Change search
ReferencesLink to record
Permanent link

Direct link
Fluorescence Properties of Quantum Dots and Their Utilization in Bioimaging
KTH, School of Engineering Sciences (SCI), Applied Physics. (Cellular Biophysics)
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 [en]
Fluorescence, Microscopy, Bioimaging, Nanomaterial, cytotoxicity, mechanism
National Category
Biophysics
Research subject
Biological Physics
Identifiers
URN: urn:nbn:se:kth:diva-191985ISBN: 78-91-7729-074-2OAI: oai:DiVA.org:kth-191985DiVA: diva2:957626
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: 2016-09-07Bibliographically approved
List of papers
1. Mechanisms of fluorescence decays of colloidal CdSe-CdS/ZnS quantum dots unraveled by time-resolved fluorescence measurement
Open this publication in new window or tab >>Mechanisms of fluorescence decays of colloidal CdSe-CdS/ZnS quantum dots unraveled by time-resolved fluorescence measurement
Show others...
2015 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 41, 27588-27595 p.Article in journal (Refereed) Published
Abstract [en]

By narrowing the detection bandpass and increasing the signal-to-noise ratio in measuring the time-resolved fluorescence decay spectrum of colloidal CdSe-CdS/ZnS quantum dots (QDs), we show that directly after the photoexcitation, the fluorescence decay spectrum is characterized by a single exponential decay, which represents the energy relaxation of the photogenerated exciton from its initial high-energy state to the ground exciton state. The fluorescence decay spectrum of long decay time is in the form of beta/t(2), where beta is the radiative recombination time of the ground-state exciton and t is the decay time. Our findings provide us with a direct and quantitative link between fluorescence decay measurement data and fundamental photophysics of QD exciton, thereby leading to a novel way of applying colloidal QDs to study microscopic, physical and chemical processes in many fields including biomedicine.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2015
Keyword
Phonon Bottleneck, Cdte Nanocrystals, Energy-Transfer, Emission, Electron, Blinking, Relaxation, Nanoparticles, Microscopy, Lifetimes
National Category
Subatomic Physics Other Physics Topics Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-176997 (URN)10.1039/c5cp03109e (DOI)000363193800038 ()26426293 (PubMedID)2-s2.0-84944339303 (ScopusID)
Funder
Swedish Research Council, 621-2011-4381Knut and Alice Wallenberg Foundation, KAW 2011.0218
Note

QC 20151116

Available from: 2015-11-16 Created: 2015-11-13 Last updated: 2016-09-02Bibliographically approved
2. Modulated fluorescence of colloidal quantum dots embedded in a porous alumina membrane
Open this publication in new window or tab >>Modulated fluorescence of colloidal quantum dots embedded in a porous alumina membrane
Show others...
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.

Keyword
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:nbn:se:kth:diva-136255 (URN)10.1021/jp409132e (DOI)000327111200024 ()2-s2.0-84887899102 (ScopusID)
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: 2016-09-02Bibliographically approved
3. Acid dissociation of 3-mercaptopropionic acid coated CdSe-CdS/Cd0.5Zn0.5S/ZnS core-multishell quantum dot and strong ionic interaction with Ca2+ ion
Open this publication in new window or tab >>Acid dissociation of 3-mercaptopropionic acid coated CdSe-CdS/Cd0.5Zn0.5S/ZnS core-multishell quantum dot and strong ionic interaction with Ca2+ ion
Show others...
2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 6Article in journal, Letter (Refereed) Published
Abstract [en]

By devising careful electrophoresis, it was shown that at pH below 7.0, the electrophoretic mobility of 3-mercaptopropionic acid (3MPA) coated CdSe-ZnS core-shell quantum dots (denoted as QD-3MPA) was very small. At pH above 7.0, QD-3MPA migrated toward the anode, implying acid dissociation, and the degree of which was proportional to the pH value. QD-3MPA's electrophoretic mobility was impaired after adding sufficient Ca2+ ions to the QD solution and revived when a similar amount of Ca2+ chelators (ethylene glycol tetraacetic acid, EGTA) was added. This demonstrated that acid dissociation and its pH dependence of 3MPA on the QD surface are critical factors in understanding the electric and optical properties of QDs. The acid dissociated QD-3MPA interacted strongly with Ca2+, forming a charge neutral QD-3MPA Ca2+ complex in the absence of EGTA. First-principles study confirmed the observed experimental evidence. The strong ionic interaction between acid dissociated QD-3MPA and Ca2+ is critical for developing reliable QD-based biosensing assays. Moreover, the strategy and techniques reported in this work are easily applicable to other fluorescent biomarkers and therefore can be important for advancing in vivo and in vitro imaging, sensing, and labeling.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-191843 (URN)10.1021/acs.jpcc.5b11023 (DOI)000370678700047 ()
External cooperation:
Note

QC 20160912

Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-12Bibliographically approved
4. Understand blinking of single colloidal CdSe-CdS/ZnS quantum dot by surface modification
Open this publication in new window or tab >>Understand blinking of single colloidal CdSe-CdS/ZnS quantum dot by surface modification
(English)Manuscript (preprint) (Other academic)
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-191844 (URN)
External cooperation:
Note

