Large Stokes Shift Research Articles

Rational design of peptide-based fluorescent probe for sequential recognitions of Cu(II) ions and glyphosate: Smartphone, test strip, real sample and living cells applications

A new peptide-based fluorescent probe named DMDH with easy-to-synthesize, excellent stability, good water solubility and large Stokes shift (225 nm) was synthesized for highly selective sequential detections of copper ions (Cu2+) and glyphosate (Glyp). DMDH demonstrated great detection performance towards Cu2+via strong fluorescence quenching, and forming non-fluorescence DMDH-Cu2+ ensemble. As a new promising cascade probe, the fluorescence of DMDH-Cu2+ ensemble was significantly recovered based on displacement approach after glyphosate was added. Interestingly, the limit of detections (LODs) for Cu2+ and glyphosate were 40.6 nM and 10.6 nM, respectively, which were far lower than those recommended by the WHO guidelines for drinking water. More importantly, DMDH was utilized to evaluate Cu2+ and glyphosate content in three real water samples, demonstrating that its effectiveness in water quality monitoring. Additionally, it is worth noting that DMDH was also applied to analyze Cu2+ and glyphosate in living cells in view of significant cells permeability and low cytotoxicity. Moreover, DMDH soaked in filter paper was used to create qualitative test strips and visually identify Cu2+ and glyphosate through significant color changes. Furthermore, smartphone RGB color recognition provided a new method for semi-quantitative testing of Cu2+ and glyphosate in the absence of expensive instruments.

Probing Alzheimer's pathology: Exploring the next generation of FDDNP analogues for amyloid β detection

Fluorescent probes are a powerful tool for imaging amyloid β (Aβ) plaques, the hallmark of Alzheimer’s disease (AD). Herein, we report the synthesis and comprehensive characterization of 21 novel probes as well as their optical properties and binding affinities to Aβ fibrils. One of these dyes, 1Ae, exhibited several improvements over FDDNP, an established biomarker for Aβ- and Tau-aggregates. First, 1Ae had large Stokes shifts (138–213 nm) in various solvents, thereby reducing self-absorption. With a high quantum yield ratio (φ(dichloromethane/methanol) = 104), 1Ae also ensures minimal background emission in aqueous environments and high sensitivity. In addition, compound 1Ae exhibited low micromolar binding affinity to Aβ fibrils in vitro (Kd = 1.603 µM), while increasing fluorescence emission (106-fold) compared to emission in buffer alone. Importantly, the selective binding of 1Ae to Aβ1–42 fibrils was confirmed by an in cellulo assay, supported by ex vivo fluorescence microscopy of 1Ae on postmortem AD brain sections, allowing unequivocal identification of Aβ plaques. The intermolecular interactions of fluorophores with Aβ were elucidated by docking studies and molecular dynamics simulations. Density functional theory calculations revealed the unique photophysics of these rod-shaped fluorophores, with a twisted intramolecular charge transfer (TICT) excited state. These results provide valuable insights into the future application of such probes as potential diagnostic tools for AD in vitro and ex vivo such as determination of Aβ1–42 in cerebrospinal fluid or blood.

A ratiometric fluorescent probe with dual-targeting capability for heat shock imaging

HSO3− is an important reactive sulfur species that maintains the normal physiological activities of living organisms and participates in a variety of redox homeostatic processes. It has been found that changes in HSO3− levels is closely related to the heat stroke phenomenon of the organism. Heat stroke causes damage to normal cells, which in turn causes damage to the body and even death. It is crucial to accurately monitor and track the physiological behavior of HSO3− during heat stroke. Herein, a ratiometric multifunctional fluorescent probe DRM-SO2 with dual-targeting ability to rapidly and precisely recognize HSO3− being constructed based on the FRET mechanism. DRM-SO2 has extra Large Stokes shift (216 nm), very high sensitivity (DL = 12.2 nM), fast response time and good specificity. When DRM-SO2 undergoes Michael addition with HSO3−, the fluorescence emission peak was blue-shifted from 616 nm to 472 nm, and a clear ratiometric signal appeared. The interaction between lysosomes and mitochondria in maintaining cellular homeostasis was investigated by the dual-targeting ability of the probe using HSO3− as a mediator. DRM-SO2 achieved successful targeting and real-time monitoring of exogenous and endogenous HSO3− in the cells. More importantly, imaging experiments in heat stroke mice revealed high HSO3− expression in intestinal tissues. This provides new ideas and research tools for early prevention of heat stroke-induced diseases such as intestinal injuries. In addition, the semi-quantitative monitoring experiments for paper-based visualization of HSO3− make the probe promising for the design of portable detectors.

