Formation and Stability of Bulk Nanobubbles by Vibration

Electrostatic-Field-Induced Collapse of Nanobubbles in Nanochannels

The adsorbed nanobubbles inside the nanochannels can cause fluid transport blockages, which will obviously degrade the nanodevice performance and reduce the lifetime. However, due to small-scale effects, the removal of nanobubbles is a huge challenge at the nanoscale. Herein, molecular dynamics simulations are carried out to study the effect of the electrostatic field on underwater nitrogen nanobubbles confined in nanochannels. It is found that the nanobubbles will collapse under an appropriate electrostatic field, thereby unblocking the transport of water in the nanochannels. The formation of ordered water structures induced by electrostatic fields plays an important role in the removal of nanobubbles from the nanochannels. Our findings provide a convenient, controllable, and remote way to address the blockage problem of nanobubbles in nanochannels, which may have potential applications in improving the performance of fuel cells.

Characterization of the Dynamic Behavior of Multinanobubble System under Shock Wave Influence

Shockwave-induced changes in nanobubbles cause cavitation erosion and membrane damage but can also be applied to biocarrier transport. Currently, research focuses on single nanobubbles; however, in reality, nanobubbles usually appear as a multibubble system. Therefore, this study proposes a method based on cutting and replicating to construct a multibubble model. This method can be widely applied to molecular dynamics (MD) models and enhance the customization capabilities of MD models. The dynamic behavior of a multinanobubble system with different numbers and arrangements of nanobubbles is investigated with the MD method under the influence of shock waves in a liquid argon system. The study also explores the range of influence between nanobubbles. The results show that in the case of two nanobubbles, when the distance between the bubbles is constant, the smaller the angle between the direction of the shock wave and the line connecting the bubbles, the greater is the influence between nanobubbles, and the moment of collapse of the nanobubbles farther away from the shock wave is slower. When three nanobubbles are arranged with a right offset, after the first bubble collapses, the effect on the other two bubbles is similar to the changes in bubbles when the angle of arrangement is 30° or 60°. Under a different arrangement, the change of shock wave velocity on the nanobubble size only affects its collapse time and contraction collapse rate. When the shock wave with a radian of about 2.87 or greater than 2.87 touches the bubbles, the collapse of the second nanobubble will not be affected.

The impact of low-velocity shock waves on the dynamic behaviour characteristics of nanobubbles

Low-velocity shock wave-induced contraction and expansion of nanobubbles can be applied to biocarriers and microfluidic systems. Although experiments have been conducted to study the application effects, the dynamic behavior characteristics of nanobubbles remain unexplored. In this work, we utilize molecular dynamics (MD) simulations to investigate the dynamic behavior characteristics of nanobubbles influenced by low-velocity shock waves in a liquid argon system. The DBSCAN (Density-Based Spatial Clustering of Applications with Noise) machine learning method is used to calculate the equivalent radius of nanobubbles. Two statistical methods are then utilized to predict the time series changes in the equivalent radius of nanobubbles without rebound shock waves. The piston velocity is analyzed using the bisection method to obtain the critical impact states of the nanobubble. The results show that at the low velocity shock wave (piston velocity of 0.1 km s-1), the shock wave pressure is small, the non-vacuum nanobubbles contract and expand in a circular shape, and the gas particles inside the bubble are not dispersed. In contrast, the vacuum nanobubbles collapse directly. As the shock wave rebounds upon impact, it triggers periodic contraction and expansion of the nanobubbles. The predictions indicate that the equivalent radius will vary within a small range according to the pre-predicted values in the absence of the rebound shock wave. Nanobubbles are present in four critical impact states: dispersed gaps, multiple smaller bubbles, two split bubbles, and a concave bubble.

Do Nanobubbles Exist in Pure Alcohol?

