Light-emitting Polymer Research Articles

Light-Emitting Coordination Polymers: Stimuli-Responsive Gels, PMMA-Based Composite Films, and UV-Shielding.

Lanthanide-based light-emitting coordination polymers (CPs) and CP gels (CPGs) have significance for applications in optical systems, image processing/multiplexing, and optical sensors. In this study, we report two new luminescent CPs (EuL-CP (1) and TbL-CP (2)) and CPGs (EuL-gel (5) and TbL-gel (6)) using lanthanide(III) ions (Ln(III) = Eu(III) and Tb(III)) and 4-(4-carboxyphenyl)-2,2:6,2-terpyridine ligand (L) capable of forming stable thermoreversible gels. Probable structures of EuL-CP (1) and TbL-CP (2) and the formations of EuL-gel (5) and TbL-gel (6) are proposed based on adequate computational studies. The CPGs are stimuli-responsive and could be utilized as invisible security inks for encryption. Further, poly(methyl methacrylate) (PMMA) polymer doped with respective CPs (0.75 wt %) is found to be suitable for forming composite films with UV-shielding properties.

Pyrene-encapsulated light-emitting π-conjugated polymer with excellent ozone tolerance capacity for large-area and flexible ultra-deep-blue PLEDs with CIEy = 0.08

Emerging flexible polymer light-emitting diodes (PLEDs) are crucial for the development of information display and solid lighting. However, achieving ultrastable light-emitting polymers with robust emissions and outstanding chem-physic stabilities, remains a serious challenge due to the intrinsic oxidative and degrading properties of aromatic units. Herein, we present a universal and convenient pyrene-encapsulation strategy to enhance the ozone tolerance capacity of deep-blue light-emitting conjugated polymers (PPyDPF) for the narrowband flexible PLEDs. More intestingly, compared to the comparison polymers, PPyDPF showed a lower free volume ratio of 71.78 %, facilitating dense interchain packing, which contributes to its excellent ozone tolerance capacity. Large-area PLEDs were fabricated, which exhibit ultra-deep-blue emission with a FWHM of 40 nm and Commission internationale de l’éclairage (CIE) coordinates of (0.16, 0.08). The demonstrated potential for application in light-emitting devices underscores the significance of this approach, providing an effective strategy for developing aging-resistant light-emitting conjugated polymers for optoelectronic applications.

Comparative study of light-emitting cement and polymer mortars for sustainable building applications: performance evaluation and analysis

Comparative study of light-emitting cement and polymer mortars for sustainable building applications: performance evaluation and analysis

Polymerization-Mediated Through-Space Charge Transfer: An Emerging Strategy for Light-Emitting Materials.

Through-space charge transfer (TSCT) has attracted increasing attention owing to its great potential in designing efficient light-emitting molecules and polymers. Complementary to through-bond charge transfer and Förster resonance energy transfer, TSCT offers an alternative approach for the manipulation of molecular fluorescence. Recently, the synergy between TSCT and polymer systems through polymerization-mediated charge transfer has fostered the advancements of innovative light-emitting functional materials featuring thermally activated delayed fluorescence and/or aggregation-induced emission. This perspective highlights the significant progress in tailoring emission properties through structural engineering of donor and acceptor groups within polymeric systems, leveraging the TSCT mechanism. This strategy has transcended the limitations of traditional charge transfer systems with its tolerance to extended donor-acceptor distance, paving the way for novel applications beyond organic light-emitting diodes. The discussion concludes with a forward-looking analysis of potential future research trajectories in the field of polymerization-mediated charge transfer for developing next-generation light-emitting materials.