Ultrabright Dibenzofluoran-Based Polymer Dots with NIR-IIa Emission Maxima and Unusual Large Stokes Shifts for 3D Rotational Stereo Imaging.

Emerging organic molecules with emissions in the second near-infrared (NIR-II) region are garnering significant attention. Unfortunately, achieving accountable organic emission intensity over the NIR-IIa (1300nm) region faces challenges due to the intrinsic energy gap law. Up to the current stage, all reported organic NIR-IIa emitters belong to polymethine-based dyes with small Stokes shifts (<50nm) and low quantum yield (QY; ≤0.015%). However, such polymethines have proved to cause self-absorption with constrained emission brightness, limiting advanced development in deep-tissue imaging. Here a new NIR-IIa scaffold based on rigid and highly conjugated dibenzofluoran core terminated by amino-containing moieties that reveal emission peaks of 1230-1305nm is designed. The QY is at least 10 times higher than all synthesized or reported NIR-IIa polymethines with extraordinarily large Stokes shifts of 370-446nm. DBF-BJ is further prepared as a polymer dot to demonstrate its in vivo 3D stereo imaging of mouse vasculature with a 1400nm long-pass filter.

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 (Ф) 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.

Quinoline based viologen as a multifunctional organic material – From crystal structures to photophysical and electrochemical properties, and application in DNA sensing and bioimaging

Developing new multifunctional organic materials is one of the current themes of research in organic materials chemistry. The class of N,N'-dialkylated bis-pyridinium compounds, namely, the viologens have been proven to offer such multifunctional materials. Herein, syntheses and crystal structure elucidation of trans-1,2-bis(4-quinolinyl)ethylene (BQE) and analogous N,N-dimethylated trans-1,2-bis(4′-quinolinium)ethylene (M2BQE) are discussed with their multifaceted materials properties. Two different crystal structures with significantly different molecular structures, namely, BQE and BQE⋅2H2O were obtained by tuning the solvent of crystallization. M2BQE showed a bathochromic shift both in its absorption by ∼ 3300 cm−1 and in emission by ∼2900 cm−1 in compared to BQE, which is the effect of quaternization. Large Stokes shifts were observed for both the BQE (∼8500 cm−1) and M2BQE (∼8050 cm−1). Both compounds showed two-step reduction events in cyclic voltammetry, of which the first steps were reversible. The pH dependent absorption and emission properties of BQE have been explored which revealed the stronger effect by methylation than protonation. M2BQE exhibited selective binding to ct-DNA, as confirmed by selective quenching of emission intensity, over AMP and ATP. Furthermore, both the BQE and M2BQE displayed very intriguing features in bioimaging by intracellular co-localization in HeLa cells. While BQE is predominantly localizes in lysosomes over mitochondria, M2BQE dication, on the other hand, explicitly localizes in mitochondria.

The deposition and the optical characteristics of Cu-based metal halide Cs3Cu2I5 thin film via mist deposition

Abstract Cu-based metal halides, such as Cs3Cu2I5, are promising materials for light-emitting diodes, photodetectors, and scintillators because of their excellent optical properties, nontoxicity, and high air stability. In this study, we demonstrated the deposition of high-coverage Cs3Cu2I5 thin films using solution-based mist deposition. By adjusting the substrate temperature appropriately, continuous Cs3Cu2I5 thin films were formed. The Cs3Cu2I5 thin films exhibited blue emission under ultraviolet irradiation, with a large Stokes shift of 1.40 eV. Furthermore, they exhibited a high photoluminescence quantum yield of over 80%.

Alkaline phosphatase activatable near-infrared fluorescent probe for in-situ diagnosis of cholestatic liver injury

Cholestatic liver injury (CLI) is a clinical syndrome caused by impaired bile excretion and is almost asymptomatic in early-stage. If CLI is not recognized timely, it will elicit more severe liver diseases. Therefore, earlier diagnosis of CLI is urgently needed but remains challenging. On the basis of the consensus that elevation of serum alkaline phosphatase (ALP) is the most susceptible indicator of earlier cholestatic diseases. Herein, we conjugated dicyanoisophorone with hydroxyl-substituted coumarin derivative to afford an intramolecular charge transfer (ICT)-based fluorophore TX-OH, and successfully constructed an enzyme activatable fluorescent probe TX-PS, which enables specifically detecting ALP with near-infrared emission (720nm), large stokes shift (198nm) and excellent linear relationship (R2 = 0.9969) between fluorescence intensity and the concentrations of ALP (0-100U/L). Moreover, TX-PS exhibits applicable for imaging of ALP activities in living cells and zebrafish with ignorable toxicity and shows great potential to visually screen ALP inhibitors. Importantly, the liver tissues from CLI mice displayed remarkably higher fluorescence intensity than that from normal mice, suggesting the valuable capability of TX-PS for evaluating CLI degree. Overall, this work affords a powerful tool for earlier diagnosis of CLI and high-throughput screening of ALP inhibitors or new drugs for CLI therapeutics.