The existence of nanobubbles in pure water has been extensively debated in recent years, and it is speculated that nanobubbles may be ion-stabilized. However, nanobubbles in the alcohol-water mixture and pure alcohols are still controversial due to the lack of ions present in the alcohol system. This work tested the hypothesis that stable nanobubbles exist in pure alcohol. The ultrasound and oscillatory pressure fields are used to generate nanobubbles in pure alcohol. The size distribution, concentration, diameter, and scattering intensity of the nanobubbles were measured by nanoparticle tracking analysis. The light scattering method measures the zeta potential. The Mie scattering theory and electromagnetic wave simulation are utilized to estimate the refractive index (RI) of nanobubbles from the experimentally measured scattering light intensity. The average RI of the nanobubbles in pure alcohols produced by ultrasound and oscillating pressure fields was estimated to be 1.17 ± 0.03. Degassing the nanobubble sample reduces its concentration and increases its size. The average zeta potential of the nanobubbles in pure alcohol was measured to be -5 ± 0.9 mV. The mechanical stability model, which depends on force balance around a single nanobubble, also predicts the presence of nanobubbles in pure alcohol. The nanobubbles in higher-order alcohols were found to be marginally colloidally stable. In summary, both experimental and theoretical results suggest the existence of nanobubbles in pure alcohol.

Oxidative Capacity of Oxygen Nanobubbles and Their Mechanism for the Catalytic Oxidation of Ferrous Ions with Copper as a Catalyst in Sulfuric Acid Medium

Nanobubble (NB) technology has demonstrated the potential to enhance or substitute for current treatment processes in various areas. However, research employing it as a novel advanced oxidation process has thus far been relatively limited. Herein, we focused on the oxidative capacity of oxygen NBs and investigated the feasibility of utilizing their enhanced oxidation of ferrous ions (Fe²⁺) in a sulfuric acid medium when using copper as a catalyst and their effect mechanism. It was demonstrated that oxygen NBs could collapse to produce hydroxyl radicals (·OH) in the absence of dynamic stimuli using electron spin resonance spectroscopy, and methylene blue was used as a molecular probe for ·OH to illustrate that NB stability, determined by their properties, is the critical factor affecting ·OH release. In subsequent Fe²⁺ oxidation experiments, it was discovered that both strong acidity and copper ions (Cu²⁺) contribute to accelerating the collapse of NBs to produce ·OH. While ·OH derived from the collapse of NBs acts on Fe²⁺, the molecular oxygen generated homologously with ·OH will further activate the catalytic oxidation of Fe²⁺ by interacting with Cu²⁺. With the synergistic effect of the above two oxidation-driven mechanisms, the oxidation rate of Fe²⁺ can be significantly increased up to 88% due to the exceptional properties of oxygen NBs, which facilitate the formation of an atmosphere with persistent oxygen supersaturation and the generation of oxidation radicals. This study provides significant insight into applying NBs as a prospective technology for enhanced oxidation processes.

Size control of precipitated particles of amino acids using a bubble column evaporator

The precipitation of five amino acids: DL-alanine, L-arginine, L-leucine, DL-methionine and L-tyrosine was studied at their solubility limits and isoelectric point by using a bubble column evaporator (BCE). The precipitation of amino acids via a bubble column evaporator and a standard stirring method were compared via turbidity measurements. Particle size, zeta potential and polydispersity index (PDI) were also measured using a Malvern Zeta-sizer and the particle morphology was examined using Scanning Electron Microscopy (SEM). The novel BCE process emerges as a much more effective method than precipitation by standard stirring methods. Better control of fine particle size and growth rates is achieved. The amino acids in zwitterionic form exhibit the same unexplained bubble coalescence inhibition phenomenon as do common salts. This suggests obvious applications in flotation technologies.

