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Acid dissociation of 3-mercaptopropionic acid coated CdSe-CdS/Cd0.5Zn0.5S/ZnS core-multishell quantum dot and strong ionic interaction with Ca2+ ion
KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
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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. Vol. 120, no 6
National Category
Nano Technology
URN: urn:nbn:se:kth:diva-191843DOI: 10.1021/acs.jpcc.5b11023ISI: 000370678700047OAI: diva2:957598

QC 20160912

Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-12Bibliographically approved
In thesis
1. 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.
TRITA-FYS, ISSN 0280-316X ; 2016:54
Fluorescence, Microscopy, Bioimaging, Nanomaterial, cytotoxicity, mechanism
National Category
Research subject
Biological Physics
urn:nbn:se:kth:diva-191985 (URN)78-91-7729-074-2 (ISBN)
External cooperation:
Public defence
2016-09-29, Seminar room Earth, Science for life laboratory, Tomtebodavägen 23A, Solna, 13:00 (English)

QC 20160905

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

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