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The results of an experiment assessing the applicability of solutions of 6-oxo-2-phenylimidazo[1,2-b]pyrido[4,3-e][1,2,4]triazine-7(6H)-yl)acetic acid on plates and cellulose substrates for detecting excessive levels of volatile organic compounds associated with endometritis inflammation relative to biologically normal levels are considered. The fluorescent properties of the dye are studied using gynecological mucus from cows collected in various periods (pre- and post-partum) and nasal mucus from newborn calves. The test system responses were compared with clinically established diagnoses and the results of a microbiological study. An evaluation of the test systems revealed a false positive rate of no more than 11% and a false negative rate of 2%. Other characteristics, such as specificity, accuracy, and precision of the test systems based on 6-oxo-2-phenylimidazo[1,2-b]pyrido[4,3-e][1,2,4]triazine-7(6H)-yl)acetic acid were also assessed. The potential application of this fluorophore to the rapid on-site diagnosis of endometritis inflammation in cows is considered promising based on these findings. [ABSTRACT FROM AUTHOR]

This article provides a comprehensive overview of the synthesis and modification of organic fluorophores, which are organic compounds that emit light when excited. It discusses various synthetic reactions used to create these fluorescent molecules, with a focus on transition-metal-catalyzed C–H activation reactions. The article categorizes recent C–H activation reactions and evaluates their advantages and limitations. This information is valuable for researchers and readers interested in the field of organic fluorophores. The document also includes biographical information about the authors, Dr. Tapasi Chand and Dr. Manmohan Kapur. [Extracted from the article]

Organic small‐molecule fluorophores, characterized by flexible chemical structure and adjustable optical performance, have shown tremendous potential in biosensing. However, classical organic fluorophore motifs feature large overlap between excitation and emission spectra, leading to the requirement of advanced optical set up to filter desired signal, which limits their application in scenarios with simple settings. Here, a series of wavelength‐tunable small‐molecule fluorescent dyes (PTs) bearing simple organic moieties have been developed, which exhibit Stokes shift up to 262 nm, molar extinction coefficients ranged 30,000–100,000 M−1 cm−1, with quantum yields up to 54.8 %. Furthermore, these dyes were formulated into fluorescent nanoparticles (PT‐NPs), and applied in lateral flow assay (LFA). Consequently, limit of detection for SARS‐CoV‐2 nucleocapsid protein reached 20 fM with naked eye, a 100‐fold improvement in sensitivity compared to the pM detection level for colloidal gold‐based LFA. Besides, combined with loop‐mediated isothermal amplification (LAMP), the LFA system achieved the visualization of single copy level nucleic acid detection for monkeypox (Mpox). [ABSTRACT FROM AUTHOR]

In today's world, the development and research of optoelectronic materials and devices based on solid‐state luminescence is essential. Due to their versatile application possibilities, e.g. as light‐emitting diodes or lasers, they are already indispensable. This work presents three halogenated anthracene derivatives [9‐PPh2‐10‐X‐(C14H8)] and their respective photoluminescent behavior in solution and in the solid state. The formation of halogen–π interactions in the solid state leads to unanticipated luminescence properties for the chlorinated species, resulting in a strong bathochromic shift, green fluorescence and a longer lifetime. In contrast, the other two derivatives, which in turn form only weak π–π interactions due to a small overlap of the anthracene rings, barely change their luminescence behavior in the solid state. By employing additional charge density studies, the structure–property correlation is also investigated. In particular, focus is given to halogen bonding and halogen–π interactions and their influence on photophysical properties of the studied compounds. Through the new knowledge gained, this study will help in the future development and selective application of the photophysical properties of solid‐state luminescent materials. [ABSTRACT FROM AUTHOR]

Single-molecule localization microscopy (SMLM) is an optical super-resolution technique that circumvents the diffraction limit of light by localizing the center point of each fluorophore's recorded point spread function. SMLM requires the use of labeling strategies and specialized fluorophores and/or buffer conditions that enable most of the fluorophores in the sample to be "turned off" during the experiment so that a sparse subset of the fluorophores in the sample can be isolated from their nearest "on" neighbors and localized to build up an image of interest. Due to the nature of super-resolution single-molecule imaging, careful sample preparation, imaging buffer preparation, and optimized imaging conditions are fundamental requirements for obtaining quality data. This article discusses key factors to consider when preparing samples and acquiring data for SMLM to serve as a starting point for sample preparation and acquisition optimization. [ABSTRACT FROM AUTHOR]