Conjugated polymer-perovskite quantum dot (MDMO-PPV:CsPbBr3) nanocomposites: Miscibility, nano-structures, and properties

All-inorganic cesium lead bromide (CsPbBr3) quantum dots (QDs) have received a surge of attention in the field of light-emitting diode (LED) display and lighting. Hence, it is interesting to study the composite film composed of CsPbBr3 and light-emitting MDMO-PPV matrix polymer. In this study, we investigate the phase behavior among the components, MDMO-PPV, toluene (solvent), and oleic acid and oleylamine (the surface ligands for QDs) based on the Flory-Huggins theory with the group contribution method for the first time. Here we find that the MDMO-PPV and ligand molecules are immiscible whereas MDMO-PPV and toluene are partially miscible. Then through the x-ray diffraction (XRD) patterns, we demonstrate that CsPbBr3 QDs form a nanoscale domain with ∼33–52 nm crystallites in the MDMO-PPV matrix. Furthermore, the scanning electron microscope (SEM) images display that CsPbBr3 QDs can be highly aggregated at MDMO-PPV:CsPbBr3= 50:50 composition. Then, through the ultraviolet-visible (UV–vis) and photoluminescence (PL) spectra, the enhancement of PL intensity is observed at ∼30–50 wt% CsPbBr3. Finally, the electrochemical impedance spectra indicate that the composite film exhibits less resistance (∼3.2×104 Ω) than the pure MDMO-PPV film (∼1.4×107 Ω), suggesting that the MDMO-PPVCsPbBr3 composite approach is promising for electrochemical and optoelectronic applications.

Antenna effect enhanced ECL immunoassay using microfloral europium porphyrin coordination polymers based on Eu3+ and TCPP for the detection of chloramphenicol in foods.

The "antenna effect" is one of the most important energy transfer modes in lanthanide light-emitting polymers. In this study, novel luminescent nanostructured coordination polymers (Eu-PCP) were synthesized in one step using Eu3+ as the central metal ion and 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) as the organic ligand. The unique "antenna effect" observed between Eu3+ and TCPP leads to a substantial improvement in the electrochemiluminescence (ECL) emission efficiency. Eu-PCP exhibits good cathodic ECL characteristics. Additionally, Au@SnS2 nanosheets exhibit favorable electrical conductivity, biocompatibility, and a significant specific surface area. This makes them a suitable choice as substrate materials for the modification of electrode surfaces and capturing antigens. Being well known, the development of sensitive and rapid methods to detect chloramphenicol is essential for food safety. Based on this, we report a novel competitive electrochemiluminescence immunoassay to achieve ultra-sensitive and highly specific detection of chloramphenicol. The linear range was 0.0002-500 ng mL-1 and the detection limit was 0.09 pg mL-1. Apart from that, the experimental results proved that it provided a new analytical tool for the detection of antibiotic residues in food safety.

Excited-State Energy Transfer-Associated Dual Emission of Light-Emitting Polymers Containing Sulfonated Graphene Oxide for Sensing of pH, Co(II), and Bi(III)

Excited-State Energy Transfer-Associated Dual Emission of Light-Emitting Polymers Containing Sulfonated Graphene Oxide for Sensing of pH, Co(II), and Bi(III)

Direct photocatalytic patterning of colloidal emissive nanomaterials.

We present a universal direct photocatalytic patterning method that can completely preserve the optical properties of perovskite nanocrystals (PeNCs) and other emissive nanomaterials. Solubility change of PeNCs is achieved mainly by a photoinduced thiol-ene click reaction between specially tailored surface ligands and a dual-role photocatalytic reagent, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP), where the thiol-ene reaction is enabled at a low light intensity dose (~ 30 millijoules per square centimeter) by the strong photocatalytic activity of PeNCs. The photochemical reaction mechanism was investigated using various analyses at each patterning step. The PTMP also acts as a defect passivation agent for the PeNCs and even enhances their photoluminescence quantum yield (by ~5%) and photostability. Multicolor patterns of cesium lead halide (CsPbX3)PeNCs were fabricated with high resolution (<1 micrometer). Our method is widely applicable to other classes of nanomaterials including colloidal cadmium selenide-based and indium phosphide-based quantum dots and light-emitting polymers; this generality provides a nondestructive and simple way to pattern various functional materials and devices.

