Yongyang Gong

Synergy between Twisted Conformation and Effective Intermolecular Interactions: Strategy for Efficient Mechanochromic Luminogens with High Contrast

A strategy towards efficient mechanochromic luminogens with high contrast is developed. The twisted propeller-like conformations and effective intermolecular interactions not only endow the luminogens with AIE characteristics and high efficiency in the crystalline state, but also render them to undergo conformational planarization and disruption in intermolecular interactions upon mechanical stimuli, resulting in remarkable changes in emission wavelength and efficiency.

Achieving Persistent Room Temperature Phosphorescence and Remarkable Mechanochromism from Pure Organic Luminogens

Persistent room temperature phosphorescence (RTP) from pure organic luminogens can be rationally realized based on the crystallization-induced phosphorescence phenomenon and severe crystallization. A perfect crystal with dense molecular packing and effective inter-molecular interactions isolates the triplet excitons from quenching sites and significantly blocks the high-energy vibrational dissipation, thus yielding long-lasting RTP.

Synthesis and self-assembly of tetraphenylethene and biphenyl based AIE-active triazoles

Self-assembly of fluorescent functional materials has attracted increasing interest in the fabrication of optoelectronic and biological nanodevices. Tetraphenylethene (TPE) is a typical dye molecule with aggregation-induced-emission (AIE) characteristics. Melding TPE carrying triple-bond functionality with diazide-containing biphenyl through “click” chemistry generates AIE-active luminogens [1,1′-biphenyl]-4,4′-diyl bis(6-(4-(4-(1,2,2-triphenylvinyl)phenyl)-1H-1,2,3-triazol-1-yl) hexanoate) [1(5)] and [1,1′-biphenyl]-4,4′-diyl bis(11-(4-(4-(1,2,2-triphenylvinyl)phenyl)-1H-1,2,3-triazol-1-yl) undecanoate) [1(10)] with solid state efficiencies up to unity. Slow addition of dilute THF solutions of 1(m) (m = 5, 10) into nonsolvents such as n-hexane and water yields self-assembled white wooly solids. TEM and SEM observations reveal the (helical) nanofibrous structure of the aggregates. Upon cooling from their concentrated hot solutions, 1(m) readily precipitate. Meanwhile, they can also form gels at high concentrations. Both precipitates and gels of 1(m) exhibit structures similar to those of the aggregates formed in nonsolvents. These results indicate that 1(m) can facilely self-assemble into high emission efficiency (helical) nanofibers, thus paving the way for their optoelectronic and biological applications.

AIE-active, highly thermally and morphologically stable, mechanochromic and efficient solid emitters for low color temperature OLEDs

Low color temperature (CT) lighting sources such as candle light are of significant importance to human health owing to their remarkably low suppression effect on the secretion of melatonin, which helps people relax. As an alternative to hydrocarbon-burning candles, spark- and smog-free low CT organic light-emitting diodes (OLEDs) are highly desired. So far, however, low CT OLEDs are mainly fabricated by doping technology with several rare-metal complexes and multiple emissive layers. Metal-free and non-doped low CT OLEDs remain challenging due to the notorious aggregation-caused quenching (ACQ) effect of traditional chromophores. In this contribution, two luminogens, namely BPA2TPAN and BNA2TPAN, consisting of bisarylamine and two triphenylacrylonitrile (TPAN) units, were designed and synthesized. Both luminogens exhibit typical aggregation-induced emission (AIE) characteristics with high solid-state efficiency up to 47.7%. They also possess high thermal stability and outstanding morphological stability as well as obvious mechanochromism. Non-doped OLED devices of the luminogens show physiologically friendly orange light (603, 606 nm) with low CT values of 2093 and 1883 K, which are much lower than those of incandescent bulbs (2000–2500 K) or even candles (∼1900 K), whereas their doped OLED devices emit yellow light (551, 559 nm) with significantly improved performance, whose maximal power, current and external quantum efficiencies are 8.3 lm W−1, 12.2 cd A−1 and 4.2%, respectively. These results suggest that AIE luminogens are suitable to fabricate metal-free and non-doped low CT OLEDs with rational molecular design; meanwhile, their electroluminescence can be easily modulated through doping technology.

Room temperature phosphorescence from natural products：Crystallization matters

Efficient room temperature phosphorescence is observed in natural compounds and polymers such as starch, cellulose, bovine serum albumin (BSA), and some other carbohydrates. Whereas being practically nonluminescent in solutions and TLC plates, they emit bright phosphorescence in the crystalline states with lifetime up to microseconds, exhibiting crystallization-induced phosphorescence (CIP) characteristics. The CIP of these natural products without any conventional chromophores offers a new platform for the exploration of conceptually novel luminogens.

