High Fluorescence Efficiency Research Articles

Rigid Fluorescent Indacenetetraone‐Based Semiconducting Polymers via Knoevenagel Condensation

AbstractThe synthesis of new donor‐acceptor polymers is reported through Knoevenagel condensation of indacenetetraone with aromatic dialdehydes. The obtained polymers possess exceptionally rigid planar backbones with a rotational barrier (for single C─C bonds) of 16–20 kcal mol−1, the highest among known conjugated polymers. These structural features confer several unusual properties, including remarkably narrow absorption bands with very high absorption coefficient (up to ≈3×105 cm−1) and efficient fluorescence in the red to near‐IR region (λmax 694–850 nm, quantum yield 10–29%). Systematic spectroscopic, electrical, and microstructural characterization supported by Density Functional Theory (DFT) calculations reveals the effects of heteroatoms and the conjugation lengths on the optoelectronic properties of these materials. The polymers exhibit ambipolar charge transport in field‐effect transistors, which can be tailored to show unipolar p‐type (0.1 cm2 V−1 s−1) and n‐type (0.05 cm2 V−1 s−1) behavior by adjusting the energy levels at the polymer/metal contacts. Additionally, their application is demonstrated as acceptors in all‐polymer organic photovoltaic devices with commercial donor polymers, achieving a power conversion efficiency (PCE) of 11%.

Design, Synthesis, and Chemical Characterization of Pyrene‐Substituted BODIPY Dyes

In this study, novel di‐ and tetra‐pyrenylated BODIPY (boron‐dipyrromethene) dyes (Bdpy2 and Bdpy4) were synthesized via the Suzuki‐Miyaura cross‐coupling reaction, incorporating pyrene units at specific positions on the BODIPY core. Comprehensive structural characterization was achieved through FT‐IR, UV‐Vis, MALDI‐mass spectrometry, and NMR techniques. The optical properties were extensively analyzed in different solvents, revealing Q‐band absorption maxima at 531 nm for Bdpy2 and 533 nm for Bdpy4 in THF, along with red‐shifted emission peaks due to increased π‐π stacking interactions. Bdpy4 displayed a fluorescence quantum yield of 0.68 and a fluorescence lifetime of 3.88 ns, surpassing Bdpy2's values of 0.61 and 3.44 ns, respectively. These improved values in Bdpy4 highlight the enhanced energy transfer efficiency provided by the additional pyrene groups. Theoretical TD‐DFT calculations supported the experimental findings, indicating effective energy transfer from pyrene to the BODIPY core. These findings suggest that the high fluorescence efficiency and extended lifetimes of pyrenylated BODIPY derivatives make them promising candidates for optoelectronic applications, including bioimaging and energy harvesting.

Integrating L-Cys-AuNCs in ZIF-8 with Enhanced Fluorescence and Strengthened Stability for Sensitive Detection of Copper Ions.

Gold nanoclusters (AuNCs) have been widely investigated because of their unique photoluminescence properties. However, the applications of AuNCs are limited by their poor stability and relatively low fluorescence. In the present work, we developed nanocomposites (L-Cys-AuNCs@ZIF-8) with high fluorescence and stability, which were constructed by encapsulating the water-dispersible L-Cys-AuNCs into a ZIF-8 via Zn2+-triggered growth strategy without high temperature and pressure. The maximum emission wavelength of the L-Cys-AuNCs@ZIF-8 composite was at 868 nm, and the fluorescence intensity of L-Cys-AuNCs@ZIF-8 was nearly nine-fold compared with L-Cys-AuNCs without the ZIF-8 package. The mechanism investigation by fluorescence spectroscopy and X-ray photoelectron spectroscopy showed that L-Cys-AuNCs@ZIF-8 impeded ligand rotation, induced energy dissipation, and diminished the self-quenching effect, attributing to the spatial distribution of L-Cys-AuNCs. Based on the high fluorescence efficiency of L-Cys-AuNCs@ZIF-8, a "signal off" detective platform was proposed with copper ions as a model analyte, achieving a sensitive detection limit of Cu2+ at 16.7 nM. The quenching mechanism was confirmed, showing that the structure of the L-Cys-AuNCs@ZIF-8 nanocomposites was collapsed by the addition of Cu2+. Attributing to the strong adsorption ability between copper ions and pyridyl nitrogen, the as-prepared L-Cys-AuNCs@ZIF-8 was shown to accumulate Cu2+, and the Zn2+ in ZIF-8 was replaced by Cu2+.