In recent years, organic fluorophores-based molecular probes with dual-fluorescence ratiometric responses to in-vitro / in-vivo pH (DFR-MPs-pH) have been attracting much interest in fundamental application research fields. More and more scientific publications have reported the exploration of various DFR-MPs-pH systems that have unique dual-fluorescence ratiometry as the signal output, in-built and signal self-calibration functions to improve precise detection of targets. DFR-MPs-pH systems possess high-performance applications in biosensing, bioimaging and biomedicine fields. This review has comprehensively summarized recent advances of DFR-MPs-pH for the first time. First of all, the compositions and types of DFR-MPs-pH are introduced by summarizing different organic fluorophores-based molecule systems. Then, construction strategies are analyzed based on specific components, structures, properties and functions of DFR-MPs-pH. Afterward, biosensing and bioimaging applications are discussed in detail, primarily referring to pH sensing and imaging detection at the levels of living cells and small animals. Finally, biomedicine applications are fully summarized, majorly involving bio-toxicity evaluation, bio-distribution, biomedical diagnosis and therapeutics. Meanwhile, the current status, challenges and perspectives are rationally commented after detailed discussions of representative and state-of-the-art studies. Overall, this present review is comprehensive, in-time and in-depth, and can facilitate the following further exploration of new and versatile DFR-MPs-pH systems toward rational design, facile preparation, superior properties, adjustable functions and highly efficient applications in promising fields. Schematic illustration of this present review about organic fluorophores-based molecular probes with dual-fluorescence ratiometric responses on in-vitro/in-vivo pH for biosensing, bioimaging and biotherapeutics applications. [Display omitted] • This review summarizes organic fluorophores-based molecular probes with ratiometric fluorescence biosensing of pH. • Compositions, constructions, biosensing, bioimaging and biomedicine applications of the probes are summarized. • Current status, challenges and perspectives are discussed. [ABSTRACT FROM AUTHOR]

Optical imaging, especially fluorescence and photoacoustic imaging, is a non‐invasive imaging approach with high spatial and temporal resolution and high sensitivity, compared to positron emission tomography (PET) or magnetic resonance imaging (MRI). Due to the merits of imaging using the second near‐infrared (NIR‐II) window, like deeper penetration depth, high signal‐to‐noise ratio, high resolution, and low tissue damage, researchers have devoted great effort to developing contrast agents with NIR‐II absorption or emission. In this Review, we summarize recently developed organic luminescent and photoacoustic materials, ranging from small molecules to conjugated polymers. Then, we systematically introduce engineering strategies and describe the imaging performance classified by the skeleton cores. Finally, we elucidate the challenges and prospects of these NIR‐II organic dyes for potential clinical applications. We expect our summary can inspire researchers to expand the spectrum of NIR‐II contrast agents for diverse bioapplications. [ABSTRACT FROM AUTHOR]

Second near-infrared window (NIR-II) fluorescence imaging has shown great potential in the field of bioimaging. However, the excitation wavelengths of most NIR-II fluorescence dyes are in the first near-infrared (NIR-I) region, which leads to limited imaging depth and resolution. To address such issue, NIR-II fluorescence dyes with 1,064 nm excitation have been developed and applied for in vivo imaging. Compared with NIR-I wavelength excited dyes, 1,064 nm excited dyes exhibit a higher tissue penetration depth and resolution. The improved performance makes these dyes have much broader imaging applications. In this mini review, we summarize recent advances in 1,064 nm excited NIR-II fluorescence fluorophores for bioimaging. Two kinds of organic fluorophores, small molecule dye and semiconducting polymer (SP), are reviewed. The general properties of these fluorophores are first introduced. Small molecule dyes with different chemical structures for variety of bioimaging applications are then discussed, followed by the introduction of SPs for NIR-II phototheranostics. Finally, the conclusion and future perspective of this field is given.

