محاضرة علمية مع د. بسّام القاضي (الفيزياء)

Physics Department

دعوة لحضور محاضرة عامة

تتشرّف دائرة ا
لفيزياء بدعوتكم لحضور محاضرة علمية مع د. بسّام القاضي

تحت عنوان:

Optical Characterization and Rotational Dynamics Observation of Colloidal G
old Nanoparticles via Polarized Light Scattering Microscopy.

Abstract: Gold nanoparticles exhibit unique optical properties compared to
the bulk form. These properties are size- and shape dependent, and origina
tes from the localized surface plasmon resonance LSPR. The enhanced absorpt
ion and scattering, photochemical stability, good biocompatibility and po
larization-sensitive optical response, make gold nanoparticles suitable pr
obes for bio-sensing and detection applications. In such applications, gol
d nanoparticles can be conjugated to a variety of bio-molecules in order tomonitor dynamics/conformations of bio-molecules during their functional ta
sk. To enhance the sensitivity in these applications, robust techniques fo
r optical characterization of nanoparticles as well as for monitoring theirdynamics are highly needed.
We propose the use of polarized light
scattering microscopy to characterize colloidal gold nanoparticles (nano-sp
heres and nanorods), as well as to observe their rotational dynamics basedon their polarization anisotropy. Optical characterization of colloidal na
noparticles was achieved by measuring the time-trace of the scattering pola
rization contrast from a nano-particle moving with Brownian motion in the f
ocal volume of the laser beam. On the other hand, rotational dynamics of c
olloidal nanoparticles were observed as fluctuations in the scattering pola
rization contrast, from which we were able to extract the rotational diffu
sion time on the microsecond time scale. The proposed method is simple and
easy to implement. Comparison of the experimental measurements with theoret
ical expectations was found in a good agreement confirming the validity of
our approach. We believe that optical characterization of colloidal gold na
noparticles using a far-field approach will open many perspectives for the
use of gold nanoparticles in ultra-sensitive bio-sensing applications.

Dr. Al-Qadi received his bachelor degree in electronics engineering from Al
-Quds University (Palestine) in 2003. He was awarded the Japanese governmen
t scholarship (Monbukagakusho) from 2005 – 2010 to Keio University (Japan).In 2007, he obtained his master degree in artificial intelligence and ima
ge processing from the center for computer science at Keio University. In 2
010, he obtained his PhD in Nano-Photonics from the center for smart devic
e and system engineering at Keio University. Then, he joined the group of
Prof. Hiro Munekata at Tokyo Institute of Technology as a postdoc researche
r, where he studied the physics and preparation of semiconductor-magnetic
hybrid structures, and its applications.

Research Interests:
[1] Nano
-Photonics: interested in Nano-materials structures with focus on Plasmonic
s metal nano-particles and their biomedical applications.
[2] Optics and O
ptical science / Microscopy / Light matter interaction.
[3] Magnetism: int
erested in the manipulation of magnetization in semiconductor-magnetic hybr
id structures (III-V semiconductors), and its applications.