Clustering‐Triggered Emission of Nonconjugated Polyacrylonitrile

Intrinsic emission from nonconjugated polymers has attracted considerable attention owing to its fundamental importance and intensive applications in diverse fields. The emission mechanism, however, is still in debate. Herein, nonconjugated polyacrylonitrile (PAN) molecules are found to be virtually nonluminescent in dilute solutions, while being highly emissive when concentrated or aggregated as nanosuspensions, solid powders, and films, exhibiting distinct aggregation-induced emission (AIE) characteristics. Moreover, triplet emissions of delayed fluorescence and room temperature phosphorescence are detected from the solid powders. Such unique emission of nonconjugated PAN is ascribed to the formation of cyano clusters, which act as the exact chromophores. In these clusters, through space electronic interactions, namely overlap of π and lone pair (n) electrons among cyano groups extend the conjugation and meanwhile rigidify the molecular conformations, thus offering remarkable emission upon irradiation. The AIE phenomenon can also be well rationalized by the formation of cyano clusters together with conformation rigidification. And the triplet emissions shall be originated from the n-π* transition owing to the presence of lone pairs. It is believed that such clustering-triggered emission mechanism is instructive for further development of unorthodox luminogens.

A gelable pure organic luminogen with fluorescence-phosphorescence dual emission

Pure organic luminogens with room temperature phosphorescence (RTP) have drawn much attention due to their fundamental importance and promising applications in optoelectronic devices, bioimaging, sensing, etc. Fluorescence-phosphorescence dual emission at room temperature, however, is rarely observed in pure organic materials. Herein, we reported a metal- and heavy-atom free pure organic luminogen with tert-butyl groups, DtBuCZBP, which is ready to form organogels in dimethylsulfoxide (DMSO). It emits prompt and delayed fluorescence, as well as RTP, namely dual emission in as-prepared solid, gels and polymeric films. To the best of our knowledge, it is the first example of metal- and heavy-atom free pure organic gelator with RTP emission. Such unique RTP and moreover dual emission properties in different states make DtBuCZBP a potential material for diverse applications.

Adsorption of hexavalent chromium onto sisal pulp/polypyrrole composites

Sisal pulp/polypyrrole composites(SP/PPy) utilized for the removal of hexavalent chromium [Cr(VI)] from wastewater, were prepared via in-situ chemical oxidation polymerization approach. The structure and morphology of the SP/PPy were analyzed by polarizing optical microscopy (POM), field-emission scanning electron microscopy (SEM)), Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), the results indicated SP could be efficient dispersion of PPy. The hexavalent chromium adsorption results indicate adsorption capacity of the SP/PPy were dependent on the initial pH, with an optimum pH of 2.0. The sorption kinetic data fitted well to the pseudo-second order model and isotherm data fitted well to the Langmuir isotherm model. The maximum adsorption capacity determined from the Langmuir isotherm is 336.70 mg/g at 25° C.

AIE-active polyanetholesulfonic acid sodium salts with room-temperature phosphorescence characteristics for Fe3+ detection

Room-temperature phosphorescent materials have been a major focus of research and development during the past decades, due to their applications in OLEDs, photovoltaic cells, chemical sensors, and bioimaging. However, achieving polymeric phosphorescent materials without heavy-metal atoms and halogens under ambient conditions remains a major challenge. Here, we report a polymeric phosphor, namely polyanetholesulfonic acid sodium salt, which not only has room temperature phosphorescence characteristic but also aggregation-induced emission and dependence on the excitation wavelength characteristics. Moreover, it can recognize Fe3+ effectively.

Superhydrophobic Melamine Sponge Coated with Striped Polydimethylsiloxane by Thiol–Ene Click Reaction for Efficient Oil/Water Separation

Superhydrophobic and oleophilic sponges have been demonstrated as promising candidates for oil/water separation. However, there are still challenges in large-scale fabrication of superhydrophobic sponges with low cost and feasible method for industrial applications. Herein, we report a superhydrophobic and oleophilic melamine sponge functionalized by a uniform polydimethylsiloxane (PDMS) film that can be easily coated onto the sponge skeleton through UV-assisted thiol–ene click reactions. The PDMS films are characterized by a hierarchically striped microstructure with an average distance less than 2 μm. Because of the striped microstructure and the hydrophobic property of silicone, a high contact angle of 156.2° was achieved. Importantly, the interconnected open-cell structure of the melamine sponge was preserved by adapting the thickness of the PDMS film. The PDMS-coated melamine sponge exhibited a desirable absorption capacity of 103–179 times its own weight with oils and organic solvents. The excellent mechanical properties of melamine and the flexibility of PDMS enable the PDMS-coated melamine sponges to be squeezed repeatedly without collapsing. This study offers a robust and effective approach in large-scale preparation of a superhydrophobic sponge for large-scale oil spill containment and environmental remediation by the inexpensive commercial polymethylvinylsilicone and facile dip-coating/UV-curing method.