Intrinsically stretchable three primary light-emitting films enabled by elastomer blend for polymer light-emitting diodes.

Intrinsically stretchable light-emitting materials are crucial for skin-like wearable displays; however, their color range has been limited to green-like yellow lights owing to the restricted stretchable light-emitting materials (super yellow series materials). To develop skin-like full-color displays, three intrinsically stretchable primary light-emitting materials [red, green, and blue (RGB)] are essential. In this study, we report three highly stretchable primary light-emitting films made from a polymer blend of conventional RGB light-emitting polymers and a nonpolar elastomer. The blend films consist of multidimensional nanodomains of light-emitting polymers that are interconnected in an elastomer matrix for efficient light-emitting under strain. The RGB blend films exhibited over 1000 cd/m2 luminance with low turn-on voltage (<5 Von) and the selectively stretched blend films on rigid substrate maintained stable light-emitting performance up to 100% strain even after 1000 multiple stretching cycles.

Tailoring Hydrogen-Bonding Strategy for Sequence-Dependent and Thermo/pH Dual-Responsive Clusteroluminescence.

Rational design of monomer sequence for desired properties is challenging. This study investigates the effect of monomer distribution of double hydrophilic copolymers (DHCs) with electron-rich units on cluster triggered emission (CTE) capacity. By means of combining latent monomer strategy, reversible addition fragmentation chain transfer (RAFT) polymerization and selective hydrolysis technology, the random, pseudo di-block and the gradient DHCs consisting of pH-responsive polyacrylic acid (PAA) segments and thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) segments were successfully synthesized in a controlled manner. Moreover, the gradient DHCs showed a tremendously increased luminescent intensity due to the distinct hydrogen-bonding interaction compared to random and pseudo di-block DHCs. To the best of our knowledge, this is the first reported the direct correlation between luminescent intensity and sequence structure of non-conjugated polymer. Meanwhile, thermo and pH dual-responsive clusteroluminescence could be easily performed. This work demonstrates a novel and facile method to tailor the hydrogen-bonding for the stimuli-responsive light-emitting polymers.

High-efficiency stretchable light-emitting polymers from thermally activated delayed fluorescence.

Stretchable light-emitting materials are the key components for realizing skin-like displays and optical biostimulation. All the stretchable emitters reported to date, to the best of our knowledge, have been based on electroluminescent polymers that only harness singlet excitons, limiting their theoretical quantum yield to 25%. Here we present a design concept for imparting stretchability onto electroluminescent polymers that can harness all the excitons through thermally activated delayed fluorescence, thereby reaching a near-unity theoretical quantum yield. We show that our design strategy of inserting flexible, linear units into a polymer backbone can substantially increase the mechanical stretchability without affecting the underlying electroluminescent processes. As a result, our synthesized polymer achieves a stretchability of 125%, with an external quantum efficiency of 10%. Furthermore, we demonstrate a fully stretchable organic light-emitting diode, confirming that the proposed stretchable thermally activated delayed fluorescence polymers provide a path towards simultaneously achieving desirable electroluminescent and mechanical characteristics, including high efficiency, brightness, switching speed and stretchability as well as low driving voltage.

Lanthanide-Directed Luminescent “Soft” Coordination Polymer Gels: White Light Emission, Anticounterfeiting, and Thin-Film-Based Sensing

