In recent years, silicon dioxide nanoparticles have been widely used in medicine and the pharmaceutical industry, however, their effect on the brain has hardly been studied. We assessed the effects of long-term consumption of 5-nm amorphous silicon dioxide nanoparticles (SiO 2 -NPs) by Syrian hamsters infected with the trematodes Opisthorchis felineus on the hippocampus and frontal cortex. Spectroscopic determination of brain neurometabolites, performed using a horizontal Magnetic Resonance Imaging system at 11.7 Tesla magnetic field, has shown that the ratio of the excitatory neurotransmitters (glutamate + glutamine + aspartate) to the inhibitory ones (GABA + glycine) was higher in the animals infected with O. felineus . However, pre-consumption of the SiO 2 -NPs solution prevented this imbalance. In addition, the protective effect of SiO 2 -NPs on the level of myo-inositol and glycine was found. It is concluded that the use of SiO 2 -NPs can neutralize the negative effects of infectious factors on the brain.

Optical structured composition chemosensor films were obtained based on photonic crystal matrices with monodisperse spherical silica particles (MSSP) 190 to 245 nm in size which were saturated with a nanosol of silica particles modified by fluorescein. As a result, the MSSP surface is covered with nanofilms of mesoporous silica, which provides the photoluminescence (PL) of the material. The photonic crystal structure of the composition film amplifies PL in comparison with a mesoporous reference.

A new method for stacking monodisperse spherical silica particles (MSSPs) into single-crystal opal films on a solid flat substrate of lyophilic MSSP suspensions in dimethyl sulfoxide was developed. This method allows high-optical-quality opal films (containing no domains or twins and a minimum number of microcracks) to be built which are higher quality than those obtained by the moving meniscus method. This method is promising for producing films on metal or plastic substrates and for directly building heterostructures.

Natural coarse-grained precious opal structures result from the concentration of suspensions of monodisperse silica spheres and their subsequent supramolecular crystallization at low pH values. These processes occur in different media and at different times. Crystal seeding is determined by the diffusion of structural units at the interface, their large volume, and the insignificant incorporation of the system into the metastable zone. On synthesis of precious opal, the rate of supramolecular crystallization is determined by sedimentation of structural units, and the frequency of crystal seeding depends mainly on the viscosity of the dispersed medium.

The effect of high temperatures on the sedimentation of suspensions of monodisperse silica spheres (MSS) is considered. Ethanol (dispersion medium) MSS suspensions chosen as a model for our research are stable to a particular temperature. The results obtained made us to study MSS suspensions in aqueous medium at much higher temperatures. With increasing temperature, the rate of sedimentation of MSS suspensions is much higher than it is on decreasing dispersion medium viscosity. This is due to the particle coagulation caused by a change in the electrolyte dissociation in the dispersion medium. With increasing temperature, the degrees of dissociation of acids and alkalies in the precritical state of solution change in the opposite manner. With decreasing temperature, the coagulation and sedimentation stabilities of positively and negatively charged particles in the dispersion media of hydrothermal solutions also show opposite tendencies. This difference must be taken into account in study of hydrothermal mineral formation involving disperse systems.