Generation and In Situ Electrochemical Detection of Transient Nanobubbles

Abstract

Nanobubbles are fascinating but controversial objects. Although there is strong evidence for the existence of surface bound nanobubbles, the possibility of stable nanobubbles in the bulk remains in question. In this work, we show how ultrasonication of electrolytes can create transient bulk nanobubbles. To do this, glass nanopores are used as Coulter counters in order to detect nanobubbles. During ultrasonication, these transient bulk nanobubbles are shown to exist in relatively high concentrations while bubble activity on the surface of a solid media close to the pore is driven by ultrasound. However, the transient nature of these bubbles is evident upon termination of the ultrasonic source. Highspeed imaging suggests that these transient nanobubbles originate from the fragmentation of larger bubbles, which skate over the surface of the structure in the acoustic field present. Transient nanobubbles as small as ~100 nm diameter are detected. In contrast to previous work with microbubbles, no evidence for the oscillation of these nanobubbles during translocation was found. The novel experimental approach presented here provides strong evidence for the existence of transient nanobubbles in bulk solution.

Stimuli-responsive nanobubbles for biomedical applications

“…50,51 Recently, it has been reported that ultrasonication of electrolytes can also create transient NBs, which are generated from the fragmentation of larger bubbles near a glass surface by an acoustic field. 52 The generation of transient bubbles can also occur as a result of a decrease and subsequent increase in the hydrostatic pressure that can be achieved by passing This journal is © The Royal Society of Chemistry 20xx…”

“…They found that the amplitude of the detected ultrasound backscatter signal is dependent on the NBs size, indicating that the acoustic flow cytometer has the potential to determine the size of individual NBs. In addition, this technique can also be applied to detect the formation of indirect NBs based on the acoustical timeresponse obtained with an ultrasound detector.Coulter counting, an analytical electrochemical technique, is also suitable for the detection of both direct and indirect NBs 52,219. This technique works by applying a voltage between two electrodes on either side of a cylindrical pore through which the NBs can flow.…”

The effect of preparation time and aeration rate on the properties of bulk micro-nanobubble water using hydrodynamic cavitation

“…Also, Sjogreen et al [11] reported that NaCl concentration, temperature, and pH had an critical impact on the nano-bubble diameter. Birkin et al [45] produced NBs by ultrasonic cavitation and measured their electrochemical properties in situ to confirm their existence. Ferraro et al [34] used a syringe to perform successive expansion-compression cycles to generate NBs.…”

Single-Entity Electrochemistry of Nano- and Microbubbles in Electrolytic Gas Evolution

“…When an analyte such as a single particle or molecule passes through the narrow pore, the electrolyte is volume excluded, causing an increase of resistance and decrease of ionic current . Similarly, individual nanobubbles passing through a pore can be detected and further characterized from the current–time traces. , For example, Dekker and co-workers reported the conductance and low-frequency current noise of a nanopore can be significantly increased when a gas nanobubble is present . Long and co-workers reported a first increase and then decrease biphase current pulse, which is a consequence of competition between nanobubble surface charge-induced ion accumulation and volume exclusion within the nanoconfinement region (Figure a) .…”