A Low-molecular-weight, Long-wavelength Emissive Coumarin: Green Synthesis, Spectral Properties, Fluorescence Enhancement and Solvatochromism Application

In this study, a novel low-molecular-weight coumarin fluorescent dye, 3,4-dicyano-7-diethylaminocoumarin, was designed. This dye features a donor-π-bridge-acceptor (D-π-A) conjugated structure, which confers superior fluorescence properties.The dye was synthesized using a simple, efficient, and environmentally friendly two-step process, facilitating the direct conversion of the key intermediate into the final product via simultaneous addition and elimination reactions. A comprehensive structural characterization of the dye was undertaken, and its UV absorption and fluorescence emission properties were extensively analyzed using spectroscopic techniques, with structural explanations of the fluorescence activities provided by the Density Functional Theory (DFT) method.Experimental results revealed that this coumarin dye emits strong fluorescence, characterized by a long wavelength, a large Stokes shift, and high fluorescence intensity. It exhibits excellent fluorescent performance in various solvents. Despite experiencing fluorescence quenching in its solid state, the formation of an inclusion complex with β-cyclodextrin restores strong red fluorescence, presenting new possibilities for biofluorescence imaging. Notably, this coumarin dye also demonstrates a significant solvatochromic effect. This effect enables rapid visual discrimination among multiple sets of structurally and chemically similar organic solvents. Consequently, the dye holds promise as a versatile solvatochromic fluorescent probe for a broad spectrum of applications.

A phenothiazine coumarin based fluorescent probe with AIE feature for real-time detecting lysosomal ClO– in living cell

A new phenothiazine coumarin based probe WX-Lyso for detection of ClO– was developed. The probe showed obvious aggregation-induced emission (AIE) characteristic and exhibited a highly selective and sensitive turn-on fluorescence signal at 544 nm for ClO– with a large Stokes shift of 144 nm. The limit of detection (LOD) of ClO– was measured as low as 0.99 μM and a good line equation was obtained in the 0–50 μM concentration range. The detection mechanism was elucidated FT-IR, ESI-MS analysis and DFT. Furthermore, the probe had been demonstrated successfully has good lysosomal-targeting and high-contrast imaging abilities, which has the potential to become a new chemical tool and provide help for detecting ClO– in living systems.

Development of a ratiometric fluorescent probe for the detection of peroxynitrite

Peroxynitrite is one of the important reactive oxygen species in the human body and is closely related to the physiological and pathological processes of many diseases. Therefore, the development of probes to detect peroxynitrite is important for diagnostic and pathologic studies of many diseases. In this work, a ratiometric probe was designed using benzopyran as the recognition site, and the sensitivity and selectivity of the probe were tuned by modification of substituents on benzopyran. Upon reaction with peroxynitrite, the color of the solution changes to the naked eye (from blue to yellow), and the fluorescence changes from red to blue. The probe SJ has the advantages of large Stokes shift (237 nm), fast response (≤10 s), wide linear range, good selectivity, low detection line (21.3 nm), and low cytotoxicity. Probe SJ has been successfully used for bioimaging of endogenous and exogenous peroxynitrite.

Design and Preparation of Multicolor Long‐Lifetime Fluorescent Material Based on Charge‐Separated States

Design and Preparation of Multicolor Long‐Lifetime Fluorescent Material Based on Charge‐Separated States

The orthogonal α‐meso‐Linked bisBODIPY photosensitizers demonstrate effective two‐photon fluorescence imaging and photodynamic therapy

Hypoxic tumor microenvironments pose significant challenges to the clinical translation of cancer photodynamic therapy (PDT). While heavy atom‐free Type‐I boron dipyrromethenes (BODIPYs) photosensitizers can alleviate this challenge by reducing oxygen dependency, but they remain scarce. Herein, heavy‐atom‐free α,meso‐linked bisBODIPYs were designed and synthesized. These bisBODIPYs exhibit remarkable red‐shifted emission (λemmax ~670 nm), large Stokes shifts (~4480 cm‐1) and they are capable of producing both superoxide anion (O2•−) and singlet oxygen (1O2) in solution and cells. Additionally, they offer a wide PDT treatment window, ranging from 0.26 to 83.5 μM. Furthermore, these bisBODIPYs also demonstrate superior two‐photon fluorescence, promising for surgical navigation and integrating diagnosis with treatment.