In this work, we first designed and synthesized tetraphenylene‐fused aryl‐imidazole derivatives TM‐1–4 via regulation of molecular structure, which were consisted of 1H‐imidazo[4,5‐f][1,10]phenanthroline, 1H‐phenanthro[9,10‐d]imidazole, 4,5‐diphenyl‐1H‐imidazole, 3,3′‐(1H‐imidazole‐4,5‐diyl)dipyridine moieties and AIE‐active tetraphenylethene units, respectively. The results illustrated that TM‐1–4 exhibited clear AIE characteristics. Meanwhile, TM‐2 and TM‐3 show excellent solid emission properties (ΦTM‐2=13.73 % and ΦTM‐3=36.21 %), whereas TM‐1 and TM‐4 exhibit the opposite properties (ΦTM‐1=1.48 % and ΦTM‐4=4.83 %). The multiple rotors (pyridine and benzene ring) causes twisted conformations of the molecule that prevents π‐π stacking and enhances solid emission(ΦTM‐2<ΦTM‐3, ΦTM‐1<ΦTM‐4). Significantly, TM‐2 and TM‐3 also exhibited reversible mechanochromic behavior (Emission red shifts: ΔλTM‐2=43 nm and ΔλTM‐3=41 nm) with color changes between blue and green emissions. The powder X‐ray diffraction (PXRD) suggested the disordered state of ground sample could be readily returned to an ordered crystalline. Therefore, the mechanochromisms of TM‐2 and TM‐3 are ascribable to the phase transformation between crystal and amorphous structure. The single crystal X‐ray analysis of TM‐2 reveals a twisted conformation for TPE moiety and the absence of π‐π intermolecular stacking. These excellent optical properties of TM‐2 and TM‐3 make them potentially applications in mechanochromic materials and imaging agents. [ABSTRACT FROM AUTHOR]

Two organic fluorophores, fluorescein (F) and rhodamine B (Rd), were entrapped in calcium phosphate nanoparticles. The as-obtained nanoparticles can be used for biological release applications. For this aim, calcium phosphate nanoparticles were synthesized using the precipitation method. Structural analysis of these nanoparticles was performed using XRD, FTIR, and Raman spectroscopy, confirming that the synthesized nanoparticles were hydroxyapatite. TEM and SEM analyses demonstrated that these nanoparticles had a size of 20 nm and a well-defined morphology. F and Rd (about 0.5 wt.%) were entrapped in these nanoparticles and their release, as a function of time, was studied via UV-Vis spectroscopy. The obtained results showed that the release of both fluorophores was progressive over time. The trapping efficiencies of the fluorophores were 67.15% and 90.76% for F and Rd, respectively. [ABSTRACT FROM AUTHOR]

Organic small molecule fluorescent groups have injected new material support into the field of medical imaging due to their unique luminescence mechanism and easy tuning of structure. The great potential of NIR-II window imaging forces us to continuously optimize the structure of organic fluorophores to design better fluorescent molecules for fluorescence imaging-guided surgery. An ideal organic small molecule fluorescent group: it can penetrate into the inside of the organism, clearly present the internal structure and the edge contour of different tissues, so as to perfectly achieve internal imaging and accurately guide external surgery. In vivo, fluorescent groups do not damage normal tissues and organs. However, problems such as low quantum yield and poor biocompatibility greatly limit the clinical transformation of NIR-II fluorescent small molecules. To avoid the shortcomings of NIR-II fluorescent probes as much as possible and better realize image-guided surgery, in this experiment, the biplane donor unit was incorporated into the twisted D-π-A-π-D structure to expand the conjugated structure of the fluorescent group, which not only realized NIR-II emission, but also had high quantum yield and biosafety. [Display omitted] • CED NPs have high quantum yield and biosafety. • CED NPs can clearly show the tumor contour of subcutaneous tumor nude mice. • CED NPs can clearly label the enlarged lymph nodes in nude mice with metastatic tumors. [ABSTRACT FROM AUTHOR]

Organic fluorophores have found broad application as emitters in luminescent solar concentrators (LSCs) for silicon photovoltaics. In particular, the preparation of organic conjugated systems with intense light-harvesting ability, emissions in the deep-red and NIR regions, and large Stokes shift values represent a very challenging undertaking. Here, we report a simple and easy way to prepare three symmetrical donor–acceptor–donor (DAD) organic-emitting materials based on a thienopyrazine core. The central core in the three dyes was modified with the introduction of aromatic substituents, aiming to affect their optical properties. The fluorophores were characterized by spectroscopic studies. In all cases, visible-NIR emissions with large Stokes shifts were found, highlighting these molecules as promising materials for the application in LSCs.

