Multistage Stimulus-Responsive Room Temperature Phosphorescence Based on Host-Guest Doping Systems.

Compared with inorganic long-lasting luminescent materials, organic room temperature phosphorescent (RTP) ones show several advantages, such as flexibility, transparency, solubility and color adjustability. However, organic RTP materials close to commercialization are still to be developed. In this work, we developed a new host-guest doping system with stimulus-responsive RTP characteristics, in which triphenylphosphine oxide (OPph3 ) acted host and benzo(dibenzo)phenothiazine dioxide derivatives as guests. Turn-on RTP effect was realized by mixing them together through co-crystallization or grinding, in which the efficient energy transfer from host to guest and the strong intersystem crossing (ISC) ability of the guest have played significant role. Further on, multistage stimulus-responsive RTP characteristics from grinding to chemical stimulus were achieved via introducing pyridine group into the guest molecule. In addition, the anti-counterfeiting printings were realized for these materials through various methods, including stylus printing, thermal printing and inkjet printing, which brings RTP materials closer to commercialization.

Elucidation of distinct fluorescence and room-temperature phosphorescence of organic polymorphs from benzophenone-borate derivatives.

The development of organic room-temperature phosphorescence (RTP) is accompanied by opportunities and challenges. RTP from crystal polymorphism has aroused much attention, due to the significant different photophysical characteristics and intermolecular packings found in the same molecule with different crystal phases. Herein, we report three organic molecules BP-o-BO, BP-m-BO, and BP-p-BO, in which two crystal polymorphisms of BP-p-BO are successfully cultivated with different emission properties. BP-p-BO-A exhibits bright cyan photoluminescence (PL) with a quantum yield of 11.3% and a distinct RTP with a lifetime of 17.1 ms, which is much higher than the deep blue PL of BP-p-BO-B (6.9%) and the corresponding RTP lifetime of 3.3 ms. Crystal structure analyses indicate that the different emission properties can be ascribed to the different intermolecular packing, further demonstrating the essential role of molecular packing in the designing of RTP materials.

Ultrafast and Noninvasive Long-Term Bioimaging with Highly Stable Red Aggregation-Induced Emission Nanoparticles.

Strongly red luminescent and water-soluble probes are very important for studying biological events and processes. Fluorescent nanoparticles (NPs) built from the aggregation-induced emission luminogen (AIEgen) and amphipathic polymeric matrixes have been considered as promising candidates for bioimaging. However, AIE NPs with long-wavelength absorption suitable for in vivo application are still scarce. In this work, three AIE-active red-emissive BODIPY derivatives with long-wavelength absorption were rationally designed and synthesized. Then three NPs based on these AIEgens exhibit bright red photoluminescence with high fluorescence quantum yield in aqueous media. These NPs uniformly dispersed in water and showed excellent stability and good biocompatibility. They can be readily internalized by HeLa cells, and the staining process is performed by simply shaking the culture with cells for just a few seconds at room temperature, which indicates an ultrafast and easy-to-operate staining protocol. More importantly, long-term tracing in living cells and mouse over 15 days is successfully achieved. The strong fluorescence signals, ultrafast staining procedure, and long-term tracing abilities indicate that these AIE NPs hold great potential for monitoring biological processes.

Thermally Activated Delayed Fluorescence in CuI Complexes Originating from Restricted Molecular Vibrations.

The mechanism of thermally activated delayed fluorescence (TADF) in molecules in aggregated or condensed solid states has been rarely studied and is not well understood. Nevertheless, many applications of TADF emitters are strongly affected by their luminescence properties in the aggregated state. In this study, two new isomeric tetradentate CuI complexes which simultaneously show aggregation induced emission (AIE) and TADF characteristics are reported for the first time. We provide direct evidence that effectively restricting the vibrations of individual molecules is a key requisite for TADF in these two CuI complexes through in-depth photophysical measurements combined with kinetic methods, single crystal analysis and theoretical calculations. These findings should stimulate new molecular engineering endeavours in the design of AIE-TADF active materials with highly emissive aggregated states.

H2O2-assisted detection of melamine using fluorescent probe based on corn cob carbon dots-Ionic Liquid-Silver nanoparticles.

In this work, a new sustainable melamine detection method was developed. Biomass-derived carbon dots (CDs) were successfully prepared by ionic liquid (1-Allyl-3-methylimidazolium chloride, IL) hydrothermal method using agricultural waste corn cob as the carbon source, and combined with silver nanoparticles (AgNPs) to construct fluorescent probe CDs@IL-AgNPs. The probe was characterized and the formation mechanism of the probe was discussed. The direct detection of H2O2 and the indirect sensitive detection of melamine were realized. The detection limit of melamine was 0.94 µmol/L, which is far lower than the minimum allowable amount of melamine in milk powder (7.95 µmol/L). The high sensitivity and selectivity probe was used to detect melamine in commercial dairy products, and the recovery rate of standard addition was between 94 % and 110 %. This study provides valuable new application ideas for the detection of melamine in dairy products and the low-carbon and environmentally friendly treatment of agricultural waste.

