Fluorescent nanorods based on 9,10-distyrylanthracene (DSA) derivatives for efficient and long-term bioimaging.

Fluorescent nanoparticles based on 9,10-distyrylanthracene (DSA) derivatives (4,4'-((1E,1'E)-anthracene-9,10-diylbis(ethene-2,1-diyl))bis(N,N-dimethylaniline) (NDSA) and 4,4'-((1E,1'E)-anthracene-9,10-diylbis(ethene-2,1-diyl))dibenzonitrile (CNDSA)) were prepared using an ultrasound aided nanoprecipitation method. The morphologies of the fluorescent nanoparticles could be controlled by adjusting the external ultrasonication time. NDSA or CNDSA could form spherical nanodots (NDSA NDs, CNDSA NDs) in a THF-H2O mixture with an 80% or 70% water fraction when the ultrasonication time was 30 s. When the ultrasonication time was prolonged to 10 min, NDSA and CNDSA could assemble into nanorods (NDSA NRs, CNDSA NRs). Meanwhile, the sizes of NDSA NRs and CNDSA NRs could be controlled by adjusting the water content in the mixture. As the water fraction was increased from 60% to 80%, the sizes of NDSA and CNDSA nanorods or nanodots reduced from 238.4 nm to 140.3 nm, and 482 nm to 198.4 nm, respectively. When the water fraction was up to 90%, irregular morphologies of NDSA and CNDSA could be observed. The nanoparticles exhibited intense fluorescence emission, good anti-photobleaching properties, as well as excellent stability and biocompatibility. In vitro cell imaging experiments indicated that the nanorods prepared by this simple method had the potential to be used for efficient and noninvasive long-term bioimaging.

Exploiting radical-pair intersystem crossing for maximizing singlet oxygen quantum yields in pure organic fluorescent photosensitizers.

Fluorescent photosensitizers (PSs) often encounter low singlet oxygen (1O2) quantum yields and fluorescence quenching in the aggregated state, mainly involving the intersystem crossing process. Herein, we successfully realize maximizing 1O2 quantum yields of fluorescent PSs through promoting radical-pair intersystem crossing (RP-ISC), which serves as a molecular symmetry-controlling strategy of donor-acceptor (D-A) motifs. The symmetric quadrupolar A-D-A molecule PTP exhibits an excellent 1O2 quantum yield of 97.0% with bright near-infrared fluorescence in the aggregated state. Theoretical and ultrafast spectroscopic studies suggested that the RP-ISC mechanism dominated the formation of the triplet for PTP, where effective charge separation and an ultralow singlet-triplet energy gap (0.01 eV) enhanced the ISC process to maximize 1O2 generation. Furthermore, in vitro and in vivo experiments demonstrated the dual function of PTP as a fluorescent imaging agent and an anti-cancer therapeutic, with promising potential applications in both diagnosis and theranostics.

High-efficiency fluorescent and magnetic multimodal probe for long-term monitoring and deep penetration imaging of tumors.

High-quality multimodal imaging requires exogenous contrast agents with high sensitivity, spatial-temporal resolution, and high penetration depth for the accurate diagnosis and surveillance of cancer. Herein, we design a highly efficient fluorescent and magnetic multimodal probe by doping fluorescent molecule 2-(4-bromophenyl)-3-(4-(4-(diphenylamino)styryl)phenyl)fumaronitrile (TB) with near-infrared (NIR) fluorescent emission (714 nm) and superparamagnetic iron oxide (SPIO) into a polystyrene-polyethylene glycol (PS-PEG) matrix to form TB/SPIO@PS-PEG nanoparticles (TSP NPs). The as-prepared TSP NPs exhibit red aggregation-induced emission (AIE) with a maximum wavelength at 655 nm and high fluorescence quantum yield (QY) of 14.6%, facilitating the improvement of sensitivity and signal-to-background ratio for fluorescence molecular imaging (FMI). Phase behavior investigation of the TB/SPIO@PS-PEG probe system by Flory-Huggins lattice theory elucidates the highly efficient fluorescence of the multimodal probe, originating from the poor miscibility between TB and SPIO. Meanwhile, the TSP NPs possess good superparamagnetism and relaxivity and can thus be used as appropriate magnetic contrast agents for magnetic resonance imaging (MRI) and magnetic particle imaging (MPI). In addition, the good biocompatibility and photostability of the TSP NPs make them suitable for long-term monitoring. In vivo fluorescence imaging results indicate that the TSP NPs can facilitate monitoring of subcutaneous tumor growth for more than 24 days in a real-time manner. Multimodal imaging consisting of FMI, MRI, and MPI reveals that TSP NPs can monitor a liver tumor in situ with almost unlimited depth in tissues and high temporal-spatial resolution. As a multimodal probe, the TSP NPs manifest obvious synergistic advantages of long-term monitoring and high penetration depth and hold great prospects in tumor imaging.

