Optical Imaging Of Nanoscale Chemical And Biological Processes

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Abstract:

The research in the Fang Laboratory aims to open new frontiers in chemical and biological discovery through the development and use of novel optical imaging platforms, which provide sub-diffraction-limited spatial resolution, high angular resolution (for anisotropic imaging probes), excellent detectability, and/or nanometer localization precision for single molecules and nanoparticles.

• Rotational Tracking: The knowledge of rotational dynamics in and on live cells remains highly limited due to technical limitations. The Single Particle Orientation and Rotational Tracking (SPORT) techniques have been developed in the Fang Laboratory to acquire accurate measurements of anisotropic plasmonic gold nanorods in complex cellular environments. Rich information in five dimensions, including the x, y, z coordinates and the two orientation angles (azimuthal angle j and polar angle q , as defined in the figure) of the probe’s transition dipole, can be obtained from SPORT experiments. The SPORT technique is capable of extracting important information (including rotational rates, modes, and directions) on the characteristic rotational dynamics involved in cellular processes, such as adhesion, endocytosis, and transport of functionalized nanoparticles, as may be relevant to drug delivery and viral entry.
• Single Molecule Imaging of Nanoconfinement: Nanoconfinement could dramatically change molecular transport and reaction kinetics in heterogeneous catalysis. A core-shell nanocatalyst with aligned linear nanopores has been specifically designed for single-molecule studies of the nanoconfinement effects. The quantitative single-molecule measurements revealed unusual lower adsorption strength and higher catalytic activity on the confined metal reaction centres within the nanoporous structure. More surprisingly, the nanoconfinement effects on enhanced catalytic activity are larger for catalysts with longer and narrower nanopores. Experimental evidence, including molecular orientation, activation energy, and intermediate reactive species, has been gathered to provide a molecular level explanation on how the nanoconfinement effects enhance the catalyst activity, which is essential for the rational design of highly-efficient catalysts.