monoxide sols produced by laser ablation in liquid resulting in the formation of titanium disilicide

In spite of advanced research on functional colloidal inorganic nanoparticles and their reactivity, room temperature reactive interactions between two different colloids have remained challenging so far. Laser ablation of titanium monoxide and silicon monoxide in ethanol and water allows the generation of TiO-derived and SiO-derived colloidal nanoparticles which were characterized for their stability, size distribution and zeta potentials with dynamic light scattering and after evaporation of solvent examined for their morphology, chemical and phase composition by scanning electron microscopy, Raman spectroscopy, high resolution transmission electron microscopy and electron diffraction and small angle X-ray scattering. Aqueous and ethanolic TiO-derived colloids consist of anatase and monoclinic TiO, while ethanolic SiO-derived colloids are composed of crystalline and amorphous Si, nanocrystalline Si and SiO₂ and aqueous SiO-derived colloids contain, in addition to these phases, a high pressure form of cristobalite. Simple room temperature mixing of ethanolic TiO- and SiO-derived colloids allows the formation of TiSi₂, which is a case of so far unreported room temperature reactive interactions between two colloidal species. All colloids absorb solar light and act as photocatalysts for methylene blue degradation. These findings present a challenge for further search for feasible room-temperature reactions between distinct colloidal particles and open the potential for green synthesis of other desirable and hardly achievable phases.

Laser-Induced Optical Breakdown of an Aqueous Colloidal Solution Containing Terbium Nanoparticles: The Effect of Oxidation of Nanoparticles

The influence of the number of oxidized terbium nanoparticles on the intensity of physicochemical processes occurring during optical breakdown in aqueous colloidal solutions of nanoparticles has been studied. It is shown that the effect of the number of oxidized terbium nanoparticles on the physicochemical processes occurring during optical breakdown depends significantly on the fluence of laser radiation. At a fluence of less than 100-110 J/cm², plasma formation processes occur more intensively on less-oxidized (metal) nanoparticles. At a fluence of more than 100-110 J/cm², the processes of plasma formation during optical breakdown occur much more intensively on more-oxidized nanoparticles. It has been established that the dependence of the rate of laser-induced decomposition of water on the concentration of nanoparticles is two-phase. The rate of generation of water decomposition products increases with an increase in the concentration of nanoparticles up to 10⁹ NP/mL. With a further increase in the concentration of nanoparticles, the rate of generation of water decomposition products decreases. In this case, more than 99% of the decomposition products of water are formed due to the action of plasma, and the share of ultraviolet and ultrasound formed during optical breakdown is approximately 0.5% on each.

Effect of Multiply Twinned Ag(0) Nanoparticles on Photocatalytic Properties of TiO2 Nanosheets and TiO2 Nanostructured Thin Films

Ag-decorated TiO2 nanostructured materials are promising photocatalysts. We used non-standard cryo-lyophilization and ArF laser ablation methods to produce TiO2 nanosheets and TiO2 nanostructured thin films decorated with Ag nanoparticles. Both methods have a common advantage in that they provide a single multiply twinned Ag(0) characterized by {111} twin boundaries. Advanced microscopy techniques and electron diffraction patterns revealed the formation of multiply twinned Ag(0) structures at elevated temperatures (500 °C and 800 °C). The photocatalytic activity was demonstrated by the efficient degradation of 4-chlorophenol and Total Organic Carbon removal using Ag-TiO2 nanosheets, because the multiply twinned Ag(0) served as an immobilized photocatalytically active center. Ag-TiO2 nanostructured thin films decorated with multiply twinned Ag(0) achieved improved photoelectrochemical water splitting due to the additional induction of a plasmonic effect. The photocatalytic properties of TiO2 nanosheets and TiO2 nanostructured thin films were correlated with the presence of defect-twinned structures formed from Ag(0) nanoparticles with a narrow size distribution, tuned to between 10 and 20 nm. This work opens up new possibilities for understanding the defects generated in Ag-TiO2 nanostructured materials and paves the way for connecting their morphology with their photocatalytic activity.