Hectogram-Scale Synthesis of Visible Light Excitable Room Temperature Phosphorescence Carbon Dots.

Carbon dots (CDs) based room temperature phosphorescence (RTP) materials can be prepared via facile procedures and exhibit excellent photostability and biocompatibility. Furthermore, doping of hetero-atoms into CDs can afford multiple triplet levels. The RTP emission generated from the resultant CDs always displays outstanding dynamic behaviors and even can be efficiently excited by visible light. Given this, CDs-based RTP materials not only can be used for anti-counterfeiting but also exhibit great application potential in signage and illumination fields. In this contribution, a type of B, N, and P co-doped CDs are prepared in hectogram scale. Upon excitation by UV lamp and white LED, the obtained CDs emit green and yellow RTP, respectively, the lifetime of which are 851 and 481 ms, respectively. It is found that the luminescence color of the CDs can be further tuned. By controlling the degree of carbonization, the RTP color of the CDs can be facilely tuned from green to orange-red. Based on an energy transfer strategy, the luminescence color can be further tuned to red. Benefited from the dynamic and visible-excited colorful RTP emission, the application of these obtained CDs in anti-counterfeiting, fingerprint collection, and luminescent traffic signage are also explored.

Photoinduced On and Off Polymeric Room Temperature Phosphorescence Based On Polycyclic Aromatic Hydrocarbon Isomers.

As family members of polycyclic aromatic hydrocarbons, compound anthracene (Ant) and phenanthrene (Phe) as isomers are widely used in organic optical materials and electronic materials. But their photochemical and physical properties are very different. In this work, the room temperature phosphorescence (RTP) properties of PVA-B-Ant and PVA-B-Phe are discussed carefully which are prepared by B-O click reaction through polyvinyl alcohol (PVA) with 9-anthraceneboronic acid (B-Ant) and 9-phenanthrenylboronic acid (B-Phe), respectively. PVA-B-Phe 1% film exhibits excellent fluorescence (FL) emission at 374 nm and RTP emission at 523 nm with green afterglow and around 1.9 s phosphorescence lifetime. However, PVA-B-Ant 1% film only shows strong blue FL emission at 414 nm, and the emission intensity decreases seriously with the extension of irradiation time. Experimental and theoretical calculations results suggest that the photodimer of Ant which is formed in PVA matrix under the UV light irradiation would be competitive with the process of RTP emission. This work demonstrates that the RTP properties of organic molecules might be probably affected by the photostability of the organic phosphor under UV irradiation.

Long-Lived Dynamic Room Temperature Phosphorescence from Carbon Dots Based Materials.

As a type of room temperature phosphorescence (RTP) material, carbon dots (CDs) always show short lifetime and low phosphorescence efficiency. To counter these disadvantages, several strategies, such as embedding in rigid matrix, introducing of heteroatom, crosslink-enhanced emission, etc., are well developed. Consequently, lots of CDs-based RTP materials are obtained. Doping of CDs into various matrix is the dominant method for preparation of long-lived CDs-based RTP materials so far. The desired CDs@matrix composites always display outstanding RTP performances. Meanwhile, matrix-free CDs and carbonized polymer dots-based RTP materials are also widely developed. Amounts of CDs possessing ultra-long lived, multiple colored, and dynamic RTP emission are successfully obtained. Herein, the recent progress achieved in CDs-based RTP materials as well as the corresponding efficient strategies and emission mechanisms are summarized and reviewed in detail. Due to CDs-based RTP materials possess excellent chemical stability, photostability and low biological toxicity, they exhibit great application potential in the fields of anti-counterfeiting, data encryption, and biological monitoring. The application of the CDs-based RTP materials is also introduced in this review. As a promising functional material, development of long wavelength RTP emitting CDs with long lifetime is still challengeable, especially for the red and near-infrared emitting RTP materials.

Cross-Linked Polyphosphazene Nanospheres Boosting Long-Lived Organic Room-Temperature Phosphorescence.

Long-lived organic room-temperature phosphorescence (RTP) has sparked intense explorations, owing to the outstanding optical performance and exceptional applications. Because triplet excitons in organic RTP experience multifarious relaxation processes resulting from their high sensitivity, spin multiplicity, inevitable nonradiative decay, and external quenchers, boosting RTP performance by the modulated triplet-exciton behavior is challenging. Herein, we report that cross-linked polyphosphazene nanospheres can effectively promote long-lived organic RTP. Through molecular engineering, multiple carbonyl groups (C═O), heteroatoms (N and P), and heavy atoms (Cl) are introduced into the polyphosphazene nanospheres, largely strengthening the spin-orbit coupling constant by recalibrating the electronic configurations between singlet (Sn) and triplet (Tn) excitons. In order to further suppress nonradiative decay and avoid quenching under ambient conditions, polyphosphazene nanospheres are encapsulated with poly(vinyl alcohol) matrix, thus synchronously prompting phosphorescence lifetime (173 ms longer), phosphorescence efficiency (∼12-fold higher), afterglow duration time (more than 20 s), and afterglow absolute luminance (∼19-fold higher) as compared with the 2,3,6,7,10,11-hexahydroxytriphenylene precursor. By measuring the emission intensity of the phosphorescence, an effective probe based on the nanospheres is developed for visible, quantitative, and expeditious detection of volatile organic compounds. More significantly, the obtained films show high selectivity and robustness for anisole detection (7.1 × 10-4 mol L-1). This work not only demonstrates a way toward boosting the efficiency of RTP materials but also provides a new avenue to apply RTP materials in feasible detection applications.

