Self-oscillating Water Chemiluminescence Modes and Reactive Oxygen Species Generation Induced by Laser Irradiation; Effect of the Exclusion Zone Created by Nafion

Water of Increased Content of Molecular Oxygen

Deionized and tap water were saturated with molecular oxygen either prior to (WST), or after (WTS), treatment with low-temperature, low-pressure glow plasma of low frequency (LPGP) for 0, 5, 15, 30, 60, 90, and 120 min. Physical and physicochemical properties of the resulting liquids were characterized, involving pH, conductivity, density, dissolved molecular oxygen, active oxygen content, differential scanning calorimetry (DSC), ultraviolet-visible (UV-VIS), Fourier transformation infrared-attenuated total reflectance (FTIR-ATR), electronic spin resonance (ESR), and Raman spectroscopies. Tap WST treated with LPGP for 30 min contained the highest level of dissolved molecular oxygen, compared to original non-treated tap water (23 and 15 mg/L, respectively). Essential differences in all investigated properties of LPGP treated tap and deionized WST, compared to those for corresponding WTS, pointed to the indispensable role of dissolved oxygen molecules in building water macrostructure. In the case of tap WST, formation of niches and/or caverns hosting anions (HCO3−, SO4=) was accompanied by cations less enveloped by hydroxyl groups of water. The WST water contained niches of larger size, hosting molecules of oxygen interacting with the environment in various manners. In WTS there was a priority for single donor, single hydrogen bonded water, and free water in building the macrostructure. Such macrostructures host molecular oxygen which, depending on the LPGP treatment time, took either a singlet of triplet state.

Exclusion Zone Phenomena in Water-A Critical Review of Experimental Findings and Theories

The existence of the exclusion zone (EZ), a layer of water in which plastic microspheres are repelled from hydrophilic surfaces, has now been independently demonstrated by several groups. A better understanding of the mechanisms which generate EZs would help with understanding the possible importance of EZs in biology and in engineering applications such as filtration and microfluidics. Here we review the experimental evidence for EZ phenomena in water and the major theories that have been proposed. We review experimental results from birefringence, neutron radiography, nuclear magnetic resonance, and other studies. Pollack theorizes that water in the EZ exists has a different structure than bulk water, and that this accounts for the EZ. We present several alternative explanations for EZs and argue that Schurr's theory based on diffusiophoresis presents a compelling alternative explanation for the core EZ phenomenon. Among other things, Schurr's theory makes predictions about the growth of the EZ with time which have been confirmed by Florea et al. and others. We also touch on several possible confounding factors that make experimentation on EZs difficult, such as charged surface groups, dissolved solutes, and adsorbed nanobubbles.

Dynamics of Nafion membrane swelling in H2O/D2O mixtures as studied using FTIR technique

Experiments with Fourier transform spectrometry of Nafion, a water-swollen polymeric membrane, are described. The transmittance spectra of liquid samples and Nafion, soaked in these samples, were studied, depending on the deuterium content in water in the spectral range 1.8-2.15 μm. The experiments were carried out using two protocols: in the first protocol we studied the dynamics of Nafion swelling in H₂O + D₂O mixtures for the deuterium concentrations 3 < C < 10⁴ ppm, and in the second protocol we studied the dynamics of swelling in pure heavy water (C = 10⁶ ppm). For liquid mixtures in the concentration range 3 < C < 10⁴ ppm, the transmittance spectra are the same, but for Nafion soaked in these fluids, the corresponding spectra are different. It is shown that, in the range of deuterium contents C = 90-500 ppm, the behavior of transmittance of the polymer membrane is non-monotonic. In experiments using the second protocol, the dynamics of diffusion replacement of residual water, which is always present in the bulk of the polymer membrane inside closed cavities (i.e., without access to atmospheric air), were studied. The experimentally estimated diffusion coefficient for this process is ≈6·10^-11 cm²/s.