Quantitative detection of L-cysteine with a ratiometric probe combined with smartphone imaging and fluorescent test strips

Cysteine is an important thiol involved in the vital activities of the human body, and many physiological processes in the body are associated with it. Accurate detection of cysteine is of great importance in monitoring the development of diseases. In this paper, we prepared a ratiometric flavonoid fluorescent probe, HDFA, that exhibits specific selectivity for L-cysteine. HDFA was the first fluorescent probe that can distinguish between L-cysteine and D-cysteine. When detecting L-cysteine, the fluorescence color changed from blue to yellow, and the fluorescence quantum yield increased from 16.96 % to 21.30 %. The probe has a short response time (90 s) to L-cysteine, a large Stokes shift (186 nm), good selectivity, and anti-interference, and the detection limit was 0.32 μM. The detection mechanism was confirmed by mass spectrometry. In addition, HDFA has good applications in cell imaging, smartphone fluorescence imaging and fluorescence test strip detection.

The Characterization of Multifaceted PREP1 Peptides Provides Insights into Correlations between Spectroscopic and Structural Properties of Amyloid-like Assemblies.

The widespread ability of proteins and peptides to self-assemble by forming cross-β structure is one of the most significant discoveries in structural biology. Intriguingly, the cross-β association of proteins/peptides may generate intricate supramolecular architectures with uncommon spectroscopic properties. We have recently characterized self-assembled peptides extracted from the PREP1 protein that are endowed with interesting structural/spectroscopic properties. We here demonstrate that the green fluorescence emission of the peptide PREP1[117-132] (λem ~ 520 nm), can be induced by excitation with UV radiation. The associated unusually large Stokes shift (Δλ ~ 150 nm) represents, to the best of our knowledge, the first evidence of an internal resonance energy transfer in amyloid-like structures, where the blue emission of some assemblies becomes the excitation radiation for others. Moreover, the characterization of PREP1[117-132] variants provides insights into the sequence/structure and structure/spectroscopic properties relationships. Our data suggests that the green fluorescence is plausibly associated with antiparallel β-sheet states of the peptide whereas parallel β-sheet assemblies are only endowed with blue fluorescence. Notably, the different PREP1[117-132] variants also form assemblies characterized by distinct morphologies. Indeed, the parent peptide and single mutants form compact but structured aggregates whereas most of the double mutants exhibit elongated and highly extended fibers.

BioAIEgens based on dehydroabietic acid and tetraphenylethene: How does isopropyl group of dehydroabietic acid affect their spectral performance

Based on dehydroabietic acid (DA) derived from natural rosin, two aggregation-induced emission luminogens (BioAIEgens) labeled as 12-DTPA-2pTPE and 13-DTPA-2pTPE were synthesized by introducing tetraphenylethylene (TPE) groups to dehydroabietic acid triarylamine (DTPA). Their structures were optimized, the spectral properties and AIE characteristics were investigated, and the compounds were prepared into nanoparticles (NPs) as fluorescent probes for cell imaging. The results show that the two BioAIEgens have typical AIE characteristics and large Stokes shifts (＞ 120 nm). Due to the electronic and spatial effects of the isopropyl group, the molecular configuration of 12-DTPA-2pTPE is more distorted, and the electron cloud distribution is also different from 13-DTPA-2TPE. The absorption and the emission peaks of 12-DTPA-2TPE are blue-shifted, and the fluorescence quantum yield in the solid is higher. In addition, the 13-DTPA-2TPE nanoparticles (NPs) have low cytotoxicity and good cell imaging effects in vitro.

A Red-Emission Fluorescent Probe with Large Stokes Shift for Detection of Viscosity in Living Cells and Tumor-Bearing Mice.

