Dual-channel Emission Research Articles

Dual Channel Emissions of Kasha and Anti-Kasha from a Single Radical Molecule.

Stable open-shell luminescent radicals have recently attracted much attention due to their unique luminescence properties. However, a radical molecule with both Kasha and anti-Kasha doublet emission properties has not been reported. Herein, we have successfully synthesized a stable chlorine-substituted Chichibabin's hydrocarbon, TTM-TTM, along with its mono-radical counterpart, TTM-HTTM. The emission of TTM-TTM follows Kasha's rule in the near infrared region. However, TTM-HTTM shows dual channel doublet emissions of Kasha and anti-Kasha. Remarkably, these two types of emission compete dynamically in both solution and condensed states. Our findings provide valuable insights into the rational design and discovery of stable radicals that possess distinctive luminescent properties, thus broadening the horizons of luminescent materials research.

Dual Channel Emissions of Kasha and Anti‐Kasha from a Single Radical Molecule

AbstractStable open‐shell luminescent radicals have recently attracted much attention due to their unique luminescence properties. However, a radical molecule with both Kasha and anti‐Kasha doublet emission properties has not been reported. Herein, we have successfully synthesized a stable chlorine‐substituted Chichibabin's hydrocarbon, TTM‐TTM, along with its mono‐radical counterpart, TTM‐HTTM. The emission of TTM‐TTM follows Kasha's rule in the near infrared region. However, TTM‐HTTM shows dual channel doublet emissions of Kasha and anti‐Kasha. Remarkably, these two types of emission compete dynamically in both solution and condensed states. Our findings provide valuable insights into the rational design and discovery of stable radicals that possess distinctive luminescent properties, thus broadening the horizons of luminescent materials research.

A quinoline-based indicator for NAD(P)H multimodal detection in vitro and in vivo: Spectrophotometry and visible near-infrared dual-channel lighting-up fluorescence imaging

Nicotinamide adenine dinucleotide (phosphate) (NAD(P)H/NAD(P)+) is crucial for oxidation-reduction equilibrium in all living cells, and disturbance of NAD(P)H/NAD(P)+ indicates many diseases. To accurately detect and track NAD(P)H in vitro and in vivo, we have developed a small organic dye (Rh-QL) based on intramolecular charge transfer (ICT) mechanism for multimodally detecting NAD(P)H by visible and near-infrared (Vis-NIR) dual-channel lighting-up fluorescence and by near-infrared spectrophotometry. This quinoline-based Indicator showed high selectivity and sensitivity toward NAD(P)H with a large redshift of absorption and dual-channel emissions at 580 nm and 750 nm, spatiotemporally and synchronously. For liquid samples, Rh-QL succeeded to screen NAD(P)H-related G6PD enzymatic activity by responsive absorption at 710 nm. In living cells, Rh-QL exhibited a good bio-compatibility and remarkable mitochondrial-targeted capacity to visualize intracellular endogenous and exogenous NAD(P)H variation utilizing Vis-NIR dual-channel fluorescence. In vivo, the near-infrared fluorescence was applied to differentiate tumor-bearing mice by NAD(P)H imaging. Moreover, “glycolysis” in both cancer cells and tumors of mice were traced to produce extra NAD(P)H using Rh-QL. As the first Vis-NIR dual-channel lighting-up probe to multimodally detect and track NAD(P)H in vitro and in vivo, it is appealing for high efficiency in understanding NAD(P)H-related physiological and pathological processes of disease diagnosis and therapy.

A dual-emission fluorescence-enhanced probe for hydrogen sulfide and its application in biological imaging

A fluorescence-enhanced probe with unique dual-channel emissions was designed for the detection and bioimaging of hydrogen sulfide.

