High Fluorescence Quantum Yield Research Articles

Green‐Solvent‐Processed High‐Performance Ternary Organic Solar Cells Comprising a Highly Soluble and Fluorescent Third Component

AbstractNowadays, it is still a great challenge to obtain high‐performance green‐solvent‐processed organic solar cells (OSCs). In this study, a ternary blend strategy (one donor and two acceptors, 1D/2A) is developed to solve the difficulty of film morphology modulation during the fabrication of high‐performance green‐solvent‐processed OSCs. A typical high‐performance halogenated‐solvent processable binary system D18:BTP‐eC9‐4F is selected as the host, its green‐solvents‐processed devices show an inferior power conversion efficiency (PCE) of ≈16%. SM16 with two 3D shape persistent end groups is selected as the third component due to its high fluorescence quantum yield, reduced intermolecular interaction, good solubility, and moderate crystallinity. As a result, the ternary devices display bicontinuous interpenetrating networks, reduced energy loss, and suppressed charge carrier recombination losses. Hence, an excellent PCE of 18.20% is achieved for the D18:BTP‐eC9‐4F:SM16 ternary devices, which is much higher than D18:BTP‐eC9‐4F‐based binary ones and also one of the highest PCEs for the green‐solvents‐processed OSCs. Besides, this strategy also demonstrates a good universality for other binary systems and becomes an effective pathway for the development of green‐solvent processable high‐performance OSCs.

Donor–Acceptor–Donor Near-Infrared-II Aggregation-Induced Emission Luminogens (AIEgens) Encapsulated within Nanometer-Sized Exosomes for Tumor Imaging

Developing organic aggregation-induced emission luminogens (AIEgens) with a donor–acceptor–donor (D–A–D) structure improves fluorescence imaging for biological applications due to their deep tissue penetration, high fluorescence quantum yield, and good biocompatibility. However, compared to the systematically well-explored near-infrared-I (NIR-I, 650–900 nm) AIEgens, the research on organic D–A–D-type near-infrared-II (NIR-II, 1000–1700 nm) AIEgens received a snub, by contrast, owing to their lack of diversity, low AIE character, and poor tumor accumulation, which has become a bottleneck in the bioimaging field. Herein, we report a D–A–D-type organic NIR-II fluorophore with typical AIE character (αAIE > 4) through careful manipulation of the electron donor and acceptor. The tumor-associated macrophage (TAM)-derived exosomes with nanometer size were used as templates to encapsulate the NIR-II AIEgens (oBBT-DPNA) in a well-defined structure (named as AIE@Exo). The AIE@Exo displayed a superb aggregation-intensified NIR-II fluorescence with a maximum emission peak at 1052 nm as well as a calculated fluorescence quantum yield (QY) of 3.1%. Moreover, the in vivo application of AIE@Exo in efficient NIR-II fluorescence imaging of whole-body vessels and tumor was successfully demonstrated in living mice. Overall, the nanometer-sized biomimetic nanoparticles represent successful NIR-II AIE nanoparticles for biomedical imaging.

Blue cadmium-free and air-fabricated quantum dot light-emitting diodes

Quantum dot (QD) materials have found increasing use in display applications because of their high color purity and fluorescence quantum yield, enabling devices with higher brightness and efficiency. However, to access large-area printing and coating methods that are carried out in ambient conditions, it is necessary to, first, move away from toxic cadmium, and second, to target materials that can be air-processed. Herein, we synthesize zinc selenide-based blue QD material and air-fabricate light-emitting diodes (LEDs) and single-carrier devices. The encapsulated devices were also measured under ambient conditions. Multi-shell-structured ZnSeTe/ZnSe/ZnS (core/shell/shell) QDs show pure deep blue/purple fluorescence emission with a high photoluminescence quantum yield of 78%. The blue QD-LED devices are fabricated in a conventional structure with bottom light emission with two electron transport materials (ZnO and ZnMgO). The QD-LED devices with ZnO electron transport layer show a maximum luminance of ∼6200 cd m−2 at 9 V with a turn-on voltage of 3.5 V and current efficacy of 0.38 cd A−1, while with ZnMgO electron transport layer, the devices show a maximum luminance of 3000 cd m−2 at 7 V with a turn-on voltage of 3 V and current efficacy of 0.6 cd A−1. Electron-only and hole-only devices were fabricated to show and confirm the underlying charge transport mechanisms. To our knowledge, these results show for the first-time air-fabricated ZnSe-based QD-LEDs, paving the way for scaling up display applications and moving toward high-performance printed electronics.

