On Nanobubble Dynamics under an Oscillating Pressure Field during Salting-out Effects and Its DLVO Potential

Removal of Nanoparticles by Surface Nanobubbles Generated via Solvent-Water Exchange: A Critical Perspective

The swift progression of technology in electronic fabrication is adhering to a trend of miniaturization, descending to the nanoscale. Surface contaminants, such as nanoparticles, can influence the performance of silicon wafers, thereby necessitating the evolution of novel cleaning methodologies. Surface nanobubbles (SNs) are phenomena that have attracted considerable attention over the past decade. A salient feature of SNs is their capacity to eliminate nanoparticles from silicon wafers. In this Perspective, our objective is to scrutinize whether this capability can be unequivocally ascribed to SNs. Initially, we offer a succinct elucidation of the nature of SNs; subsequently, we evaluate the claims regarding the cleaning efficacy of SNs; finally, we present our interpretation of the operative forces and propose potential scenarios of the interaction between SNs and nanoparticles. Consequently, the aim of this Perspective is to emphasize the significance of comprehending the interaction between SNs and nanoparticles with the intent to delineate new research trajectories bearing both fundamental and industrial ramifications.

Chitosan-functionalized nanobubbles for precision oncology: advances in targeted cancer therapeutics

The convergence of nanotechnology and cancer therapeutics has opened new frontiers in the development of advanced drug delivery systems. Among the various nanocarriers, nanobubbles offer significant potential due to their unique properties, such as high payload capacity, responsiveness to external stimuli like ultrasound, and enhanced permeability and retention (EPR) effects. Functionalizing these nanobubbles with chitosan, a naturally derived biopolymer known for its biocompatibility, biodegradability, and ability to enhance cellular uptake, further improves their therapeutic efficacy. This review provides a comprehensive analysis of the synthesis, functionalization, and application of chitosan-functionalized nanobubbles in cancer therapy. We discuss their mechanism of action, including targeted drug delivery, ultrasound-mediated release, and immune modulation, alongside recent advancements and challenges in their clinical translation. This review also explores future directions in this rapidly evolving field, aiming to offer insights into the development of next-generation cancer therapeutics.

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.

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.

Electrochemically reactive colloidal nanobubbles by water splitting

HYPOTHESIS

The existing literature reports have conflicting views on reactive oxygen species (ROS) generation by bulk nanobubbles. Consequently, we propose the hypothesis that (i) ROS may be generated during the process of nanobubble generation through water splitting, and (ii) bulk nanobubbles possess electrochemical reactivity, which could potentially lead to continuous ROS generation even after the cessation of nanobubble production.

EXPERIMENTS

A comprehensive set of experiments was conducted to generate nanobubbles in pure water using the water-splitting method. The primary aims of this study are as follows: (i) nanobubble generation by electrolysis and its characterization; (ii) to provide conclusive evidence that the nano-entities are indeed nanobubbles; (iii) to quantify the production of reactive oxygen species during the process of nanobubble generation and (iv) to establish evidence for the presence of electrochemically reactive nanobubbles. The findings of our experiment suggest that bulk nanobubbles possess the ability to generate reactive oxygen species (ROS) during the process of nanobubble nucleation. Additionally, our results indicate that bulk nanobubbles are electrochemically reactive after the cessation of nanobubble production. The electron spin spectroscopy (ESR) response and degradation of the dye compound over time confirm the electrochemical reactivity of bulk nanobubbles.

Colloidal Zeta Potential Modulation as a Handle to Control the Crystallization Kinetics of Tin Halide Perovskites for Photovoltaic Applications

Tin halide perovskites (THPs) have demonstrated exceptional potential for various applications owing to their low toxicity and excellent optoelectronic properties. However, the crystallization kinetics of THPs are less controllable than its lead counterpart because of the higher Lewis acidity of Sn2+, leading to THP films with poor morphology and rampant defects. Here, a colloidal zeta potential modulation approach is developed to improve the crystallization kinetics of THP films inspired by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. After adding 3-aminopyrrolidine dihydro iodate (APDI2) in the precursor solution to change the zeta potential of the pristine colloids, the total interaction potential energy between colloidal particles with APDI2 could be controllably reduced, resulting in a higher coagulation probability and a lower critical nuclei concentration. In situ laser light scattering measurements confirmed the increased nucleation rate of the THP colloids with APDI2. The resulting film with APDI2 shows a pinhole-free morphology with fewer defects, achieving an impressive efficiency of 15.13 %.

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.