Resonance-Induced Reduction of Interfacial Tension of Water-Methane and Improvement of Methane Solubility in Water

Molecular dynamics simulations were performed to study the effect of the periodic oscillating electric field on the interface between water and methane. We propose a new strategy that utilizes oscillating electric fields to reduce the interfacial tension (IFT) between water and methane and increase the solubility of methane in water simultaneously. These are attributed to the hydrogen bond resonance induced by an electric field with a frequency close to the natural frequency of the hydrogen bond. The resonance breaks the hydrogen bond network among water molecules to the maximum, which destroys the hydration shell and reduces the cohesive action of water, thus resulting in the decrease of IFT and the increase of methane solubility. As the frequency of the electric field is close to the optimum resonant frequency of hydrogen bonds, IFT decreases from 56.43 to 5.66 mN/m; water and methane are miscible because the solubility parameter of water reduces from 47.63 to 2.85 MPa^1/2, which is close to that of methane (3.43 MPa^1/2). Our results provide a new idea for reducing the water-gas IFT and improving the solubility of insoluble gas in water and theoretical guidance in the fields of natural gas exploitation, hydrate generation, and nanobubble nucleation.

Proliferative effects of nanobubbles on fibroblasts

In recent years, the potential of nanobubbles (NBs) for biological activation has been actively investigated. In this study, we investigated the proliferative effects of nitrogen NBs (N-NBs) on fibroblast cells using cell assays with image analysis and flow cytometry. A high concentration of N-NBs (more than 4 × 10⁸ NBs/mL) was generated in Dulbecco’s modified Eagle’s medium (DMEM) using a gas–liquid mixing method. In image analysis, the cells were counted and compared, which showed an 11% increase in cell number in the culture medium with N-NBs. However, in two further cell cytometry analyses, the effect of nanobubbles on cell division was found to be insignificant (approximately 2%); as there is insufficient evidence that N-NB is involved in cell division mechanism, further studies are needed to determine whether NB affects other cellular mechanisms such as apoptosis. This study presents the first successful attempt of directly generating and quantifying N-NBs in a culture medium for cell culture. The findings suggest that the N-NBs in the culture medium can potentially facilitate cell proliferation.

Formation of Bulk Nanobubbles Induced by Accelerated Electrons Irradiation: Dependences on Dose Rates and Doses of Irradiation

Radiation on aqueous solutions can induce water radiolysis with products of radicals, H₂, H₂O₂, and so on, and their consequent biological effects have long been interested in radiation chemistry. Unlike the decomposition of water by electric current that produces a significant number of bubbles, the gas products from the radiolysis of water are normally invisible by bare eyes, little is known on whether nanosized bubbles can be produced and what their dynamics are upon irradiation. Here, we first presented the formation of nanoscale bulk bubbles by irradiating pure water with accelerated electrons and their concentration and size distribution changes with the dose and rate of irradiation. The nanoparticle tracking analysis showed that irradiation can actually produce a certain amount of bulk nanobubbles in pure water. They exhibited a dependence on the irradiation dose rates and irradiation doses. The results indicated that the concentration of formed bulk nanobubbles increased as the irradiation dose rates increased, but it will increase and then decrease with the increased irradiation doses. The formed bulk nanobubbles could maintain stability for several hours. Our findings will provide a new angle of view for the radiation chemistry of water, and the formed nanobubbles may help elucidate the biological effects of irradiated solutions.

Generation methods, stability, detection techniques, and applications of bulk nanobubbles in agro-food industries: a review and future perspective

Nanobubble (NB) technologies have received considerable attention for various applications due to their low cost, eco-friendliness, scale-up potential, process control, and unique physical characteristics. NB stands for nanoscopic gaseous cavities, typically <1 μm in diameter. NBs can exist on surfaces (surface or interfacial NBs) and be dispersed in a bulk liquid phase (bulk NBs). Compared to the microbubbles, NBs exhibit high specific surface area, negative surface charge, and better adsorption. Bulk NBs can be generated by hydrodynamic/acoustic cavitation, electrolysis, water-solvent mixing, nano-membrane filtration, and so on. NBs exhibit extraordinary longevity compared to microbubbles, prompting the interest of the scientific community aiming for potential applications including medicine, agriculture, food, wastewater treatment, surface cleaning, and so on. Based on the limited amount of research work available regarding the influence of NBs on food matrices, further research, however, needs to be done to provide more insights into its applications in food industries. This review provides an overview of the generation methods for NBs, techniques to evaluate them, and a discussion of their stability and several applications in various fields of science were discussed. However, recent studies have revealed that, despite the many benefits of NB technologies, several NB generating approaches are still limited in their application in specific agro-food industries. Further study should focus on process optimization, integrating various NB generation techniques/combining with other emerging technologies in order to achieve rapid technical progress and industrialization of NB-based technologies.HighlightsNanobubbles (NBs) are stable spherical entities of gas within liquid and are operationally defined as having diameters less than 1 µm.Currently, various reported theories still lack the ability to explain the evidence and stability of NBs in water, numerous NB applications have emerged due to the unique properties of NBs.NB technologies can be applied to various food and dairy products (e.g. yogurt and ice cream) and other potential applications, including agriculture (e.g. seed germination and plant growth), wastewater treatment, surface cleaning, and so on.

