A Dual-Fluorescent Composite of Graphene Oxide and Poly(3-Hexylthiophene) Enables the Ratiometric Detection of Amines

A composite prepared by grafting a conjugated polymer, poly(3-hexylthiophene) (P3HT), to the surface of graphene oxide was shown to result in a dual-fluorescent material with tunable photoluminescent properties. Capitalizing on these unique features, a new class of graphene-based sensors that enables the ratiometric fluorescence detection of amine-based pollutants was developed. Moreover, through a detailed spectroscopic study, the origin of the optical properties of the aforementioned composite was studied and was found to be due to electronic decoupling of the conjugated polymer from the GO. The methodology described herein effectively overcomes a long-standing challenge that has prevented graphene based composites from finding utility in sensing and related applications.Meng, Dongli, Shaojun Yang, Dianming Sun, Yi Zeng, Jinhua Sun, Yi Li, Shouke Yan, Yong Huang, Christopher W. Bielawski, and Jianxin Geng. "A dual-fluorescent composite of graphene oxide and poly (3-hexylthiophene) enables the ratiometric detection of amines." Chemical Science 5, no. 8 (Apr., 2014): 3130-3134.Chemistr

1,3,5-Triazine-functionalized thermally activated delayed fluorescence emitters for organic light-emitting diodes

D.S acknowledges support from the Royal Academy of Engineering Enterprise Fellowship (EF2122-13106). This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłødowska-Curie grant agreements No. 897098 (AIE-RTP-PLED). T.W. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship. C.S. acknowledges support from the China Scholarship Council (201806890001). The authors thank the EPSRC (EP/P010482/1) for financial support.The 1,3,5-triazine electron acceptor has become one of the most popular building blocks for the design of thermally activated delayed fluorescence (TADF) materials. Many TADF design strategies are first applied in compounds that contain triazines, and there are numerous examples of organic light-emitting diodes (OLEDs) with triazine-containing emitters that show high efficiencies and long operating lifetimes. A comprehensive review of triazine-containing TADF emitters is provided. This review is organized according to the triazine-derived structural motifs, such as number and position of electron-donor groups in donor?acceptor-type emitters, the π-bridging linkers employed, orientation control of the transition dipole moment, and the design of chiral and through-space charge-transfer emitters. The structure of the compounds with their optoelectronic properties and the corresponding performance of the OLED devices is correlated.Publisher PDFPeer reviewe

Arylsilanes and siloxanes as optoelectronic materials for organic light-emitting diodes (OLEDs)

Organic light emitting diodes (OLEDs) are currently receiving much attention for applications in new generation full-colour flat-panel and flexible displays and as sources for low energy solid-state lighting. Arylsilanes and siloxanes have been extensively studied as components of OLEDs, mainly focusing on optimizing the physical and electronic properties of the light-emitting layer and other functional layers within the OLED architecture. Arylsilanes and siloxanes display the advantages of good solubility in common organic solvents and excellent resistance to thermal, chemical and irradiation degradations. In this review, we summarize the recent advances in the utilization of arylsilanes and siloxanes as fluorophore emitters, hosts for phosphor emitters, hole and exciton blocking materials, and as electron and hole transporting materials. Finally, perspectives and challenges related to arylsilanes and siloxanes for OLED applications are proposed based on the reported progress and our own opinions

The influence of nitrogen doping of the acceptor in orange–red thermally activated delayed fluorescence emitters and OLEDs