Synthesis and biological evaluation of vanadium complexes as novel anti-tumor agents.

A class of vanadium complexes were prepared and investigated for their antiproliferative effects by MTT assay. The structure-activity relationship was extensively studied through the ligand variation. The results showed that the synthetic vanadium complexes demonstrated moderate to good antiproliferative activities against the four cancer cell lines including MGC803, EC109, MCF7 and HepG2, respectively. Of note was that most of the complexes showed preferential growth inhibitory activity to some degree toward gastric cancer line MGC803. Among them, complex 19 exhibited the most and broad-spectrum proliferative inhibition against the tested cell lines. In addition, mechanism studies illustrated that complex 19 could prevent the colony formation, migration and EMT process, as well as induce apoptosis of MGC803 cells. Furthermore, Western blot experiments revealed that the expression of apoptosis-related proteins changed, including up-regulation of Bax, PARP and caspase-3/9, as well as down-regulation of Bcl-2.

Facile, Efficient Copolymerization of Ethylene with Norbornene-Containing Dienes Promoted by Single Site Non-Metallocene Oxovanadium(V) Catalytic System.

Non-metallocene oxovanadium(V) complexes bearing either [ONNO]-type amine pyridine bis(phenolate) ligands or [ONN]-type amine pyridine phenolate ligands were employed as efficient catalysts to copolymerize ethylene with several unsymmetrical norbornene-containing dienes, such as 5-vinyl-2-norbornene (VNB), 5-ethylidene-2-norbornene (ENB) or dicyclopentadiene (DCPD), producing copolymers with high comonomer incorporations (VNB: 33.0 mol %; ENB: 30.4 mol %; DCPD: 31.6 mol %, respectively) and high molecular weight (VNB: 86.4 kDa; ENB: 256 kDa; DCPD: 86.4 kDa, respectively). The enchainment of the dienes was proven to be exclusive of vinyl-addition via the C=C double bond of the norbornene ring while the other double bond was retained near the backbone without crosslinking. During the copolymerization of ethylene with ENB, a positive 'comonomer effect' was observed. The catalytic activities of the catalysts as well as the molecular weights and comonomer incorporations of the resultant copolymers could be tuned within a wide range by varying the structures of the catalysts and copolymerization conditions. The [ONN]-type oxovanadium(V) complexes showed higher catalytic activities than those of [ONNO]-type oxovanadium(V) complexes, irrespective of the structure of the dienes. In addition, the dominant chain transfer pathway of the non-metallocene oxovanadium(V) catalytic system promoted copolymerization was proven to be transfer to aluminum compounds.

Novel zirconium complexes with constrained cyclic ß-enaminoketonato ligands: improved catalytic capability toward ethylene polymerization.

Novel Zr(iv) and Hf(iv) complexes bearing two constrained bulky ß-enaminoketonato ligands {[ArN[double bond, length as m-dash]CH-C8H3(CH2)n(R)O]2MBn2, M = Zr or Hf; n = 1, 2 or 3; R = H or C6H5; Ar = C6H5 or C6F5} were synthesized and clearly characterized. X-ray crystal structure analysis reveals that these complexes adopt a distorted octahedral geometry. Compared with non-constrained analogues, the Zr(iv) complexes with a cyclic skeleton exhibited high catalytic activities (up to 16.4 kgPE mmolZr(-1) h(-1)) toward ethylene polymerization at ambient pressure and elevated temperatures. Moreover, the catalytic properties of these complexes could be governed exquisitely by appropriate variation of the N-aryl substituents and the size of the benzocyclane. The Zr(iv) complexes bearing a non-fluorinated N-aryl group yielded oligomers, while the fluorinated analogues bearing a five-membered or six-membered cyclane group produced high molecular weight polyethylenes (33.4-306 kg mol(-1)) under similar conditions on account of the suppression effects on ß-H elimination. The Zr(iv) complexes are more active toward ethylene polymerization than the Hf(iv) analogues, and the resulting polymers exhibited higher molecular weight and narrower molecular weight distribution.