Stimuli-responsive light-emitting materials are of great interest owing to their potential use in encryption and multilevel security. In this context, herein, the synthesis of light-emitting multifunctional coordination polymer gels (CPGs) was accomplished by the self-assembly of europium and terbium acetate with a bifunctional (amide/carboxylic acid) gelator. The as-synthesized luminescent CPGs are stable up to 300 °C. The FESEM micrograph exhibits pebble-like morphology, and the TEM images reveal a sheet-like structure which is grown on top of each other. The optical properties of the as-synthesized CPGs are readily tuneable over a broad spectrum, including white-light emission, simply by modulating the europium and terbium ion stoichiometry. The as-synthesized luminescent materials have the potential to be used as invisible security inks for high-security information encoding. Additionally, water-resistant luminescent thin films were fabricated by incorporating Eu@BTT or Tb@BTT (BTT: 5,5′,5″-((benzene-1,3,5-tricarbonyl)tris(azanediyl))triisophthalic acid) into the poly(methyl methacrylate) (PMMA) polymer matrix for the naked eye test of nitro-explosive compounds (2,4,6-trinitrophenol and nitrophenol). The sensing mechanism is proposed based on the DFT and time-resolved photoluminescence studies.

Blue light-emitting fluorene–dendron hybridized polymers: optophysical features

In this manuscript, we have demonstrated an efficient and rapid synthetic strategy for preparation of new fluorene–dendron-hybridized blue light-emitting polymers P1–P7 by the reaction of 9,9 long-chain dialkylated fluorenes M2–M8 with dendronized monomer (M1) under microwave-assisted reaction condition. These fluorene–dendron-hybridized polymers P1–P7 were characterized using different spectroscopic techniques. Furthermore, the optophysical properties of these polymers P1–P7 were studied which revealed that these synthesized polymers P1–P7 have potential to emerge as capable materials in the development of diodes, particularly for blue light emission. In the future, similar approaches would be utilized for preparation of light-emitting polymer composite.

Laser ablated silver nanoparticles doped blue light-emitting polymer optical fiber with enhanced photostability

Here, we demonstrate the fabrication of a stable polymer optical fibre doped with 1,4-bis (2-methylstyryl) benzene (Bis-MSB) that contains silver nanoparticles. Spherical silver nanoparticles of approximate size 15 nm were fabricated using nanosecond laser ablation. A Q-switched Nd: YAG laser operating at 355 nm was used to pump the polymer optical fiber in order to analyse its emission characteristics. The pump pulse energy (PPE) dependent emission spectra from the fiber were analyzed. The observed fluorescence emission was turned to amplified spontaneous emission (ASE) at a PPE of 2.5 mJ. The study demonstrates that the fibre offers superior photostability at an optimum concentration of Ag nanoparticles. The proposed fiber may find potential applications in the development of stable directional optical sources in the blue region.

Nanofloating gate modulated synaptic organic light-emitting transistors for reconfigurable displays.

The use of postsynaptic current to drive long-lasting luminescence holds a disruptive potential for harnessing the next-generation of smart displays. Multiresponsive long afterglow emission can be achieved by integrating light-emitting polymers in electric spiked transistors trigged by distinct presynaptic signals inputs. Here, we report a highly effective electric spiked long afterglow organic light-emitting transistor (LAOLET), whose operation relies on a nanofloating gate architecture. Long afterglow emission with reconfigurable brightness and retention time is observed upon applying specific positive gate voltage spiked. Conversely, when negative gate voltage stimulus is applied, these LAOLETs function as click-on display. Interestingly, upon endowing the device with force sensing capabilities, it can operate as a long afterglow pressure sensor that emits long-lasting green light subsequently to a controlled extrusion action.

Coupled modes enhance random lasing in plasmonic double grating structure

In this work, we experimentally and theoretically proved a flexible fine random laser from a two-face double grating plasmonic structure based on PDMS. Accordingly, PDMS was fabricated using the nanoimprint lithography method and coated by a thin gold layer with a thickness of 35 nm using a PVD device and light-emitting polymer (F8PT) to enhance the scattering and efficiency of the random laser. Using a plasmonic gold grating as a substrate, the simulation results compared the upside and downside of the plasmonic double grating structure. Moreover, an enhancement was observed in light transmission, and it is common to predict high efficiency in random lasing properties. The experimental results showed a comparison between normal plasmonic double grating samples and symmetric and asymmetric double grating -based nanostructures with thicknesses of 200, 400 and 600 μm and reported that random lasing properties had better results for samples with thinner spaces based on coupled mode effects. Correspondingly, this was done by increasing the intensity and decreasing the lasing threshold from 22 μJ in normal double grating to 16 μJ in the thinnest double grating structure.