Bright red aggregation-induced emission nanoparticles for multifunctional applications in cancer therapy.

Developing multifunctional photosensitizers (PSs) is needed to effectively simplify cancer treatment, but it remains a big challenge. Here, two red-emitting AIE-active, donor-acceptor (D-A) PSs with small ΔE ST and their AIE nanoparticles, are rationally designed and synthesized. The PS1 NPs exhibit bright red-emission with high quantum yield, appropriate 1O2 generation ability and good biocompatibility. More importantly, PS1 NPs can strongly light up the cytoplasm by gently shaking the cells for only 5 s at room temperature, indicating ultrafast staining and mild incubation conditions. In vitro and in vivo cell tracing demonstrate that PS1 NPs can track cells over 14 days, and effectively inhibit tumor growth upon irradiation. To the best of our knowledge, this work is the first example of a PS that integrates image-guided PDT, ultrafast staining and long-term tracing functions, demonstrating the "all-in-one" concept which offers great advantages for potential clinical applications.

A remarkable phosphorescent sensor for acid-base vapours based on an AIPE-active Ir(iii) complex.

A novel AIPE-active neutral Ir(iii) complex has been synthesized for rapid and reversible phosphorescent sensing of acid-base vapours due to the reversible protonation and deprotonation process occurring on functional Schiff base ligands.

Reversible tricolour luminescence switching based on a piezochromic iridium(iii) complex.

On the basis of rational molecular design, the tricolour luminescence switching of an Ir(iii) complex is achieved for the first time. The transformation between two crystalline states and an amorphous state is responsible for the switching behaviour of this complex between blue, green and yellow states. Solvent molecules are shown to play a crucial role in the crystallization and luminescence processes.

AIE Multinuclear Ir(III) Complexes for Biocompatible Organic Nanoparticles with Highly Enhanced Photodynamic Performance.

The singlet oxygen (1O2) generation ability of a photosensitizer (PS) is pivotal for photodynamic therapy (PDT). Transition metal complexes are effective PSs, owing to their high 1O2 generation ability. However, non-negligible cellular toxicity, poor biocompatibility, and easy aggregation in water limit their biomedical applications. In this work, a series of red-emitting aggregation-induced emission (AIE) Ir(III) complexes containing different numbers of Ir centers (mono-, di-, and trinuclear) and the corresponding nanoparticles (NPs) AIE-NPs, are designed and synthesized. The increase of 1O2 generation ability is in line with the increasing number of Ir centers. Compared with the pure Ir(III) complexes, the corresponding NPs offer multiple advantages: (i) brighter emission; (ii) higher phosphorescence quantum yields; (iii) longer excited lifetime; (iv) higher 1O2 generation ability; (v) better biocompatibility; and (vi) superior cellular uptake. Both in vitro and in vivo experiments corroborate that AIE-NPs with three iridium centers possess potent cytotoxicity toward cancer cells and effective inhibition of tumor growth. To the best of knowledge, this work is the first example of NPs of multinuclear AIE Ir(III) complexes as PSs for enhanced PDT. This study offers a new method to improve the efficiency of PSs for clinical cancer treatments.

Selective sensing of 2,4,6-trinitrophenol (TNP) in aqueous media with "aggregation-induced emission enhancement" (AIEE)-active iridium(iii) complexes.

A series of new phosphorescent cyclometalated iridium(iii) complexes which possess aggregation-induced emission enhancement (AIEE) detect 2,4,6-trinitrophenol (TNP) selectively with high quenching constants in aqueous media. The sensing mechanism was systematically investigated by mass spectrometry, 1H and 19F NMR spectroscopy. X-ray crystal structure analysis reveals an O-HO interaction between TNP and the ancillary ligand which explains the high selectivity for TNP compared to other nitro-aromatics.

A neutral dinuclear Ir(iii) complex for anti-counterfeiting and data encryption.

A neutral dinuclear Ir(iii) Schiff base complex PIBIP has been synthesized and shown to exhibit both piezochromic luminescence (PCL) and aggregation induced emission (AIE) behaviour. An efficient second-level anti-counterfeit trademark and a data encryption device were fabricated using PIBIP as the active material.

New AIE-active dinuclear Ir(III) complexes with reversible piezochromic phosphorescence behaviour.

Two new AIE-active dinuclear Schiff base Ir(III) complexes exhibit highly reversible piezochromic phosphorescence behaviour enabling the construction of a re-writable phosphorescence data recording device.

New ionic dinuclear Ir(III) Schiff base complexes with aggregation-induced phosphorescent emission (AIPE).

Two new ionic dinuclear Ir(III) Schiff base complexes which are straightforward to synthesise have luminescence quantum yields as high as 37% in neat films. These are the first examples of dinuclear ionic Ir(III) complexes that display aggregation-induced phosphorescent emission (AIPE).