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Nanobubbles and Their Applications

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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Environmental Nanoscience and Nanotechnology".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 27610

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Special Issue Editors

Prof. Dr. Lijuan Zhang

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Guest Editor

1. Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
2. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
Interests: nanobubbles; nanodroplets; colloids; cell; nano image techniques

Prof. Dr. Seiichi Oshita

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Co-Guest Editor

Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
Interests: nanobubbles; nanobubbles used in agricultrure

Prof. Dr. Xianren Zhang

E-Mail Website
Co-Guest Editor

State Key Laboratory of Organic−Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China
Interests: thermodynamics; nanodroplets and nanobubbles

Special Issue Information

Dear Colleagues,

Nanobubbles, also called ultrafine bubbles, are submicron gaseous domains dispersed in solutions or sit on liquid/solid surface, which are supposed to survive for several hours or even days. Another important gas state on liquid/solid surface is micropancake, which has a very thin thickness with several nanometers but a larger lateral size about several microns. It has been recognized that the stable existence of nanobubbles/micropancakes may have significant effects on many important processes such as protein folding, peptide self-assembly, boundary slip, and activities of electrochemical reactions. Also, in recent years, nanobubbles have been widely used in water treatment, aquaculture, agricultural cultivation, health preservation, mineral flotation, and many other fields. However, the fundamental question, why the surface and bulk nanobubbles could exist stably, is still under the way because the paradox of a short lifetime predicted by the Epstein-Plesset theory and the observed long lifetime of nanobubbles in water is not yet been resolved. Moreover, many mechanism of nanobubbles used in various applications, for example, aggregation states in different solutions, biological effects and interfacial properties, are need further exploitation.

The present Special Issue of Nanomaterials is aimed at presenting the current state-of-the-art in the fundamental research of nanobubbles and their applications, a field that has blossomed since the first images of atomic force microscopy were published in 2000s. Nanobubbles have some unique properties, such as higher stability, higher mass transfer efficiency, possible higher density inside and surface charges, etc. it is hoped that nanobubbles would play a very important roles in many fields such as water recovering, cleaning, medical contrast agent, floatation, and so on. In the present Special Issue, we have invited contributions from leading groups in the field with the aim of giving a balanced view of the current state-of-the-art in this discipline.

Prof. Dr. Lijuan Zhang
Prof. Dr. Seiichi Oshita
Prof. Dr. Xianren Zhang
Guest Editors

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Keywords

nanobubbles
interfacial properties
aggregation
micropancake
gas clusters
growth promotion
medical diagnosis
water remediation

Published Papers (12 papers)

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Research

Jump to: Review

10 pages, 3421 KiB

Open AccessCommunication

Green Cleaning of 3D-Printed Polymeric Products by Micro-/Nano-Bubbles

by Haoxiang Gao, Fenghua Zhang, Kangkang Tang, Xianyu Luo, Ziang Pu, Jiuzhou Zhao, Zhiwei Jiao and Weimin Yang

Nanomaterials 2023, 13(11), 1804; https://doi.org/10.3390/nano13111804 - 05 Jun 2023

Viewed by 1407

Abstract

3D printing technology has been used to directly produce various actual products, ranging from engines and medicines to toys, especially due to its advantage in producing items of complicated, porous structures, which are inherently difficult to clean. Here, we apply micro-/nano-bubble technology to the removal of oil contaminants from 3D-printed polymeric products. Micro-/nano-bubbles show promise in the enhancement of cleaning performance with or without ultrasound, which is attributed to their large specific surface area enhancing the adhesion sites of contaminants, and their high Zeta potential which attracts contaminant particles. Additionally, bubbles produce tiny jets and shock waves at their rupture, driven by coupled ultrasound, which can remove sticky contaminants from 3D-printed products. As an effective, efficient, and environmentally friendly cleaning method, micro-/nano-bubbles can be used in a range of applications. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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10 pages, 1325 KiB

Open AccessArticle

Promotion Effects of Ultrafine Bubbles/Nanobubbles on Seed Germination

by Seiichi Oshita, Surina Boerzhijin, Hiromi Kameya, Masatoshi Yoshimura and Itaru Sotome