Boosting the properties of a fluorescent dye by encapsulation into halloysite nanotubes

The synthesis of a new biocompatible bichromophoric system (CURBO) was developed, by connecting the skeleton of the naturally occurring curcumin to a BODIPY derivative. The system exhibited an intense fluorescence band with maximum at about 510 nm in organic solvent, while its emission spectra in aqueous solution were more complicated and slightly red-shifted, due to the effect of aggregation for the poor solubility of the dyad. To overcome these problems, the bichomophoric system has been loaded into the halloysite nanotubes (HNT). The HNT/CURBO nanocomposite, suspended in aqueous solution, showed an intensity of emission in the red region of the spectrum higher than the one exhibited by the pristine CURBO. The biocompatibility and photophysical behavior of HNT/CURBO nanocomposite were studied using ASC52Telo, h-TERT immortalized adipose-derived mesenchymal stem cells. To investigate the localization of the CURBO alone and in HNT/CURBO, fluorescence epimicroscopy was performed. The HNT/CURBO nanocomposite showed a high propensity to cross cell membranes, resulting in a massive cell uptake around the cell nucleus. Moreover, it lighted up ASC52Telo cells both with intense green and red fluorescence while excited in the blue portion of the electromagnetic spectrum, a phenomenon that could not be observed for the free CURBO. Dual-channel emissions dyes and, in particular, materials, such as the HNT/CURBO nanocomposite, emitting in the red portion of the spectrum have become, in recent decades, particularly fascinating since they can minimize the autofluorescence detection of the cell medium and allow interesting microscopy applications.

Membrane lipid raft organization during cotton fiber development

BackgroundCotton fiber is a single-celled seed trichome that originates from the ovule epidermis. It is an excellent model for studying cell elongation. Along with the elongation of cotton fiber cell, the plasma membrane is also extremely expanded. Despite progress in understanding cotton fiber cell elongation, knowledge regarding the relationship of plasma membrane in cotton fiber cell development remains elusive.MethodsThe plasma membrane of cotton fiber cells was marked with a low toxic fluorescent dye, di-4-ANEPPDHQ, at different stages of development. Fluorescence images were obtained using a confocal laser scanning microscopy. Subsequently, we investigated the relationship between lipid raft activity and cotton fiber development by calculating generalized polarization (GP values) and dual-channel ratio imaging.ResultsWe demonstrated that the optimum dyeing conditions were treatment with 3 μmol·L− 1 di-4-ANEPPDHQ for 5 min at room temperature, and the optimal fluorescence images were obtained with 488 nm excitation and 500–580 nm and 620–720 nm dual channel emission. First, we examined lipid raft organization in the course of fiber development. The GP values were high in the fiber elongation stage (5–10 DPA, days past anthesis) and relatively low in the initial (0 DPA), secondary cell wall synthesis (20 DPA), and stable synthesis (30 DPA) stages. The GP value peaked in the 10 DPA fiber, and the value in 30 DPA fiber was the lowest. Furthermore, we examined the differences in lipid raft activity in fiber cells between the short fiber cotton mutant, Li-1, and its wild-type. The GP values of the Li-1 mutant fiber were lower than those of the wild type fiber at the elongation stage, and the GP values of 10 DPA fibers were lower than those of 5 DPA fibers in the Li-1 mutant.ConclusionsWe established a system for examining membrane lipid raft activity in cotton fiber cells. We verified that lipid raft activity exhibited a low-high-low change regularity during the development of cotton fiber cell, and the pattern was disrupted in the short lint fiber Li-1 mutant, suggesting that membrane lipid order and lipid raft activity are closely linked to fiber cell development.

A fluorescent light-up probe for selective detection of Al3+ and its application in living cell imaging

A new fluorescent probe NADH, namely N'1,N'3-bis((E)-(2-hydroxy- naphthalen-1-yl)methylene)isophthalohydrazide, derived from isophthalic dihydrazide and naphthaldehyde was synthesized and characterized. NADH displayed an excellent selectivity towards Al3+ over other cations with dual channel emissions (460 nm & 486 nm) in DMSO-Tris (v/v, 8:2) buffer solution. Job‘s plot analysis confirmed a 1:1 binding ratio between NADH and Al3+. NADH had a good anti-interference ability from most coexisted species according to competition study. The detection limit was estimated to be 0.219 μM by 3σ method, which was far below the acceptable limit in drinking water of WHO. A rational binding mode was proposed by means of Job’s plot and 1H NMR titration experiment. Furthermore, NADH was found to be biocompatible and it was applied to image intracellular Al3+ in living cells successfully.

An effective FRET-based two-photon ratiometric fluorescent probe with double well-resolved emission bands for lysosomal pH changes in living cells and zebrafish.