Funding: C. Si thanks the China Scholarship Council (201806890001). D.S acknowledges support from the Royal Academy of Engineering Enterprise Fellowship (EF2122-13106). The St Andrews team thanks EPSRC for financial support (EP/P010482/1). X.-H. Zhang acknowledges support from the National Natural Science Foundation of China (Grant Nos. 52130304, 51821002), Suzhou Key Laboratory of Functional Nano & Soft Materials, Collaborative Innovation Center of Suzhou Nano Science & Technology, the 111 Project.Nitrogen-containing polycyclic aromatic hydrocarbons (N-PAH) have been widely used as deep lowest unoccupied molecular orbital (LUMO) acceptors in donor-acceptor (D-A) red thermally activated delayed fluorescent (TADF) emitters and their use in organic light-emitting diodes. However, most of the studies have focused disparately on donor/acceptor combinations to yield efficient emitters, while it is rare that there is a methodological study to investigate the influence of the nitrogen (N) doping ratios on the ground and excited states of PAH acceptors. Here, we report a family of four different N-PAH acceptors containing different numbers of nitrogen atoms within the N-PAH and their use in D-A TADF emitters, DMACBP, DMACPyBP, DMACBPN and DMACPyBPN, when coupled to the same donor, 9,9-dimethyl-9,10-dihydroacridine (DMAC). As the nitrogen content in the acceptor increases the LUMO becomes progressively more stabilized while the singlet-triplet energy gap (ΔEST) decreases and the rate constant for reverse intersystem crossing (kRISC) increases. In particular, introducing nitrogen at the 10-position of the dibenzo[a,c]phenazine (BP) leads to a more than ten-fold enhancement in kRISC in DMACPyBP and DMACPyBPN compared to DMACBP and DMACBPN. Among the OLEDs with all four emitters that with DMACBPN demonstrates the highest EQEmax of 19.4% at an emission peak of 588 nm. while the deepest red emitting device employed DMACPyBPN (λEL = 640 nm) with an EQEmax of 5.4%.Publisher PDFPeer reviewe

Rational molecular design of efficient yellow-red dendrimer TADF for solution-processed OLEDs : a combined effect of substitution position and strength of the donors

Funding: Changfeng Si thanks the China Scholarship Council (201806890001). Dianming Sun acknowledges support from the Royal Academy of Engineering Enterprise Fellowship (EF2122-13106). We thank EPSRC (EP/W015137/1, EP/W524505/1) for financial support. Open Access funding enabled and organized by Projekt DEAL.The development of high-performance solution-processed red organic light-emitting diodes (OLEDs) remains a challenge, particularly in terms of maintaining efficiency at high luminance. Here, we designed and synthesized four novel orange-red thermally activated delayed fluorescence (TADF) dendrimers that are solution-processable: 2GCzBP , 2DPACzBP , 2FBP2GCz and 2FBP2DPACz . We systematically investigated the effect of substitution position and strength of donors on the optoelectronic properties. The reverse intersystem crossing rate constant (kRISC) of the emitters having donors substituted at positions 11 and 12 of the dibenzo[a,c]phenazine (BP) is more than 10-times faster than that of compounds substituted having donors substituted at positions 3 and 6. Compound 2DPACzBP , containing stronger donors than 2GCzBP , exhibits a red-shifted emission and smaller singlet-triplet energy splitting, ΔEST, of 0.01 eV. The solution-processed OLED with 10 wt% 2DPACzBP doped in mCP emitted at 640 nm and showed a maximum external quantum efficiency (EQEmax) of 7.8%, which was effectively maintained out to a luminance of 1,000 cd m−2. Such a device∙s performance at relevant display luminance is among the highest for solution-processed red TADF OLEDs. The efficiency of the devices was improved significantly by using 4CzIPN as an assistant dopant in a hyperfluorescence (HF) configuration, where the 2DPACzBP HF device shows an EQEmax of 20.0% at λEL of 605 nm and remains high at 11.8% at a luminance of 1,000 cd m−2, which makes this device one of the highest efficiency orange-to-red HF SP-OLEDs to date.Peer reviewe

A versatile hybrid polyphenylsilane host for highly efficient solution-processed blue and deep blue electrophosphorescence

A universal hybrid polymeric host (PCzSiPh) for blue and deep blue phosphors has been designed and synthesized by incorporating electron-donating carbazole as pendants on a polytetraphenylsilane main chain. The polymer PCzSiPh (4) has a wide bandgap and high triplet energy (ET) because of the tetrahedral geometry of the silicon atom in the tetraphenylsilane backbone. The distinct physical properties of good solubility, combined with high thermal and morphological stability give amorphous and homogenous PCzSiPh films by solution processing. As a result, using PCzSiPh as host with the guest iridium complex TMP-FIrpic gives blue phosphorescent organic light-emitting diodes (PhOLEDs) with overall performance which far exceeds that of a control device with poly(vinylcarbazole) (PVK) host. Notably, FIrpic-based devices exhibit a maximum external quantum efficiency (EQE) of 14.3% (29.3 cd A−1, 10.4 lm W−1) which are comparable to state-of-the-art literature data using polymer hosts for a blue dopant emitter. Moreover, the versatility of PCzSiPh extends to deep blue PhOLEDs using FIr6 and FCNIrpic as dopants, with high efficiencies of 11.3 cd A−1 and 8.6 cd A−1, respectively

