Emissive Polymer Research Articles

Mechanistic insight into Pb2+ and Hg2+ ion sensing using cobalt-based coordination polymer in aqueous phase.

Emissive inorganic-organic hybrid materials open up a new prospect of fast and efficient heavy metal ion sensing in an aqueous medium. Here, we demonstrate highly sensitive lead(II) ion detection attributed to excited-state host-guest interaction, where mercury(II) shows lesser quenching efficiency due to both ground- and excited-state interaction.

Tunable emissive carbon polymer dots with solvatochromic behaviors for trace water detection and cell imaging

The solvatochromic behavior of CPDs in aprotic or protic solvents affected by hydrogen bonding (R = H, alkyl chain), which can be applied in trace water detection and multi-color imaging.

A benzothiadiazole-based Pt(II) coordination polymer as an efficient heterogeneous photocatalyst for visible-light-driven aerobic oxidative coupling of amines.

An emissive Pt(II) coordination polymer (TBP) was synthesized by assembling a benzothiadiazole-based Pt(II) acceptor (A) with a tetraphenylethene (TPE) containing donor (L). Multiple benzothiadiazole units in the polymeric array of the TBP rendered it with reactive oxygen species generation ability. TBP was found to be an excellent photocatalyst for oxidative coupling of benzylamine under visible light with full conversion within 2 hours at room temperature and reusability for multiple cycles. Such photocatalytic efficiency under ambient conditions, reusability of the catalyst, and easy separation of the product are noteworthy.

Emissive lanthanide dicyanoaurate coordination polymers with 2,2′-bipyridine dioxide antenna groups and their hydration states

Ln–Au(CN)2-based coordination polymers with 2,2′-bipyridine dioxide ligands in several hydration states show aurophilic interactions, hydrogen bonding and high quantum yields for Ln = Eu and Tb, which decrease with a lowering of the hydration level.

Pioneering research on blue "hot exciton" polymers and their application in solution-processed organic light-emitting diodes.

An innovative novel category of polymeric hybridized local and charge-transfer (HLCT) blue materials prepared via solution processing has yet to be reported. This study introduces three polymers, namely PZ1, PZ2, and PZ3, incorporating donor-acceptor-donor (D-A-D) structures with carbazole functioning as the donor and benzophenone as the acceptor. To regulate the luminescence mechanism and conjugation length, carbonyl and alkyl chains are strategically inserted into the backbone. Theoretical calculation and transient absorption spectroscopy illustrate that the robust spin-orbit coupling between high-lying singlet excited states (Sm: m ⩽ 4) and triplet excited states (Tn: n ⩽ 7) of the polymers hastens and significantly heightens the efficiency of reverse intersystem crossing processes from Tn states. Furthermore, the existence of multiple degenerated frontier molecular orbits and significant overlaps between Tn and Sm states give rise to added radiative pathways that boost the radiative rate. This study marks a fundamental and initial manifestation of HLCT materials within the polymer field and provides a new avenue for the design of highly efficient polymeric emitters.

Effect of the cyano group on colour-tunability of aryl-substituted buta-1,3-diene based solid-state emissive copolymers

Solid-state emissive copolymers with varying cyano groups have been developed and are utilised for the PLED device applications to demonstrate the effect of acceptor strength.

Cs-Symmetric, Peripherally Fluorinated Boron Subphthalocyanine–Subnaphthalocyanine Hybrids: Shedding New Light on Their Fundamental Photophysical Properties and Their Functionality as Optoelectronic Materials

