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Modulated fluorescence of colloidal quantum dots embedded in a porous alumina membrane
KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.ORCID iD: 0000-0002-4720-2756
KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
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2013 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 177, no 45, 14151-14156 p.Article in journal (Refereed) Published
Abstract [en]

The fluorescence spectrum of CdSe core-CdS/ZnS shell colloidal quantum dots (QDs) embedded in porous alumina membrane was studied. Small peaks, superimposed on the principal QD fluorescence spectrum, were observed. Finite-difference time-domain simulation indicates that the QD point radiation emitting from within the membrane is strongly modulated by the photonic band structure introduced by the membrane pores, leading to the observed fine spectral features. Moreover, the principal QD fluorescence peak red-shifted when the optical excitation power was increased, which is attributed to QD material heating due to emitted phonons when the photoexcited electron and hole relax nonradiatively from high-energy states to the ground exciton state before fluorescence.

Place, publisher, year, edition, pages
2013. Vol. 177, no 45, 14151-14156 p.
Keyword [en]
Colloidal quantum dots, Finite difference time domain simulations, Fluorescence peak, Fluorescence spectra, Photoexcited electrons, Photonic band structures, Porous alumina membranes, Spectral feature
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-136255DOI: 10.1021/jp409132eISI: 000327111200024Scopus ID: 2-s2.0-84887899102OAI: oai:DiVA.org:kth-136255DiVA: diva2:675658
Funder
Swedish Research Council, 621-2011-4381 B0460801Science for Life Laboratory - a national resource center for high-throughput molecular bioscience
Note

QC 20131217

Available from: 2013-12-04 Created: 2013-12-04 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Time-Resolved Optical Properties of Colloidal CdSe-CdS/ZnS Core-Multishell Quantum Dots in Bioimaging
Open this publication in new window or tab >>Time-Resolved Optical Properties of Colloidal CdSe-CdS/ZnS Core-Multishell Quantum Dots in Bioimaging
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Semiconductor quantum dots (QDs) have attracted great attention as a novel fluorescent material in the last twenty years. Their superior optical properties such as high brightness and photostability, broad absorption spectrum, narrow and size-tunable emission spectrum, enable them great application in bioimaging.

However, the fluorescence from single QDs shows irregular on (bright) and off (dark) switches under continuous irradiation which is known as blinking. QD blinking may lead to information loss in single particle tracking and lower brightness in other bioimaging applications. We studied the blinking behavior and its mechanism by using CdSe-core QDs with different shell thicknesses under different excitations. We observed two types of fluorescence behavior, blinking with apparent on and off states and flickering without distinguishable on and off states under low (1.8 and 3.9 W/cm2) and high (12.1 and 25 W/cm2) excitations, respectively. The transfer of photoexcited electron or hole from CdSe core to the QD surface is responsible for QD blinking under low excitations. And further intraband excitation of photoexcited electron and hole is responsible for QD flickering under high excitations.

Ca2+ serves as the second messenger in signal transduction. Monitoring Ca2+ concentration in live cell is a key technique in biological research especially in neuroscience. Most of the commercial Ca2+ indicators are organic dyes which are easy to be photobleached. In order to develop QD-based Ca2+ indicator, we investigated the effect of Ca2+ on the QD fluorescence. We found that the fluorescence intensity, lifetime, and on-state ratio in single QD fluorescence were all decreased by Ca2+ ion. Theoretical study shows that one free Ca2+ could attach stably to the surface of one QD, attracting the photogenerated electron and repel the photogenerated hole, suppressing the radiative recombination between them, and resulting in the reduction of fluorescence intensity, lifetime and on-state ratio.

Overexpression of vascular adhesion molecule-1 (VCAM-1) in endothelial cells is a hallmark of inflammation-induced activation of endothelium and may serve as a target for evaluation atherogenesis in early stages. We conjugated VCAM-1 binding peptide to amino-coated QDs and employed the functionalized QDs (VQDs) to specifically image activated endothelial cells. Upon the interaction between VQDs and endothelial cells, a blue-shift of about 30 nm in the QD fluorescence peak was observed. We anticipate that the VQDs and the blue-shift phenomenon could be very useful for VCAM-1 detection in vitro and in vivo.

