Zhiwei Li

FFT-weighted background-free bioimaging by in vivo tuning plasmonic excitation of Fe3O4@Au hybrid nanorods

Abstract:

Optical imaging uses photonic singles of molecules or nanoparticles for high-resolution imaging of biological tissues and functions. During imaging, however, signals from endogenous biological molecules may appear as background noises, which blur the images and decrease imaging sensitivity. In this seminar, I will introduce fast Fourier transform (FFT)-weighted photoacoustic imaging and optical coherence tomography by actively modulating the plasmonic excitation of Fe3O4@Au hybrid nanorods using magnetic fields. The nanorods are prepared using a chemical confined growth method and contain magnetic Fe3O4 nanorod cores and plasmonic Au nanoshells. Driven by Zeeman coupling, the nanorods prefer to align their long axes to an external magnetic field. Their coupled magnetic and plasmonic anisotropy further allows active and reversible tuning of the plasmonic excitation of the Au shells by magnetically aligning the nanorods. Using the hybrid nanorods as responsive imaging contrast agents, we monitor the nanorod rotation and in vivo optical signal changes under an alternating magnetic field in real time. The coherent rotation of the nanorods with the field produces periodic optical signals (such as photoacoustic signals and plasmonic scattering), and FFT is then applied to convert the periodic optical signals in the time domain to a single peak in the frequency domain. This technique allows automatic screening of nanorod signals from the random biological noises and reconstruction of FFT-weighted images using a computer program based on a time-sequence image set. Compared with conventional optical bioimaging, the FFT-weighted imaging technique creates enhanced images of biological tissues and organs with dB-scale contrast over an order of magnitude higher than the original images.

Speaker: Zhiwei Li, University of Maryland College Park

Dr. Zhiwei Li is an assistant professor in the Department of Chemistry and Biochemistry at the University of Maryland, College Park. He received his PhD in chemistry from the University of California, Riverside in 2019. He was a Richard P. Van Duyne postdoctoral fellow in the Department of Chemistry and the International Institute for Nanotechnology (IIN) at Northwestern University. He joined the Department of Chemistry and Biochemistry at the University of Maryland College Park in 2024. His research is focused on harnessing structural chemistry for nanophotonics and quantum physics.

Host: Jeffery Klauda

Seminars start at 4:00 pm, and refreshments will be served at 3:45 pm. All seminars are held in the 2136 Physical Sciences Complex (#415) unless otherwise noted.