Nanomaterials 2023, 13(10), 1677; https://doi.org/10.3390/nano13101677 - 19 May 2023

Cited by 2 | Viewed by 1624

Abstract

The number concentrations of air UFBs were controlled, approximately, by adjusting the generation time. UFB waters, ranging from 1.4 × 10⁸ mL⁻¹ to 1.0 × 10⁹ mL⁻¹, were prepared. Barley seeds were submerged in beakers filled with distilled water and UFB water in a ratio of 10 mL of water per seed. The experimental observations of seed germination clarified the role of UFB number concentrations; that is, a higher number concentration induced earlier seed germination. In addition, excessively high UFB number concentrations caused suppression of seed germination. A possible reason for the positive or negative effects of UFBs on seed germination could be ROS generation (hydroxyl radicals and ∙OH, OH radicals) in UFB water. This was supported by the detection of ESR spectra of the CYPMPO-OH adduct in O₂ UFB water. However, the question still remains: how can OH radicals be generated in O₂ UFB water? Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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12 pages, 1817 KiB

Open AccessArticle

Impacts of Nanobubbles in Pore Water on Heavy Metal Pollutant Release from Contaminated Soil Columns

by Yihan Zhang, Zimu Song, Kosuke Sugita, Shan Xue and Wen Zhang

Nanomaterials 2023, 13(10), 1671; https://doi.org/10.3390/nano13101671 - 18 May 2023

Viewed by 1455

Abstract

This study investigated the release of heavy metals from polluted soil under the pore water flow containing nanobubbles (NBs) to simulate natural ebullition. Three types of NBs (CH₄, H₂, and CO₂) were generated in water and characterized, including bubble size, zeta potential, liquid density, and tension. The flow rate used in column tests was optimized to achieve proper soil fluidization and metal desorption or release. The leachate chemistries were monitored to assess the effect of NBs on conductivity, pH, oxidation–reduction potential (ORP), and dissolved oxygen (DO). The results showed that NBs in the pore water flow were significantly more effective in releasing Pb compared to DI water, with CO₂ NB water being the most effective and H₂ NB water being the least effective. CO₂ NB water was also used to rinse column soil contaminated with four different metals (Pb, Cu, Zn, and Cr), which exhibited different leaching kinetics. Moreover, a convective–dispersion–deposition equation (CDDE) model accurately simulated the leaching kinetics and explained the effects of NBs on the key parameters, such as the deposition rate coefficient (K_d), that affect the released metal transport. The findings could provide new insights into soil pollutant release under ebullition and soil remediation using water wash containing NBs. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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17 pages, 11589 KiB

Open AccessArticle

Effects of Gas Type, Oil, Salts and Detergent on Formation and Stability of Air and Carbon Dioxide Bubbles Produced by Using a Nanobubble Generator

by Kaiyu Zhou, Vincent Maugard, Wenming Zhang, Joe Zhou and Xuehua Zhang

Nanomaterials 2023, 13(9), 1496; https://doi.org/10.3390/nano13091496 - 27 Apr 2023

Cited by 1 | Viewed by 1993

Abstract

Recent developments in ultrafine bubble generation have opened up new possibilities for applications in various fields. Herein, we investigated how substances in water affect the size distribution and stability of microbubbles generated by a common nanobubble generator. By combining light scattering techniques with optical microscopy and high-speed imaging, we were able to track the evolution of microbubbles over time during and after bubble generation. Our results showed that air injection generated a higher number of microbubbles (<10

μ

m) than CO₂ injection. Increasing detergent concentration led to a rapid increase in the number of microbubbles generated by both air and CO₂ injection and the intensity signal detected by dynamic light scattering (DLS) slightly increased. This suggested that surface-active molecules may inhibit the growth and coalescence of bubbles. In contrast, we found that salts (NaCl and Na₂CO₃) in water did not significantly affect the number or size distribution of bubbles. Interestingly, the presence of oil in water increased the intensity signal and we observed that the bubbles were coated with an oil layer. This may contribute to the stability of bubbles. Overall, our study sheds light on the effects of common impurities on bubble generation and provides insights for analyzing dispersed bubbles in bulk. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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18 pages, 3896 KiB