Efficient orange organic light-emitting diodes employing a central aniline bridged multiresonant thermally activated delayed fluorescence emitter

Funding: S. W. and J. X. W. thank the China Scholarship Council (201906250199, 202006250026) for support. Dianming Sun acknowledges support from the Royal Academy of Engineering Enterprise Fellowship (EF2122-13106). E. Z.-C. thanks the Engineering and Physical Sciences Research Council (EP/W015137/1, EP/W007517/1). X.-H. Z. acknowledges support by the National Natural Science Foundation of China (Grant No. 52130304, 51821002) and the Collaborative Innovation Center of Suzhou Nano Science & Technology.Multiresonant thermally activated delayed fluorescence (MR-TADF) compounds are attractive for use in organic light-emitting diodes as they show narrowband emission, are bright, and can harvest both singlet and triplet excitons for the emission of light. Reflected in the paucity of examples of orange-to-red emitters, developing MR-TADF emitters that emit beyond the green remains an outstanding materials design challenge. In this work, we report one of the first carbonyl-based orange MR-TADF emitters, DDiKTa-A , which is based on the dimerization of the sky-blue emitting DiKTa through a central aniline bridge. DDiKTa-A emits at λPL of 562 nm and has high photoluminescence quantum yield of 92% in 2 wt% doped films in mCP. DDiKTa-A exhibits temperature dependent steady-state photoluminescence in 2-MeTHF, acting as an indirect indicator of the polarity of the medium. The OLEDs with DDiKTa-A showed an EQEmax of 20.3%, but with significant efficiency roll-off (EQE100 of 13.2%). The EQEmax was improved, and the efficiency roll-off mitigated by incorporating an assistant dopant, 4CzIPN, within the emissive layer of the device. The hyperfluorescence device showed an EQEmax of 24.3%, which decreased to 22.5 and 14.6% at 100 and 1000 cd m−2, respectively.Peer reviewe

Thermally activated delayed fluorescent dendrimers that underpin high-efficiency host-free solution-processed organic light emitting diodes

This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreements No. 838009 (TSFP) and No 812872 (TADFlife). D.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship (TSFP), the National Postdoctoral Program for Innovative Talents (BX201700164), and the Jiangsu Planned Projects for Postdoctoral Research Funds (2018K011A). S.B. acknowledges support from the German Science Foundation (392306670/HU2362). The St Andrews team thank the Leverhulme Trust (RPG2016047) and EPSRC (EP/P010482/1) for financial support. X.Z. would like to thank the support from the National Key Research & Development Program of China (Grant No. 2020YFA0714601, 2020YFA0714604), the National Natural Science Foundation of China (Grant No. 52130304, 51821002), Suzhou Key Laboratory of Functional Nano & Soft Materials, Collaborative Innovation Center of Suzhou Nano Science & Technology, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the 111 Project, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices. E. Z.-C. is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089).The development of high-performance solution-processed organic light-emitting diodes (OLEDs) remains a challenge. An effective solution, highlighted in this work, is to use highly efficient thermally activated delayed fluorescence (TADF) dendrimers as emitters. Here, the design, synthesis, density functional theory (DFT) modeling, and photophysics of three triazine-based dendrimers, tBuCz2pTRZ , tBuCz2mTRZ , and tBuCz2m2pTRZ , is reported, which resolve the conflicting requirements of achieving simultaneously a small ΔEST and a large oscillator strength by incorporating both meta- and para-connected donor dendrons about a central triazine acceptor. The solution-processed OLED containing a host-free emitting layer exhibits an excellent maximum external quantum efficiency (EQEmax) of 28.7%, a current efficiency of 98.8 cd A−1, and a power efficiency of 91.3 lm W−1. The device emits with an electroluminescence maximum, λEL, of 540 nm and Commission International de l'Éclairage (CIE) color coordinates of (0.37, 0.57). This represents the most efficient host-free solution-processed OLED reported to date. Further optimization directed at improving the charge balance within the device results in an emissive layer containing 30 wt% OXD-7, which leads to an OLED with the similar EQEmax of 28.4% but showing a significantly improved efficiency rolloff where the EQE remains high at 22.7% at a luminance of 500 cd m−2.Publisher PDFPeer reviewe