Abstract The review is focused on the recent advances devoted to the diversity of the structures of a number of fluorescent dyes, in particular, dipyrrin complexes of boron – bodipy, their derivatives, analogs and related organic luminophores obtained on the basis of preorganization principles and directed molecular design. The properties of these dyes found in modern materials and acting either as independent preorganized molecules or as a part of complex molecular assemblies obtained by means of self-assembly and self-organization are being discussed. The possibilities of using fluorescent techniques and realizing the potential of optically active materials as high-performance sensors of self-assembly processes were also shown. The obtaining features and spectral characteristics of ionic and coordinate self-assemblies, including individual preorganized fluorophores, supramolecular gels, and polymers, as well as various nanomaterials based on the principles of supramolecular chemistry are being considered. The objective of this review is to show the relationship between unique properties of preorganized fluorophores and related dye-contained systems and their advantages in influencing on/taking part in supramolecular self-assemblies with a further design of new functionalized nano- and micro-sized objects and high-tech materials. Applications of fluorescent technics and optically active materials are also being discussed. Graphical abstract Image 1 Highlights • Preorganized fluorophores form lots of self-assemblies and supramolecular systems. • Structural changes of dipyrrin moieties allowed their controlled self-assembly. • Preorganized bodipy dyes and their assembles possess unique optical properties. • Bodipy dyes can be used as sensors of self-assembly processes. • Supramolecular assembles have many biological and chemical applications. [ABSTRACT FROM AUTHOR]

New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λmax due to intermolecular interactions in the lattice, along with an emission-band broadening, as compared to the solution fluorescence spectra.

In this study, we report on the synthesis of new organic fluorophores containing either the benzo[1,2‐d:4,5‐d′]bisthiazole or the dithieno[3,2‐b:2′,3′‐d]silole heterocyclic unit, and on their application for the fabrication of luminescent solar concentrators (LSCs) made of poly(methyl methacrylate) (PMMA) thin films. In solution, the new compounds absorbed light in the visible region and displayed a brilliant green emission in the 500–600 nm range with moderate‐to‐good fluorescence quantum yields (0.25–0.68). Dispersions of selected fluorophores in PMMA thin films mostly maintained the light absorption features observed in solution, although in the case of benzobisthiazole‐based fluorophore 1a an evident fluorescence red‐shift was observed when increasing the compound concentration in the film. In agreement with its promising optical properties, LSCs prepared with the latter compound yielded interesting optical efficiencies up to 6.42 %, not far from those of state‐of‐the‐art PMMA LSC devices. [ABSTRACT FROM AUTHOR]

Organic fluorophores are essential for organic optoelectronic and bioelectronic applications. Heavier halogens have been found to enhance fluorescence of organic aggregates, breaking the traditional view that heavy-atom effect leads to fluorescence quenching. Herein, we proposed that the bromine atoms show a limited acceleration to intersystem crossing (ISC) process, but largely reduce the vibronic coupling of singlet excitons, by inspecting TPE fluorophores and brominated analogs, achieving fluorescence enhancement of bromo-organic aggregates. This is because the lowest singlet excited state S 1 have lower energy than triplet state T 2 and large gap Δ E ST with T 1 , and strong oscillator strength. Moreover, the excited-state dynamics further demonstrate that the bromine substituents hugely decelerate the internal conversion process, and make a slow ISC rates (∼106 s−1), in contrast to the fast radiative transition (∼108 s−1), which is responsible for the abnormal fluorescence enhancement in brominated organic aggregates. [ABSTRACT FROM AUTHOR]

