Chiral-Induced, Ultra-Thin COF Nanosheets Developed to Obtain Circularly Polarized Luminescence Materials

In a recently published study, Professor Zhang Jian, Proof. Zhang Jian, Prof. Gu Zhigang. And their colleagues from the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences created and developed chiral-induced, ultra-thin chiral covalent organic framework or COF nanosheets.

They also reported on their employment "in circularly polarized luminescence," a Phys.org report specified.

Compared to traditional materials with circularly polarized luminescence or CPL activity, COFs, a new type of crystalline porous material, have high potential due to their constructional designability, flexibility, and functional adjustability not to mention chemical stability.

Currently, COFs with CPL activity and good crystallinity have not been created. 2D COFs with ultra-thin nanosheet structures can efficiently stop fluorescence quenching "caused by π-π stacking," as indicated in this report.

Chiral and Luminescence Functions

The introduction of chiral and luminescent functions into 2D COFs is an effective way to obtain CPL materials, although it remains a challenge.

In their study published in the Journal of the American Chemical Society, the authors first prepared ultra-thin COFs nanosheets-based CPL materials using coral induced-synthesis technique.

Chiral amines functioned as chiral inducers to provide COF TpBpy with chirality and took part in the modification of TpBpy, hindering the fluorescence quenching resulting from π-π stacking tp form ultrathin luminescent chiral COFs or chirCOFs NS.

The obtained chirCOFs R-/S-TpBpy NS had strong chirality and intense red CPL property with a glum of approximately 0.2.

A New Technique to Prepare Ultrathin chirCOFs NS

The researchers then postmodified the carboxyl containing blue and green fluorescent dye molecules onto the chirCOFs NS or chirCOFs/Dyes to attain color-adjustable CPL.

Because of the chirality and transfer of energy between chirCOFs and dye groups, the obtained chirCOFs/Dyes exhibited strong chirality and augmented and tunable photoluminescence, showing excellent, tunable, and boosted CPL performance with a maximum glum of approximately 0.1, which was around five times more intensified compared to that of as-prepared chirCOFs NS.

Furthermore, the study investigators dispersed the corresponding chirCOFs NS into a PDMS or polydimethylsiloxane matrix to create wafer size, highly transparent, and adjustable COFs/PDMS films for practical application of CPL.

This new research opens a new technique to prepare ultrathin chirCOFs NS with robust and flexible CPL by chiral induction and offers a new strategy for preparing transport, large size, and adjustable COFs composite films in chiral optical applications.

Nanosheet Technology

According to a study published in the Nanomaterials journal, the fabrication approach of the ultrathin film, commonly called nanosheets, has been substantially developed through the years.

The mechanical properties of nanosheets, like high levels of flexibility and adhesion, made nanosheets a perfect candidate for biomedical applications.

In this particular research, innovative biomedical employments of nanosheets are explained. Such nanosheets include delivery of drugs, treatment of wounds, and functional nanosheets for flexible biodevices, among others.

Related information about nanosheets is shown on PolyU FAST's YouTube video below:

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