In this work, the size transformation of the TiO₂ nanofraction from pharmaceutical grade E171 powder was studied during its transit through the gastrointestinal tract (GIT). It was shown that pharmaceutical-grade TiO₂ powder contained about 0.68% (w/w) of particles smaller than 240 nm in diameter. In the observed GIT transit process the TiO₂ nanoparticles were agglomerated up to 150–200 nm in simulated salivary fluid, with gradual agglomerate enlargement up to 300–600 nm and more than 1 micron in simulated gastric fluid. In the intestinal fluid the reverse process occurred, involving a decrease of agglomerates accompanied by the formation of a small fraction with ~50 nm average size. This fraction can be further involved in the histohematic transport process. The acidity degree (pH) and mineral composition of solutions, as well as the transit speed along the gastrointestinal tract, influence the nature of the particle transformation significantly. The rapid passing between the gastrointestinal tract sections creates conditions for a decrease in part of the TiO₂ particles, up to 100 nm, and may be associated with the violation of the structural and functional integrity of the intestinal mucus layer.

This paper demonstrates a significant increase in the efficiency of second-harmonic generation in a suspension of lithium niobate (LiNbO₃) particles during freezing at nano and picosecond pum pulse durations. The amplification is caused by the formation of close-packed structures during the solidification process. The energy dependences of the second-harmonic generation, the angular distributions of the scattering intensity, conversion coefficients and the scattering regime in a suspension and in other lithium niobate particle-based samples are studied. This effect can be used for phase transition sensing in a medium, visualization of the particle organization process in ice-templating, and significantly increasing the efficiency of other nonlinear effects in particle matter.

Depending on the active acidity of an aqueous solution, the colloidal stability of a titanium dioxide suspension in the form of anatase (food additive E171

In this work, for the first time, the property of particles to form close-packed layer in front of the freezing interface was used to increase the luminescent efficiency response for ruby and titanium-sapphire microcrystals water suspensions. An increase in the efficiency of luminescence response due to an increase in the concentration of particles at the freezing front, can be used for phase transition sensing. In addition, particles packing by freezing method can be used for tuning random laser generation or increasing the efficiency of different nonlinear optical effects in suspensions of particles.

Subablative exposure of tightly focused visible-range femtosecond laser pulses on a thin translucent nanocrystalline copper(I) oxide on a silica glass substrate results not only in its annealing (resolidification), but apparently also in reduction of copper ions to the metallic state via single-photon absorption and the following thermal decomposition (disproportioning). Partial or complete ablation of the film within the laser focal spot and also its subablative optically contrast modification through formation of colloidal nanoparticles or annealing (resolidification) make it possible to consider this material in the thin-film form as a novel optical platform for direct laser writing of vis-IR metasurfaces and thin-film sensing plasmonic and all-dielectric nanostructures.