Considerable research efforts have been dedicated to understanding ovarian and breast cancer mechanisms, but there has been little progress translating the research into effective clinical applications. Hence, personalized/ precision medicine has emerged because of its potential to improve the accuracy of tumor targeting and minimize toxicity to normal tissue. Targeted therapy in both breast and ovarian cancer has focused on antibodies, antibody drug conjugates (ADCs), and very recently the introduction of human antibody fusion proteins. Small molecule inhibitors and monoclonal antibodies (mAbs) are used in conjunction with chemotherapeutic drugs as a form of treatment but problems arise from a board expression of the target antigen in healthy tissues. Also, insufficient tumor penetration due to tight binding affinity and macromolecular size of mAbs compromise the efficacy of these ADCs. A more targeted approach is thus needed, and ADCs were designed to meet this need. However, in ADCs the method of conjugation of drug to antibody is >1, altering the structure of the drug which leads to off-target effects. Random conjugation also causes the drug to affect the pharmokinetics and biodistribution of the antibody and may cause nonspecific binding and internalization. Recombinant therapeutic proteins achieve controlled conjugation reactions and combine cytotoxicity and targeting in one molecule. They can also be engineered to extend half-life, stability and mechanism of action, and offer novel delivery routes. SNAP-tag fusion proteins are an example of a theranostic recombinant protein as they provide a unique antibody format to conjugate a variety of benzyl guanine modified labels, e.g. fluorophores and photosensitizers in a 1: 1 stoichiometry. On the one hand, SNAP tag fusions can be used to optically image tumors when conjugated to a fluorophore, and on the other hand the recombinant proteins can induce necrosis/apoptosis in the tumor when conjugated to a photosensitizer upon exposure to a changeable wavelength of light. The dual nature of SNAP-tag fusions as both a diagnostic and therapeutic tool reinforces its significant role in cancer treatment in an era of precision medicine. [ABSTRACT FROM AUTHOR]

The application of two-photon absorption (2PA) materials is a classical research field and has recently attracted increasing interest. It has generated a demand for new dyes with high 2PA cross-sections. In this short review, we briefly cover the structure-2PA property relationships of organic fluorophores, organic-inorganic nanohybrids and metal complexes explored by our group. (1) The two-photon absorption cross-section (d) of organic fluorophores increases with the extent of charge transfer, which is important to optimize the core, donor-acceptor pair, and conjugation-bridge to obtain a large d value. Among the various cores, triphenylamine appears to be an efficient core. Lengthening of the conjugation with styryl groups in the D-π-D quadrupoles and D-π-A dipoles increased δ over a long wavelength range than when vinylene groups were used. Large values of d were observed for extended conjugation length and moderate donor-acceptors in the near-IR wavelengths. The d value of the three-arm octupole is larger than that of the individual arm, if the core has electron accepting groups that allow significant electronic coupling between the arms; (2) Optical functional organic/inorganic hybrid materials usually show high thermal stability and excellent optical activity; therefore the design of functional organic molecules to build functional organic-inorganic hybrids and optimize the 2PA properties are significant. Advances have been made in the design of organic-inorganic nanohybrid materials of different sizes and shapes for 2PA property, which provide useful examples to illustrate the new features of the 2PA response in comparison to the more thoroughly investigated donor-acceptor based organic compounds and inorganic components; (3) Metal complexes are of particular interest for the design of new materials with large 2PA ability. They offer a wide range of metals with different ligands, which can give rise to tunable electronic and 2PA properties. The metal ions, including transition metals and lanthanides, can serve as an important part of the structure to control the intramolecular charge-transfer process that drives the 2PA process. As templates, transition metal ions can assemble simple to more sophisticated ligands in a variety of multipolar arrangements resulting in interesting and tailorable electronic and optical properties, depending on the nature of the metal center and the energetics of the metal-ligand interactions, such as intraligand charge-transfer (ILCT) and metal-ligand charge-transfer (MLCT) processes. Lanthanide complexes are attractive for a number of reasons: (i) their visible emissions are quite long-lived; (ii) their absorption and emission can be tuned with the aid of appropriate photoactive ligands; (iii) the accessible energy-transfer path between the photo-active ligands and the lanthanide ion can facilitate efficient lanthanide-based 2PA properties. Thus, the above materials with excellent 2PA properties should be applied in two-photon applications, especially two-photon fluorescence microscopy (TPFM) and related emission-based applications. Furthermore, the progress of research into the use of those new 2PA materials with moderate 2PA cross section in the near-infrared region, good biocompatibility, and enhanced two-photon excited fluorescence for two-photon bio-imaging is summarized. In addition, several possible future directions in this field are also discussed (146 references). [ABSTRACT FROM AUTHOR]

Extracting biological information from awake and unrestrained mice is imperative to in vivo basic and pre-clinical research. Accordingly, imaging methods which preclude invasiveness, anesthesia, and/or physical restraint enable more physiologically relevant biological data extraction by eliminating these extrinsic confounders. In this article, we discuss the recent development of shortwave infrared (SWIR) fluorescent imaging to visualize peripheral organs in freely-behaving mice, as well as propose potential applications of this imaging modality in the neurosciences., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Arús, Cosco, Yiu, Balba, Bischof, Sletten and Bruns.)

