Do Nanobubbles Exist in Pure Alcohol?

The endothelial surface layer-glycocalyx - Universal nano-infrastructure is fundamental to physiology, cell traffic and a complementary neural network

The glycocalyx and its associated endothelial surface layer which lines all cell membranes and most tissues, dwarfs the phospholipid membrane of cells in extent. Its major components are sulphated polymers like heparan and chondroitin sulphates and hyaluronic acid. These form a fuzzy layer of unknown structure and function. It has become increasingly clear that the ESL-GC complex must play many roles. We postulate it has a self-organised infrastructure that directs cell traffic, acts in defence against pathogens and other cells, and in diseases like diabetes, and heart disease, besides being a playground for a host of biochemical activity. Based on an analogous sulphated polymeric system Nafion, the fuel cell polymer, we suggest a model for the structure of the ESL-GC complex and how it functions. Taken together with parallel developments in physical chemistry, in nanobubbles, their stability in physiological media, and reactivity, we believe the model may throw light on a variety of phenomena, diabetes and some other diseases.

The Existence and Stability Mechanism of Bulk Nanobubbles: A Review

Since they were shown to be a potential phenomenon through experimentation, bulk nanobubbles (BNBs) have been a long-standing controversy. The controversy mainly originates from the fact that their stability cannot be well explained by the established theories. Although nanobubbles have been applied in many fields, the controversial stability issue has been a hanging "cloud" looming over the nanobubble research. This review focuses on why the stability of nanobubbles cannot be depicted by the current theories from thermodynamics and dynamics perspectives. Moreover, a number of current models pertaining to bulk nanobubble stability are compiled. It is anticipated that this review will give readers a better grasp of the current state of bulk nanobubble research and provide some insight for further studies in this area.

Impact of Water Purity and Oxygen Content in Gas Phase on Effectiveness of Surface Cleaning with Microbubbles

Cleaning of surfaces without complex cleaning agents is an important subject, especially in food, pharmaceutical, and biomedical applications. The subject of microbubble and nanobubble cleaning is considered one of the most promising ways to intensify this process. In this work, we check whether and how the purity of water used for microbubble generation, as well as the gas used, affects the effectiveness of cleaning stainless-steel surfaces. Surfaces contaminated with Pluronic L-121 solution were cleaned by water of three purities: ultrapure water (<0.05 μS/cm), water after reversed osmosis (~6.0 μS/cm), and tap water (~0.8 mS/cm). Similarly, three different gases were supplied to the generation setup for microbubble generation: air, oxygen, and nitrogen. Stainless steel plates were immersed in water during microbubble generation and cleaned for a given time. FTIR (Fourier Transform Infrared Spectroscopy) and contact angle analysis were employed for the analysis of surfaces. The results of cleaning were repeatable between plates and showed different cleaning effects depending on both the purity of water (concentration of ions) and gas composition. We have proposed different mechanisms that are dominant with respect to specific combinations of ion concentration and oxygen content in gas, which are directly connected to the microbubble stability and reactivity of gas.

Polarizing Perspectives: Ion- and Dipole-Induced Dipole Interactions Dictate Bulk Nanobubble Stability

The origin of the stability of bulk Nanobubbles (NBs) has been the object of scrutiny in recent years. The interplay between the surface charge on the NBs and the Laplace pressure resulting from the surface tension at the solvent-NB interface has often been evoked to explain the stability of the dispersed NBs. While the Laplace pressure is well understood in the community, the nature of the surface charge on the NBs has remained obscure. In this work, we aim to show that the solvent and the present ions can effectively polarize the NB surface by inducing a dipole moment, which in turn controls the NB stability. We show that the polarizability of the dispersed gas and the polarity of the dispersing solvent control the dipole-induced dipole interactions between the solvent and the NBs, and that, in turn, determines their stability in solution.

Nanobubbles produced by nanopores to probe gas-liquid mass transfer characteristics

HYPOTHESIS

This study tested the hypothesis of how the nanopore size of membranes and how the surface charge of nanobubbles responds to its pinch-off from the nanopore. This study also tested the hypothesis that nanobubbles that remain in solution after production may increase the dissolved oxygen content in water.

EXPERIMENTS

The effect of membrane pore size, hydrodynamic conditions (gas and liquid flow rates), and physicochemical parameters (pH and temperature) on volumetric mass transfer coefficient (kLa) for oxygen nanobubbles formed by the nanopore diffusion technique was investigated. This study experimentally determined the kLa by carefully removing the dissolved oxygen by nitrogen purging from nanobubble suspension to examine the sole contribution of nanobubble dissolution in water to the reaeration.

RESULTS

Scaling estimates indicate that the nanobubble pinch-off radius and nanopore radius have a power-law correlation and that nanobubble size declines with the nanopore size. This is in line with our experimental results. The surface charge of nanobubbles delays its pinch-off at the gas-liquid interface. Nanobubbles offered 3-4 times higher kLa than microbubbles. Standard oxygen transfer efficiency in water was found to be 78%, significantly higher than that in microbubbles. However, dissolving stable nanobubbles in water does not considerably increase dissolved oxygen levels.

Advancing nanobubble technology for carbon-neutral water treatment and enhanced environmental sustainability

Gaseous nanobubbles (NBs) with dimensions ranging from 1 to 1000 nm in the liquid phase have garnered significant interest due to their unique physicochemical characteristics, including specific surface area, low internal gas pressure, long-term stability, efficient mass transfer, interface potential, and free radical production. These remarkable properties have sparked considerable attention in the scientific community and industries alike. These hold immense promise for environmental applications, especially for carbon-neutral water remediation. Their long-lasting stability in aqueous systems and efficient mass transfer properties make them highly suitable for delivering gases in the vicinity of pollutants. This potential has prompted research into the use of NBs for targeted delivery of gases in contaminated water bodies, facilitating the degradation of harmful substances and advancing sustainable remediation practices. However, despite significant progress in understanding NBs physicochemical properties and potential applications, several challenges and knowledge gaps persist. This review thereby aims to summarize the current state of research on NBs environmental applications and potential for remediation. By discussing the generation processes, mechanisms, principles, and characterization techniques, it sheds light on the promising future of NBs in advancing environmental sustainability. It explores their role in improving oxygenation, aeration, and pollutant degradation in water systems. Finally, the review addresses future research perspectives, emphasizing the need to bridge knowledge gaps and overcome challenges to unlock the full potential of this frontier technology for enhanced environmental sustainability.

Bulk Nanobubbles through Gas Supersaturation Originated by Hot and Cold Solvent Mixing

The nucleation mechanism of bulk nanobubbles remains unclear despite the considerable attention they have received in recent years. We propose two hypotheses: (i) The gas supersaturation in the bulk liquid is the primary factor for nanobubble nucleation, and (ii) the mixing of the same solvent at varying gas solubilities should produce nanobubbles, provided that the first hypothesis is correct. To test this hypothesis, we performed extensive experiments on nanobubble nucleation in both water and organic solvents. The temperature difference between hot and cold samples ranged from 10 to 80 °C in pure solvents such as water, methanol, ethanol, propanol, and butanol prepared and mixed in equal proportions. To the best of our knowledge, we report bulk nanobubble nucleation by mixing hot and cold solvents for the first time. The refractive index value calculations using Mie scattering theory confirmed the existence of nanobubbles. When surface tension dominates over surface charge, the critical work for nanobubble formation is ΔFc ∝ 1/ξ2, and when surface charge dominates over surface tension, the critical work is ΔFc ∝ ξ1/4. Our experimental results verify such dependency by measuring nanobubbles nucleated with varying degrees of gas supersaturation.