Hybridization of boron subphthalocyanine (BsubPc) and boron subnaphthalocyanine (BsubNc) has been modestly explored in the past, and was therefore carried out herein to access a subclass of these chromophores denoted as Ra-FxBsub(Pc3–p-Ncp) hybrids, where Ra is the axial halide substituent (axial chloride, Cl-, or axial fluoride, F-), x = 8, and p = 1. These chromophores were targeted as new candidate materials for organic electronic applications due to their Cs symmetry, in-plane dipole moment, and unique photophysical properties. Cl-/F- F8Bsub(Pc2-Nc1) hybrids were compared to Cl-/F- F8BsubPc hybrids, which are analogous compounds with an identical number of peripheral fluorine atoms but lower degree of π-conjugation. Upon photoexcitation of dilute toluene solutions and doped thin films with polystyrene as a nonemissive host, F8Bsub(Pc2-Nc1) hybrids exhibited distinctively broad absorption spectra and narrow emission profiles with red-shifted peak photoluminescence wavelengths in the 618–623 nm region compared to F8BsubPc hybrids (581–584 nm). Electroluminescence properties were probed in simple solution-cast organic light-emitting diodes (OLEDs) in which all four hybrids were diluted within an F8BT emissive polymer host. Upon electronic excitation, electroluminescence (EL) of Cs-symmetric hybrids followed the same trends as photoluminescence (PL), with OLED devices displaying narrow EL in the orange region (588–592 nm) for F8BsubPc hybrids and in the near-red region for F8Bsub(Pc2-Nc1) hybrids (627–632 nm). The photophysical processes important to OLEDs moderately improved with less π-conjugation in the periphery of the Cs-symmetric hybrids [F8Bsub(Pc2-Nc1) vs F8BsubPc; EQEMax: 0.099% vs 0.129%; luminance: 500 cd/m2 vs 1000 cd/m2 at maximum current density; relative PL quantum yields (QYs) ≈ 17–22% vs ≈ 35–44%]. Electrochemical data showed that Cs symmetry introduces reversibility or quasi-reversibility in the oxidation regime at potentials >1 V, and peripheral fluorination enables reversibility in the reduction process. Overall, F8Bsub(Pc2-Nc1) hybrids embody several unique physical characteristics into one: broad absorption spectra (full width at half-maximum height, FWHMsolabs = 53–55 nm, FWHMfilmabs = 71 nm), narrow near-red electroluminescence (FWHMOLEDEL = 33 nm), and photoluminescence (FWHMsolPL = 25–26 nm, FWHMfilmPL = 32 nm) emission, small energy band gaps (1.95–1.96 eV), high extinction coefficients (ε ≈ (5.65–6.16) × 104 M–1 cm–1), and dual electrochemical versatility. These results provide new physical insights into the material properties of Cs-symmetric macrocycles and advance the consideration of F8Bsub(Pc2-Nc1) and F8BsubPc hybrids for optoelectronic applications.

Rational design of AIE-active biodegradable polycarbonates for high-performance WLED and selective detection of nitroaromatic explosives

Luminescent polymers have garnered considerable research attention for their excellent properties and wide range of applications in multi-responsive materials, bioimaging, and photoelectric devices. Thereout, various modulations of polymer structure are often the main approach to obtaining materials with different luminescent colors and functions. However, polymers with biodegradability, tunable color, and efficient emission simultaneously remain a challenge. Herein, we report a feasible strategy to achieve degradable and highly emissive polymers by exquisite combination and interplay of aggregation-induced emission (AIE) unit and environmental-friendly epoxide/CO2 copolymerization. A series of polycarbonates P-TEPxCNy (x = 0, 1, 2, 4, 30, 120; y = 0, 1) were prepared, with emission color changed from blue to yellow by controlling the proportion of two designed AIE-active monomers. Among them, Using P-TCN as emitting layer, high performance white light-emitting diode (WLED) device with an external quantum efficiency (EQE) of 26.09% and CIE coordinates of (0.32, 0.32) was achieved. In addition, the designed polymers can be used as selective sensors for nitroaromatic compounds in their nanoaggregate states.

Polymeric Emissive Materials Based on Dynamic Covalent Bonds.

Dynamic covalent polymers, composed of dynamic covalent bonds (DCBs), have received increasing attention in the last decade due to their adaptive and reversible nature compared with common covalent linked polymers. Incorporating the DCBs into the polymeric material endows it with advanced performance including self-healing, shape memory property, and so forth. However, the emissive ability of such dynamic covalent polymeric materials has been rarely reviewed. Herein, this review has summarized DCBs-based emissive polymeric materials which are classified according to the different types of DCBs, including imine bond, acylhydrazone bond, boronic ester bond, dynamic C-C bond, as well as the reversible bonds based on Diels–Alder reaction and transesterification. The mechanism of chemical reactions and various stimuli-responsive behaviors of DCBs are introduced, followed by typical emissive polymers resulting from these DCBs. By taking advantage of the reversible nature of DCBs under chemical/physical stimuli, the constructed emissive polymeric materials show controllable and switchable emission. Finally, challenges and future trends in this field are briefly discussed in this review.

