Browsing by Author "He T."

Now showing 1 - 3 of 3

Open Access
Blue liquid lasers from solution of CdZnS/ZnS ternary alloy quantum dots with quasi ‐ continuous pumping
(Wiley - VCH Verlag GmbH & Co. KGaA, 2015) Wang Y.; Leck K.S.; Ta, V. D.; Chen R.; Nalla, V.; Gao, Y.; He T.; Demir, Hilmi Volkan; Sun, H.
A blue (ca. 440 nm) liquid laser with an ultra‐low threshold through which quasi‐continuous wave pumping is accessible is achieved by engineering unconventional ternary CdZnS/ZnS alloyed‐core/shell QDs. Such an achievement is enabled by exploiting the novel gain media with minimal defects, suppressed Auger recombination, and large gain cross‐section in combination with high‐quality‐factor whispering gallery mode resonators.
Open Access
Robust whispering-gallery-mode microbubble lasers from colloidal quantum dots
(American Chemical Society, 2017) Wang Y.; Ta, V. D.; Leck K.S.; Tan, B. H. I.; Wang, Z.; He T.; Ohl, C.-D.; Demir, Hilmi Volkan; Sun, H.
Microlasers hold great promise for the development of photonics and optoelectronics. Among the discovered optical gain materials, colloidal quantum dots (CQDs) have been recognized as the most appealing candidate due to the facile emission tunability and solution processability. However, to date, it is still challenging to develop CQD-based microlasers with low cost yet high performance. Moreover, the poor long-term stability of CQDs remains to be the most critical issue, which may block their laser aspirations. Herein, we developed a unique but generic approach to forming a novel type of a whispering-gallery-mode (WGM) microbubble laser from the hybrid CQD/poly(methyl methacrylate) (PMMA) nanocomposites. The formation mechanism of the microbubbles was unraveled by recording the drying process of the nanocomposite droplets. Interestingly, these microbubbles naturally serve as the high-quality WGM laser resonators. By simply changing the CQDs, the lasing emission can be tuned across the whole visible spectral range. Importantly, these microbubble lasers exhibit unprecedented long-term stability (over one year), sufficient for practical applications. As a proof-of-concept, the potential of water vapor sensing was demonstrated. Our results represent a significant advance in microlasers based on the advantageous CQDs and may offer new possibilities for photonics and optoelectronics.
Open Access
Unusual fluorescent properties of stilbene units and cdzns/zns quantum dots nanocomposites: white-light emission in solution versus light-harvesting in films
(Wiley - V C H Verlag GmbH & Co. KGaA, 2016) He T.; Gao, Y.; Gao, y.; Lin, X.; Chen R.; Hu, W.; Zhao, X.; Wang Y.; Demir, Hilmi Volkan; Fan, Q.; Grimsdale, A. C.; Sun, H.
Nanocomposites with organic–inorganic properties represent a new fi eld of basic research and offer prospects for many novel applications in extremely diverse fi elds, due to their remarkable emerging new properties and multifunctional nature. However, controllable manipulation of their fl uorescent properties in different phases is still challenging, which seriously limits the related applications of nanocomposites. In this work, a convenient protocol to fabricate organic–inorganic nanocomposites composed of stilbene chromophores and CdZnS/ZnS quantum dots (QDs) pairs, with controllable fl uorescent properties is presented. It is found that stable white-light emission can be achieved only in solution phase, with negligible energy transfer or reabsorption between chromophores and QDs pairs. By contrast, when the nanocomposites are deposited as blended fi lms, they cannot give rise to white-light emission, no matter what donor/acceptor volume ratios are used. However, the blended fi lms can exhibit near-unity effi ciency (94%) of Förster resonance energy transfer from QDs to chromophores. The underlying physical mechanisms are revealed through comprehensive steady-state and time-resolved spectroscopic analysis. This work suggests that the CdZnS/ZnS QDs/stilbene nanocomposites can be directly used for fl uorescence sensors and probes in biological system as well as fundamental investigation of lightharvesting, and also sheds light on developing other new materials for artifi cial photosynthesis and optoelectronics.