In cells, lysosome is an acidic organelle (approximately pH 4.5-5.5), whose pH changes plays a key role in mediating various biological processes. To address this issue, a lot of fluorescent probes have been developed and prepared for tracking lysosomal pH changes. However, few of these probes can realize the imaging of lysosomal pH changes in biosystems. Herein, a new two-photon (TP) ratiometric fluorescent probe (NpRhLys-pH) by adopting the fluorescence resonance energy transfer (FRET) strategy has been developed for imaging of lysosomal pH changes in living cells and zebrafish. In this probe NpRhLys-pH, constructed by conjugating a TP fluorophore (D-Π-A-structured naphthalimide derivative) with a rhodamine B fluorophore via a non-conjugated flexible linker, the morpholine moiety serves as a targeting unit for anchoring lysosomes, and the xanthane derivative shows a pH-modulated open/close form of the spirocycle. Such a scaffold affords the NpRhLys-pH is a reliable and specific probe for anchoring lysosomes in living cells and zebrafish with dual-channel emission peaks separated by 85 nm, and responds to lysosomal pH rapidly and reversibly with high selectivity and sensitivity, demonstrating it can be used as a powerful tool for the biological research of the relationship between physiology and pathology and lysosomal pH changes in biological systems.

Tumor microenvironment-responsive fluorogenic nanoprobe for ratiometric dual-channel imaging of lymph node metastasis.

Fluorogenic nanoprobes capable of providing microenvironmental information have extensively been developed to improve the diagnostic accuracy for early or metastatic cancer detection. In cancer-associated microenvironment, matrix metalloproteinase-2,9 (MMP-2,9) has drawn attention as a representative enzymatic marker for diagnosis, prognosis, and prediction of various cancers, which is overexpressed in the primary site as well as metastatic regions. Here, we devised dual-emissive fluorogenic nanoprobe (DFNP) emitting both MMP-2,9-sensitive and insensitive fluorescence signals, for accurate monitoring of the MMP-2,9 activity in metastatic regions. DFNP was nanoscopically constructed by amphiphilic self-assembly between a constantly fluorescent polymer surfactant labeled with Cy7 (F127-Cy7) and an initially nonfluorescent hydrophobic peptide (Cy5.5-MMP-Q) that is fluorogenic in response to MMP-2,9. Ratiometric readout (Cy5.5/Cy7) by dual-channel imaging could normalize the enzyme-responsive sensing signal relative to the constantly emissive internal reference that reflects the probe amount, allowing for semi-quantitative analysis on the MMP-2,9-related tissue microenvironment. In addition to the dual-channel emission, the nanoconstructed colloidal structure of DFNP enabled efficient accumulation to lymph node in vivo. Because of these two colloidal characteristics, when injected intradermally to a mouse model of lymph node metastasis, DFNP could produce reliable ratiometric signals to provide information on the MMP-2,9 activity in the lymph nodes depending on metastatic progression, which corresponded well to the temporal histologic analysis. Furthermore, ratiometric lymph node imaging with DFNP after photodynamic therapy allowed for monitoring a therapeutic response to the given cancer treatment, demonstrating diagnostic and prognostic potential of the nanoconstructed colloidal sensor of tumor microenvironment in cancer treatment.

Two-Dimensional Excitonic Metal-Organic Framework: Design, Synthesis, Regulation, and Properties.

A family of two-dimensional (2D) Zn-based metal-organic frameworks (MOFs) with exitonic emission have been successfully synthesized under hydrothermal conditions. When isophthalic acid ligands with different substitutions are introduced, the crystal structures and fluorescence properties are significantly changed. Hirshfeld surface calculation is used to study the nuances of diverse substitutions during the construction of all of the crystals. The solid fluorescence results indicate that there are obvious two-channel emissions, including intralayer excimers and interlayer trapped excitons, both in 1 and 2 with a double-layer structure and in 3 with a single-layer structure, mainly exhibiting intralayer emission. Furthermore, the fluorescence changes on morphology transformations are explored after mechanical exfoliation consisting of grinding and ultrasonicaation of MOFs 1-3. The regulation and control of crystal structure and morphology can suppress emission based on interlayer excitons, achieving adjustment of the overall emitting color. To the best of our knowledge, this is the first report of 2D bilayer MOFs with dual-channel emissions, which provides a new structural model for synthesizing new exciton materials.

A selective diaminomaleonitrile-based dual channel emissive probe for Al3+ and its application in living cell imaging.