Pulmonary surfactant and COVID-19: A new synthesis

Chapter 1

COVID-19 pathogenesis poses paradoxes difficult to explain with traditional physiology. For instance, since type II pneumocytes are considered the primary cellular target of SARS-CoV-2; as these produce pulmonary surfactant (PS), the possibility that insufficient PS plays a role in COVID-19 pathogenesis has been raised. However, the opposite of predicted high alveolar surface tension is found in many early COVID-19 patients: paradoxically normal lung volumes and high compliance occur, with profound hypoxemia. That 'COVID anomaly' was quickly rationalised by invoking traditional vascular mechanisms-mainly because of surprisingly preserved alveolar surface in early hypoxemic cases. However, that quick rejection of alveolar damage only occurred because the actual mechanism of gas exchange has long been presumed to be non-problematic, due to diffusion through the alveolar surface. On the contrary, we provide physical chemical evidence that gas exchange occurs by an process of expansion and contraction of the three-dimensional structures of PS and its associated proteins. This view explains anomalous observations from the level of cryo-TEM to whole individuals. It encompasses results from premature infants to the deepest diving seals. Once understood, the COVID anomaly dissolves and is straightforwardly explained as covert viral damage to the 3D structure of PS, with direct treatment implications. As a natural experiment, the SARS-CoV-2 virus itself has helped us to simplify and clarify not only the nature of dyspnea and its relationship to pulmonary compliance, but also the fine detail of the PS including such features as water channels which had heretofore been entirely unexpected.

Chapter 2

For a long time, physical, colloid and surface chemistry have not intersected with physiology and cell biology as much as we might have hoped. The reasons are starting to become clear. The discipline of physical chemistry suffered from serious unrecognised omissions that rendered it ineffective. These foundational defects included omission of specific ion molecular forces and hydration effects. The discipline lacked a predictive theory of self-assembly of lipids and proteins. Worse, theory omitted any role for dissolved gases, O2, N2, CO2, and their existence as stable nanobubbles above physiological salt concentration. Recent developments have gone some way to explaining the foam-like lung surfactant structures and function. It delivers O2/N2 as nanobubbles, and efflux of CO2, and H2O nanobubbles at the alveolar surface. Knowledge of pulmonary surfactant structure allows an explanation of the mechanism of corona virus entry, and differences in infectivity of different variants. CO2 nanobubbles, resulting from metabolism passing through the molecular frit provided by the glycocalyx of venous tissue, forms the previously unexplained foam which is the endothelial surface layer. CO2 nanobubbles turn out to be lethal to viruses, providing a plausible explanation for the origin of 'Long COVID'. Circulating nanobubbles, stable above physiological 0.17 M salt drive various enzyme-like activities and chemical reactions. Awareness of the microstructure of Pulmonary Surfactant and that nanobubbles of (O2/N2) and CO2 are integral to respiratory and circulatory physiology provides new insights to the COVID-19 and other pathogen activity.