QC 20160912

Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-12Bibliographically approved
5. Electron transition pathways of photoluminescence from 3C-SiC nanocrystals unraveled by steady-state, blinking and time-resolved photoluminescence measurement
Open this publication in new window or tab >>Electron transition pathways of photoluminescence from 3C-SiC nanocrystals unraveled by steady-state, blinking and time-resolved photoluminescence measurement
Show others...
2016 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 27Article in journal (Refereed) Published
Abstract [en]

The cubic phase SiC nanocrystals (3C-SiC NCs) have been extensively studied for electronics and photonics applications. In this work we study the electron transition pathways of photoluminescence (PL) from 3C-SiC NCs. It is found through measuring the steady-state, blinking and time-resolved PL spectra that surface passivation by glycerol improved the steady-state PL intensity (it does not modify the emission wavelength) and the NCs fluoresced more steadily. The PL decay lifetimes are shown to be the same when the detection wavelength is modified to scan the broad PL peak, implying that the broad PL peak is originated from the distribution of NCs' sizes. Furthermore, the PL decay lifetimes are not modified by the surface passivation. It is concluded that for PL, the electron is photoexcited from the ground state in the NC to a high-energy excited state, relaxes to the first excited state then radiatively recombines to the ground state to emit a photon. The photoexcited electron at the high-energy excited state could transit to the surface state, resulting in a reduced PL intensity and a decreased on-state dwell time in the blinking trajectory. The PL decay lifetime data implies that the two principal electron transition pathways of (a) high-energy excited state double right arrow the first excited state double right arrow the ground state, and (b) high-energy excited state double right arrow surface state double right arrow the ground state are independent from each other. We strongly believe that such a deep knowledge about 3C-SiC NCs will open new doors to harness them for novel applications.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2016
Keyword
3C-SiC nanocrystal, blinking, photoluminescence, time-resolved photoluminescence
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-191845 (URN)10.1088/0022-3727/49/27/275107 (DOI)000380763700015 ()2-s2.0-84978229473 (ScopusID)
External cooperation:
Funder
Science for Life Laboratory - a national resource center for high-throughput molecular bioscience
Note

QC 20160912

Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-13Bibliographically approved
6. Bioelectric and Morphological Response of Liquid-Covered Human Airway Epithelial Calu-3 Cell Monolayer to Periodic Deposition of Colloidal 3-Mercaptopropionic-Acid Coated CdSe-CdS/ZnS Core-Multishell Quantum Dots
Open this publication in new window or tab >>Bioelectric and Morphological Response of Liquid-Covered Human Airway Epithelial Calu-3 Cell Monolayer to Periodic Deposition of Colloidal 3-Mercaptopropionic-Acid Coated CdSe-CdS/ZnS Core-Multishell Quantum Dots
Show others...
2016 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 2, e0149915Article in journal (Refereed) Published
Abstract [en]

Lung epithelial cells are extensively exposed to nanoparticles present in the modern urban environment. Nanoparticles, including colloidal quantum dots (QDs), are also considered to be potentially useful carriers for the delivery of drugs into the body. It is therefore important to understand the ways of distribution and the effects of the various types of nanoparticles in the lung epithelium. We use a model system of liquid-covered human airway epithelial Calu-3 cell cultures to study the immediate and long-term effects of repeated deposition of colloidal 3-mercaptopropionic-acid coated CdSe-CdS/ZnS core-multishell QDs on the lung epithelial cell surface. By live confocal microscope imaging and by QD fluorescence measurements we show that the QD permeation through the mature epithelial monolayers is very limited. At the time of QD deposition, the transepithelial electrical resistance (TEER) of the epithelial monolayers transiently decreased, with the decrement being proportional to the QD dose. Repeated QD deposition, once every six days for two months, lead to accumulation of only small amounts of the QDs in the cell monolayer. However, it did not induce any noticeable changes in the long-term TEER and the molecular morphology of the cells. The colloidal 3-mercaptopropionic-acid coated CdSe-CdS/ZnS core-multishell QDs could therefore be potentially used for the delivery of drugs intended for the surface of the lung epithelia during limited treatment periods. © 2016 Turdalieva et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Place, publisher, year, edition, pages
Public Library of Science, 2016
Keyword
Tight Junctions, Primary Cilia, Lung-Cells, In-Vitro, Nanoparticles, Toxicity, Promotes, Mucus, Line
National Category
Biomaterials Science
Identifiers
urn:nbn:se:kth:diva-191847 (URN)10.1371/journal.pone.0149915 (DOI)000371175700035 ()26913754 (PubMedID)2-s2.0-84977674241 (ScopusID)
Funder
Swedish Research Council, 621-2011-4381Science for Life Laboratory - a national resource center for high-throughput molecular bioscience
Note

QC 20160927 QC 20160927

Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-27Bibliographically approved

Open Access in DiVA

fulltext(5057 kB)12 downloads
File information
File name FULLTEXT02.pdfFile size 5057 kBChecksum SHA-512
e565cd6d2f74bf450f246140f6f8f7d39d6107220df995a717c14793a8afe863068f123432ac0520d7a6ab2c2419738434fc40134ede04c497e2751f1b03da50
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Xu, Hao
By organisation
Applied Physics
Biophysics

Search outside of DiVA

GoogleGoogle Scholar
Total: 13 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 51 hits
ReferencesLink to record
Permanent link

Direct link