Carbon Quantum Dots Based on Marine Polysaccharides: Types, Synthesis, and Applications.

The marine environment offers a vast array of resources, including plants, animals, and microorganisms, that can be utilized to extract polysaccharides such as alginate, carrageenan, chitin, chitosan, agarose, ulvan, porphyra, and many more. These polysaccharides found in marine environments can serve as carbon-rich precursors for synthesizing carbon quantum dots (CQDs). Marine polysaccharides have a distinct advantage over other CQD precursors because they contain multiple heteroatoms, including nitrogen (N), sulfur (S), and oxygen (O). The surface of CQDs can be naturally doped, reducing the need for excessive use of chemical reagents and promoting green methods. The present review highlights the processing methods used to synthesize CQDs from marine polysaccharide precursors. These can be classified according to their biological origin as being derived from algae, crustaceans, or fish. CQDs can be synthesized to exhibit exceptional optical properties, including high fluorescence emission, absorbance, quenching, and quantum yield. CQDs' structural, morphological, and optical properties can be adjusted by utilizing multi-heteroatom precursors. Moreover, owing to their biocompatibility and low toxicity, CQDs obtained from marine polysaccharides have potential applications in various fields, including biomedicine (e.g., drug delivery, bioimaging, and biosensing), photocatalysis, water quality monitoring, and the food industry. Using marine polysaccharides to produce carbon quantum dots (CQDs) enables the transformation of renewable sources into a cutting-edge technological product. This review can provide fundamental insights for the development of novel nanomaterials derived from natural marine sources.

Color-tunable photoluminescent discotic liquid crystal based on perylene – Pentaalkynylbenzene triad

This article describes the design and development of a discotic triad, where perylene is sandwiched between two pentaalkynyl benzene units, linked via a flexible alkyl spacer. The thermotropic liquid crystalline properties of the compound were analyzed by differential scanning calorimetry (DSC), polarising optical microscopy (POM), and wide-angle X-ray diffraction (WXRD) techniques. The compound exhibits columnar oblique (Colob) mesophase that sustains over a significant temperature range. The corresponding electron density map was derived from the intensities observed in the diffraction pattern. The photophysical behaviour of the compound in various solvents of varying polarity has been studied. The compound shows positive solvatochromism with a significant increase in Stoke's shift of around 91 nm between toluene and ethanol. The compound shows high fluorescence quantum yield in non-polar solvents and the lowest in polar solvents. The presented luminescent material with positive solvatochromism will reveal its potential application in fluorescence imaging and the field of optoelectronic organic materials.

A multifunctional sensing of two carbon dots based on diaminonaphthalenes for detection of ofloxacin drug

Fluorescent carbon quantum dots (CQDs) have gained increased attention due to their diverse properties in the development of sensors and visualizing dynamic processes. This contribution demonstrates the synthesis of two carbon quantum dots, 2,3-CQDs and 1,8-CQDs from 2,3-Diaminonaphthalene and 1,8-Diaminonaphthalene, respectively by hydrothermal process. The results showed that the two CQDs had distinct optical properties with different sizes and therefore we observed different sensing performance and different dynamics interactions, which is dependent on the geometrical structure of precursors. Both CQDs exhibit bi-exponential decay curves with long and short-lived decay components, corresponding to recombination from the defect and intrinsic states, respectively. The sensing performance of 2,3-CQDs which possess high fluorescence quantum yield (0.2) demonstrates an ability to detect Ofloxacin based on fluorescence-enhanced turn off- on with a low detection limit of 0.46 μM and good linear range of 0–120 μM. Meanwhile the sensing of 1,8-CQDs with a quantum yield of 0.17 was performed for detection of Ofloxacin based on fluorescent turn-on–off due to energy transfer mechanism with wide linear response range of 0–120 μM and a satisfactory detection limit of 24 nM. These results indicate that we can adapt our systems to the intended applications by specifically and selectively altering carbon dots.

Green synthesized nitrogen-doped carbon quantum dots for the sensitive determination of larotrectinib in biological fluids and dosage forms: Evaluation of method greenness and selectivity

Recently, the kinase receptor inhibitor drug larotrectinib has been approved as a monotherapy for the treatment of patients with solid tumors containing the neurotrophic receptor tyrosine kinase gene fusion. In this paper, a novel sensitive spectrofluorimetric method was proposed for the determination of larotrectinib based on nitrogen-doped carbon quantum dots (N-CQDs) fluorescent probes. The proposed method is the first spectroscopic method for analysis of the cited drug, which is simple to implement and involves no pre-treatment steps or complicated techniques. The N-CQDs synthesis was performed by adopting a straightforward, fast, and environmentally friendly approach. It was achieved by means of a standard domestic microwave with inexpensive and readily available starting materials: orange juice (carbon source) and urea (nitrogen source). The synthesized N-CQDs were subjected to microscopic and spectroscopic characterization procedures. They were found to be stable with a sufficiently high fluorescence quantum yield (25.3%) and a small particle size distribution (2–5 nm). The motivation for the use of N-CQDs in this study arose from their excellent fluorescence intensities at 417 nm when excited at 325 nm. Larotrectinib was found to have a quantitative and selective quenching effect on the QDs fluorescence allowing for its sensitive determination. The drug’s quenching mechanism was investigated and found to be of the static type. Under optimal conditions, the proposed approach permitted the determination of larotrectinib over the concentration interval of 5.0–28.0 µg/mL. The method showed sufficient sensitivity with a detection limit of 0.19 µg/mL and a quantitation limit of 0.57 µg/mL, enabling the determination of LARO in spiked human plasma samples. The approach’s recovery percentage was found to be in the range of 99.09–100.73% for pure samples and 97.35–102.59% for plasma samples. The study also successfully applied the proposed approach to the commercial oral solution form of larotrectinib (Vitrakvi®) with high selectivity. Method greenness was further evaluated by adopting two metric tools, including the complementary green analytical procedure index (ComplexGAPI) and Analytical GREENNESS metric approach (AGREE), and it was confirmed to be excellent green. The proposed method was validated in accordance with the ICHQ2 (R1) recommendations and is considered an excellent candidate for potential application in the therapeutic monitoring of larotrectinib.

AIE properties of blue-light-emitting molecules based on triazine derivatives

Novel star-shaped molecules of triazine with different terminal oxyalkyl chains were synthesized and systematically investigated by aggregation induced emission (AIE) studies, photophysical properties, and electrochemical properties. These triazine derivatives have a broad absorbance range and good intramolecular charge transfer (ICT) character. They have a non-planar structure with a triazine as an acceptor and a benzene ring attached by a carbon-carbon single bond. The existence of terminal alkoxy chains increases steric hindrance, which is beneficial for limiting intramolecular motion and achieving AIE effect. They exhibit positive solvatochromism effect, high stokes shift and good fluorescence quantum yield. They exhibit AIE properties in N,N-dimethylformamide (DMF)/H2O mixtures. Among them, the AIE properties of 3-5OBCT is the most excellent and fluorescence intensity of 3-5OBCT in DMF/H2O mixtures with water fraction of 40% is 26.7 times that in pure DMF. Purely organic luminescent materials with AIE features exhibit high efficiency in non-doped OLEDs. Therefore, these materials have broad application prospects in the field of OLEDs.

Environmentally benign sensing platform for label free detection of Fe3+ and tobramycin using highly fluorescent carbon dots valorized from sweet potato roasting residues

A novel sustainable source with zero intended energy consumption is introduced for the first time for obtaining carbon dots (CDs). These CDs were spontaneously formed during the ordinary roasting of sweet potato (SPCDs) with a yield of 160.54 mg/kg. The obtained SPCDs exhibited high fluorescence quantum yield (53%) at 442 nm after excitation at 360 nm, narrow particle size distribution (3.54 ± 1.08 nm) and negative zeta potential (-12.2 mV). Using the obtained SPCDs, a sensitive, selective, rapid, and effortless turn off–on fluorescent sensing platform was constructed for label free detection of the non chromophoric drug, tobramycin (TOB). The proposed sensing strategy was based on the possible Fe3+ induced mixed mode static quenching/inner filter effect and fluorescence recovery through its complexation by TOB. The sensor demonstrated good performance for TOB detection with a linear range of 10.69 – 106.90 µM (5–50 µg/mL). The sensing platform was successfully applied for TOB detection in its ophthalmic solution, with good accuracy (100.39% ± 2.19) and precision (RSD, 2.18%), and can be adopted for its routine analysis without any chemical derivatization. Moreover, the developed sensor was successfully applied for TOB detection in real samples including honey and river water. Such sustainable and cost-effective carbon dots require neither special equipment nor hazardous chemicals so that it can be adopted as a source for CDs.

Palladium Catalyzed, Annulative Multiple C-H Bond Activations of BODIPYs to Access π-Extended Polycyclic Heteroaromatic Molecules with Deep Red Emissions and self-aggregation Behaviors.

Aromatic ring fusion on BODIPY core can effectively tune its electronic property, and red-shift the absorption and emission wavelength. In this work, we report that a one-pot Pd(II) catalyzed multiple C-H activation to access acenaphtho[b]-fused BODIPYs though the reaction of α,β-unsubstituted-BODIPYs and 1,8-dibromonaphthalenes. These newly synthesized acenaphtho[b]-fused BODIPYs revealed intensified deep red absorptions (639 - 669 nm) and emissions (643 - 683 nm), with high fluorescence quantum yields (0.53 - 0.84) in dichloromethane. Notably, these acenaphtho[b]-fused BODIPYs exhibited well-defined self-aggregation behavior in water/THF mixture, and for instance, the absorption of 3a was red-shifted by 53 to 693 nm after formingaggregates.

Fluorescence Decay Analysis of the Model Compounds as an Approach to Photophysical Engineering of Fluorescent Proteins

Studying of structure-function relationships between a chromophore and its protein environment plays a key role in photophysical engineering of fluorescent proteins (FPs), specifically, in the guided designing of their new variants with a higher fluorescence quantum yield (FQY). Known approaches to FQY increasing mostly rely on suppression of the excited state nonradiative processes, but no tools have been suggested for the tuning of the radiative rate constant (kr), which is also a potentially “adjustable” value. Here, we propose an experimental approach in which the synthetic chromophore of FP models the “fixation” of the most important radiationless constants and allows monitoring of the fluorescence lifetime flexibility (as an indicator of the kr value). As a proof-of-concept, we studied the time-resolved fluorescence behavior of the green and blue FP chromophore analogs in diverse chemical environments. The conformationally locked analog of the GFP chromophore in most cases showed monophasic fluorescence decay kinetics with a lifetime of 2.7–3.0 ns, thus adequately modeling the typical behavior of GFPs with the highest FQYs. Under the conditions of stimulated ionization of this chromophore, we observed increased (up to 4.3–4.6 ns) fluorescence lifetimes, which can be interpreted in terms of an increase in the radiative constant (kr). The conformationally locked analog of the Sirius chromophore showed biexponential fluorescence decay kinetics, partly simulating the properties of the blue FPs. In an acetic acid solution, this compound exhibited distinct fluorescent properties (elevated fluorescence intensity with a major lifetime population of ~4 ns), which can be interpreted as the emission of an unusual cationic form of the chromophore.

Quinolinium-Based Fluorescent Probes for Dynamic pH Monitoring in Aqueous Media at High pH Using Fluorescence Lifetime Imaging.

Spatiotemporal pH imaging using fluorescence lifetime imaging microscopy (FLIM) is an excellent technique for investigating dynamic (electro)chemical processes. However, probes that are responsive at high pH values are not available. Here, we describe the development and application of dedicated pH probes based on the 1-methyl-7-amino-quinolinium fluorophore. The high fluorescence lifetime and quantum yield, the high (photo)stability, and the inherent water solubility make the quinolinium fluorophore well suited for the development of FLIM probes. Due to the flexible fluorophore-spacer-receptor architecture, probe lifetimes are tunable in the pH range between 5.5 and 11. An additional fluorescence lifetime response, at tunable pH values between 11 and 13, is achieved by deprotonation of the aromatic amine at the quinolinium core. Probe lifetimes are hardly affected by temperature and the presence of most inorganic ions, thus making FLIM imaging highly reliable and convenient. At 0.1 mM probe concentrations, imaging at rates of 3 images per second, at a resolution of 4 μm, while measuring pH values up to 12 is achieved. This enables the pH imaging of dynamic electrochemical processes involving chemical reactions and mass transport.

Synthesis of Nanocellulose‐Based Nitrogen‐Doped Carbon Quantum Dots with High Fluorescence Quantum Yields for Multifunctional Applications

AbstractCarbon quantum dots (CQDs) are one of the most promising luminescent nanomaterials for anti‐counterfeiting due to their excellent optical properties, low toxicity, and environmental friendliness. With the development of green chemistry, biomass carbon sources have attracted attention. Herein, nitrogen‐doped carbon quantum dots (N‐CQDs) are synthesized using waste corn bract nanocellulose as the carbon source and L‐histidine as the nitrogen source in a simple and quick one‐step microwave method. It is found that a raw material mass ratio of 1:4, a temperature of 100 °C, and a preparation time of 5 min are the optimum preparation conditions. The fluorescence quantum yield of N‐CQDs obtained under these conditions is 32.64%. Under the excitation of light at a wavelength of 365 nm, the emission peak of N‐CQDs is located at 430 nm and emits blue light. This study also provides a method to prepare fluorescent anti‐counterfeiting films with excellent performance and fluorescent detection probes solely from waste biomass corn bract leaves and L‐histidine.

Preparation of One-Emission Nitrogen-Fluorine-Doped Carbon Quantum Dots and Their Applications in Environmental Water Samples and Living Cells for ClO- Detection and Imaging.

Hypochlorite (ClO-) has received extensive attention owing to its significant roles in the immune defense and pathogenesis of numerous diseases. However, excessive or misplaced production of ClO- may pose certain diseases. Thus, to determine its biological functions in depth, ClO- should be tested in biosystems. In this study, a facile, one-pot synthesis of nitrogen-fluorine-doped carbon quantum dots (N, F-CDs) was developed using ammonium citrate tribasic, L-alanine, and ammonium fluoride as raw materials under hydrothermal conditions. The prepared N, F-CDs demonstrate not only strong blue fluorescence emission with a high fluorescence quantum yield (26.3%) but also a small particle size of approximately 2.9 nm, as well as excellent water solubility and biocompatibility. Meanwhile, the as-prepared N, F-CDs exhibit good performance in the highly selective and sensitive detection of ClO-. Thus, a wide concentration response range of 0-600 μM with a low limit of detection (0.75 μM) was favorably obtained for the N, F-CDs. Based on the excellent fluorescence stability, excellent water solubility, and low cell toxicity, the practicality and viability of the fluorescent composites were also successfully verified via detecting ClO- in water samples and living RAW 264.7 cells. The proposed probe is expected to provide a new approach for detecting ClO- in other organelles.

Conformational effect on the photophysics of two BODIPY dyes in a mixture of butanol and acetonitrile: Insight from the steady-state, fluorescence time-resolved spectroscopy and TD-DFT calculations

We studied the effect of acetonitrile-butanol-1 mixture composition on the photophysics (absorption, fluorescence emission spectra, the quantum yield as well as the relaxation of the excited state) of two BODIPY derivatives with an aryl and pyridine substituent in the meso position and methyl (ethyl) in α,β-position. The behavior of these photophysical properties (fluorescence quantum yields, fluorescence lifetimes, radiative and nonradiative constants) as a function of the mixture composition points to its correlation with the rotation of the phenyl group that is possible in BDP2 while it is hindered in BDP1 as a channel of the excited state energy relaxation. As a consequence, the photophysical properties of BDP1 are weakly dependent on the mixture composition while those of BPD2 undergo two stages of variation. In the low mole fraction of Butanol-1 (lower than 0.48), where the viscosity changes by 0.8 MPa.s, the BDP2 photophysical properties are slightly dependent on the mixture composition. We conjecture that the free rotation of the phenyl group allows both radiative and nonradiative excited state relaxation to occur. This is shown by a relatively high fluorescence quantum yield and nonradiative constant values that remain constant in this range of butanol-1 mol fraction. For its further increase, the photophysical properties become strongly dependent on the change of the mixture composition and this was associated with the gradual increase of the viscosity by a factor of 1.7 MPa.s that results in a hindrance of the rotation of the phenyl group. This makes 8-phenyl substituted BDP2 a sensitive molecular rotor for small changes in viscosity between 0.2 and 3 MPa.s.

Naphthalimide-Annulated [n]Helicenes: Red Circularly Polarized Light Emitters

Two [n]heliceno-bis(naphthalimides) 1 and 2 (n = 5 and 6, respectively) where two electron-accepting naphthalimide moieties are attached at both ends of helicene core were synthesized by effective two-step strategy, and their enantiomers could be resolved by chiral stationary-phase high-performance liquid chromatography (HPLC). The single-crystal X-ray diffraction analysis of enantiopure fractions of 1 and 2 confirmed their helical structure, and together with experimental and calculated circular dichroism (CD) spectra, the absolute configuration was unambiguously assigned. Both 1 and 2 exhibit high molar extinction coefficients for the S0-S1 transition and high fluorescence quantum yields (73% for 1 and 69% for 2), both being outstanding for helicene derivatives. The red circularly polarized luminescence (CPL) emission up to 615 nm for 2 with CPL brightness (BCPL) up to 66.5 M-1 cm-1 demonstrates its potential for applications in chiral optoelectronics. Time-dependent density functional theory (TD-DFT) calculations unambiguously showed that the large transition magnetic dipole moment |m| of 2 is responsible for its high absorbance dissymmetry (gabs) and luminescence dissymmetry (glum) factor.

Facile synthesis of efficient red-emissive carbon quantum dots as a multifunctional platform for biosensing and bioimaging

The red-emissive carbon quantum dots (r-CQDs) have gained considerable interest in the field of fluorescence imaging as they can effectively overcome short-wave background interference. However, the development of efficient and simple synthetic pathways for the preparation of r-CQDs with high production yield and fluorescence quantum yield remains a great challenge. Herein, we prepared the intense red-emissive carbon quantum dots (r-CQDs) through one-pot hydrothermal treatment of methylene violet. The morphology and structure of the as-prepared r-CQDs were characterized through transmission electron microscopy, Raman spectra, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. r-CQDs were well dispersed in water with an average size of 2.39 nm. The surface of r-CQDs was full of oxygen-containing functional groups, which contributed to their high solubility in water. Under ultraviolet light (365 nm) irradiation, both the aqueous solution and powder of r-CQDs emitted intense red luminescence. r-CQDs exhibited the excitation-independent emission property with the maximum fluorescence peak at 596 nm. The fluorescence quantum yield of r-CQDs was calculated to be 26.46% in water using rhodamine B as a reference. Due to the significantly different fluorescence intensity in water and organic solvents, r-CQDs could be applied as the fluorescence sensor to quickly detect the trace amounts of water in various organic solvents. Moreover, the fluorescence of r-CQDs showed selective response to hypochlorite (ClO−) through an “on-off” sensing mechanism. The good biocompatibility of r-CQDs was verified by the cell counting kit-8 (CCK-8) method against mouse hepatocellular carcinoma (Hepa 1–6) cells. Finally, the r-CQDs were successfully used in cellular imaging and they were mainly located in the lysosomes of cancel cells. Thus, r-CQDs could be served as a powerful fluorescence nano-platform for biosensing and bioimaging.

Carbon dots doped with nitrogen as an ultrasensitive fluorescent probe for thrombin activity monitoring and inhibitor screening

A simple and sensitive fluorometric assay based on nitrogen-doped carbon dots (N-CDs) was developed for the determination of thrombin (TB) activity in human serum samples and living cells. The novel N-CDs were prepared by a facile one-pot hydrothermal method using 1,2-ethylenediamine and levodopa as precursors. Such N-CDs exhibited green fluorescence with excitation/emission peaks at 390/520 nm and a high fluorescence quantum yield of approximately 39.2%. H-D-Phenylalanyl-L-pipecolyl-Larginine-p-nitroaniline-dihydrochloride (S-2238) was hydrolyzed by TB to produce p-nitroaniline which was capable of quenching the fluorescence of N-CDs due to an inner filter effect. This assay was used to detect TB activity with a low detection limit of 11.3 fM. The proposed sensing method was then expanded to the TB inhibitor screening and exhibited excellent applicability. As a typical TB inhibitor, argatroban was determined in a concentration as low as 1.43 nM. The method has also been successfully employed for the determination of TB activity in living HeLa cells. This work showed significant potential for TB activity assay in clinical and biomedicine applications.

Recent Advances in Highly Fluorescent Hydrazine-Inserted Pyrrole-Based Diboron-Anchoring Fluorophores: Synthesis and Properties

AbstractHydrazine-inserted pyrrole-based diboron fluorophores that display strong fluorescence in either the solution or solid state are widely used in biomedicine and optoelectronic materials science. A growing demand calls for multiple strategies for generating novel fluorophores to solve problems of small Stokes shifts and poor solid-state fluorescence. By changing their frameworks, several series of novel diboron compounds have recently been developed as increasingly valuable classes of fluorophores owing to their tunable structures and outstanding spectroscopic properties, such as high fluorescence quantum yields, large Stokes shifts, high photostability, and low LUMO energy levels due to the presence of electron-deficient BF2 groups. This review mainly highlights key synthetic strategies for the fluorophores BOPHY, BOPPY, and BOAPY developed by our group, together with the superior properties of these compounds. Significant photophysical data for these fluorophores in solution and solid states are included within the scope of this review. The facile functionalization of these fluorophores permits practical structural modifications to generate novel versatile dyes with excellent chemical and photophysical properties. We believe that these fluorophores hold promise to make important contributions in a wide range of applications.1 Introduction2 BOPHY Fluorophore2.1 Discovery of BOPHY and its Fundamental Properties2.2 Synthesis and Properties of Modified BOPHY Derivatives3 BOPPY and BOPYPY Fluorophores3.1 Discovery of BOPPY and BOPYPY, and Their Fundamental Properties3.2 Synthesis and Properties of Benzo-Fused BOPPYs from Isoindoles3.3 Nucleophilic Substitution and Cross-Coupling Reactions of Halogenated BOPPYs3.4 Knoevenagel Reaction4 BOAPY and BOPAHY Fluorophores5 Conclusion

Role of functionalization in the fluorescence quantum yield of graphene quantum dots

As graphene is sculptured into quantum dots, quantum confinement and edge effects induce a finite energy gap and trigger exotic photoluminescent behavior. However, synthesis of graphene quantum dots (GQDs) with high fluorescence quantum yield and designated emission color remains challenging, due to a lack of knowledge in the exact influences of various structural and chemical factors. Herein, we explore the optical absorption and emission in GQDs with surface functionalization, heteroatom doping, or edge modification. Their fluorescence spectra are systematically compared by time-dependent density functional theory calculations. It shows that the sp3-type surface functionalization by O, OH, or F groups can effectively increase the fluorescence intensity by five orders of magnitude with regard to pristine GQDs, ascribed to the localization of excited carriers that enlarges the transition dipole moment for radiative decay. The functional groups also play a key role in fluorescent sensing of toxic metal species with high selectivity and sensitivity.