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Electron transition pathways of photoluminescence from 3C-SiC nanocrystals unraveled by steady-state, blinking and time-resolved photoluminescence measurement
KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
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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. Vol. 49, no 27
Keyword [en]
3C-SiC nanocrystal, blinking, photoluminescence, time-resolved photoluminescence
National Category
Nano Technology
URN: urn:nbn:se:kth:diva-191845DOI: 10.1088/0022-3727/49/27/275107ISI: 000380763700015ScopusID: 2-s2.0-84978229473OAI: diva2:957603
Science for Life Laboratory - a national resource center for high-throughput molecular bioscience

QC 20160912

Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-13Bibliographically 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)
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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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