Nafion Swelling in Salt Solutions in a Finite Sized Cell: Curious Phenomena Dependent on Sample Preparation Protocol

When a membrane of Nafion swells in water, polymer fibers "unwind" into the adjoining liquid. They extend to a maximum of about ~300 μm. We explore features of Nafion nanostructure in several electrolyte solutions that occur when the swelling is constrained to a cell of size less than a distance of 300 μm. The constraint forces the polymer fibers to abut against the cell windows. The strongly amphiphilic character of the polymer leads to a shear stress field and the expulsion of water from the complex swollen fiber mixture. An air cavity is formed. It is known that Nafion membrane swelling is highly sensitive to small changes in ion concentration and exposure to shaking. Here we probe such changes further by studying the dynamics of the collapse of the induced cavity. Deionized water and aqueous salt solutions were investigated with Fourier IR spectrometry. The characteristic times of collapse differ for water and for the salt solutions. The dynamics of the cavity collapse differs for solutions prepared by via different dilution protocols. These results are surprising. They may have implications for the standardization of pharmaceutical preparation processes.

Vibration influence on the O2-dependent processes activity in human erythrocytes

The early signs of vibration effects on the human body are microcirculation and transcapillary metabolism disorders, accompanied by disruption of the supply to and utilization of oxygen in the tissues and organs. However, there are few experimental studies aimed at finding targets of vibration in cells and determining the action mechanism of vibration. In in vitro experiments, human erythrocytes in buffer solution were exposed to low-frequency vibration (frequency range 8–32 Hz, amplitudes 0.5–0.9 mm) for 3 hours. The dynamics of the accumulation of membrane-bound catalase and hemoglobin and the distribution of ligand hemoglobin in the membrane-bound fraction were studied as the indicators of functional activity of cells. The choice of these indicators is justified by the participation of catalase and hemoglobin in O2-dependent cellular reactions as a part of protein complexes. Since pО2 is a trigger of conformational transitions in the hemoglobin molecule, simultaneously with oxygen transport, hemoglobin signals to different metabolic systems about oxygen conditions in the environment. The studies revealed that in the conditions of vibration, the activity of membrane-associated catalase increased by 40–50% in the frequency range of 12–24 Hz (amplitude 0.5 ± 0.04 mm), by 20–30% in the amplitude of 0.9 mm, but after about 100–120 min exposure the enzyme activity decreased even below the control level. There was a dose-dependent accumulation of membrane-bound hemoglobin during exposure to vibration. In the membrane-bound fraction of hemoglobin, oxyhemoglobin had the highest content (60–80%), while the content of methemoglobin varied 5–20%. During vibrations in the frequency range 12–28 Hz, 0.5 mm, we recorded 10–30% increase in oxyhemoglobin. With increase in the vibration amplitude (0.9 mm) in the frequency range of 16–32 Hz, constant content of oxyhemoglobin was noted at the beginning of the experiment, which tended to decrease during the last exposure time. Frequency of 32 Hz caused increase in the deoxyhemoglobin content in the membrane-bound fraction. The content of methemoglobin (metHb) in erythrocytes significantly increased during exposure to the frequency range of 12–24 Hz, with the amplitude of 0.5 mm (1.3–2.4 times). During the exposure to frequencies of 28 and 32 Hz, we observed the transition of methemoglobin to hemichrome. The content of methemoglobin in the cells was lower and decreased at the end of the experiment when the vibration amplitude was 0.9 mm. In these experimental conditions, no increase in hemichrome content in the membrane-bound fraction was recorded. Therefore, the degree of binding of catalase and hemoglobin with the membrane of erythrocytes that were exposed to vibration and the changes in the content of ligand forms in the composition of membrane-bound hemoglobin are dose-dependent. Low-frequency vibration initiates O2-dependent processes in erythrocytes. Targets of such an influence are nanobubbles of dissolved air (babstons), retained on the surface of erythrocytes due to Coulomb interactions, capable of coagulation and increase in size under the action of vibration. At first, the consequences of these processes are increase in oxygen content in the surface of erythrocytes, and then decrease as a result of degassing. Thus, increase in oxygen content on the surface initiates redox reactions, whereas decrease in oxygen content leads to reconstruction of metabolic processes oriented at overcoming hypoxia.

