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SUMMARY:Dr. Barış Demirbay
DTSTART:20261028T100000Z
DTEND:20261028T120000Z
DTSTAMP:20261111T142600Z
UID:indico-event-21@indico.itu.edu.tr
DESCRIPTION:Probing molecular environments through fluorescence-based phot
 ophysics: transient-state dynamics\, spectroscopy and predictive modeling\
 n \nAbstract\nPhotoinduced transitions to long-lived\, non-emissive elect
 ronic states play a fundamental role in determining the photophysical beha
 vior of fluorescent molecules. Although these transient states often limit
  fluorescence brightness and photostability\, their population kinetics ar
 e highly sensitive to local physicochemical conditions\, offering addition
 al observables for molecular characterization and optical sensing. This se
 minar addresses how such dynamics can be quantitatively investigated and e
 xploited by combining experimental fluorescence spectroscopy\, analytical 
 theory and computational modeling methods.\nTime-resolved fluorescence cor
 relation spectroscopy (FCS) and transient state (TRAST) spectroscopy techn
 iques provide complementary approaches for resolving singlet-triplet trans
 itions\, photoinduced trans-cis isomerization and radical-state dynamics i
 n organic fluorophores. Applications to brominated-fluoresceins reveal the
  influence of internal and external heavy-atom effects on intersystem cros
 sing and triplet-state relaxation\, while the environmental sensitivity of
  fluorescence blinking enables characterization of membrane microenvironme
 nts\, RNA G-quadruplex folding and fluorescence-based chromophore multiple
 xing. Extending these principles from wide-field illumination scheme to mi
 crofluidic systems\, flow-controlled fluorescence microscopy provides a us
 eful framework for investigating the interplay between molecular transport
 \, optical excitation and transient-state populations of fluorophores. Exp
 erimentally informed numerical simulations further predict distinct photoi
 somerization responses of free and vesicle-bound cyanine dyes under varyin
 g flow and excitation conditions. Complementary analytical solutions based
  on eigenmode decomposition establish explicit relationships between photo
 physical transition rates\, excitation parameters and time-dependent fluor
 escence responses.\nBeyond synthetic fluorophores\, conventional UV-visibl
 e absorption and steady-state fluorescence spectroscopy measurements are e
 mployed to investigate the molecular interactions and quenching behavior o
 f intrinsically fluorescent tyrosine amino acid in the presence of ionic q
 uenchers and sodium ascorbate. Molecular dynamics simulations provide comp
 lementary insight into the intermolecular interactions and solvation struc
 tures underlying these spectroscopic responses. In parallel\, machine lear
 ning approaches applied to carbon nanotube-based polymer nanocomposites de
 monstrate the importance of physically interpretable and rigorously valida
 ted predictive models for identifying electrical conductivity regimes. Alt
 ogether\, the investigations that will be presented in this seminar highli
 ght the integration of optical spectroscopy\, kinetic theory and computati
 onal methods as a versatile strategy for understanding molecular dynamics 
 and developing quantitative approaches to molecular sensing in life-scienc
 es and materials characterization.\n \nShort Bio: Dr. Barış Demirbay re
 ceived his B.Sc. degree in Physics Engineering from Istanbul Technical Uni
 versity in 2015\, ranking third among the graduates of his department. He 
 earned his M.Sc. degree from the same department in 2017. He subsequently 
 joined the Department of Materials Science and Nanoengineering at Sabancı
  University as a research assistant and doctoral student. In early 2018\, 
 he moved to KTH Royal Institute of Technology in Stockholm\, Sweden\, wher
 e he pursued his doctoral research in the Department of Applied Physics an
 d received his Ph.D. in Experimental Biomolecular Physics in June 2023.\nF
 ollowing his doctoral studies\, he served as a research engineer in the De
 partment of Applied Physics at KTH\, where he also provided training in fl
 uorescence-based spectroscopic techniques employed during his doctoral res
 earch. In October 2023\, he joined the Department of Natural and Mathemati
 cal Sciences at Özyeğin University as a part-time lecturer\, teaching un
 dergraduate physics courses in the Faculty of Engineering. Since September
  2024\, he has been serving as a full-time lecturer and academic researche
 r at Özyeğin University\, where he teaches undergraduate physics courses
  and conducts independent scientific research projects. His research inter
 ests are mainly focused on experimental and theoretical biomolecular physi
 cs\, molecular photophysics\, the development of time-resolved fluorescenc
 e spectroscopy and imaging techniques\, microfluidic detection systems\, m
 athematical and computational modeling\, polymer physics and applications 
 of machine learning methods in materials science.\n\nhttps://indico.itu.ed
 u.tr/event/21/
LOCATION:Fizik Mühendisliği Bölümü Seminer Salonu
URL:https://indico.itu.edu.tr/event/21/
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