Abnormal viscosity is closely related to the occurrence of many diseases, such as cancer. Therefore, real-time detection of changes in viscosity in living cells is of great importance. Fluorescent molecular rotors play a critical role in detecting changes in cellular viscosity. Developing red emission viscosity probes with large Stokes shifts and high sensitivity and specificity remains an urgent and important topic. Herein, a novel viscosity-sensitive fluorescent probe (TCF-VIS1) with a large stokes shift and red emission was prepared based on the 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) skeleton. Due to intramolecular rotation, the probe itself does not fluorescence at low viscosity. With the increase in viscosity, the rotation of TCF-VIS1 is limited, and its fluorescence is obviously enhanced. The probe has the advantages of simple preparation, large Stokes shift, good sensitivity and selectivity, and low cytotoxicity, which make it successfully used for viscosity detection in living cells. Moreover, TCF-VIS1 showed its potential for cancer diagnosis at the cell level and in tumor-bearing mice by detecting viscosity. Therefore, the probe is expected to enrich strategies for the detection of viscosity in biological systems and offer a potential tool for cancer diagnosis.

Dual-Emission Origins in Bi3+-Doped M2O3 Sesquioxides (M = Sc, Y, Gd and Lu): A First-Principles Study.

Bi3+-doped sesquioxides exhibit dual emissions, marked by distinct Stokes shift and bandwidth, meaning unraveling their underlying origins is particularly intriguing. In this study, we employ first-principles calculations to investigate the luminescence mechanisms within the M2O3:Bi3+ (M = Sc, Y, Gd, Lu) series, with the goal of addressing the posed inquiry. Our investigation commences with the analysis of the site occupancy and charge state of bismuth ions in the two cationic sites through formation energy calculations. Additionally, we examine the local coordination environments for various excited states of Bi3+ dopants, including the 3P0,1 state and two types of charge transfer states, by evaluating their equilibrium geometric structures. The utilization of the hybrid functional enables us to obtain results of electronic structures and optical properties comparable with experiments. Importantly, the calculated energies for the 6s-6p transitions of Bi3+ dopants in the M2O3 series align well with the observed dual-emission energies. This alignment challenges the conventional spectroscopic sense that emission bands with large Stokes shifts can be exclusively ascribed to charge transfer transitions. Consequently, the integration of experimental and theoretical approaches emerges as the optimal strategy for designing novel Bi3+-doped phosphors.

A V-shaped bis-coumarin based fluorescence probe for F- detection in tea infusions and potable water and bioimaging applications in living systems

Fluorine (F) is a pivotal element in the formation of human dental and skeletal tissues, and the consumption of water and tea constitutes a significant source of fluoride intake. However, prolonged ingestion of water and tea with excessive fluoride content can lead to fluorosis, which poses a serious health hazard. In this manuscript, a novel turn-on fluorescent probe DCF synthesized by bis-coumarin and tert-butyldiphenylsilane (TBDPS) was introduced for detecting F- in potable water and tea infusions. By leveraging the unique chemical affinity between fluoride and silicon, F- triggers the silicon-oxygen bond cleavage in DCF, culminating in a conspicuous emission of yellow fluorescence. Validated through a succession of optical tests, this probe exhibits remarkable advantages in terms of superior selectivity, a low detection limit, a large Stokes shift, and robust interference resistance when detecting inorganic fluoride. Moreover, it can serve as portable test strips for on-site real-time identification and quantitative analysis of F-. Furthermore, the application of DCF for in-situ monitoring and imaging of F- in zebrafish and soybean root tissues proved its significant value for F- detection in both animal and plant systems. This probe potentially functions as an efficient instrument for delving into the toxic mechanisms of fluoride in physiological processes.

Synthesis, structure, photophysical properties and DFT investigation of novel Zn(II) complexes bearing π-extended 8-hydroxyquinoline-derived ligands

Six new Zn(II) complexes (Zn1–Zn6) were synthesized from 2,4-diaryl-8-hydroxyquinoline derivatives (HQ1–HQ6) and structurally characterized by ESI-MS, 1H NMR spectra and SC XRD. The analysis of NMR and XRD results revealed that all the complex geometries are tetrahedral in which the ligands coordinated with Zn(II) via the N and O atoms. The investigation of photophysical properties showed that the ligands themself are non-fluorescent, while the complexes displayed a strong emission at 597–628 nm, characterized by a fluorescence quantum yield of 0.36–0.98 with a large Stokes shift of 174–202 nm, except complex Zn2. Notably, the quantum yields of the complexes in the solvents and emission intensity in the solid state tend to increase in the presence of electron-donating substituents. Quantum chemical computations were conducted to investigate the electronic structure and optical characteristics of the compounds, yielding outcomes consistent with experimental observations.