Regiochemistry of donor dendrons controls the performance of thermally activated delayed fluorescence dendrimer emitters for high efficiency solution-processed organic light-emitting diodes

This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 838009 (TSFP) and No 812872 (TADFlife). D.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship, the National Postdoctoral Program for Innovative Talents (BX201700164), the Jiangsu Planned Projects for Postdoctoral Research Funds (2018K011A). E.Z.-C. is a Royal Society Leverhulme Trust Senior Research fellow (SRF∖R1∖201089). The St Andrews team would also like to thank the Leverhulme Trust (RPG-2016047) and EPSRC (EP/P010482/1) for financial support. This work was also supported by Comunidad de Madrid (Spain) – multiannual agreement with UC3M (“Excelencia para el Profesorado Universitario” – EPUC3M14) – Fifth regional research plan 2016-2020 and by the Spanish Ministry of Science, Innovation and Universities (MICINN) through project RTI2018-101020-B-100. X.Z. would like to thank the support from the National Key Research & Development Program of China (Grant No. 2020YFA0714601, 2020YFA0714604), the National Natural Science Foundation of China (Grant No. 52130304, 51821002), Suzhou Key Laboratory of Functional Nano & Soft Materials, Collaborative Innovation Center of Suzhou Nano Science & Technology, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the 111 Project, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices.The potential of dendrimers exhibiting thermally activated delayed fluorescence (TADF) as emitters in solution-processed organic light-emitting diodes (OLEDs) has to date not yet been realized. This in part is due to a poor understanding of the structure–property relationship in dendrimers where reports of detailed photophysical characterization and mechanism studies are lacking. In this report, using absorption and solvatochromic photoluminescence studies in solution, the origin and character of the lowest excited electronic states in dendrimers with multiple dendritic electron-donating moieties connected to a central electron-withdrawing core via a para- or a meta-phenylene bridge is probed. Characterization of host-free OLEDs reveals the superiority of meta-linked dendrimers as compared to the already reported para-analogue. Comparative temperature-dependent time-resolved solid-state photoluminescence measurements and quantum chemical studies explore the effect of the substitution mode on the TADF properties and the reverse intersystem crossing (RISC) mechanism, respectively. For TADF dendrimers with similarly small ∆EST, it is observed that RISC can be enhanced by the regiochemistry of the donor dendrons due to control of the reorganization energies, which is a heretofore unexploited strategy that is distinct from the involvement of intermediate triplet states through a nonadiabatic (vibronic) coupling with the lowest singlet charge transfer state.Publisher PDFPeer reviewe

Strigolactone alleviates the salinity-alkalinity stress of Malus hupehensis seedlings

Salinity-alkalinity stress can remarkably affect the growth and yield of apple. Strigolactone (SL) is a class of carotenoid-derived compounds that functions in stress tolerance. However, the effects and mechanism of exogenous SL on the salinity-alkalinity tolerance of apple seedlings remain unclear. Here, we assessed the effect of SL on the salinity-alkalinity stress response of Malus hupehensis seedlings. Results showed that treatment with 100 μM exogenous SL analog (GR24) could effectively alleviate salinity-alkalinity stress with higher chlorophyll content and photosynthetic rate than the apple seedlings without GR24 treatment. The mechanism was also explored: First, exogenous GR24 regulated the expression of Na+/K+ transporter genes and decreased the ratio of Na+/K+ in the cytoplasm to maintain ion homeostasis. Second, exogenous GR24 increased the enzyme activities of superoxide, peroxidase and catalase, thereby eliminating reactive oxygen species production. Third, exogenous GR24 alleviated the high pH stress by regulating the expression of H+-ATPase genes and inducing the production of organic acid. Last, exogenous GR24 application increased endogenous acetic acid, abscisic acid, zeatin riboside, and GA3 contents for co-responding to salinity-alkalinity stress indirectly. This study will provide important theoretical basis for analyzing the mechanism of exogenous GR24 in improving salinity-alkalinity tolerance of apple