Multi-stimuli responsive fluorescence switching behaviours of AIE polymers for acid-base vapour sensing and highly sensitive ferric ion detection

Novel aggregation-induced emission (AIE) polymers, i.e., P1-SP and P2-SP, consisting of AIEgenic tetraphenylethylene (TPE) and photochromic spiropyran (SP) units are reported. Both P1-SP and P2-SP exhibit excellent AIE behaviours of TPE moieties in near-aqueous solutions THF/H2O (95% water) and solid states with strong cyan and blue emissions at 494 and 477 nm, respectively. Upon acidification, the close forms of P1-SP and P2-SP can be opened and switched to open P1-MCH+ and P2-MCH+ structures of protonated merocyanine (MCH+), resulting in fluorescence quenching of TPE units through corresponding intramolecular charge transfer (ICT) and Förster resonance energy transfer (FRET) processes. The fluorescence recovery of TPE can be monitored by the neutralization of P1-MCH+ and P2-MCH+ with base solutions under ambient/visible light attributed to the re-close P1-SP and P2-SP structures, which led to respective turn-off ICT and FRET phenomena. Distinct fluorescence quenching behaviours of P1-SP and P2-SP can be observed under various stimuli, including acid conditions and ferric ion interactions, which are also confirmed by theoretical studies. Moreover, P1-SP and P2-SP can be utilized as fluorescence quenching sensors for nanomolar level detections of ferric ion (LOD = 166 and 110 nM for corresponding P1-SP and P2-SP) with excellent selectivities in near-aqueous solutions and paper test strips. Additionally, the interesting visible and fluorescence colour changes of coated cellulosic papers, blended PMMA films and powder forms based on P1-SP and P2-SP under multi-external stimuli (acid-base vapour and visible light/heating processes) are also explored in this report.

An AIEgen-based hydrazone-linked covalent organic polymer for solid-state fluorescent materials

The construction of high quantum yield solid-state fluorescent materials is of great importance in preparing organic light-emitting devices. Herein we report an AIEgen-based emissive hydrazone-linked covalent organic polymer (TFBE-TD COP) prepared by a simple solid-state mechanochemical grinding method from 1,1,2,2-tetrakis(4-formyl-(1,1′-biphenyl))ethane (TFBE) and terephthalic tihydrazide (TD) at room temperature. The COP exhibits good emission and very high fluorescence quantum yield (ΦF = 37.7%) in the solid-state because of the synergistic effect of rigid skeleton structure and aggregation induction that restricts the relaxation of tetraphenylethylene (TPE) molecules in the TFBE-TD COP. TFBE-TD COP shows a rapid response and high sensitivity toward trifluoroacetic aid (TFA) gas with significant changes in visual color and luminescence, which could be recovered upon exposure to triethylamine vapor. And the TFBE-TD COP was further coated onto the blue LED to achieve white-light emission. The work provides a general method for preparing AIEgen-based COP and explores its applications in solid-state fluorescent materials for the sensing of toxic gases and the preparation of white LED, offering a new route to the design and application of AIEgen-based COPs.

Diketopyrrollopyrrole anchored carbazole-alt-thiophene based Fe3+-coordinated metallopolymer for the selective recognition of ATP

The emissive π-conjugated polymers are attractive candidates as sensory materials for environmentally and biologically relevant species. In this work, we report design and synthesis of carbazole-thiophene based A- alt -B type efficient fluorescent π-conjugated copolymer probe with diketopyrrollopyrrole units through Pd(II)-catalyzed Sonogashira polymerization from the respective monomers. The well-defined and soluble π-conjugated polymer has been characterized by multinuclear NMR spectra as well as tetradetector GPC studies, showing molecular weight (M w ) of 33.1 kDa. The emissive π-conjugated macromolecular probe consisting of the carbazole-thiophene backbone with diketopyrrolopyrrole ( P1 ) anchoring unit shows selectivity toward Fe 3+ ions inducing quenching of the fluorescence by ca. 72%. More interestingly, the resulting P1· Fe 3+ metallopolymer exhibits high sensitivity and selectivity toward adenosine 5′-triphosphate (ATP) over the other representative pyrophosphate anions. Most importantly, the probe discriminates it from adenosine 5′-diphosphate (ADP) and adenosine 5′-monophosphate (AMP), presumably due to the much stronger electrostatic interaction between polymer and ATP than the others. To understand the sensing mechanism, the detailed photophysical and sensing studies have been carried out to understand the insight of metallopolymer-ATP interaction, which is responsible for selective fluorescence enhancing of P1· Fe 3+ metallopolymer. The limit of detection of the metallopolymer probe towards ATP was found to be in the range of 7.92 × 10 −7 M (365 ppb) with a high association constant in the order of 1.96 × 10 5 M −1 . FLIM analysis and the time-resolved fluorescence anisotropy study have also been carried out to investigate molecular interaction between P1· Fe 3+ metallopolymer and ATP. • Design and synthesis of well-defined diketopyrrolopyrrole anchored carbazole-thiophene emissive polymers. • Selective and sensitive turn-off fluorescent probe for Fe 3+ . • Trace and selective detection of ATP in ppb level. • Efficient strategy to develop simple, sensitive and reusable fluorescent probe for biologically relevant species.

