Quantum dots absorbing mid-infrared light have been synthesized and electron dynamics induced by infrared field is examined with IR pump-probe (IRPP) spectroscopy. We observed the ultrafast electron relaxation dynamics of dodecanethiol-doped HgS CQDs. IR pump-probe experiments reported pump power-independent ultrafast decaying dynamics (1.2 ± 0.1 ps) accelerated by Auger process in CQDs with biexciton generation and slow decay process (>300 ps) caused by Phonon bottleneck for CQDs with single photon absorption. However, the origin of the observed intermediate component (20~60 ps) remains unclear although the inter-sublevel transition between the split states due to spin-orbit coupling was suggested. To further study these intermediate dynamics and the size-dependence of intra-band Auger process, we prepared HgSe CQDs with three different size and investigated intraband exciton dynamics with IR pump-probe spectroscopy. Surprisingly, we found that the oscillation signal, appearing around 10 ps, becomes more pronounced with the increase in CQD size. Furthermore, the observed oscillation signal shows the contribution of photoinduced absorption and excludes the previous assignment of oscillation with the increased bleaching signal from the refilling electrons after Auger process. To reveal the origin of oscillation signal, we employed two-color IRPP (2CIRPP) to track the electron dynamics within the whole intraband.
Being a label-free technique, iSCAT has emerged as a powerful tool complementary to fluorescence microscopy because its superb spatio-temporal resolution holds great promise in biological investigations ranging from detection of nm-sized proteins to real-time dynamics of organelles in vivo. Here we present the polarization-selective iSCAT (psiSCAT) microscopy to detect the orientation and anisotropy of nano-objects. We also succeeded in developing the remote-focusing iSCAT (RF-iSCAT) to realize fast, vibration-free, 3D imaging over a long z-tracking range (< 5 μm). We envisage that our achievement would greatly advance the field of single-particle tracking into new dimensions with superb precision and sensitivity.
We introduce the cargo-localization iSCAT microscopy, label-free, live-cell imaging technique, that visualizes the traffic of cargos in a massively parallel fashion and hence uncovers the actively-used cytoskeletal network from cargos’ traces. By applying a particle localization algorithm to over a hundred cargos moving in a lamellipodium, the fine architecture of the cytoskeletal highway could be reconstructed. We also discuss a host of interesting kinetic events associated with cargo transport such as intermittent pausing, turnover, and frequent jamming of cargos due to physical collision with other obstacles or at the intersection of the highway.
As an alternative imaging technique to conventional IR microscopy, a mid-infrared photothermal microscopy has been suggested to achieve spatial resolution at the submicrometer level and the inherent chemical contrast upon vibrational excitation. It also has substantial potential for real-time imaging of live organisms to observe the cellular dynamics without photodamage or photobleaching of fluorescent labels. We performed real-time imaging of oligodendrocytes to investigate cellular dynamics and observed a photothermal contrast associated with traveling protein complexes on an axon of live neutrons. We anticipate that mid-infrared photothermal imaging will be of great use for gaining insights into the field of biophysical science, especially with regard to cellular dynamics and functions.
Conference Committee Involvement (6)
Advanced Chemical Microscopy for Life Science and Translational Medicine 2025
25 January 2025 | San Francisco, California, United States
Advanced Chemical Microscopy for Life Science and Translational Medicine 2024
27 January 2024 | San Francisco, California, United States
Advanced Chemical Microscopy for Life Science and Translational Medicine 2023
28 January 2023 | San Francisco, California, United States
Advanced Chemical Microscopy for Life Science and Translational Medicine 2022
23 January 2022 | San Francisco, California, United States
Advanced Chemical Microscopy for Life Science and Translational Medicine 2021
6 March 2021 | Online Only, California, United States
Advanced Chemical Microscopy for Life Science and Translational Medicine
1 February 2020 | San Francisco, California, United States
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