Vol 27, No 2 (2019)

The influence of optical, plasma, and mechanical effects on the macroscopic properties of aqueous solutions is discussed. An important role of the nano-objects that are spontaneously formed in a liquid or generated by external perturbation sources in the formation of these properties is stated. It is suggested that the presence of nano-objects in aqueous solutions determines the behavior of most various processes: from the formation of shock waves to the change in the ion composition and regulation of biological activity. Nonmonotonic dependences of the absorption and luminescence efficiency on the concentration of ion impurity centers in crystals are demonstrated. One of the causes of nonmonotonicity is the aggregation of active centers from neighboring lattice cells. Active aggregates are identified based on a thermodynamic calculation, in agreement with the spectral and relaxation experimental data. Particular analytical models of the thermodynamic state of water and aqueous solutions and the kinetics of chemical reactions occurring in them are reviewed. Here, a key point is the consideration of short-lived hydrogen bonds between water and solute molecules The formalism of the theory of dichotomous noise is used to describe these twinkling hydrogen bonds. Its application indicates, in particular, the possibility of forming a low-concentration droplet phase in solutions. A scheme of successive unification of particular models of thermodynamics and kinetics of aqueous solutions, based on an analogy with the theory of luminescence effects in ion impurity centers, is proposed.

It is shown by optical methods using light scattering intensity and shift of the stimulated low- frequency Raman scattering line that emulsion particles of the Emulson EM-1 lubricant-coolant are not monolithic drops but rather rigid aggregates of micelles. As the emulsion concentration decreases, the drops undergo a transition from the state of a monolithic droplet or a dense micellar aggregate to the state of a micellar aggregate with interlayers. The same also applies to water emulsions in transformer oil.

The dispersed composition of water samples prepared by the multiple-dilution technique has been investigated opto-physically using two laser diagnostics methods: dynamic light scattering and laser phase microscopy. We studied suspensions of antibodies (Ab) to the human interferon-gamma (IFNγ) in water with an initial concentration of 0.125 mg ml⁻¹ (5×10¹⁴ mol cm⁻³), which were subjected to 12 successive 100-multiple volume dilutions (C12) in water. Individual antibodies and particles of about 300 nm in size, which can be considered as aggregates of individual antibodies, have been found in the initial suspensions. It turned out that some mesoparticles with a concentration on the order of 10³ cm⁻³ exist also in suspensions subjected to C12 dilution. These particles have a refractive index close to typical values of protein refractive indices. A possible explanation of the origin of particles with sizes on the order of several hundreds of nanometers, revealed in highly diluted suspensions, is proposed. On the one hand, some of these particles may be aggregates of antibodies from the initial suspension, which remained (due to the flotation effect) in the bulk of the liquid after dilutions. On the other hand, the appearance of solid contaminant particles at the same mesoscopic scale (i.e., on the order of several hundreds of nanometers) cannot be excluded in the dilution process.

The formation of selenium nanoparticles by laser ablation of its target in pure water and water containing biocompatible surfactants has been experimentally investigated. Experiments were performed using three different techniques: ablation in a stationary liquid, ablation in a continuous-flow cell, and laser fragmentation of the obtained mixture of selenium micro- and nanoparticles. The mass and size distribution functions of selenium nanoparticles were determined by sedimentation analysis. A production rate of 20mg min⁻¹ was implemented for selenium nanoparticles. These nanoparticles (less than 100 nm in diameter) were found to be amorphous.

It is found that electrical conduction of highly diluted aqueous diclofenac solutions nonmonotonically depends on their concentration under serial centesimal dilutions with vigorous shaking. Nonmonotonic dependence is also observed under further serial centesimal dilutions by the same technique applied to the solutions, in which the notion of concentration of initial substance loses its meaning. Conductivity of the samples evolve for 14 days, within which it increases, and the extrema become sharper. Permittivity of the samples at the frequencies of 100 kHz to 3 MHz remains almost constant (to an accuracy of 0.2%). No relaxation processes and permittivity increment are observed in the solutions. At lower frequencies of 10 kHz to 20 Hz, capacitance considerably increases with increasing conductivity of the solution, but this is due to the diffusion process at the solution−electrode interface and has nothing to do with the solution bulk properties. It is shown in the Introduction that water is a complex heterogenic nonequilibrium system sensitive to weak effects of physical nature and capable of self-organization.

The degree of water structuring in solutions of four salts (CsCl, KBr, and KI with a concentration of 1M and CaCl₂ with a concentration of 0.5M) has been analyzed using THz time-domain spectroscopy. It is shown that the degree of water structuring in a solution of salt, prepared based on a highly diluted aqueous solution of the same salt, differs in some cases from the degree of structuring of similar solutions prepared on the basis of highly diluted aqueous solutions of other salts and similarly prepared water. The degree of water structuring increases in salt solutions containing ions with pronounced positive hydration, decreases in salt solutions containing ions with pronounced negative hydration, and does not differs from control in salt solutions containing no ions with pronounced positive or negative hydration.

An experiment has been performed, where water enriched in hydrogen peroxide was subjected to multiply dilution under mechanical action. It is established that, when the number of dilutions reaches a certain level, the correlation between the hydrogen peroxide concentration and the number of dilutions is lost; i.e., the concentration ceases to depend on the number of dilutions. Moreover, it is even somewhat increases because of the mechanical action accompanying the dilution. The hydrogen peroxide generation rate amounts to 10⁻⁹ (mol l⁻¹)min⁻¹ for impact times of few minutes.

A considerable increase in the concentration of H₂O ortho spin isomers and H₂O₂ molecules in the hydration layer at the interface of water and molecules of DNA, denatured DNA, and protein α- chymotrypsin is found using low-frequency laser spectroscopy of four-photon scattering (FPS). Spectra of rotational resonances of H₂O ortho and para spin isomers in aqueous solutions of various biopolymers and in distilled water are obtained in the range of 0 to 100 cm−1 with a spectral resolution of ≈0.12 cm⁻¹. Numerical analysis of the FPS spectra shows that concentration of H₂O₂ molecules in the DNA hydration layer increases by a factor of three after denaturation. In addition, FPS spectra of aqueous α-chymotrypsin solutions are obtained in the spectral range of ±7 cm⁻¹ at concentrations of 0 to 20mgcm⁻³. It is found out that the speed of hypersound in the aqueous protein solution measured by the shift of the Brillouin components in the scattering spectrum increases and cubically depends on the concentration.