Publications by authors named "Michidmaa Khorloo"

3 Publications

  • Page 1 of 1

Enantiomeric Switching of the Circularly Polarized Luminescence Processes in a Hierarchical Biomimetic System by Film Tilting.

ACS Nano 2021 01 4;15(1):1397-1406. Epub 2020 Dec 4.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Circularly polarized luminescence (CPL) switching has attracted great attention due to the potential applications in chiral photonics and electronics. However, the lack of examples to achieve switchable CPL within a single material in the dry solid state hampers the scope of applications. Herein, we demonstrate a crystalline chiral polymer film as a polarizing medium consisting of radially assembled twisted crystallites, where achiral aggregation-induced emissive luminogens (AIEgens) are confined between the twisted crystalline stacks, eventually yielding handedness-switchable CPL by simple film tilting. Hierarchically organized twisted crystallites create the selective reflection activity of the polarizing medium. Upon film tilting, enantiomeric switching is realized by selectively collecting transmitted and reflected CPL components. The confined AIEgens in the crystalline polarizing system show a great enhancement of the luminescence efficiency. Moreover, the approach is general with broadband activity, and various AIEgens could be applied to generate full-color-tunable CPL. Additionally, the rigid and continuous nature of this polarizing system affords enhanced optical stability and facile modulation, developing a general route for designing chiroptical materials.
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http://dx.doi.org/10.1021/acsnano.0c08665DOI Listing
January 2021

Solid-state intramolecular motions in continuous fibers driven by ambient humidity for fluorescent sensors.

Natl Sci Rev 2021 Apr 17;8(4):nwaa135. Epub 2020 Jun 17.

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.

One striking feature of molecular rotors is their ability to change conformation with detectable optical signals through molecular motion when stimulated. However, due to the strong intermolecular interactions, synthetic molecular rotors have often relied on fluid environments. Here, we take advantage of the solid-state intramolecular motion of aggregation-induced emission (AIE) molecular rotors and one-dimensional fibers, developing highly sensitive optical fiber sensors that respond to ambient humidity rapidly and reversibly with observable chromatic fluorescence change. Moisture environments induce the swelling of the polymer fibers, activating intramolecular motions of AIE molecules to result in red-shifted fluorescence and linear response to ambient humidity. In this case, polymer fiber provides a process-friendly architecture and a physically tunable medium for the embedded AIE molecules to manipulate their fluorescence response characteristics. Assembly of sensor fibers could be built into hierarchical structures, which are adaptive to diverse-configuration for spatial-temporal humidity mapping, and suitable for device integration to build light-emitting sensors as well as touchless positioning interfaces for intelligence systems.
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http://dx.doi.org/10.1093/nsr/nwaa135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8288334PMC
April 2021

Polymorph selectivity of an AIE luminogen under nano-confinement to visualize polymer microstructures.

Chem Sci 2019 Nov 22;11(4):997-1005. Epub 2019 Nov 22.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China

Despite the huge progress of luminescent molecular assemblies over the past decade, it is still challenging to understand their confined behavior in semi-crystalline polymers for constrained space recognition. Here, we report a polymorphic luminogen with aggregation-induced emission (AIE), capable of selective growth in polymer amorphous and crystalline phases with distinct color. The polymorphic behaviors of the AIE luminogen embedded within the polymer network are dependent on the size of nano-confinement: a thermodynamically stable polymorph of the AIE luminogen with green emission is stabilized in the amorphous phase, while a metastable polymorph with yellow emission is confined in the crystalline phase. The information on polymer crystalline and amorphous phases is transformed into distinct fluorescence colors, allowing a single AIE luminogen as a fluorescent marker for visualization of polymer microstructures in terms of amorphous and crystalline phase distribution, quantitative polymer crystallinity measurement, and spatial morphological arrangement. Our findings demonstrate that confinement of the AIE luminogen in the polymer network can achieve free space recognition and also provide a correlation between microscopic morphologies and macroscopic optical signals. We envision that our strategy will inspire the development of other materials with spatial confinement to incorporate AIE luminogens for various applications.
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http://dx.doi.org/10.1039/c9sc04239cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8146380PMC
November 2019
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