A selective diaminomaleonitrile-based fluorescent probe for Al3+(L) has been synthesized and characterized. The sensing behavior of L towards different metal ions was investigated by fluorescent spectra and competition experiment. The results showed that L exhibited a dual channel emission (λem 522 & 558 nm) with yellow fluorescence in the presence of Al3+ over other metal ions in EtOH solution. The probe L was bound to Al3+ in a 1:2 stoichiometric manner as supported by Job's plot analysis. The binding constant was 9.55 × 108 M-2 with the detection limit of 10.3 nM. The turn-on response was attributed to the inhibition of PET and CN isomerization after binding with Al3+ while the dual emissions were due to ESIPT and ICT processes. In addition, the application of L for imaging Al3+ in living Hela cells was achieved.

Disaggregation-induced ESIPT: a novel approach towards development of sensors for hyperglycemic condition

An oxazolonapthoimidazo[1,2-a]pyridine-based fluorescence probeONIP1was designed and synthesizedviamulticomponent reaction.ONIP1was able to distinguish human serum albumin (HSA) from and glycated-HSAviamodulation of AIEE- and ESIPT-based dual channel emission properties.

Dual-emissive fluorescent probe based on phenolphthalein appended diaminomaleonitrile for Al3+ and the colorimetric recognition of Cu2+

A novel dual emissive fluorescent probe was designed and synthesized by linking phenolphthalein and diaminomaleonitrile units. The present probe (PDM) can be used not only for fluorogenic detection of Al3+ by way of the excited enol-keto forms but also colorimetric detection of Cu2+. PDM probe showed a selective fluorescence enhancement with dual channel emissions for Al3+ in a mixture of EtOH/H2O (9/1). 1H NMR and DFT methods were also carried out to support the complexation between PDM and Al3+ ion. In addition, PDM presented highly selective colorimetric response for Cu2+ over other metal ions. The reversibility of PDM-Al3+ and PDM-Cu2+ complexes was successively established with the addition of TBAF and EDTA, respectively. The detection limits were determined to be 92.0 nM for Al3+ and 2.81 μM for Cu2+. The obtained results revealed that the designed PDM probe could be suitable for monitoring Al3+ under UV lamp and Cu2+ in water samples with the naked eye, which was rapid, convenient, low-cost and environmental friendly.

Tailoring exciton and excimer emission in an exfoliated ultrathin 2D metal-organic framework

Two-dimensional (2D) metal–organic frameworks have exhibited a range of fascinating attributes, of interest to numerous fields. Here, a calcium-based metal-organic framework with a 2D layered structure has been designed. Dual emissions relating to intralayer excimers and interlayer trapped excitons are produced, showing excitation-dependent shifting tendency, characteristic of a low dimensional semiconductor nature. Furthermore, the layer stacking by weak van der Waals forces among dynamically coordinated DMF molecules enables exfoliation and morphology transformation, which can be achieved by ultrasound in different ratios of DMF/H2O solvents, or grinding under appropriate humidity conditions, leading to nano samples including ultrathin nanosheets with single or few coordination layers. The cutting down of layer numbers engenders suppression of interlayer exciton-related emission, resulting in modulation of the overall emitting color and optical memory states. This provides a rare prototypical model with switchable dual-channel emissions based on 2D-MOFs, in which the interlayer excitation channel can be reversibly tuned on/off by top-down exfoliation and morphology transformation.

An ''off-on-off'' sensor for sequential detection of Cu2+ and hydrogen sulfide based on a naphthalimide-rhodamine B derivative and its application in dual-channel cell imaging.

A novel colorimetric and fluorometric sensor with unique dual-channel emission to sequentially detect Cu2+ and hydrogen sulfide (H2S) was synthesized from naphthalimide–rhodamine B through the PET and FRET mechanism. The sensor showed a selective “off–on” fluorescence response with a 120-fold increase toward Cu2+, and its limits of detection were 0.26 μM and 0.17 μM for UV-vis and fluorescence measurements, respectively. In addition, 1–Cu2+ was an efficient “on–off” sensor to detect H2S with detection limits of 0.40 μM (UV-vis measurement) and 0.23 μM (fluorescence measurement), respectively. Furthermore, the sensor can also be used for biological imaging of intracellular staining in living cells. Therefore, the sensor should be highly promising for the detection of low level Cu2+ and H2S with great potential in many practical applications.

