Freddy T. Nguyen, MD, PhD

Research Fellow @ Massachusetts Institute of Technology

Physician-scientist developing biophotonics and nano technologies for functional precision medicine to provide the right treatment to the right patient at the right time.

Laser Fluence Dependent Modulation of Single Walled Carbon Nanotube Photoluminescence

Naveed Ali Bakh, Xun Gong, Kevin S. Silmore, Michael A. Lee, Daniel Salem, Volodymyr B. Koman, Freddy T. Nguyen, Michael S. Strano. ECS Meeting Abstracts 2023-08-28. Full Text
Single-walled carbon nanotubes (SWCNT) have a unique, non-photobleaching, bandgap photoluminescence (PL) that has been of interest for sensor development. Take advantage of these properties, colloidal dispersions of single SWCNTs in aqueous solvents are often formed by creating a surface corona phase (CP) using amphiphilic materials. As SWCNT PL emission following photoexcitation can be significantly dependent on its local environment, the CP can be used to tune its photophysical properties, often as a design parameter for sensor development. Recent sensor experiments have shown that reporting and controlling laser excitation can be a method to significantly reduce measurement variability. In this work, we study this phenomenon of excitation fluence (EF) (mW/area) dependent PL modulation for aqueous dispersed SWCNTs. By using a continuously stirred chamber excited at a single location, the stirring rate can be a means of controlling SWCNT excitation exposure. SWCNT wrapped in both DNA and SDS SWCNT CPs showed a decreased quantum yield of nearly 40% with increasing EF while those with sodium cholate and phospholipid-PEG CPs remain invariant. Through spectroscopy and heat transfer modeling, we determined that the observed effect is unlikely to have a significant direct local solution heating contribution from SWNCT photoabsorption. Finally, we used previously studied SWCNT sensor constructs, for ascorbic acid and dopamine, to show how EF can affect calibration and eventual sensor applications. This work highlights the importance of measuring, testing, reporting and controlling for EF while developing SWCNT based photophysical sensors. This newly characterized property can also serve as a unique parameter to tune optical responsivity.
Laser Fluence Dependent Modulation of Single Walled Carbon Nanotube Photoluminescence

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