Realizing External Quantum Efficiency over 25% with Low Efficiency Roll-Off in Polymer-Based Light-Emitting Diodes Synergistically Utilizing Intramolecular Sensitization and Bipolar Thermally Activated Delayed Fluorescence Monomer

Realizing External Quantum Efficiency over 25% with Low Efficiency Roll-Off in Polymer-Based Light-Emitting Diodes Synergistically Utilizing Intramolecular Sensitization and Bipolar Thermally Activated Delayed Fluorescence Monomer

Blue light polymeric emitters for the development of OLED devices

Blue light polymeric emitters for the development of OLED devices

A NIR-II emissive polymer AIEgen for imaging-guided photothermal elimination of bacterial infection

The development of antibiotics resistance has made multidrug-resistant (MDR) bacterial infection one of the most serious global health issues. Photothermal therapy (PTT) is an emerging therapeutic mode which can be applied to bacterial infection without inducing resistance. Moreover, enhanced therapeutic efficacy and less tissue damage can be realized with NIR-II fluorescence imaging (FLI) guided PTT. Herein, a polymeric luminogen with aggregation-induced emission (AIEgens) characteristics, poly(dithieno[3,2-b:2′,3′-d]pyrrole-benzo[1,2-c:4,5-c']bis([1,2,5]thiadiazole)) (PDTPTBT), was synthesized and used as a photothermal agent for PTT of bacterial infections. PDTPTBT was encapsulated into liposomes (L-PDTPTBT) for improved water dispersibility. Upon 808 nm NIR irradiation, L-PDTPTBT can eliminate multiple bacteria including the Gram-positive methicillin-resistant Staphylococcus aureus and Enterococcus faecalis, the Gram-negative Escherichia coli and Pseudomonas aeruginosa. Serious damage of bacterial membrane and leakage of cytoplasm is observed after photothermal treatment using L-PDTPTBT. The potential of the formulation has been demonstrated in two infected animal models: (i) a subcutaneous abscess model and (ii) a diabetic skin infection model. In the diabetic skin infection model, the death of mice is largely suppressed and the wounds can heal more quickly with treatment of L-PDTPTBT under NIR irradiation. The excellent photothermal bactericidal ability and low cytotoxicity make L-PDTPTBT potential candidate for treating MDR bacterial infections in the future.

On-package ratiometric fluorescent sensing label based on AIE polymers for real-time and visual detection of fish freshness

Freshness is an important parameter of fish quality. This study aims to develop a ratiometric fluorescent sensing label that is responsive to volatile amines, affording real-time and visual detection of fish freshness. For developing of the sensing label, an aggregation-induced emissive (AIE) polymer was prepared from the stimuli-responsive polymer polymethacrylic acid and the AIE molecule tetraphenylethylene and coated on to filter paper with rhodamine B as an internal reference. By exploiting the ratiometric response, the freshness of fish could be identified clearly and easily according to the color of on-package label, which changes from pink (fresh) to dark blue. The difference was linearly correlated with the total volatile basic nitrogen (TVB-N, R2 = 0.995 and 0.994 at 25 °C and 4 °C, respectively) in the range of 15–25 mg/100 g for the salmon samples, which indicated that the sensing label feasibly and non-destructively quantified TVB-N.

Metal-Organic Frameworks in Mixed-Matrix Membranes for High-Speed Visible-Light Communication.

Mixed-matrix membranes (MMMs) based on luminescent metal-organic frameworks (MOFs) and emissive polymers with the combination of their unique advantages have great potential in separation science, sensing, and light-harvesting applications. Here, we demonstrate MMMs for the field of high-speed visible-light communication (VLC) using a very efficient energy transfer strategy at the interface between a MOF and an emissive polymer. Our steady-state and ultrafast time-resolved experiments, supported by high-level density functional theory calculations, revealed that efficient and ultrafast energy transfer from the luminescent MOF to the luminescent polymer can be achieved. The resultant MMMs exhibited an excellent modulation bandwidth of around 80 MHz, which is higher than those of most well-established color-converting phosphors commonly used for optical wireless communication. Interestingly, we found that the efficient energy transfer further improved the light communication data rate from 132 Mb/s of the pure polymer to 215 Mb/s of MMMs. This finding not only showcases the promise of the MMMs for high-speed VLC but also highlights the importance of an efficient and ultrafast energy transfer strategy for the advancement of data rates of optical wireless communication.