Nd3+-Sensitized Upconversion Nanostructure as a Dual-Channel Emitting Optical Probe for Near Infrared-to-Near Infrared Fingerprint Imaging.

Lanthanide upconversion nanophosphors (Ln-UCNPs) have attracted great attention in a variety of fields, benefiting from low background fluorescence interference and a high signal-to-noise ratio of upconversion luminescence. However, the establishment of Ln-UCNPs with dual near-infrared (NIR) emission channels still remains challenging. Herein, we report the design and synthesis of Nd3+-sensitized NaYbF4:Tm@NaYF4:Yb@NaNdF4:Yb hierarchical-structured nanoparticles that emit NIR luminescence at 696 and 980 nm under excitation at 808 nm. The sensitizer-rich NaYbF4 core promotes efficient energy transfer to Tm3+. The interlayer of NaYF4:Yb effectively prevents the cross-relaxation process from Tm3+ to Nd3+ and thus enhances the luminescence emission. The introduction of Nd3+ ion as the sensitizer transforms the excitation wavelength from 980 to 808 nm, which subtly averts the laser-induced thermal effect and offers a new pathway for the NIR emission channel at 980 nm. The as-prepared nanoparticles were further applied in developing latent and blood fingerprint images, which exhibited high signal-to-noise ratio and distinguishable details under 808 nm excitation with negligible thermal damage to the sample. Our work provides a promising strategy to realize NIR-to-NIR dual-channel emissions in Ln-UCNPs. With further functionalization, such nanoparticles are expected to have great potential in forensic and biological sciences.

A dual-emission fluorescence-enhanced probe for imaging copper(ii) ions in lysosomes.

We have developed the first example of a fluorescence-enhanced and lysosome-targeted Cu2+ probe (Lys-Cu) with unique dual-channel emissions. The newly synthesized fluorescent probe Lys-Cu, which contains two recognition sites with different sensing mechanisms for Cu2+, displays fluorescence-enhanced dual-channel emissions with fluorescence response to Cu2+ in the lysosome pH environment. Fluorescence imaging shows that Lys-Cu is membrane-permeable and suitable for visualization of Cu2+ in lysosomes of living cells by dual-channel imaging.

Differential Spectral Imaging of the CN Violet Band in Laser-Induced Plasmas on TNT Simulant Molecules

Dual channel emission imaging of m-nitrobenzoic acid and benzoic acid was performed in order to visualize the morphology of the CN violet band emission of a TNT analogue. The CN channel was corrected for continuum emission using a simultaneously imaged background channel. Simultaneous dual channel imaging alleviated problems with shot to shot variation in the plasma morphology due to the friable substrates and showed differences between plasmas formed on the two targets.

Salicylideneimines as efficient dual channel emissive probes for Al3+: Harnessing ESIPT and ICT processes

Two simple fluorescent chemosensors (CS1 &CS2) based upon salicylideneimine derivatives were evaluated for their selective fluorescent sensing of Al3+. An attractive glowing green/blue colour was observed in the presence of Al3+ with dual channel emissions for CS1 (λem 499 & 535nm) and CS2 (λem 485 & 515nm) both. The inhibition of PET and CN isomerization after Al3+ binding was responsible for the turn ‘on’ fluorescence response while the dual emissions were well justified in terms of ESIPT and ICT. The binding stochiometries between CS1/CS2 and Al3+ were found to be 1:1 and 2:1 respectively while the limit of detection (LOD) of Al3+ by CS1 was found to be ∼10 times lower than that of CS2.

Ratiometric and simultaneous estimation of Fe3+ and Cu2+ ions: 1,3,5-substituted triethylbenzene derivatives coupled with benzimidazole

We synthesized a novel 1,3,5-substituted triethylbenzene derivative with a benzimidazole moiety as a binding and signalling subunit. The triethylbenzene platform was judiciously incorporated into the receptor design such that all the fluorophores are in close proximity to each other in order to facilitate stacking. The advantage of this approach lies in the fact that the receptor will offer a dual channel emission for the multiple ratiometric determination of metal ions. The sensor was tested in a CH3CN/H2O (7:3, v/v, pH 7.1) HEPES buffered solution and successfully developed for the ratiometric and simultaneous estimation of Fe3+ and Cu2+ ions in aqueous samples.