Through‐Space vs Through‐bond Charge Transfer Fluorophores as Emitters for Efficient Blue Electroluminescent Devices

AbstractHerein, we report the design, synthesis, and properties of two donor‐π‐acceptor (D‐π‐A) charge transfer fluorophores pursuing an efficient deep blue emitter for organic light‐emitting diode (OLED). TCyCN and TPhCN comprise triphenylamine as a donor and benzonitrile as an acceptor connecting by either [2.2]paracyclophane (Cy) as a through‐space π‐linker or phenyl ring (Ph) as a through‐bond π‐linker, respectively. In thin film, TCyCN shows deep blue emission with moderate fluorescence efficiency, while TPhCN displays cyan blue emission with a high fluorescence efficiency. The two molecules feature hybridized local and charge‐transfer states with good thermal stability and balanced charge transport properties. They are successfully employed as non‐doped blue emissive layers in OLEDs. The TCyCN‐based device emits deep blue light peaked at 425 nm (CIE coordinates of (0.157, 0.076)) with a moderate electroluminescent (EL) performance (EQEmax=3.23 % and CEmax=2.06 cd A−1), while the TPhCN‐based device attains an excellent EL performance (EQEmax=6.24 % and CEmax=8.26 cd A−1) with cyan blue emission peaked at 490 nm. This work provides insight into the relationship between molecular design and properties of D‐π‐A emitters, offering a guideline for tailoring new organic compounds for organic optoelectronics.

Recent progress in high-performance thermally activated delayed fluorescence exciplexes based on multiple reverse intersystem crossing channels

In the field of organic light-emitting diodes (OLEDs), exciplex materials with thermally activated delayed fluorescence (TADF) characteristics have garnered significant attention in recent years owing to their potential for high fluorescence efficiency, primarily achieved through the reverse intersystem crossing (RISC) process. By converting non-radiative triplet states to radiative singlet states, the RISC process can effectively regulate exciton behavior, resulting in the harvest of triplet excitons and the improvement of luminescence efficiency. Recently, multi-RISC strategies have been developed to further enhance the performance of TADF exciplex materials and devices. In this paper, we review these research progress in this area. We classify molecular design strategies according to the composition of exciplexes, discuss the design principles and energy-harvesting mechanism of high-performance TADF exciplexes based on multi-RISC strategies, and prospect their further research and development. The progressive endeavors summarized in this review may inspire further research on material design and device fabrication, and promote the development of OLED applications.

A novel terpene-BODIPY conjugates based fluorescent probes: Synthesis, spectral properties, stability, penetration efficiency into bacterial, fungal and mammalian cells

The design of fluorescent probes based on biocompatible luminophores for medical diagnostics is one of the rapidly developing areas worldwide. Here, we report the synthesis of a novel BODIPYs containing a propanoic acid residue at the α-position of one of the pyrrole rings conjugated to (+)-myrtenol or thiotherpenoid. Both conjugates are quite photostable (t1/2 ∼ 40 h) and exhibit high fluorescence efficiency (φfl ∼ 77–90 %). The advantage of the newly synthesized terpene-BODIPY conjugates lies in their stability and absence of fluorescence quenching over a wide pH range (1.65–9.18). Moreover, the affinity of the conjugates for lipid biostructures was significantly improved compared to the original α-BODIPY carboxylic acid. As opposed to unconjugated BODIPY, which shows negligible activity against any cell type used in the study, the luminophores with either (+)-myrtenol or thioterpenoid effectively stained the membranes of Gram-positive bacteria, while Gram-negative bacteria were not stained. In eukaryotic cells, both conjugates readily stained organelles, but not the cell and nuclear membranes, suggesting these compounds as tools for differential staining of microbes or cell structures. Taken together, our data demonstrates that conjugation of BODIPY to terpenoids significantly improves the fluorescence abilities and modulates the selectivity of the conjugates against various cells.

Fabrication of a novel mixed-valent copper-based coordination polymer as a fluorescent sensor for selective and efficient detection of multiple analytes

A novel three-dimensional fluorescent mixed-valent copper-based coordination polymer (CP), namely {[CuICuII4(triazol)6(bpta)2]Cl}n (Cu-CP), was synthesized hydrothermally in the presence of Cu(II) ion, 2,4,6-tri(1H-1,2,4-triazol-1-yl)-1,3,5-triazine (TTT), and 2,2′,4,4′-biphenyltetracarboxylic acid (H4bpta). The structure of the Cu-CP was studied using single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD). Interestingly, the crystallographic data revealed that a part of Cu(II) ions were reduced in situ to Cu(I) ions as well as the nitrogen-containing ligand TTT was converted to triazol, which possessed excellent fluorescence characteristics as a transition metal ion with a d10 electronic configuration, prompting further investigation into the fluorescence sensing properties of Cu-CP. The results confirmed that Cu-CP exhibited excellent fluorescence performance which an outstanding candidate as a fluorescence sensor for Fe3+, Cr2O72−, CrO42−, MnO4− and nitrobenzene (NB), with a low limit of detection. For ethylene glycol (EG) detection, Cu-CP showed high-efficiency fluorescence enhancement across a range of temperatures. The underlying mechanism of fluorescence enhancement was investigated through comprehensive experimental studies.

Organoboron Polymorphs with Different Molecular Packing Modes for Optical Waveguides.

Organoboron compounds offer a new strategy to design optoelectronic materials with high fluorescence efficiency. In this paper, the organoboron compound B-BNBP with double B←N bridged bipyridine bearing four fluorine atoms as core unit is facilely synthesized and exhibits a narrowband emission spectrum and a high photoluminescence quantum yield (PLQY) of 86.53 % in solution. Its polymorphic crystals were controllable prepared by different solution self-assembly methods. Two microcrystals possess different molecular packing modes, one-dimensional microstrips (1D-MSs) for H-aggregation and two-dimensional microdisks (2D-MDs) for J-aggregation, owing to abundant intermolecular interactions of four fluorine atoms sticking out conjugated plane. Their structure-property relationships were investigated by crystallographic analysis and theoretical calculation. Strong emission spectra with the full width at half maximum (FWHM) of less than 30 nm can also be observed in thin film and 2D-MDs. 1D-MSs possess thermally activated delayed fluorescence (TADF) property and exhibit superior optical waveguide performance with an optical loss of 0.061 dB/μm. This work enriches the diversity of polymorphic microcrystals and further reveals the structure-property relationship in organoboron micro/nano-crystals.

A novel rhodamine B fluorescence probe for rapid identification of different amino acids by high efficiency fluorescence spectrum-mass spectrometry.

Rapid detection of amino acids plays an important role in the field of medical diagnosis. By combining Rhodamine B with triphenylamine, a novel double-response fluorescence probe (E)-4-((4-(((3',6'-bis(diethylamino)-3-oxospiro[isoindoline-1,9'-xanthen]-2-yl)imino)methyl)phenyl)(phenyl)amino)benzaldehyde (RBTPA) was prepared for rapid identification of different amino acids. Under daylight and 365 nm irradiation, it was found that the color change was most bright at pH = 3, and changed to dim at pH = 4. When pH = 3 and pH = 4, the photophysical properties of the two strong acids are very different. The maximum redshift of UV absorption light is 110nm, and the maximum fluorescence emission intensity is 4 times different. In order to further observe their binding structure analysis with different amino acids, qualitative analysis of each response structure was determined by mass spectrometry according to different molecular weights. The fluorescence probe RBTPA has two different isomers for recognition response in aldehyde group and imine group, respectively.

Substituent effects on the mechanochromic behaviour of pyrene-based AIEgens

It is extremely significant and desirable to integrate the fascinating properties of mechanochromism and aggregation-induced emission (AIE) in one simple molecule. Herein, pyrene-based aggregation-induced emission luminogens (AIEgens) with mechanofluorochromic (MFC) properties solve the traditionally existing aggregation-caused quenching (ACQ) challenge. Three cyanoethylene-functionalized pyrene-based derivatives were designed and synthesized. All compounds exhibit remarkable aggregation-enhanced emission (AEE) activity by a 3–20 times enhancement in mixed H2O/THF solutions. More importantly, high fluorescence efficiency was recorded in the solid state, especially for the luminogen 2c, with more than 200 times observed increased efficiency from 0.3% in solution to 69.8% in the solid state. Meanwhile, excellent mechanochromism properties and reversibility against the grinding treatment was systematically investigated. The excellent fatigue resistance properties are a necessity for potential applications in the field of anti-counterfeiting fluorescent inks and for the encryption of security information.

Bidirectional hybridized hairpin DNA fluorescent aptasensor based on Au-Pd NPs and CDs for ratiometric detection of AFB1.

Anovel and simple ratiometric fluorescent aptasensor was developed for the sensitive detection of aflatoxin B1 (AFB1). A hairpin DNA (h-DNA) was independently synthesized as the basic skeleton, and the bidirectional hybridization of h-DNA can increase the load of aptamer and signal probes, thereby realizing signal amplification. The high-efficiency fluorescence resonance energy transfer interaction between gold-palladium nanoparticles (Au-Pd NPs) and the self-synthesized fluorescent probe carbon dots (CDs) was utilized. Moreover, the label-free probe SYBR Green I (SG I) dye was introduced to form a double-signal probe with CDs, and a ratiometric sensor with FCDs/FSG I as a response signal was constructed. The ratio strategy can eliminate the fluctuation of external factors, thus improving the accuracy and reliability of the sensor. The quenching effect of Au-Pd NPs on CDs was 1.4 times that of AuNPs and 3.4 times that of Pd NPs, respectively. In the range 1-100ng/mL, FCDs/FSG I showed a good linear relationship with the logarithm of the concentration of AFB1, and the limit of detection was as low as 0.07ng/mL. The sensor was used to detect AFB1 in spiked peanuts and wine samples, and the recovery was between 91 and 115%, indicating that the sensor has high application potential in real sample analysis.

Facile synthesis of sulfur quantum dots with red light emission: Implications for electrochemiluminescence analysis application

Sulfur quantum dots (SQDs) have been reported as a potential candidate due to their low toxicity and high luminescent performance. Here, SQDs with red light fluorescence (FL) emission were synthesized by a one-step hydrothermal method using Na2CO3 as an etching agent, using sublimed sulfur powder as a sulfur source, and using bovine serum albumin (BSA) as a stabilizer. The choice of etching agent (NaOH or Na2CO3) realized the tuning of SQDs’ FL emission with blue and red light. The synthesized SQDs showed good FL stability and high FL efficiency, with a quantum yield of 1.03 % in an aqueous solution at 575 nm. In addition, stable and efficient electrochemiluminescence (ECL) emission was achieved by employing SQDs as ECL emitters with K2S2O8 as the co-reactant. The resorcinol (RS) can enhance the ECL intensity of the SQDs-K2S2O8 system, and the ECL intensity had a good linear relationship with the concentration of RS in a range from 2.5 nM to 25 nM with a detection limit of 0.61 nM. This work provides an emerging red-light luminescent SQDs, which would open up a way for the development of new types of luminophor in FL or ECL analysis. It also provides convenience for bio-labeling of live cells, in vivo imaging and provide new materials for photoelectric devices.

Application of hyperbranched polysiloxanes in biomedical materials based on AIE polymer properties

Application of hyperbranched polysiloxanes in biomedical materials based on AIE polymer properties

Theoretical Insights into the Photophysical Properties of 4CzIPN Doped in Different Hosts: A Multiscale Study.

As a typical thermally activated delayed fluorescence (TADF) emitter with green emission, 4CzIPN has attracted much attention recently. Most studies indicated that 4CzIPN doped in different hosts presented different performances; thus, the hosts should have an obvious influence on its photophysical properties. Herein, the influence of four kinds of hosts, including m-CzPym, m-CzTrz, p-CzPym, and p-CzTrz, on the photophysical properties of 4CzIPN is investigated. Molecular dynamics simulations were performed to simulate the host-guest conformations, and the photophysical properties were studied using the combined quantum mechanics/molecular mechanics method coupled with the thermal-vibration correlation function method. It is found that 4CzIPN in doped films has larger transition dipole moments and spin-orbital coupling constants compared to that in nondoped films. Faster radiative decay, intersystem crossing rates, and higher fluorescence efficiency could be obtained in doped films. Our work helps to better understand the photophysical properties of 4CzIPN in doped films and may favor the design of new hosts.

Color-tunable circularly polarized luminescence from liquid crystalline polymer networks

Chiroptical materials with circularly polarized luminescence (CPL) activities have attracted increasing interest because of their promising applications in optoelectronics, biosensing and imaging. Nevertheless, the construction of CPL-active materials with large luminescence dissymmetry (glum) factors and high emission efficiency is still challenging. Herein, a series of liquid crystalline polymer network films have been prepared by photopolymerization of cholesteric liquid-crystalline mixtures doped with aggregation-induced emission-active luminogens, TPE-TA and BDABFN. Through adjustment of the mass ratio of the two luminogens, the resultant films exhibit multicolour CPL from blue to red to white with absolute glum values up to 0.71 and fluorescence quantum yields up to 44 %. This work provides a strategy for fabricating polymeric film materials with color-tunable CPL properties and high fluorescence efficiency.

Integration of jackfruit seed-derived carbon dots and electronic nose for a sensitive detection of formaldehyde vapor

The preparation of carbon dots from jackfruit seeds through a pyrolysis method at 280℃ and their use for the detection of formaldehyde were reported. The as-prepared carbon dots showed a high fluorescence efficiency with a quantum yield of 12.7% and excellent photostability and dispersibility in aqueous solution with a zeta potential of ‒62.5 mV. The integration of carbon dot thin film and a home-made optical electronic nose system possessed sensitivity towards formaldehyde vapor with a detection limit of 24.7%v/v across a linear range of 25%v/v to 100%v/v. Furthermore, the sensor showed the highest sensitivity towards formaldehyde against other volatile organic compounds through a strong interaction between the carbonyl groups and the carbon dots. Additionally, principal component analysis (PCA) was conducted to achieve quantitative measurements of formaldehyde content in different formaldehyde volume ratios with substantial variance. Due to the significance of methanol as a typical chemical precursor for the industrial manufacturing of formaldehyde, the quantitative analytical method is essential to determining formaldehyde or methanol concentration. The sensing ability of carbon dot film-integrated electronic nose towards formaldehyde in formaldehyde/methanol mixtures was measured to be 10.74%v/v in a linear range of 25%v/v to 100%v/v. The PCA showed orderly linear combinations of the data set, which can be potentially utilized to analyze formaldehyde and methanol content in industrial processes. The results indicate the significant potential of carbon dots and optical electronic nose system as an effective formaldehyde sensing platform. Potential applications include the quantification of formaldehyde from methanol conversion and determination of methanol contaminant in formaldehyde.

Fluorescent polymer as a biosensing tool for the diagnosis of microbial pathogens

Diseases and diagnoses are predominant in the human population. Early diagnosis of etiological agents plays a vital role in the treatment of bacterial infections. Existing standard diagnostic platforms are laborious, time-consuming, and require trained personnel and cost-effective procedure, though they are producing promising results. These shortcomings have led to a thirst for rapid diagnostic procedures. Fluorescence-based diagnosis is one of the efficient rapid diagnostic methods that rely on specific and sensitive bacterial detection. Emerging bio-sensing studies on conducting polymers (CPs) are gaining popularity in medical diagnostics due to their promising properties of high fluorescence efficiency, good light stability, and low cytotoxicity. Poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), is the first identified soluble polymer and model material for understanding the fundamental photophysics of conventional CPs. In this present study, MEH-PPV is used as a fluorescent dye for direct pathogen detection applications by interacting with the microbial cell surface. An optimized concentration of MEH-PPV solution used to confirm the presence of selective bacterial structures. The present study endeavours towards bacterial detection based on the emission from bacteria due to interfacial interaction between polymer and bacterial surface.

Energy landscape of perylenediimide chromophoric aggregates.

Understanding the self-assembly of conjugated organic materials at the molecular level is crucial in their potential applications as active components in electronic and optoelectronic devices. The type of aggregation significantly influences the intriguing electronic and optical characteristics differing from their constituent molecules. Perylenediimides (PDIs), electron-deficient molecules exhibiting remarkable n-type semiconducting properties, are among the most explored organic fluorescent materials due to their high fluorescence efficiency, photostability, and optoelectronic properties. PDI derivatives are reported to form well-tailored supramolecular architectures: cofacial with minor slip (H-aggregates), staggered with major slip (J-aggregates), magic angle stacking (M-aggregates), rotated (X-aggregates), rotated orthogonal ((+)-aggregates), etc. H*-aggregates are defined here as an ideal case of H-aggregate with an eclipsed configuration. Although numerous reports regarding the formation and optical properties of various PDI aggregates are known, the key driving force within the PDI units guiding the self-assembly to form distinct aggregate systems remains elusive. To unravel the molecular-level mechanisms behind the self-assembly of PDI units by probing the intermolecular interactions, symmetry-adapted perturbation theory-based energy decomposition, potential energy surface scans, and non-covalent interaction index analyses were employed on PDI dimer models. Quantum theory of atoms in molecules and frontier molecular orbital analyses were implemented on the dimer models to comprehend the effect of heteroatoms and orbital interactions in stabilising the X-aggregates over the other PDI aggregate systems. Competition between the attractive and repulsive non-covalent interactions dictates a stability order of X > H > J > M > (+) > H* for the PDI aggregate system, while in the parent perylene system, the stability order was found to be X > (+) > H > M > J > H*.

Efficient solution-processed fluorescent OLEDs realized by removing charge trapping emission loss of BODIPY fluorochrome.

The thermally activated delayed fluorescence (TADF)-sensitized fluorescent (TSF) dye strategy has been used successfully in thermally evaporated organic light-emitting diodes (eOLEDs), but the development of solution-processed TSF-OLEDs (TSF-sOLEDs) is still very limited to date. Previously, the introduction of electronically inert shielding terminal groups for TADF sensitizer and/or fluorescent dyes was commonly used in TSF-sOLEDs, which aimed to achieve sufficient Förster energy transfer (FET) while restraining notorious Dexter energy transfer (DET) at a high doping concentration of fluorescent dyes. However, this approach has not yet enabled efficient TSF-sOLEDs owing to severe charge trapping emission (CTE) for triplet loss. In this study, by simply utilizing highly efficient boron-dipyrromethene derivatives (BODIPYs) that simultaneously feature high fluorescent quantum efficiency and narrow-band emission spectra, we developed highly efficient and super color-purity TSF-sOLEDs using a 0.1 wt% ultralow doping strategy. As confirmed, the resultant ultralow doping TSF-sOLEDs achieved sufficient FET from sensitizer to fluorochrome without noticeable CTE issues. The device achieves record maximum external quantum efficiency (EQEmax) and current efficiency (CEmax) of 21.5% and 78.8 cd A-1, respectively, and an ultrapure green emission with Commission International de l'Eclairage (CIE) coordinates of (0.28, 0.65). This study validates the new device architecture of ultralow doping TSF-sOLEDs, which paves the way for future development of high-resolution TSF-sOLED displays via a simple solution-processed manufacturing approach.

High-efficiency multicolor fluorescent indoleninonaphthooxazole derivatives with adjustable excitation

Solvatochromic fluorophores are one of the most investigated dyes because they exhibit multi-color luminescence properties as the polarity of the solvent changes. It remains a challenge to regulate solvatochromism with a large emission shift and maintain high fluorescence efficiency from apolar to polar solvents. Herein, we report a new type of solvatochromic fluorophore that exhibits both multicolor solvatochromism and stable high fluorescence efficiency in polar solvents. The unique solvatochromic properties of indoleninonaphthooxazole derivatives are realized by constructing a single carbon-bond-linked coplanar scaffold containing indolenine and naphthooxazole components with different substituents. We propose a possible mechanism to explain the unique solvatochromism. Excited USTS-3 and USTS-4 exhibit LE state in non-polar solvent and different HLCT states in polar solvents with both high luminescence efficiency. And the excitation of USTS-3 and USTS-4 is determined by aggregation states of molecular USTS-3 and USTS-4 under different concentrations, which exhibits different relaxations but share the same luminescence decay pathway. Benefitting from the unique luminescence properties of indoleninonaphthooxazole derivatives, they exhibit potential applications in solvent polarity detection, bioimaging, anticounterfeiting, electroluminescence, and lighting in different matrix. Our results also provide a new perspective on designing novel fluorophores based on indolenine and naphthoxazole moieties.