A Self‐Assembled 3D Penetrating Nanonetwork for High‐Performance Intrinsically Stretchable Polymer Light‐Emitting Diodes

The emergence of wearable technology can significantly benefit from electronic displays fabricated using intrinsically stretchable (is-) materials. Typically, an improvement in the stretchability of conventional light-emitting polymers is accompanied by a decrease in charge transportability, thus resulting in a significant decrease in device efficiency. In this study, a self-assembled 3D penetrating nanonetwork is developed to achieve increased stretchability and mobility simultaneously, based on high-molecular-weight phenylenevinylene (L-SY-PPV) and polyacrylonitrile (PAN). The mobility of L-SY-PPV/PAN increases by 5-6 times and the stretchability increases from 20% (pristine L-SY-PPV film) to 100%. A high current efficiency (CE) of 8.13cd A-1 is observed in polymer light-emitting diodes (PLEDs) fabricated using 40% stretched L-SY-PPV/PAN. Furthermore, using a polyethyleneimine ethoxylated (PEIE), an 1,10-phenanthroline monohydrate (pBphen), and a reduced Triton X-100 (TR) chelated Zn-based is- electron-injection layer of Zn-PEIE-pBphen-TR, an is-PLED is realized with a turn-on voltage of 6.5V and a high CE of 2.35cd A-1 . These results demonstrate the effectiveness of using the self-assembled 3D penetrating nanonetwork for the fabrication of is-PLEDs.

Optimizing Interfacial Energetics for Conjugated Polyelectrolyte Electron Injection Layers in High Efficiency and Fast Responding Polymer Light Emitting Diodes.

Modification of the π-conjugated backbone structure of conjugated polyelectrolytes (CPEs) for use as electron injection layers (EILs) in polymer light emitting diodes (PLEDs) has previously brought conflicted results in the literature in terms of device efficiency and turn-on response time. Herein, we determine the energetics at the CPE and the light emitting polymer (LEP) interface as a key factor for PLED device performance. By varying the conjugated backbone structure of both the LEP and CPE, we control the nature of the CPE/LEP interface in terms of optical energy gap offset, interfacial energy level offset, and location of the electron–hole recombination zone. We use a wide gap CPE with a shallow LUMO (F8im-Br) and one with a smaller gap and deeper LUMO (F8imBT-Br), in combination with three different LEPs. We find that the formation of a type II heterojunction at the CPE/LEP interfaces causes interfacial luminance quenching, which is responsible for poor efficiency in PLED devices. The effect is exacerbated with increased energy level offset from ionic rearrangement and hole accumulation occurring near the CPE/LEP interface. However, a deep CPE LUMO is found to be beneficial for fast current and luminance turn-on times of devices. This work provides important CPE molecular design rules for EIL use, offering progress toward a universal PLED-compatible CPE that can simultaneously deliver high efficiency and fast response times. In particular, engineering the LUMO position to be deep enough for fast device turn-on while avoiding the creation of a large energy level offset at the CPE/LEP interface is shown to be highly desirable.

Ratiometric pH Sensing, Photophysics, and Cell Imaging of Nonaromatic Light-Emitting Polymers.