Fully Vacuum-Free Fabrication of Bi-Directional Polymer Light-Emitting Diodes Based on a Hybrid Lamination Top Electrode

This study investigates a hybrid lamination electrode based on a silver nanowire and a conductive polymer for the top electrode of bi-directional polymer light-emitting diodes (PLEDs). Through a vacuum-free hot-press lamination step, the proposed hybrid electrode employed a complete and concrete electrical contact with the underlying emissive polymer layer. In addition, by inserting a hole injecting poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer to increase the level of work function, the bi-directional PLED device with a laminated top electrode showed a more competitive device performance such as an operating voltage, a current efficiency, and a total external quantum efficiency compared to the counterpart device with a multilayered electrode of MoO3/Ag/MoO3 by the vacuum thermal evaporation method. An analysis carried out on the angular characteristics of bi-directional PLEDs including the variation of color coordinates and change in luminance values according to emission angles confirmed that the hybrid lamination electrode provided a more uniform angular distribution regardless of the direction of emission without any optical micro-cavity effect. Detailed optical and electrical analyses were also performed to evaluate the compatibility of the hybrid lamination electrode for the low-cost fabrication of efficient PLEDs.

Rubbed PFN−Br as an Alignment Layer for Liquid Crystalline Conjugated Polymer Chain Orientation**

AbstractWe report poly[(9,9‐bis(3’‐((N,N‐dimethyl)‐N‐ethylammonium)‐propyl)‐2,7‐fluorene)‐alt‐2,7‐(9,9‐dioctylfluorene)]dibromide (PFN−Br), a previously reported charge transfer interlayer for organic optoelectronic devices, as an orientation/alignment layer and rubbing as a means to achieve chain orientation for liquid crystalline conjugated polymers (LCCP). Polyfluorene and its derivatives, namely blue emission polymer poly(9,9‐dioctylfluorene) (PFO), green‐yellow emission polymer poly(9,9‐dioctylfluorene‐cobenzothiadiazole) (F8BT), and binary blend red emission polymer F8BT/Red F (Ref F=poly(triphenylamine‐co‐4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole‐co‐benzo[c]thiadiazole‐co‐9,9‐dioctyl‐9H‐fluorene)), demonstrated clear polarized absorption when PFN−Br was used as the orientation layer. We have studied the effects of rubbing times of a PFN−Br layer, and molecular weight, film thickness and annealing temperature of LCCP on the orientation degree. A high absorption anisotropy ratio of 12.22 was achieved for 106 nm thick F8BT film with a molecular weight of 55000 at the annealing temperature 265 °C, which is close to the theoretical limitation of the dichroic ratio of F8BT derived previously. Finally, we studied the amplified spontaneous emission (ASE) in chain oriented F8BT and PFO films. It showed that chain orientation made the ASE threshold anisotropic and lowers the threshold compared to the isotropic films if pumped under the favored configuration. This work provides a novel approach to reduce laser threshold and improve charge transfer simultaneously for electrically pumped devices when combined with the conductive property of PFN−Br.

Solution-processed light-emitting diodes consisting of metal-oxide and organic–inorganic hybrid emissive thin films

We prepared organic–inorganic hybrid emissive thin films using a simple sol-gel method containing an emissive polymer for improving the operating lifetime of organic materials. The hybrid films can be developed using a precursor solution of tetraethoxysilane (TEOS) and an emissive polymer. In the films, the emissive polymer is encapsulated in SiO2 and not exposed to the atmosphere, thus improving the photoluminescence lifetime of the hybrid films with this sealing effect. We also prepared vanadium pentoxide (V2O5) thin films using a vanadium(V) oxytriisopropoxide (VTIP) precursor solution for application to hole-injection layers in light-emitting diodes (LEDs). The fabricated LEDs consisting of a solution-processed bilayer (hybrid and V2O5) showed improved operating lifetime. These results clearly demonstrate that a good sealing effect on the emissive polymer can be realized in hybrid films using a simple sol-gel method and that V2O5’s hygroscopicity and strong acidity are better than those of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS).