High Fluorescence Quantum Yield Research Articles

Living Hybrid Exciton Materials: Enhanced Fluorescence and Chiroptical Properties in Living Supramolecular Polymers with Strong Frenkel/Charge-Transfer Exciton Coupling.

A family of chiral perylene diimides (PDIs) was newly developed as excellent circularly polarized luminescence (CPL) materials. They are asymmetrically derivatized with a double-alkyl-chained L- or D-glutamate unit and a linear or branched alkyl chain. When water is added to the tetrahydrofuran (THF) solution of glutamate-PDI-linear-alkyl chain compounds, kinetically formed H-aggregates are formed in globular nanoparticles (NPs). These NPs undergo spontaneous transformation into thermodynamically stable nanotubes via helical nanostructures, which showed structured broad spectra originating from the strong coupling of delocalized Frenkel excitations (FE) and charge transfer excitations (CTE). Significant enhancement of circular dichroism (CD), fluorescence quantum yield, and circularly polarized luminescence (CPL) with luminescence dissymmetry factor (glum) are observed during the transformation of NPs to the FE/CTE-coupled helical and tubular structures. This transformation process is significantly accelerated by applying physical stimuli, i.e., ultrasonication or adding helical aggregates as seed crystals, a feature unique to living supramolecular polymerization. Meanwhile, the branched chain-containing PDIs only form H-aggregates and did not show FE/CTE hybrid exciton states with living supramolecular polymerization properties. This study unveils that suitably designed chiral PDI derivatives show FE/CTE coupling accompanied by high fluorescence quantum yields, enhanced chiroptical properties, and supramolecular living polymerization characteristics.

Quantum dots as a fluorescent labeling tool for live-cell imaging of Leptospira.

Leptospirosis is a global public health problem caused by Gram-negative pathogenic bacteria belonging to the genus Leptospira. The disease is transmitted through the urine of infected animals, which contaminates water and soil, leading to the infection of other animals and humans. Currently, several approaches exist to detect these bacteria; however, a new sensitive method for the live-cell imaging of Leptospira is required. In this study, we report the green synthesis of cadmium telluride quantum dots (CdTe QDs) which are unique fluorescent nanocrystals with a high fluorescence quantum yield capable of modifying cell surfaces and are biocompatible with cells. The fabrication of QDs with concanavalin A (ConA), a carbohydrate-binding lectin and known biological probe for Gram-negative bacteria, produced ConA-QDs which can effectively bind on Leptospira and exhibit strong fluorescence under simple fluorescence microscopy, allowing the live-cell imaging of the bacteria. Overall, we performed the simple synthesis of ConA-QDs and demonstrated their potential use as versatile fluorescent probes for the live-cell imaging of Leptospira. This technique could be further applied to track leptospiral cells and study the infection mechanism, contributing to a more thorough understanding of leptospirosis and how to control it in the future.

Structural Fine‐tuning to Achieve Highly Fluorescent Organic and Water‐soluble Thiazolo[5,4‐d]thiazole Chromophores

Fluorescent molecular systems are important for various applications such as sensing of analytes, probes for biologically relevant processes and as optoelectronic materials. Achieving high fluorescence quantum yield across the spectrum of solvent polarity and in solid‐state is challenging in molecular materials. Herein, we present a strategy to achieve strongly fluorescent molecular materials based on weak intramolecular charge‐transfer (ICT) in a family of unsymmetrical donor‐thiazolo[5,4‐d]thiazoles‐acceptor systems (both neutral and cationic). Detailed photophysical studies reveal that the delicate balance between the donor and acceptor result in high solution‐state fluorescence quantum yield (> 80%) in both polar protic and apolar solvents. Quantum chemical computations uncover a hitherto unappreciated insight that the extent of ICT is aptly represented by the change in Mulliken charges between the ground and excited‐state for different fragments rather than the classical approach of monitoring the change in dipole moment for the entire molecule. This insight rationalizes the observed photophysical properties and can have implications in the design of tuneable donor‐π‐acceptor systems.

Carbon dots with tunable excitation-independent fluorescence and organelle-specific targeting via core graphitization and surface groups engineering

Single-emission fluorescence and non-specific cellular organelle-targeting limit the application of carbon dots (CDs) in bio-imaging. Here, we proposed an adjustable strategy for synthesis of four CDs: Tm1-, Tm2-, Tma-, and Tp-CDs. The synthetic scheme was designed with tartaric acid and m-/p-phenylenediamine as precursors and water/acetone as solvent through hydrothermal/solvothermal synthesis and (or) column chromatography isolation. The maximum productivity of the CDs was 56.2 % and the highest fluorescence quantum yield was 47.8 %. These CDs emitted excitation-independent blue, green, and yellow fluorescence, respectively. The red shift of CDs fluorescence was caused by increasing graphitized conjugated sp2 domain and graphitic nitrogen content of carbon core. The hydrophilicity/lipophilicity and protonation ability of CDs determined their cellular uptake, intracellular trafficking and subcellular targets, including endoplasmic reticulum, lysosomes and nucleus. These CDs have the potential application in fluorescence visualization of live bacteria and in the organelle-targeted imaging of living mammalian, fungal, and plant cells. The study provides novel insights into rational design of CDs with multi-color fluorescence and organelle-specific targeting in live cells.

Novel triphenylamine-pyrene-based AIEgens: Specific detection and imaging of H2O2 in aqueous solution and cells

H2O2 plays a key regulatory role as a bioendogenous reactive oxygen species in cells and organisms. However, excessive production or accumulation of H2O2 during mitochondrial oxidative stress may lead to oxidative damage of cellular proteins and trigger rheumatic diseases, cancers, and a variety of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. In addition, H2O2 is a very useful chemical widely employed in the textile and chemical industries, and its excessive emission not only pollutes the environment but also jeopardizes human health. Therefore, the sensitive and specific detection and removal of H2O2 is important for early diagnosis of diseases, treatment prognosis and environmental pollution monitoring. We have designed two novel triphenylamine-based AIEgens MOTPP and MOTPP-B, which each have a high solid-state fluorescence quantum yield and excellent aggregation-induced emission properties. MOTPP-B has high selectivity and anti-interference ability toward H2O2, a wide pH tolerance range, a sensing process that is complete in under 40 min, and a low detection limit of 120.77 nM. It has been successfully applied for the detection of low concentrations of H2O2 in the environment and to dual-channel imaging of low concentrations of exogenous H2O2 in living cells.

Cyclic Azahelicene Dimers Showing Bright Circularly Polarized Luminescence and Selective Fluoride Recognition

AbstractAlthough helicenes are promising molecules, the synthetic difficulty and tediousness have often been problems, and only small amounts of optically pure helicenes have been obtained by using chiral HPLC in most cases. Herein, aza[7]helicenes or closed‐aza[7]helicenes with (1R)‐menthyl substituents were selectively synthesized via the intramolecular Scholl reaction, and the diastereomeric pairs were separated by silica gel column chromatography. The optically pure helicenes were further transformed into the corresponding cyclic dimers, and the chiroptical properties were investigated. The rigid π‐frameworks of the dimers led to the high molar extinction coefficients and fluorescence quantum yields, while the twisted helicene moieties induced clear Cotton effects and CPL in the visible region, and the high CPL brightness (BCPL) was achieved. Furthermore, the cyclic dimers were found to have the macrocyclic cavity with the two NH groups suitable for the selective binding of a fluoride anion, which induced significantly redshifted fluorescence and CPL in the red region.

Fluorescent octahydrophenazines as novel inhibitors against herpes simplex viruses

A new series of racemic fluorescent octahydrophenazines (rac-PZ1–11) have been designed and synthesized via the efficient nucleophilic aromatic substitution (SNAr) of tetrafluorobenzenedinitriles (1a–c) and racemic cyclohexane-1,2-diamines (rac-2a and b). The bioactivities of these racemic rac-PZs (20 μM) against herpes simplex virus type-1 (HSV-1) were evaluated by the relative cell viability of Vero cells infected with HSV-1. It was found that rac-PZ3 shows much higher anti-HSV-1 activity than others, with EC50 = 9.2 ± 1.4 μM. Further investigation into the anti-HSV activities of rac-PZ3 and its enantiomers RR- and SS-PZ3 indicates that rac-PZ3 can also efficiently inhibit HSV-2 and even ACV-resistant HSV-2 (EC50 = 11.0 ± 2.3 and 14.9 ± 2.8 μM, respectively), SS-PZ3 has better activities against HSV-1, HSV-2 and ACV-resistant HSV-2 (EC50 = 4.1 ± 1.1, 5.8 ± 1.0 and 7.9 ± 1.2 μM, respectively), but RR-PZ3 has almost no antiviral activities. The primary mechanism study indicates that rac-PZ3 efficiently reverses the HSV-1/2-induced cytopathic effect and suppresses the expression of viral mRNA and proteins. In addition, rac-, RR- and SS-PZ3 possess excellent fluorescence properties with almost the same emission wavelength and high fluorescence quantum yields (ΦF = 90.3–92.3 % in cyclohexane solutions and 54.4–57.3 % in solids) and can target endoplasmic reticulum and cell membrane. The efficient anti-HSV bioactivities and excellent fluorescence of PZ3 prove its potential applications in antiviral therapy and biological imaging.

Benzo-Crown-Ether functionalized O-BODIPY Probes for Cations - A Selective Fluorescent Probe for Ba2.

Herein, we report the synthesis and sensing characteristics of 4,4'-methoxy-substituted BODIPY fluorescent probes (OBODIPYs) 3, 4 and 5 equipped with differently sized benzo-crown ethers (cf. Scheme 1, 3 (benzo-15-crown-5), 4 (benzo-18-crown-6) and 5 (benzo-21-crown7)). O-BODIPYs 3, 4 and 5 exhibited in comparison to their known F-BODIPY analogues 3a, 4a and 5a (cf. Scheme 1) an improved solubility in aqueous medium and higher fluorescence quantum yields. Fluorometric study in aqueous solutions of 3, 4 and 5 in the presence of different cations show cation induced fluorescence enhancements (FE). Compared to the benzo-crown ether substituted F-BODIPY analogues 3a, 4a and 5a, we found for the free O-BODIPYs 3, 4 and 5 higher fluorescence quantum yields (ϕf ) but lower cation induced FEs. We show that in aqueous medium the fluorescence quenching process (OFF switching), a photoinduced electron transfer, in O-BODIPYs 3, 4 and 5 is less effective and consequently sensitive and selective ON switching of the fluorescence by cations, too. Albeit these observations the novel benzo-21-crown-7 equipped fluorescent probe 5 exhibits a good fluorometric Ba2+ selectivity and Ba2+ sensitivity in conjunction to their superior aqueous solubility.

Facile green synthesis of dual stabilized near-infrared CuInSe/ZnS quantum dots as fluorescent probes for cancer-bacteria imaging

Imaging is a critical step in diagnosis and therapy; thus, developing a non-carcinogenic near-infrared (NIR) emitting probe for guided therapy remains a priority for effective bacteria and cancer treatment. Herein, we report the effect of dual stabilization in producing NIR fluorescent CuInSe/ZnS quantum dots (QDs) and their use as imaging probes in cancer-bacteria therapy. The as-synthesised NIR QDs were stabilized using different combinations of hydrophilic dual capping agents, MPA-Gelatine, TGA-Gelatine, MPA-Citrate and TGA-Citrate. The optical characteristics of the prepared dual-stabilized CuInSe/ZnS QDs indicate that the material has high stability and fluorescence quantum yield. The dual stabilization resulted in varied emission positions as well as fluorescence intensity for the as-synthesized QDs. The cytotoxicity evaluation showed that cells treated with dual stabilised CuInSe/ZnS QDs displayed good cell viability against malignant fibrous histiocytoma-like (KM-Luc/GFP) cells, mouse colon carcinoma (C26) cells and mouse mammary carcinoma (FM3A-Luc) cells. It also showed high affinity to prostate and human adenocarcinoma cells with no indication of QDs uptake by normal prostate cells. The biofilm analysis showed that the QDs uptake was elevated in Staphylococcus aureus (Gram-positive bacteria) than in Escherichia coli (Gram-negative bacteria). The dual stabilized QDs remain a promising study as future fluorescence probes for early diagnosis and guided cancer therapy.

Excited state dynamics of Rhodamine B and its excitonically coupled dimer: A computational and experimental approach

Rhodamine B (RhB) is widely used for its high fluorescent quantum yield and strong absorption in the visible range of the spectrum; however, its facile aggregation in aqueous solutions dramatically affects its photophysical properties. Surprisingly, the excited state dynamics of rhodamines are not fully understood despite the extensive literature around them. Here, we present a complete picture of the photophysics of RhB and the most likely dimer formed in aqueous solution. We deconvolved the excited state dynamics of RhB and its non-covalent dimer using a combination of steady-state (SS) and time-resolved spectroscopic methods supported by density functional theory (DFT) and time-dependent DFT (TD-DFT). In particular, we have determined the dimerization equilibria constant in sodium perchlorate solutions and measured the dimer’s photo-induced charge separation and charge-recombination events. Additionally, we studied 12 DFT exchange–correlation functionals (XCF), and determined which are appropriate and which are not appropriate for studying and interpreting the excited state dynamics observed through femtosecond transient absorption (fsTA).

Synergistic Modulation of Excited State Ingredients and Chiroptical Activity for High‐Performance Pure‐Green Circularly Polarized Electroluminescence

Synergistic Modulation of Excited State Ingredients and Chiroptical Activity for High‐Performance Pure‐Green Circularly Polarized Electroluminescence

Emission behaviors from ZnO microwire pumped CsPbBr3 perovskite microwire.

Perovskite semiconductor materials have attracted significant attention in the fields of photovoltaics and luminescence due to their excellent photoelectric properties, such as high carrier mobility, high absorption coefficient, and high fluorescence quantum yield. In particular, low-dimensional metal-halide perovskite microcrystalline materials have been reported to exhibit low-dimensional lasing phenomena and laser devices due to their high gain and widely tunable bandgap. In this Letter, one-dimensional (1-D) ZnO microwires with their ultraviolet lasing emissions are utilized as an excitation source to pump CsPbBr3 microwire on hybrid ZnO-CsPbBr3 microscale structures. At higher excitation, the amplified spontaneous emission (ASE) behaviors from CsPbBr3 microwire are realized with ultralow threshold by indirect pumping from the ZnO lasing emission for the first time, to the best of our knowledge. In comparison, the ASE behaviors from the CsPbBr3 microwire directly pumped by Nd:YAG Q-switched laser and continuous wave laser are also performed at room temperature. There are also no multimode lasing behaviors observed. The paper provides a new method to achieve a low threshold on-chip microlaser by a high-quality perovskite micro-nano structure.

Responsive Organic Fluorescent Aggregates Based on Ion‐π Interactions Away from Fluorescent Conjugated Groups

Responsive organic luminescent aggregates have a wide range of application fields, but currently there is still a lack of reasonable molecular design strategies. Introducing ion‐π interactions into molecules can effectively alter their luminescent properties. However, current research typically focuses on ion localization at luminescent conjugated groups with the strong interaction forces. In this work, we introduce the flexible alkoxy chain spacers between fluorescent conjugated groups and ion‐π interaction sites, and then adjust the fluorescence performance of the molecule by changing the strength of ion‐π interactions. Bromine ion‐based molecules with strong ion‐π interactions exhibit high and stable fluorescence quantum yields in crystals and amorphous powders under the external stimuli. Hexafluorophosphate ion‐based molecules with weak ion‐π interactions have the high fluorescence quantum yield in crystals and very low fluorescence quantum yield in amorphous powders, showing variable fluorescence intensities under external stimuli. This demonstrates a new class of responsive organic luminescent solid‐state materials.

Responsive Organic Fluorescent Aggregates Based on Ion-π Interactions Away from Fluorescent Conjugated Groups.

Responsive organic luminescent aggregates have a wide range of application fields, but currently there is still a lack of reasonable molecular design strategies. Introducing ion-π interactions into molecules can effectively alter their luminescent properties. However, current research typically focuses on ion localization at luminescent conjugated groups with the strong interaction forces. In this work, we introduce the flexible alkoxy chain spacers between fluorescent conjugated groups and ion-π interaction sites, and then adjust the fluorescence performance of the molecule by changing the strength of ion-π interactions. Bromine ion-based molecules with strong ion-π interactions exhibit high and stable fluorescence quantum yields in crystals and amorphous powders under the external stimuli. Hexafluorophosphate ion-based molecules with weak ion-π interactions have the high fluorescence quantum yield in crystals and very low fluorescence quantum yield in amorphous powders, showing variable fluorescence intensities under external stimuli. This demonstrates a new class of responsive organic luminescent solid-state materials.

Bright luminescent Zn2GeO4:Mn NP/MXene hydrogel-based ECL biosensor for glioblastoma diagnosis

In this work, miRNA-10b in the glioblastoma (GBM) tumor tissues has been detected by a novel electrochemiluminescence (ECL) biosensor. Firstly, a new kind of bright luminescent Zn2GeO4:Mn NPs were prepared as ECL nanoprobe, which possessed high fluorescence quantum yield and ECL quantum efficiency. Secondly, Ti3C2 MXene hydrogel (MXG) have been developed as the sensing interface. The MXG retained the inherent biocompatibility and mechanical features of hydrogel. Furthermore, the uniform distribution of metallic Ti3C2 MXene in the hydrogel microstructure provided the good conductivity and multiple binding sites for biomolecules. MXene also can promote the separation of the electrons and holes to accelerate the electron-transfer rate and improve ECL efficiency. Due to these synergistic effects, the screen printed electrode was successfully modified with MXG as sensing platform to enhance the ECL intensity of Zn2GeO4:Mn NP, which greatly improved the detection efficiency and facilitated the high-throughput analysis. Finally, the toehold mediated strand displacement (TMSD) strategy was employed with then biosensor to detect miRNA-10b with the range of 10 fM to 1 nM. The limit of detection was 5 fM. This ECL biosensor has been used to analyze miRNA-10b expression in GBM tumor tissues, which possessed the great potential value for clinical diagnosis.

A facile green synthesis of photoluminescent carbon dots using Pumpkin seeds for ultra-sensitive Cu2+ and Fe3+ ions detection in living cells

A facile and efficient green synthesis of photoluminescent carbon dots (CDs) was achieved using pumpkin seeds (PS) through the hydrothermal-carbonization method. Pumpkin seeds, well-known for their nutrient-rich composition, offer potential health benefits, including heightened fertility, enhanced heart health, and improved blood sugar regulation. The as-synthesized PS-CDs characterization through UV–vis, photoluminescence (PL), FTIR, XRD, and HR(TEM) analysis. The PL PS-CDs exhibited an excitation-dependent behavior, with the peak shifting from 410 nm to 475 nm under excitation wavelengths ranging from 270 nm to 400 nm. Notably, the synthesized PS-CDs displayed outstanding advantages, such as a high fluorescent quantum yield of 12.7 % with bright blue emissions when exposed to UV light at 365 nm. High-resolution TEM images revealed an average size of approximately 4.0 ± 0.2 nm for the synthesized PS-CDs, ranging from 2 to 7 nm with interlayer distance of 0.21 nm. PL spectra of PS-CDs solution, with an excitation wavelength of 338 nm and emission wavelength of 420 nm, were examined in the presence of various metal ions (50 μM). The fluorescence lifetime of the PS-CDs showed an exponential curve, with an average lifetime (τav) of 8.47 ns for Cu2+and 3.61 ns for Fe3+ ions, respectively, which is strongly indicates that quenching occurs through a static mechanism. The PS-CDs exhibited high sensitivity and selectivity towards Cu2+ and Fe3+ ions, with a linear relationship observed up to a concentration of 50 μM and detection limits of 0.43 and 0.11 μM (S/N = 3), respectively. Moreover, the low-toxicity and strongly fluorescent PS-CDs were successfully applied for cell imaging. The practical utility of the developed sensor was determined through the analysis of Cu2+ and Fe3+ ions in spiked water samples, highlighting its considerable analytical and bioanalytical applications.

Carbohydrate-Functionalized Anthracene Carboximides as Multivalent Ligands and Bio-Imaging Agents.

Anthracene carboximides (ACIs) conjugated with gluco-, galacto- and mannopyranosides are synthesized, by glycosylation of N-hydroxyethylanthracene carboximide acceptor with glycosyl donors. Glycoconjugation of anthracene carboximide increases the aq. solubility by more than 3-fold. The glycoconjugates display red-shifted absorption and emission, as compared to anthracene. Large Stokes shift (λabs/λem=445/525 nm) and high fluorescence quantum yields (Φ) of 0.86 and 0.5 occur in THF and water, respectively. The ACI-glycosides undergo facile photodimerization in aqueous solutions, leading to the formation of the head-to-tail dimer, as a mixture of syn and anti-isomers. Solution phase and solid-state characterizations by dynamic light scattering (DLS), microscopic imaging by atomic force (AFM) and transmission electron (TEM) microscopies reveal self-assembled vesicle structures of ACI glycosides. These self-assembled structures act as multivalent glycoclusters for ligand-specific lectin binding, as evidenced by the binding of Man-ACI to Con A, by fluorescence and turbidity assays. The conjugates do not show cellular cytotoxicity (IC50) till concentrations of 50 μM with HeLa and HepG2 cell lines and are cell-permeable, showing strong fluorescence inside the cells. These properties enable the glycoconjugates to be used in cell imaging. The non-selective cellular uptake of the glycoconjugates suggests a passive diffusion through the membrane.

Engineering Cyanine- and Hemicyanine-Based Probes for Optical Imaging of Kidney Diseases.

Molecular optical probes play pivotal roles in in vivo imaging of biomarkers associated to kidney diseases. Relying on structural tunability and high fluorescence quantum yields, versatile optical probes have been constructed on cyanine or hemicyanine-based scaffold in recent years. This review summaries the recent progress on the development of optical probes for imaging of kidney diseases, particularly through near-infrared fluorescence, chemiluminescence and photoacoustic imaging modalities. The chemical design and sensing mechanisms are discussed along with applications in the detection of renal cell carcinoma and acute kidney injury. This progress provides insights and directions for the development of next generation kidney-targeted probes and for pushing their further applications in preclinical and clinical research.

Conjugated molecularly imprinted polymers based on covalent organic frameworks: Fluorescent sensing platform for specific capture of urea and elimination of ethyl carbamate

This study described the preparation of an azide covalent organic framework-embedded molecularly imprinted polymers (COFs(azide)@MIPs) platform for urea adsorption and indirect ethyl carbamate (EC) removal from Chinese yellow rice wine (Huangjiu). By modifying the pore surface of COFs using the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction, COFs(azide) with a high fluorescence quantum yield and particular recognition ability were inventively produced. In order to selectively trap urea, the COFs(azide) were encased in an imprinted shell layer via imprinting technology. With a detection limit (LOD) of 0.016 μg L-1 (R2 = 0.9874), the COFs(azides)@MIPs demonstrated a good linear relationship with urea in the linear range of 0–5 μg L-1. Using real Huangjiu samples, the spiking recovery trials showed the viability of this sensing platform with recoveries ranging from 88.44 % to 109.26 % and an RSD of less than 3.40 %. The Huangjiu processing model system achieved 38.93 % EC reduction by COFs(azides)@MIPs. This research will open up new avenues for the treatment of health problems associated with fermented alcoholic beverages, particularly Huangjiu, while also capturing and removing hazards coming from food.

Aggregation-Induced Modulation of Ground and Excited State Photophysics of 5-(tert-Butyl)-2-Hydroxy-1,3-Isophthalaldehyde (5-tBHI).

5-(tert-Butyl)-2-hydroxy-1,3-isophthalaldehyde (5-tBHI) is a photochromic material susceptible to either excited state proton transfer or excited state intramolecular proton transfer, depending upon the solvent. However, it has also been found to aggregate in the presence of sodium dodecyl sulfate. In this current study, based on the steady-state and time-resolved spectroscopy, supported by crystallography, quantum chemical density functional theory calculation, and molecular dynamics (MD) simulation, we report on the aggregation of this potential single benzene-based emitter (SBBE) in neat solvents as well as solid phase to modulate its photophysics. It has been found that 5-tBHI forms mixed aggregates of different orders, owing to the presence of both enolic and tautomeric forms, to yield tunable emission, although the emission intensity is quenched. These findings suggest that the intramolecular hydrogen bonding of 5-tBHI not only limits intermolecular interactions but also promotes nonradiative deactivation pathways. Hence, designing and structural engineering, with a focus to suppressing intramolecular hydrogen bonding as well as increasing through space conjugation by replacing the aldehydic moieties with bulky aliphatic or aromatic ketonic groups, can be a plausible approach to yielding improved probes with tunable emission and higher fluorescence quantum yields.