Here, four nontraditional fluorescent polymers (NTFPs) of varying N,N-dimethyl-2-propenamide (DMPA) and butyl prop-2-enoate (BPE) mole ratios, i.e., 2:1 (NTFP1), 4:1 (NTFP2), 8:1 (NTFP3), and 16:1 (NTFP4), are prepared via random polymerization in water. The maximum fluorescence enhancement of NTFP3 makes it suitable for ratiometric pH sensing, Cu(II) sensing, and pH-dependent cell imaging of Madin-Darby canine kidney (MDCK) cells. The oxygen donor functionalities of NTFP3 involved in binding and sensing with Cu(II) ions are studied by absorption, emission, electron paramagnetic resonance, Fourier transform infrared (FTIR), and O1s/Cu2p X-ray photoelectron spectroscopies (XPS). The spectral responses of the ratiometric pH sensor within 1.5-11.5 confirm 22 and 44 nm red shifts in absorption and ratiometric emission, respectively. The striking color changes from blue (436 nm) to green (480 nm) via an increase in pH are thought to be the stabilization of the charged canonical form of tertiary amide, i.e., -C(O-)═N+(CH3)2, realized from the changes in the absorption/fluorescence spectra and XPS/FTIR analyses. The through-space n-π* interactions in the NTFP3 aggregate, N-branching-associated rigidity, and nonconventional intramolecular hydrogen bondings of adjacent NTFP3 moieties in the NTFP3 aggregate contribute to aggregation-enhanced emissions (AEEs). Here, structures of NTFP3, NTFP3 aggregate, and Cu(II)-NTFP3; absorption; n-π* interactions; hydrogen bondings; AEEs; and binding with Cu(II) are ascertained by density functional theory, time-dependent density functional theory, and reduced density gradient calculations. The excellent limits of detection and Stern-Volmer constants of NTFP3 are 2.24 nM/0.14234 ppb and 4.26 × 103 M-1 at pH = 6.5 and 0.95 nM/0.06037 ppb and 4.90 × 103 M-1 at pH = 8.0, respectively. Additionally, the Stokes shift and binding energy of NTFP3 are 13,636 cm-1/1.69 eV and -4.64 eV, respectively. The pH-dependent MDCK cell imaging ability of noncytotoxic NTFP3 is supported via fluorescence imaging and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Light-Emitting Redox Polymers for Sensing and Removal-Reduction of Cu(II): Roles of Hydrogen Bonding in Nonconventional Fluorescence

Here, intrinsically luminescent multifunctional n-butyl prop-2-enoate-co-butyl 3-(N-(hydroxymethyl)prop-2-enamido)propanoate-co-N-(hydroxymethyl)prop-2-enamide (NBP-co-BHMPP-co-HMP) luminogens with 1:2, 1:4, 1:8, and 1:20 mole ratios of NBP/HMP are synthesized via free radical polymerization, where the amidic BHMPP comonomer is anchored via N–C coupling of HMP and NBP. The optimum nonconventional fluorescent polymer (NCFP, NBP/HMP = 1:8) is suitable for sensitive detection, selective binding, and removal-reduction of Cu(II). The structures and light-emitting properties of NCFP, NCFP aggregates, Cu(II)-NCFP, and Cu(I)-NCFP; oxygen donor selective coordinations; and removal-reduction of paramagnetic Cu(II) are explored via spectroscopic, microscopic, density functional theory-reduced density gradient, rapid color change under visible light, chromaticity-1931 plots, and electrochemical measurements. The striking aggregation-enhanced green fluorescence is associated with extensive nonconventional and conventional hydrogen bondings in NCFP aggregates and through space electronic interactions involving NBP, HMP, and BHMPP moieties. Here, the Cu(II)/Cu(I) redox couple is confirmed via shifting of Epc from −1.08/+0.15 to +0.95/+0.16 V; Epc and Epa at +0.15 and −0.34/+0.41 V, respectively; green color of Cu(I)-NCFP under visible light; Fourier transform infrared and Cu 2p X-ray photoelectron spectroscopies; and computational studies. The limit of detection, Stern–Volmer constant, redox potentials, and adsorption capacity of NCFP are 3.61 nM/0.229 ppb, 4.27 × 103 [M]−1, and +0.15/+0.41/–0.34 V, and 49.41 mg g–1, respectively.