Open AccessArticle

Efficient mRNA Delivery with Lyophilized Human Serum Albumin-Based Nanobubbles

by Hiroshi Kida, Yutaro Yamasaki, Loreto B. Feril Jr., Hitomi Endo, Keiji Itaka and Katsuro Tachibana

Nanomaterials 2023, 13(7), 1283; https://doi.org/10.3390/nano13071283 - 05 Apr 2023

Cited by 2 | Viewed by 1989

Abstract

In this study, we developed an efficient mRNA delivery vehicle by optimizing a lyophilization method for preserving human serum albumin-based nanobubbles (HSA-NBs), bypassing the need for artificial stabilizers. The morphology of the lyophilized material was verified using scanning electron microscopy, and the concentration, size, and mass of regenerated HSA-NBs were verified using flow cytometry, nanoparticle tracking analysis, and resonance mass measurements, and compared to those before lyophilization. The study also evaluated the response of HSA-NBs to 1 MHz ultrasound irradiation and their ultrasound (US) contrast effect. The functionality of the regenerated HSA-NBs was confirmed by an increased expression of intracellularly transferred Gluc mRNA, with increasing intensity of US irradiation. The results indicated that HSA-NBs retained their structural and functional integrity markedly, post-lyophilization. These findings support the potential of lyophilized HSA-NBs, as efficient imaging, and drug delivery systems for various medical applications. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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17 pages, 7415 KiB

Open AccessArticle

Influence of Bulk Nanobubbles Generated by Acoustic Cavitation on Powder Microstructure and Rehydration Characteristics of Spray-Dried Milk Protein Concentrate Powders

by Karthik Sajith Babu and Jayendra K. Amamcharla

Nanomaterials 2023, 13(6), 1093; https://doi.org/10.3390/nano13061093 - 17 Mar 2023

Cited by 2 | Viewed by 1506

Abstract

Bulk nanobubbles (BNBs) have widespread applications in various fields of science due to numerous peculiar characteristics. Despite significant applications, only limited investigations are available on the application of BNBs in food processing. In the present study, a continuous acoustic cavitation technique was used to generate bulk nanobubbles (BNBs). The aim of this study was to evaluate the influence of BNB incorporation on the processability and spray drying of milk protein concentrate (MPC) dispersions. MPC powders were reconstituted to the desired total solids and incorporated with BNBs using acoustic cavitation as per the experimental design. The control MPC (C-MPC) and BNB-incorporated MPC (BNB-MPC) dispersions were analyzed for rheological, functional, and microstructural properties. The viscosity significantly decreased (p < 0.05) at all the amplitudes studied. The microscopic observations of BNB-MPC dispersions showed less aggregated microstructures and greater structural differences compared with C-MPC dispersions, therefore lowering the viscosity. The viscosity of BNB incorporated (90% amplitude) MPC dispersions at 19% total solids at a shear rate of 100 s⁻¹ significantly decreased to 15.43 mPa·s (C-MPC: 201 mPa·s), a net decrease in viscosity by ~90% with the BNB treatment. The control and BNB incorporated MPC dispersions were spray-dried, and the resultant powders were characterized in terms of powder microstructure and rehydration characteristics. Focused beam reflectance measurement of the BNB-MPC powders indicated higher counts of fine particles (<10 μm) during dissolution, signifying that BNB-MPC powders exhibited better rehydration properties than the C-MPC powders. The enhanced powder rehydration with the BNB incorporation was attributed to the powder microstructure. Overall, reducing the viscosity of feed by BNB incorporation can enhance the performance of the evaporator. This study, therefore, recommends the possibility of using BNB treatment for more efficient drying while improving the functional properties of the resultant MPC powders. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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14 pages, 6255 KiB

Open AccessEditor’s ChoiceArticle

Effect of Polyphenols on the Ice-Nucleation Activity of Ultrafine Bubbles

by Tsutomu Uchida and Yukiharu Fukushi

Nanomaterials 2023, 13(1), 205; https://doi.org/10.3390/nano13010205 - 02 Jan 2023

