Two-photon excited perovskite nanocrystals for bio-imaging

In single perovskite nanocrystals, two-photon excitation promises better optical properties than one-photon excitation and may improve efficiency in numerous applications such as bio-imaging, bio-labelling, and even quantum information processing.

“Single colloidal nanocrystals can be used to label various biological samples, and their laser-excited fluorescence is capable of imaging the underlying static structures and dynamic evolutions for the diagnostic purpose,” said Xiaoyong Wang, a co-author of the latest paper.

Cao et al. measured the single-particle optical properties of the perovskite nanocrystal CsPbI₃. They compared the differences in photoluminescence blinking and decay dynamics in the nanocrystals under one-photon and two-photon excitations and found two-photon excitation suppresses the background fluorescence usually found in one-photon excitation.

“Compared to the one-photon excitation with a UV or visible laser, the two-photon excitation with a near-infrared laser is featured with higher spatial resolution, deeper penetration depth, smaller sample damage and more reduced background fluorescence,” said Wang.

The team used a picosecond laser with a fixed wavelength to induce two-photon excitation. To find the optimal condition for two-photon excitation, Wang says the team hopes to try femtosecond laser excitation or other laser wavelengths.

“Now having realized efficient two-photon excitation of single perovskite nanocrystals, we are optimistic that they would serve as a potent competitor that can rival with or even surmount traditional dye molecules and colloidal nanocrystals in the bio-imaging and bio-labelling applications,” said Wang.

Source: “Two-photon excited photoluminescence of single perovskite nanocrystals,” by Zengle Cao, Bihu Lv, Huichao Zhang, Yan Lv, Chunfeng Zhang, Yong Zhou, Xiaoyong Wang, and Min Xiao, Journal of Chemical Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5124734 .