Double helicenes have attracted increasing attention of researchers for their unique structures as well as potential application in material science. Most of the double helicene compounds are all-carbon helicenes, and nitrogen-doped double helicenes are rarely synthesized and studied. As polycyclic aromatic hydrocarbons doped with heteroatoms could show specific optoelectronic properties, it is necessary to develop new strategy for the synthesis of double azahelicenes. In this work, three double aza [5]helicene compounds have been designed and synthesized through Bischler-Napieralski cyclization. These molecules have symmetrical saddle-type conformations and P/M configurations. Moreover, these molecules could exhibit positive solvatochromic properties and have large Stokes shifts in various organic solvents. According to the DFT calculation results, the distributions of HOMOs are mainly over bilateral aromatic rings, while the LUMOs are delocalized over the central benzothiadiazole or benzopyrazine moiety. The calculation results are in consistent with the fluorescent properties of these molecules. This work provides a new strategy for the synthesis of double aza [5]helicene molecules with fluorescent properties. Double aza [5]helicene derivatives have been synthesized. These compounds have symmetrical saddle-type conformations and PM configurations. These double aza [5]helicenes have large Stokes shifts and could exhibit positive solvatochromic properties in solutions. [Display omitted] • Three double aza [5]helicene derivatives have been synthesized. • These double helicene molecules have symmetrical saddle-type conformations and P/M configurations. • These molecules have large Stokes shifts. • These molecules could exhibit positive solvatochromic properties in solutions. [ABSTRACT FROM AUTHOR]

As the use and importance of fluorescent materials in biomedical fields increase, the demand for stable and bright fluorescent materials in biological environment is increasing. Herein, a new fluorescent scaffold that satisfies the demands named 1,5-naphthyridine-2,6-dione (NTD) was developed and used for staining cells. Thienyl-flanked NTD (NTDT) exhibited photoluminescence quantum yield of 0.98 and brightness of 4.01 × 104, which was 1.2–1.6 times larger than those of diketopyrrolopyrrole-based model compound (DPPT). K r and k nr values of NTDT were twice larger and one order of magnitude smaller than those of DPPT , respectively. Theoretical calculation supported the better photophysical properties via lower reorganization energy and 1.9 times of oscillator strength of NTDT than those of DPPT , originated from rigid and planar structure of NTDT. Especially, NTDT showed no degradation and 62% maintenance of fluorescence in organic solvent and HeLa cells, respectively, while DPPT showed below 50% and 35% maintenances, respectively at the same light irradiation condition. Based on the synthetic flexibility of NTD core, colors are tuned from blue to red and solubility is adjusted for aqueous environment. As a result, various fluorophores emitting blue to red are developed and red, green, and blue staining is successfully performed in the HeLa cells. • Fluorophores based on new scaffold named 1,5-naphthyridine-2,6-dione (NTD) were developed and characterized. • Thienyl NTD (NTDT) exhibited excellent photophysical properties and photostability in organic solvent. • NTDT showed much better photostability than DPPT in HeLa cells, which is comparable to a commercial probe, Mitotracker Red. • Water soluble NTD molecules were developed by substituting side solubilizing unit. • Full color fluorescence from blue to red was demonstrated in organic solvents and cells with NTD derivatives. [ABSTRACT FROM AUTHOR]

The fluorescence polarization kinetics of fluorescent organic molecules and molecules with two interconverting photoisomeric forms and fixed molecular skeletons were investigated by numerical methods based on the solution of population balance equations. The depolarizing effect of the lowest triplet T state and the polarization time dependence for quasi-continuous-wave (cw) and pulsed photoexcitation were studied using model compounds. The fluorescence depolarization with cw excitation was characterized by times that were shorter than the T-state lifetime; for the isomers, also by times that correlated with the photoisomerization times. Intense pulsed photoexcitation distorted significantly the initial oscillator orientation distribution in the singlet S and S states and could lead to sign reversal of the polarization. [ABSTRACT FROM AUTHOR]