Cited by 2 | Viewed by 2101

Abstract

Ultrafine bubbles (UFBs) in water provide a large amount of gas and a large gas–liquid interfacial area, and can release energy through their collapse. Such features may promote ice nucleation. Here, we examined the nucleation of ice in solutions containing polyphenols and UFBs. To reduce the likelihood of nucleation occurring on the container walls over that in previous studies, we used a much larger sample volume of 1 mL. In our experiments, UFBs (when present) had a number concentration of 10⁸ mL⁻¹. We quantified changes to the nucleation activity by examining the shift in the cumulative freezing (nucleation) probability distribution. Compared to pure water, this freezing curve shifts approximately 0.6 °C higher with the UFBs. Then, to the water, we added three polyphenols (tannic acid TA, tea catechin TC, and oligonol OLG), chosen because they had been reported to reduce the ice-nucleation activity of heterogeneous ice nuclei (e.g., AgI). We found experimentally that, without UFBs, all polyphenols instead shift the pure-water freezing curve to a higher temperature. Then, when UFBs are added, the additional temperature shift in the freezing curve is slightly higher for OLG, essentially unchanged for TA, and slightly lower for TC. To help to explain these differences, we examined the UFB size distributions using dynamic light scattering and freeze-fractured replicas with transmission electron microscopy, finding that OLG and TC alter the UFBs, but that TA does not. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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17 pages, 7667 KiB

Open AccessArticle

Coupling Effects of Ionic Surfactants and Electrolytes on the Stability of Bulk Nanobubbles

by Xiaotong Ma, Mingbo Li, Xuefei Xu and Chao Sun

Nanomaterials 2022, 12(19), 3450; https://doi.org/10.3390/nano12193450 - 02 Oct 2022

Cited by 8 | Viewed by 1910

Abstract

As interest in the extensive application of bulk nanobubbles increases, it is becoming progressively important to understand the key factors affecting their anomalous stability. The scientific intrigue over nanobubbles originates from the discrepancy between the Epstein–Plesset prediction and experimental observations. Herein, the coupling effects of ionic surfactants and electrolytes on the stability of bulk nanobubbles is studied. Experimental results show that ionic surfactants not only reduce the surface tension but also promote the accumulation of net charges, which facilitate the nucleation and stabilization of bulk nanobubbles. The addition of an electrolyte in a surfactant solution further results in a decrease in the zeta potential and the number concentration of nanobubbles due to the ion shielding effect, essentially colloidal stability. An adsorption model for the coexistence of ionic surfactants and electrolytes in solution, that specifically considers the effect of the adsorption layer thickness within the framework of the modified Poisson–Boltzmann equation, is developed. A quantitative agreement between the predicted and experimental surface tension is found in a wide range of bulk concentrations. The spatial distribution of the surface potential, surfactant ions and counterions in the vicinity of the interface of bulk nanobubbles are described. Our study intrinsically paves a route to investigate the stability of bulk nanobubbles. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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11 pages, 5544 KiB

Open AccessArticle

Degradation Mechanism of Micro-Nanobubble Technology for Organic Pollutants in Aqueous Solutions

by Youbin Zhou, Dapeng Cao and Xianren Zhang

Nanomaterials 2022, 12(15), 2654; https://doi.org/10.3390/nano12152654 - 02 Aug 2022

Cited by 5 | Viewed by 2554

Abstract

Micro-nanobubbles (MNBs) technology has emerged as an effective means of sewage treatment, while the molecular mechanism for its pollutant degradation is still unknown. In this paper, the reactive molecular dynamics simulation technique is used to study the degradation mechanism of pollutants caused by shock-induced nanobubble collapse. We first demonstrate that the propagating shock wave can induce nanobubble collapse, and the collapsing nanobubble has the ability to focus mechanical energy via the converging motion of liquid in the interior of the bubble, leading to the formation of a high-speed jet with a much higher energy density. We also unveil the mechanical nature of long-chain pollutant degradation and the mechanism of free radical generation. Due to the impacting jet, the high-gradient flow has the ability to stretch the long-chain molecule and cause mechanical scission of the molecule in a homolytic manner. Finally, our simulation results reveal that adding ozone molecules to the collapsing bubble would introduce an additional dehydrogenation mechanism. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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Review