Micellization Transformations of Sodium Oleate Induced by Gas Nucleation

The interfacial properties of surfactant solutions are closely related to the micellization of surfactants. Temperature, salt type and concentration, pH, and other parameters affecting the micellization of surfactants have all been extensively investigated previously. However, the effect of dissolved gas on surfactant micellization and associated interfacial properties' transformations is not completely understood yet. In this study, sodium oleate (NaOl) was chosen as the research object, and the role of gas/gas nucleation in NaOl micellization was systematically investigated. The results indicated that the solution changed to be more turbid and the dissolved oxygen content increased after NaOl solutions were subjected to compression-decompression treatments. Meanwhile, the surface tension of the NaOl solution was altered, which was more pronounced when the concentration of NaOl was close to the critical micelle concentration. Given that the surface tension was a good indicator of the assembly and distribution state of the soluble monomers and insoluble micelles of NaOl, interactions between nucleated bubbles originating from the gas nucleation and NaOl molecules were unveiled through the analysis of the size distribution and zeta potential of sub-micro- and nanoscale particles in bulk solutions. Finally, possible micellization models of NaOl molecules, fully considering the role of gas/gas nucleation, were proposed under varying NaOl concentration conditions.

Recent advances for understanding the role of nanobubbles in particles flotation

Traditional froth flotation is the primary method for the separation and upgrading of fine mineral particles. However, it is still difficult for micro-fine and low-quality minerals to effectively separate. It is generally believed that bubble miniaturization is of great significance to improve flotation efficiency. Due to their unique physical and chemical properties, the application of nanobubbles (NBs) in ore flotation and other fields has been widely investigated as an important means to solve the problems of fine particle separation. Therefore, a fundamental understanding of the effect of NBs on flotation is a prerequisite to adapt it for the treatment of fine and low-quality minerals for separation. In this paper, recent advances in the field of nanobubble (NB) formation, preparation and stability are reviewed. In particular, we highlight the latest progress in the role of NBs on particles flotation and focus in particular on the particle-particle and particle-bubble interaction. A discussion of the current knowledge gap and future directions is provided.

Free-Radical Generation from Bulk Nanobubbles in Aqueous Electrolyte Solutions: ESR Spin-Trap Observation of Microbubble-Treated Water

Microbubbles are very fine bubbles that shrink and collapse underwater within several minutes, leading to the generation of free radicals. Electron spin resonance spectroscopy (ESR) confirmed the generation of hydroxyl radicals under strongly acidic conditions. The drastic environmental change caused by the collapse of the microbubbles may trigger radical generation via the dispersion of the elevated chemical potential that had accumulated around the gas-water interface. The present study also confirmed the generation of ESR signals from the microbubble-treated waters even after several months had elapsed following the dispersion of the microbubbles. Bulk nanobubbles were expected to be the source of the spin-adducts of hydroxyl radicals. Such microbubble stabilization and conversion might be caused by the formation of solid microbubble shells generated by iron ions in the condensed ionic cloud around the microbubble. Therefore, the addition of a strong acid might cause drastic changes in the environment and destroy the stabilized condition. This would restart the collapsing process, leading to hydroxyl radical generation.

Generating Bulk Nanobubbles in Alcohol Systems

Bulk nanobubbles (NBs) have attracted wide attention due to their peculiar physicochemical properties and great potential in applications in various fields. However, so far there are no reports on bulk NBs generated in pure organic systems, which we think is very important as NBs would largely improve the efficiency of gas-liquid mass transfer and facilitate chemical reactions to take place. In this paper, we verified that air and N₂ NBs could be generated in a series of alcohol solutions by using various methods including acoustical cavitation, pressurization-depressurization, and vibration. The experiments proved that NBs existed in alcohol solutions, with a highest density of 5.8 × 10⁷ bubble/mL in propanol. Our results also indicated that bulk NBs could stably exist for at least hours in alcohol systems. The parameters in generating NBs in alcohols were optimized. Our findings open up an opportunity for improving gas-liquid mass transfer efficiency in the field of the chemical industry.