A cyanide-sensing detector in aqueous solution based on anion-π interaction-driven electron transfer.

A "turn on" fluorescent and colorimetric sensor, HAT(CN)6, was developed for the light-up detection of cyanide. It was implemented through its strong anion-π interaction, inducing thermal CN- → HAT(CN)6 electron transfer, to give the dianion product [HAT(CN)6]2-, which exhibits unexpected fluorescence. The sensor shows high selectivity, rapid response and a low detection limit towards CN- in aqueous solution, hence indicating its enormous potential in practical applications.

Redox-responsive Fluorescent Nanoparticles Based on Diselenide-containing AIEgens for Cell Imaging and Selective Cancer Therapy.

A fluorescent, diselenide-containing 9,10-distyrylanthracene (DSA) derivative (SeDSA) with aggregation-induced emission (AIE) characteristic was successfully synthesized and SeDSA nanoparticles (NPs) were prepared through a nanoprecipitation method. SeDSA could coassemble with an antitumor prodrug, diselenide-containing paclitaxel (SePTX), which could be obtained by precipitation, to form SeDSA-SePTX Co-NPs (Co-NPs). Molecular dynamics (MD) simulations reveal that the driving forces for the self-assembly behaviors of SeDSA NPs and SePTX NPs are π-π interactions and hydrophobic interactions, respectively, while the driving forces for Co-NPs include hydrophobic interactions between SeDSA and SePTX, π-π interactions between SeDSA molecules and hydrophobic interactions between SePTX molecules. Meanwhile, Se-Se bonds play a crucial role in balancing the intramolecular forces. These diselenide-containing nanoparticles (SeDSA NPs, SePTX NPs and Co-NPs) exhibit a high stability under physiological conditions and excellent reduction-sensitivity in the presence of the redox agent glutathione (GSH) because of the selenium-sulfur exchange reaction between diselenide and GSH. Both SeDSA NPs and Co-NPs show strong orange fluorescence emissions on the account of the AIE feature of SeDSA and they were easily internalized by HeLa and HepG2 cells. Distinctively, the Co-NPs combine the advantage of SeDSA and SePTX for cell imaging and antineoplastic activity, and exhibit selectivity of cytotoxicities between neoplasia cells and normal cells. This study highlights the development of diselenide-containing AIEgens as a unique approach to prepare uniform and stable fluorescent nanoparticles for the application in cell imaging and tumor treatment.

Green-solvent-processed hybrid solar cells based on donor-acceptor conjugated polyelectrolyte.

In this work, a quaternary ammonium side chain modified conjugated polyelectrolyte PFBTBr, with excellent solubility in nonaromatic and nonhalogenated solvents, was designed and synthesized as the donor material for the green-solvent-processed hybrid solar cells (HSCs). By introducing the donor-acceptor structure, PFBTBr shows a lower lying highest occupied molecular orbital (HOMO) level and a broad absorption from 300 to 700 nm. Incorporating the water soluble CdTe nanocrystals (NCs) as acceptor, the green-solvent-processed HSCs based on conjugated polyelectrolyte and inorganic NCs were fabricated. Through the active layer optimization, a well blended donor/acceptor active layer with continuous electron/hole transport pathway and smoother surface was achieved. As a result, a photovoltaic efficiency of 3.67% was realized. After the further interfacial modification and chloride treatment, the power conversion efficiency of the green-solvent-processed HSCs was improved to 5.03% with the maximum external quantum efficiency value of 87.01% at 400 nm under the AM 1.5 G 100 mW cm-2 illumination.

A novel cascade strategy with supramolecular and chemodosimetric methods for designing a fluorescent ratiometric detector hypersensitive to trace water.

An intensely fluorescent zinc-salicylideneimine complex (-Zn(II)) was developed as a fluorescent ratiometric detector for the quantitative determination of trace water contents both in THF and methanol. It works based on a water-triggered cascade process: the dissociation reaction of the supramolecular ensemble and the subsequent hydrolysis reaction of its ligand.