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13 pages, 2164 KiB

Open AccessReview

Lipid-Coated Nanobubbles in Plants

by Stephen Ingram, Steven Jansen and H. Jochen Schenk

Nanomaterials 2023, 13(11), 1776; https://doi.org/10.3390/nano13111776 - 31 May 2023

Cited by 1 | Viewed by 1474

Abstract

One of the more surprising occurrences of bulk nanobubbles is in the sap inside the vascular transport system of flowering plants, the xylem. In plants, nanobubbles are subjected to negative pressure in the water and to large pressure fluctuations, sometimes encompassing pressure changes of several MPa over the course of a single day, as well as wide temperature fluctuations. Here, we review the evidence for nanobubbles in plants and for polar lipids that coat them, allowing nanobubbles to persist in this dynamic environment. The review addresses how the dynamic surface tension of polar lipid monolayers allows nanobubbles to avoid dissolution or unstable expansion under negative liquid pressure. In addition, we discuss theoretical considerations about the formation of lipid-coated nanobubbles in plants from gas-filled spaces in the xylem and the role of mesoporous fibrous pit membranes between xylem conduits in creating the bubbles, driven by the pressure gradient between the gas and liquid phase. We discuss the role of surface charges in preventing nanobubble coalescence, and conclude by addressing a number of open questions about nanobubbles in plants. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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21 pages, 3740 KiB

Open AccessReview

On Some Aspects of Nanobubble-Containing Systems

by Kyuichi Yasui

Nanomaterials 2022, 12(13), 2175; https://doi.org/10.3390/nano12132175 - 24 Jun 2022

Cited by 11 | Viewed by 2607

Abstract

Theoretical studies are reviewed for bulk nanobubbles (ultrafine bubbles (UFBs)), which are gas bubbles smaller than 1 μm in diameter. The dynamic equilibrium model is discussed as a promising model for the stability of a UFB against dissolution; more than half of the surface of a UFB should be covered with hydrophobic material (impurity). OH radicals are produced during hydrodynamic or acoustic cavitation to produce UFBs. After stopping cavitation, OH radicals are generated through chemical reactions of H₂O₂ and O₃ in the liquid water. The possibility of radical generation during the bubble dissolution is also discussed based on numerical simulations. UFBs are concentrated on the liquid surface according to the dynamic equilibrium model. As a result, rupture of liquid film is accelerated by the presence of UFBs, which results in a reduction in “surface tension”, measured by the du Noüy ring method. Finally, the interaction of UFBs with a solid surface is discussed. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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18 pages, 2818 KiB

Open AccessReview

Interaction Mechanisms and Application of Ozone Micro/Nanobubbles and Nanoparticles: A Review and Perspective

by Wei Xiao, He Zhang, Xiaohuan Wang, Biao Wang, Tao Long, Sha Deng and Wei Yang

Nanomaterials 2022, 12(12), 1958; https://doi.org/10.3390/nano12121958 - 07 Jun 2022

Cited by 6 | Viewed by 3052

Abstract

Ozone micro/nanobubbles with catalytic processes are widely used in the treatment of refractory organic wastewater. Micro/nanobubble technology overcomes the limitations of ozone mass transfer and ozone utilization in the application of ozone oxidation, and effectively improves the oxidation efficiency of ozone. The presence of micro/nanobubbles keeps the catalyst particles in a dynamic discrete state, which effectively increases the contact frequency between the catalyst and refractory organic matter and greatly improves the mineralization efficiency of refractory organic matter. This paper expounds on the characteristics and advantages of micro/nanobubble technology and summarizes the synergistic mechanism of microbubble nanoparticles and the mechanism of catalyst ozone micro/nanobubble systems in the treatment of refractory organics. An interaction mechanism of nanoparticles and ozone microbubbles is suggested, and the proposed theories on ozone microbubble systems are discussed with suggestions for future studies on systems of nanoparticles and ozone microbubbles. Full article

(This article belongs to the Special Issue Nanobubbles and Their Applications)

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