[Display omitted] In this paper, we designed and synthesized six 6-substituted quinolines-fused α-cyanovinyl derivatives QM-1 ∼ 3 and QS-1 ∼ 3 through π-expansion system with "pull–push" systems. QM-1 ∼ 3 and QS-1 ∼ 3 have large absorption extinction coefficients. QM-1 ∼ 2 and QS-1 ∼ 2 (H-, CH 3 O–) showed blue/green fluorescence emission. However, QM-3 / QS-3 ((CH 2 CH 3) 2 N–) exhibited large bathochromic shifts in emission maxima of QM-3 (form 544 to 627 nm), QS-3 (from 570 to 668 nm), large stokes shifts and relatively high fluorescent quantum yields (Φ QM-3,max = 0.49, Φ QS-3,max = 0.25) in different polar solvents. The results of emission spectra in water/DMSO mixtures (λ QM-3,max = 655 and λ QS-3 , max = 687 nm) and DFT calculations further proved that QM-3 / QS-3 had a significant intramolecular charge transfer (ICT) process. Moreover, QM-3 and QS-3 were suitable for fluorescence bio-imaging. [ABSTRACT FROM AUTHOR]

Studying the structure and dynamics of proteins in live cells is essential to understanding their physiological activities and mechanisms, and to validating in vitro characterization. Improvements in labeling and imaging technologies are starting to allow such in vivo studies; however, a number of technical challenges remain. Recently, we developed an electroporation-based protocol for internalization, which allows biomolecules labeled with organic fluorophores to be introduced at high efficiency into live E. coli (Crawford et al. in Biophys J 105 (11):2439-2450, ). Here, we address important challenges related to internalization of proteins, and optimize our method in terms of (1) electroporation buffer conditions; (2) removal of dye contaminants from stock protein samples; and (3) removal of non-internalized molecules from cell suspension after electroporation. We illustrate the usability of the optimized protocol by demonstrating high-efficiency internalization of a 10-kDa protein, the ω subunit of RNA polymerase. Provided that suggested control experiments are carried out, any fluorescently labeled protein of up to 60 kDa could be internalized using our method. Further, we probe the effect of electroporation voltage on internalization efficiency and cell viability and demonstrate that, whilst internalization increases with increased voltage, cell viability is compromised. However, due to the low number of damaged cells in our samples, the major fraction of loaded cells always corresponds to non-damaged cells. By taking care to include only viable cells into analysis, our method allows physiologically relevant studies to be performed, including in vivo measurements of protein diffusion, localization and intramolecular dynamics via single-molecule Förster resonance energy transfer. [ABSTRACT FROM AUTHOR]

Highly planar organic emitters have been developed from 4-styrylbenzonitrile structure, which show strong AIE properties and deep blue emission in solid state with good to excellent fluorescence quantum efficiency. [Display omitted] • 4-Styrylbenzonitrile derivatives are synthesized. • These planar fluorophores show strong AIE properties. • These compounds are efficient deep blue emitters in solid states with high quantum yields. Organic fluorescent molecules with π-conjugated system have shown great importance in numerous applications including bioimaging and optoelectronics. Planar aggregation-induced emissive (AIE) organic compounds with efficient solid-state luminescence are rarely developed and urgently needed in various applications. In this work, highly planar 4-styrylbenzonitrile derivatives have been synthesized. Most of these compounds show strong AIE properties with hundred-fold fluorescent enhancement. Moreover, these molecules are deep blue emissive in solid state, exhibiting good to excellent fluorescence quantum efficiency. The single crystal analysis shows that adjacent molecules could form special J-type aggregation. The intramolecular rotations are efficiently restricted by various noncovalent interactions. These molecular arrangements could be essential for the observed strong emission in aggregated and solid state. This work has paved a new path to efficient AIE-active organic emitters with highly planar conformations from 4-styrylbenzonitrile structure. [ABSTRACT FROM AUTHOR]

The kinetics of rapid fluorescence fading and recovery (anti-fading) of photostable organic fluorophores under two-stage rectangular modulated photoexcitation was studied using computer modeling in the framework of a three-level energy diagram. The fading and recovery were due to an abrupt change in the population rate of the metastable T state. The calculations revealed the presence of an anti-fading process. The modeling results were confirmed by experimental measurements of the fluorescence of a zinc complex of a substituted tetrabenzoporphyrin in an organic polymer. Precise analytical expressions establishing the relationship between the intramolecular rate constants of the photophysical processes and the measured fluorescence parameters were derived. [ABSTRACT FROM AUTHOR]

