Multimodal Optical Nanoscopy for In-Liquid Bioimaging with Few Nanometer Spatial Resolution

Authors:

Brian T. O’Callahan* ([email protected]), Chih-Feng Wang, Patrick Z. El-Khoury, Scott Lea (PI)

Institutions:

Pacific Northwest National Laboratory

Abstract

The ability to perform chemical nanoimaging of biosystems in liquid remains challenging despite recent experimental advances. Fluorescence-based super-resolution techniques such as stimulated emission depletion microscopy and stochastic optical reconstruction microscopy allow tracking of tagged analytes with nanoscale spatial resolution. However, the development of generic chemical nanoimaging techniques is needed to study systems or analytes for which fluorescent tags are unavailable or infeasible.

Towards this goal, this team designed and built a multimodal hyperspectral micro/nanoscope (MHNano), which combines optical spectroscopy with scanning probe microscopy to enable (non)linear optical measurements with scales from hundreds of micrometers to a few nanometers in a single platform. Compatible with nonlinear imaging, perform micro- to nanoscale resolution the linear and nonlinear optics, [e.g., tip- enhanced (two-photon) photoluminescence (TEPL/ TE2PPL)]. In this work, researchers demonstrate the spatial resolution of TEPL and TE2PPL with sub 5 nm from cadmium selenide and zinc sulfide semiconductor quantum dots (QDs) using sputtered plasmonic gold probe under ambient conditions. A custom liquid cell allows high numerical aperture split excitation and collection for in situ Raman and nonlinear measurements. The capability of TEPL/TE2PPL paves the way for (non)linear photoluminescence-based or Raman spectral nanoimaging of biosystems in their native environment.