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It has been suggested that electrostatic stress arising from charges accumulated at the surface of nanobubbles might balance Laplace pressure leading to their stability. This mechanism has been widely discussed in the nanobubble field for the past decade. However, the stress in the diffusive double layer was overlooked when calculating the electrostatic effect in previous theories. In this communication, we recalculated this effect using the classical double layer theory. Combined with experimentally measured zeta potential, we find that the ratio of electrostatic pressure to Laplace pressure is much less than 10−2, which suggests that electrostatic interaction may not be the main factor for stabilizing bulk nanobubbles. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (2D-TMDs) and semiconductor metal oxides (MOs) have triggered enormous research attention in the fields of energy storage, catalysis, and gas sensing. However, the poor stability of TMDs in air and the high operating temperature of MOs remain critical bottlenecks for their application in practical gas sensing. In this work, a hydrothermal method was developed to convert rhombic p–p MoS2@ZIF-8 into rodlike p–n MoS2@ZnO heterostructure at 150 °C, which displays a large surface area, strong interaction between MoS2 and ZnO, and fast electron transportation. The as-synthesized p–n heterostructure was used to construct a gas sensor for the detection of NO2 at room temperature in air. The sensor showed an over 30-fold enhancement in the response compared to that of pristine MoS2 nanosheets and displayed short response/recovery time while lowering the detection limit of NO2 to 10 ppb. The sensor retained high stability upon sensing repetition for 10 consecutive weeks. This work demonstrated a facile strategy for the synthesis of p–n MoS2–ZnO heterostructures for reliable NO2 gas sensing at room temperature. [ABSTRACT FROM AUTHOR]

We report the synthesis of silver-based Janus micromotors that self-propel at 3.5 μm s−1 and speed up to 45 μm s−1 in 0.044 and 1.5 mM of H2O2, respectively, via ionic diffusiophoresis. Morphology optimization further accelerates the speed to 90 μm s−1, which leads to a force of 1 pN and a power of 0.1 fW, similar to biomolecular motors. Their efficiency reaches 10−5, at least two orders of magnitude higher than other chemically-driven micromotors. These micromotors hold great promises in various applications. [ABSTRACT FROM AUTHOR]

We investigated the effect of the adsorbed ions on the stability of nanobubbles suspended in the liquid in a recent article published in Physical Chemistry Chemical Physics. We calculated the electrostatic pressure using the classical electrical double layer (EDL) theory and pointed out that the electrostatic pressure is overestimated in previous theories due to the overlook of the stress in the diffusive double layer. Recently, S. I. Koshoridze and Yu. K. Levin questioned our calculations and results based on their intuition that diffusive ions in the EDL will drift and, therefore, not contribute to hydrostatic pressure. In this reply, we explain why mobile ions can also produce hydrostatic pressure from a hydrodynamic perspective.