Response to "Comment on Bulk Nanobubbles or Not Nanobubbles: That is the Question"

Advanced techniques that combine high spatial resolution with chemical sensitivity to directly probe the observed nanoentities and provide direct evidence that they are truly gas-filled nanobubbles do not exist. Therefore, in our paper, we focused on providing, for the first time, multiple types of indirect evidence using a variety of physical and chemical techniques that the nanoentities are not due to contamination and, hence, they must be bulk nanobubbles (BNBs). It should be noted that such techniques require good experimental skills, sound protocols, good scientific expertise, and reliable equipment. While no single piece of indirect evidence on its own can be considered as conclusive proof, we estimate that our results combined provide strong evidence that bulk nanobubbles do exist and they are stable. The work presented in our paper is the culmination of a series of studies, and many authors have either directly or indirectly confirmed our findings. Nonetheless, in their Comment, Rak & Sedlak reject all of the work we reported. We here address their comments point by point and show that their criticisms are unwarranted and unfounded, as follows.

Formation of Water-Free Cavity in the Process of Nafion Swelling in a Cell of Limited Volume; Effect of Polymer Fibers Unwinding

When Nafion swells in water, colloidal particles are repelled from the polymer surface; this effect is called the formation exclusion zone (EZ), and the EZ size amounts to several hundred microns. However, still no one has investigated the EZ formation in a cell whose dimension is close to the EZ size. It was also shown that, upon swelling in water, Nafion fibers “unwind” into the water bulk. In the case of a cell of limited volume, unwound fibers abut against the cell windows, and water is completely pushed out from the region between the polymer and the cell window, resulting in a cavity appearance. The temporal dynamics of the collapse of this cavity was studied depending on the cell size. It is shown that the cavity formation occurs due to long-range forces between polymer strands. It turned out that this scenario depends on the isotopic composition of the water, ionic additives and water pretreatment. The role of nanobubbles in the formation and collapse of the cavity were analyzed. The results obtained allowed us to conclude that the EZ formation is precisely due to the unwinding of polymer fibers into the liquid bulk.

Spraying Small Water Droplets Acts as a Bacteriocide

Disinfectants are important for arresting the spread of pathogens in the environment. Frequently used disinfectants are often incompatible with certain surfaces, expensive and can produce hazardous by-products. We report that micron-sized water droplets can act as an effective disinfectant, which were formed by spraying pure bulk water with coaxial nebulizing airflow. Spraying for 20 min onto Escherichia coli and Salmonella typhimurium on stainless-steel discs caused inactivation of over 98% of the bacteria. Control experiments resulted in less than 10% inactivation (water stream only and gas only) and 55% inactivation with 3% hydrogen peroxide. Experiments have shown that cell death results from cell wall destruction. We suggest that the combined action of reactive oxygen species present in water droplets (but not in bulk water) along with the droplet surface charge is responsible for the observed bactericidal activity.

Shaking-Induced Aggregation and Flotation in Immunoglobulin Dispersions: Differences between Water and Water-Ethanol Mixtures

Structural characterization by three complementary methods of laser diagnostics (dynamic light scattering, laser phase microscopy, and laser polarimetric scatterometry) has established that shaking of immunoglobulin G (IgG) dispersions in water and ethanol-water mixtures (36.7 vol %) results in two effects. First, it intensifies the aggregation of IgG macromolecules. Second, it generates bubbles with a size range that is different in each solvent. The aggregation is enhanced in ethanol-water mixtures because of IgG denaturation. IgG aggregates have a size of ∼300 nm in water and ∼900 nm in ethanol-water mixtures. The flotation of IgG is much more efficient in water. This can be explained by a better adsorption of IgG particles (molecules and aggregates) on bubbles in water as compared to ethanol-water mixtures. Bulk nanobubbles and their association with IgG aggregates were visualized by laser phase microscopy in water but were not detected in ethanol-water mixtures. Therefore, the nanobubble flotation mechanism for IgG aggregates acting in water is not feasible for ethanol-water mixtures.