Bulky 4,6-disubstituted tetraphenylethene-naphthalimide dyad: synthesis, copolymerization, stimuli-responsive fluorescence and cellular imaging.

We report the design and synthesis of a tetraphenylethene substituted with naphthalimide at the 4, 6 positions, named NI-2TPE. NI-2TPE exhibits strong solvent-dependent emission properties with combined ICT and AIE characteristics in THF-H2O systems. This probe was used directly on test papers to distinguish normal organic solvents using their emission colours under UV light based on its AIE and ICT nature. Thanks to the vinyl group in NI-2TPE, we synthesized a copolymer of NIPAM and NI-2TPE, termed P(NIPAM-co-NI-2TPE). The resulting polymer is highly soluble and fluorescent in water (ΦF = 15.4%). Due to the well-known thermo-responsive character of NIPAM, P(NIPAM-co-NI-2TPE) exhibits an interesting fluorescence change in response to various temperatures. Due to the thermo-induced shrinking of the PNIPAM chain, the fluorescence intensity gradually increased from 20 to 34 °C. As the temperature further increased from 34 to 90 °C, the fluorescence intensity decreased sharply, which was caused by the well-known thermal effects. Furthermore, we synthesized a P(HEA-co-NI-2TPE-TPP acrylate) copolymer, in which HEA is a hydrophilic unit, TPP is a mitochondria label and NI-2TPE a fluorescent probe. The corresponding polymer probe is highly soluble in water with FLQY = 7% and we have further applied this probe as a mitochondria targeted imaging tracker in HeLa cells successfully.

Monodisperse AIE-Active Conjugated Polymer Nanoparticles via Dispersion Polymerization Using Geminal Cross-Coupling of 1,1-Dibromoolefins.

Monodisperse AIE (aggregation-induced emission)-active conjugated polymer nanoparticles are synthesized by dispersion polymerization using geminal Suzuki cross-coupling of 1,1-dibromoolefins. The size of the nanoparticles can be adjusted by varying the concentration of the initial monomer.

Optical nanoimaging for block copolymer self-assembly.

One approach toward optical nanoimaging involves sequential molecular localization of photoswitchable fluorophores to achieve high resolution beyond optical limit of diffraction. Block copolymer micelles assembled from polystryrene-block-poly(ethylene oxide) block copolymers (PSt-b-PEO) are visualized in optical nanoimaging by staining the polystyrene blocks with spiropyrans (SPs). SPs localized in hydrophobic phase of block copolymer micelles exhibit reversible fluorescence on-off switching at alternating irradiation of UV and visible light. Phase-selective distribution of SPs in block copolymer micelles enables optical nanoimaging of microphase structures of block copolymer self-assembly at 50-nm resolution. To date, this is the sturdiest realization of optical nanoimaging with subdiffraction resolution for solution self-assembly of block copolymers.

Hydrophilic AIE-Active Tetraarylethenes for Fluorescence Sensing and Super-Resolution Imaging of Amyloid Fibrils from Hen Egg White Lysozyme.

Hen egg white lysozyme (HEWL) is frequently applied as a model protein for research on protein folding, unfolding, and fibrillization identified by featured fluorescent probes. Here, a series of hydrophilic, pH-sensitive tetraarylethene (TAE)-type AIEgens are synthesized via a geminal cross-coupling (GCC) reaction and evaluated for their capabilities of fluorescence sensing and super-resolution localization imaging of HEWL fibrils. With superior optical and sensing properties, the selected TAE-type AIEgen probe is weakly emissive in aqueous media, without dependence on the pH value and buffer concentration, but exhibits "turn-on" fluorescence upon interaction with HEWL amyloid fibrils in a spontaneous and reversible way that just meets the requirement of fluorescence random switching for super-resolution imaging. The selected probe has the strongest fluorescence response to HEWL amyloid fibrils exhibiting a limit of detection of 0.59 nmol/L and enables super-resolution fluorescence imaging of amyloid aggregates with a high resolution of 40 nm.

Geminal cross-coupling synthesis, ion-induced emission and lysosome imaging of cationic tetraarylethene oligoelectrolytes.

Neutral conjugated tetraarylethenes OFn (n = 1-3) and the corresponding cationic conjugated oligoelectrolytes OFn+ (n = 1-3) with aggregation-induced emission activity have been designed and synthesized using geminal cross-coupling. OFn+ (n = 1-3) feature ion-induced emission in aqueous solution. They are used for lysosomal fluorescence imaging and tracing of lysosome events.

Direct validation of the restriction of intramolecular rotation hypothesis via the synthesis of novel ortho-methyl substituted tetraphenylethenes and their application in cell imaging.

We demonstrate a novel synthetic approach to ortho-methyl substituted tetraphenylethene materials, which can be utilised for directly validating the restriction of intramolecular rotation hypothesis as the basic mechanism of aggregation-induced emission phenomenon and cell imaging.

Spiropyran-based biodegradable polymer all-optical transistors integrate the switching and modulation of visible light frequency.

All-optical modulation of a spiropyran-based device, integrating the transmittance switching (absorption) and wavelength modulation (emission) of visible light frequency induced by alternating UV/visible light irradiation is demonstrated. As an alternative to conventional organic transistors, all-optical devices based on SP-PCL have potential utility as single molecular transistors for optical switching and visible wavelength modulation.