Announcements

PHYSICS SEMINAR by Yazgan Tuna

Author: COLLEGE OF SCIENCES
Time: 10:00
Location: SCI 103

KOÇ UNIVERSITY PHYSICS SEMINAR
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Speaker          :
Yazgan Tuna, Max-Planck-Institute for the Science of Light, Erlangen, Germany

Title                : Trapping of Nanoparticles with and without External Fields

Date                : June 18, 2019, Tuesday
Time               : 10:00   
Cookie & Tea: 09:45 SCI 103 
Place               : SCI 103  


Abstract         :

Trapping and manipulation of small objects have always been of great interest for

a range of applications. Here, I will report on electrostatic trapping of charged nanoparticles

between the aperture of a nanopipette and a glass substrate without the need for external

potentials [1]. We employ our technique to the manipulation of a plasmonic nanoantenna in

an aqueous solution in order to scan a trapped gold nanosphere in the near field of a single

colloidal quantum dot embedded under the substrate surface. We demonstrate about 10-fold

fluorescence enhancement over a lateral full width at half-maximum of about 45 nm [2]. We

analyse our results with the outcome of numerical electromagnetic simulations under

consideration of the electrostatic free energy in the trap.

In the second part of the talk, I will present our recent work that we trap gold nanoparticles

with asymptotically logarithmic electrostatic fields which play a major role in a variety of

cases including microtubules, DNA bubbles as well as optical lattices. Statistical properties

of the diffusion under such potential shapes cannot be represented by Boltzmann-Gibbs

distribution. We investigate these unique properties in the context of ergodicity, a central

concept in the theory of stochastic process. We observed the diffusion of a nano particle at its

intermediate transition steps from non-ergodic free diffusion to ergodic sub-diffusion by

simply tuning the potential depth. We also confirm our findings with extensive Langevin

simulations.

[1] J-T. Kim et al. Nat. Commun. 5, 3380 (2014).

[2] Y. Tuna et al. ACS Nano. 11, 7674 (2017).

 

Biography: Dr. Yazgan Tuna has expertise in label-free imaging, single molecule

fluorescence microscopy, optical tweezers, nano-electrostatics, and micro/nano fabrication.

He is currently with the Nano-optics Division of Prof. Vahid Sandoghdar at Max-Planck-

Institute for the Science of Light (MPI), Erlangen working on levitating nano-antennas in

liquid, and ergodic transitions under logarithmic electrostatic potentials. Previously, he was

at Bilkent University, Ankara working in the Soft-Matter Laboratory with Dr. Giovanni

Volpe, on the measurement of the critical Casimir forces via holographic optical tweezers

(HOTs), an on theory and simulation of intra-cavity optical trapping with feedback-lock

diode lasers. Previously, he worked at the Ultrafast Optics Lab with Dr. F. Ömer Ilday at

Bilkent University on modeling the interaction of ultrafast laser pulses with metals.