Furthermore, we studied the fluorescence of QDs embedded in a porous alumina membrane which is widely used as biomolecule and cell filter for biological research. We found that the fluorescence spectrum has small peaks superimposed on the principle curve. Theoretical study identifies that this modulation is due to the photonic band structure introduced by the membrane pores. This work could supply information about the interaction between QD fluorescence and porous membrane structure which would be useful when applying QDs to image biomolecules or cells filtered by the porous alumina membrane.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xvi, 69 p.
Series
TRITA-FYS, ISSN 0280-316X ; 2015:11
National Category
Physical Sciences
Research subject
Biological Physics
Identifiers
urn:nbn:se:kth:diva-160939 (URN)978-91-7595-473-8 (ISBN)
Public defence
2015-03-27, Seminar room Air på SciLifeLab, Science for Life Laboratory, Tomtebodavägen 23A, Solna, 13:00 (English)
Opponent
Supervisors
Note

QC 20150306

Available from: 2015-03-06 Created: 2015-03-04 Last updated: 2015-03-06Bibliographically approved
2. Fluorescence Properties of Quantum Dots and Their Utilization in Bioimaging
Open this publication in new window or tab >>Fluorescence Properties of Quantum Dots and Their Utilization in Bioimaging
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Quantum dots (QDs), especially colloidal semiconductor QDs, possess properties including high quantum yields, narrow fluorescence spectra, broad absorption and excellent photostability, making them extremely powerful in bioimaging. In this thesis, we studied the fluorescence properties of QDs and attempted multiple ways to boost applications of QDs in bioimaging field.

By time-correlated single photon counting (TCSPC) measurement, we quantitatively interpreted the fluorescence mechanism of colloidal semiconductor QDs.

To enhance QD fluorescence, we used a porous alumina membrane as a photonic crystal structure to modulate QD fluorescence.

We studied the acid dissociation of 3-mercaptopropionic acid (MPA) coated QDs mainly through electrophoretic mobility of 3-MPA coated CdSe QDs and successfully demonstrated the impact of pH change and Ca2+ ions.

Blinking phenomena of both CdSe-CdS/ZnS core-shell QDs and 3C-SiC nanocrystals (NCs) were studied. A general model on blinking characteristics relates the on-state distribution to CdSe QD surface conditions. The energy relaxation pathway of fluorescence of 3C-SiC NCs was found independent of surface states.

To examine QD effect on ciliated cells, we conducted a 70-day long experiment on the bioelectric and morphological response of human airway epithelial Calu-3 cells with periodic deposition of 3-MPA coated QDs and found the cytotoxicity of QDs was found very low.

In a brief summary, our study of QD could benefit in bioimaging and biosensing. Especially, super-resolution fluorescent bioimaging, such as, stochastic optical reconstruction microscopy (STORM) and photo-activated localization microscopy (PALM), may benefit from the modulation of the QD blinking in this study. And fluorescence lifetime imaging (FLIM) microscopy could take advantage of lifetime modulation based on our QD lifetime study.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. 77 p.
Series
TRITA-FYS, ISSN 0280-316X ; 2016:54
Keyword
Fluorescence, Microscopy, Bioimaging, Nanomaterial, cytotoxicity, mechanism
National Category
Biophysics
Research subject
Biological Physics
Identifiers
urn:nbn:se:kth:diva-191985 (URN)978-91-7729-074-2 (ISBN)
Public defence
2016-09-29, Seminar room Earth, Science for life laboratory, Tomtebodavägen 23A, Solna, 13:00 (English)
Opponent
Supervisors
Note

QC 20160905

Available from: 2016-09-07 Created: 2016-09-02 Last updated: 2017-02-22Bibliographically approved

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Manneberg, OttoGylfason, Kristinn B.Brismar, HjalmarFu, Ying

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