posted on 2023-05-22, 19:35authored byKai Zhou, Aosheng Chang, Xue Wang, Yingyan Jiang, Yongjie Wang, Xinchao Lu, Wei Wang
Here, we report a label-free optical
relative refractive index
(RI) sensing technique based on the image contrast of surface plasmon
resonance microscopy (SPRM). The positive or negative contrast of
a SPRM pattern reflects the relative RI of a nanosized object to the
medium. Through directly imaging the relative RI, we classified two
kinds of surface nanobubbles generated by varied pathways. The former
type
of nanobubbles nucleated from local oversaturation of gas molecules
had a RI lower than that of water and a transient lifetime. The second
type of nanobubbles formed by a methanol–water exchange process
had a RI higher than that of water and a long lifetime. The relative
RI of surface nanobubbles indicated that the gas state is sparse for
transient nanobubbles and compressed inside the stable nanobubbles.