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Imaging Membrane Potential with Semiconductor Nanoparticle

— filed under:

  • PhD Defenses
When Apr 23, 2014
from 11:00 AM to 01:00 PM
Where Engr. IV Bldg., Maxwell Room 57-124
Contact Name
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Kyoungwon Park

Advisor: Bahram Jalali


Understanding electrical activity of neural network is of great interest. Although electrodes and optical voltage sensors have been evolved over the past few decades, there is no such probe satisfying not only large enough sensitivity but also fast enough time response in large scale yet. Therefore, the reverse engineering on brain circuitry such that ‘every action potential in every neuron in large field of view’ is still far-off.                                                 

In this study, I introduce the inorganic voltage sensor for neural electricity imaging, based on semiconductor nanoparticles (NPs) via quantum-confined Stark effect (QCSE). Firstly, I validate NPs’ QCSE at room temperature at single molecule level. Based on the experimental results and theoretical investigation, I optimize the NP structure displaying the largest QCSE. Besides, undiscovered physical phenomena including wavelength blue-shift, linear energy-field relation, and field dependent Auger recombination rate are revealed from the QCSE experiment for the first time. Secondly, I predict the performance of membrane inserted NPs by self-consistent Schrödinger-Poisson calculation, and propose voltage imaging strategies.

Thirdly, novel surface modification technique is developed which successfully delivers NPs to the cell membrane. Lastly, delivered NPs are tested under voltage oscillating HEK293 cells and they generate voltage dependent emission fluorescence. This voltage information is finally captured and imaged by the charge coupled device and analyzed. This result first demonstrates the inorganic voltage sensor’s high throughput simultaneous multisite voltage imaging.


Kyoungwon Park is a Ph.D. candidate in Electrical Engineering Department at UCLA under the supervision of Prof. Bahram Jalali and Prof. Shimon Weiss in Dept. of Chemistry and Biochemistry. He obtained his B.S. degree in Electronic Engineering, Korea University, Seoul, Korea in 2007 and M.S degree in Electrical Engineering from UCLA in 2009. Since 2010, he devoted to develop semiconductor voltage sensor for imaging neural electricity. His work was published in ACSnano in 2012. He held an internship at Samsung Advanced Institute of Technology in 2008 and 2009. His research interests are in developing voltage sensor and stimulator of neurons

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