Abstract: A novel N-substituted 4-methoxy-1,8-naphthalimide (NAFTA 8) especially designed for fluorescent labeling of gold nanoparticles has been synthesized. NAFTA 8 bears a long methylene chain at the imide N atom and has a terminal SH group, which enables its chemical binding to gold nanostructures. The longest wavelength absorption maximum of NAFTA 8 in chloroform is at 370nm, the fluorescent maximum is at 430nm and the fluorescent quantum yield is 0.95. The newly synthesized fluorophore is applied for functionalization of gold nanoparticles with diameter 1.5±0.5nm prepared through chemical reduction. The obtained Monolayer Protected Clusters are characterized by elemental analysis, TEM, XPS, FT-IR, absorption and fluorescence spectroscopy. The performed investigations provide evidence for the formation of chemical bond between the thiol ligand and the gold surface. They also show that the obtained metal/dielectric 3D structures are highly fluorescent. [Copyright &y& Elsevier]

• Super-resolution imaging is important to break the Abbe's diffraction limit in biological research and material science. • Aggregation-induced emission luminogens (AIEgens) are one of the most promising candidates for super-resolution imaging. • An overview on AIEgens for super-resolution imaging is provided. • A deep understanding of the relationship between the AIEgens' properties and their imaging performance is provided. • The guidelines to develop new AIEgens to achieve superior resolution are provided. Super-resolution imaging (SRI) is of great significance to break the Abbe's diffraction limit, enabling visualization and dynamic monitoring with ultra-high resolution in both material science and biology. Fluorophores play an important role in SRI. Among them, aggregation-induced emission (AIE) luminogens (AIEgens) are one of the most promising imaging agents for SRI. They are easy to be synthesized and possess high tailoring ability, high brightness in aggregated states, large Stokes' shift, good photo-stability, and also excellent biocompatibility. Based on this consideration, the recent progress on AIEgens for SRI is summarized here. The working principles of AIEgens and several SRI techniques are also introduced to illustrate the material requirements. The new achievements in AIEgens research for SRI, including their chemical structures, optical properties, and applications, are highlighted in detail. The goal is to provide the readers with an overview of the recent advances in AIEgens for SRI. It is also anticipated that a deep understanding of the relationship between the AIEgens' properties and their imaging performance can be obtained. This review also aims to provide a set of guidelines to develop new AIEgens for fluorescence imaging to achieve superior resolution, thus resulting a better understanding of their mechanism in both biology and material science. [ABSTRACT FROM AUTHOR]

A series of nine phenothiazine-based derivatives (PTZ 1 -PTZ 9) have been computationally designed and investigated as organic fluorophores by employing two different topologies i.e., D-π-D-π-D and D-π-D-π-A in our scheme of study. All these designed derivatives consist of a phenothiazine core as central donor fragment (DF), thiophene/furan/pyrrole as π-spacers (P1/P2/P3), triphenylamine as terminal electron donor unit (DF1), and terminal acceptor unit (A1/A2). The effect of these substituents was studied on their optoelectronic and stability characteristics. TD-DFT calculations explores that bathochromically-shifted absorption (423–994 nm) and emission (524–1103 nm) bands of the designed derivatives cover the visible region and are also extended to the infrared regions of the spectrum. Among all designed fluorescent emitters, PTZ 7 -PTZ 9 derivatives exhibit the lowest energy levels, energy gaps (1.44–1.57 eV), exclusive broad absorption, and emission peaks owing to their strong electron-withdrawing fragments. The computational analysis of frontier molecular orbitals, population analysis, and natural transition orbital analysis has revealed that PTZ 1 -PTZ 3 derivatives exhibited π-π* excitations while the remaining six molecules (PTZ 4 -PTZ 9) displayed ICT in addition to π-π* electronic transitions. The dipole moments of all investigated molecules (3.30–18.78 D) are higher than the reference molecule (2.20 D), indicating their greater solubility in dichloromethane solvent. The nine newly designed fluorescent materials are also studied for their charge transport/injection properties like radiative lifetime and light harvesting efficiency. This theoretical study has disclosed PTZ-derivatives as potential fluorescent emitters with intense and pure color emission for semiconductor devices. [Display omitted] • Our approach was to design a novel series of phenothiazine derivatives that were functionalized by using different fragments to change the emission color. • Some fundamental optoelectronic properties of the studied molecules were computed. • The red-shifted absorption and emission wavelengths of all investigated emitters cover the Vis-NIR region in DCM solvent. [ABSTRACT FROM AUTHOR]