The passage you’ve provided discusses the behavior of hydroxide ions (OH⁻) and hydronium ions (H₃O⁺) at the nitrogen-water interface in a nanobubble system over a duration of 20 nanoseconds. Here are some key points highlighted in your text:
Stability of OH⁻ Distribution: The concentration distribution of OH⁻ ions at the interface is noted to be stable over 20 ns, suggesting that these ions maintain a consistent presence despite changes occurring in their environment.
H₃O⁺ Concentration Decline: Although H₃O⁺ ions have a higher peak concentration than OH⁻ ions, their concentration diminishes after approximately 10 ns due to the shrinking of the nanobubble. This indicates dynamic changes in ion concentrations as the nanobubble evolves.
Distribution Characteristics: The distribution of OH⁻ ions is described as more delocalized across a range from -15 to -4 Å, while H₃O⁺ ions are confined to a narrower distribution. This suggests differences in how these ions interact with their surrounding environment.
Charge Interactions: The positive charge from H₃O⁺ ions appears to be partially offset or screened by the neighboring layer of OH⁻ ions, which possess a more significant negative charge. This implies an electrostatic balance at play within the interface region.
Relation to Experimental Observations: The outer layer of OH⁻ surrounding the nanobubble may correspond to areas detected experimentally, supporting macroscopic measurements that indicate bulk nanobubbles typically exhibit negative zeta potential values ranging from -50 mV to -20 mV.
This analysis provides insights into the ionic dynamics at play within nanoscale systems and could have implications for understanding surface interactions and properties related to nanobubbles in various contexts such as materials science or biophysics. If you have any specific questions about this content or need further explanation on certain aspects, feel free to ask!
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