Refractive Index of Single Surface Nanobubbles

Area of Science:

• Nanotechnology
• Optical Sensing
• Surface Science

Background:

• Surface plasmon resonance microscopy (SPRM) is a powerful tool for nanoscale imaging.
• Characterizing nanobubbles and their properties is crucial for understanding interfacial phenomena.

Purpose of the Study:

• To develop a label-free optical sensing technique for measuring the relative refractive index (RI) of nanosized objects.
• To classify different types of surface nanobubbles based on their RI and lifetime.

Main Methods:

• Utilized surface plasmon resonance microscopy (SPRM) for label-free imaging.
• Analyzed image contrast to determine the relative refractive index (RI) of nanobubbles.
• Investigated nanobubbles generated through different pathways (nucleation vs. exchange).

Main Results:

• Developed a technique where SPRM pattern contrast directly reflects the relative RI of nanobubbles.
• Classified two types of surface nanobubbles: transient nanobubbles with lower RI than water and stable nanobubbles with higher RI than water.
• Relative RI measurements indicated sparse gas in transient nanobubbles and compressed gas in stable nanobubbles.

Conclusions:

• Label-free SPRM imaging provides a direct method for assessing nanobubble RI and internal gas state.
• The RI of nanobubbles is a key indicator of their formation pathway and stability.
• This technique offers new insights into the physical state of gas within nanobubbles.