Dual Fluorescence Research Articles

Modulating Dual Fluorescence Emissions in Imine-Based Probes to Distinguish D2O and H2O.

How to distinguish D2O and H2O and determine the trace H2O content in D2O solvent, by using molecule-based spectral probes, is an intriguing topic in analytical chemistry, yet considerably few examples remain up to now, likely due to the very similar physical/chemical properties between D2O and H2O. In this work, we found that both the hydrolysis reactions to release fluorescent amines and aggregation-induced emission (AIE) of imines, functioning as dual fluorescence signals to distinguish D2O and H2O, could be modulated by changing the imine structures. The hydrophobicity of imines showed an important contribution to the ability of modulating the hydrolysis reactions and AIE, demonstrating a significant difference on fluorescence signals in D2O and H2O solvents. Among all tested imines, probe 3, condensed from 2-naphthylamine and salicylaldehyde, was found to have the potential ability to act as an ideal candidate for probing the H2O content in D2O solvent, particularly in a low H2O content range, using the ratiomeric emission signals.

Fluorescence Angiography with Dual Fluorescence for the Early Detection and Longitudinal Quantitation of Vascular Leakage in Retinopathy

Diabetic retinopathy (DR) afflicts more than 93 million people worldwide and is a leading cause of vision loss in working adults. While DR therapies are available, early DR development may go undetected without treatment due to the lack of sufficiently sensitive tools. Therefore, early detection is critically important to enable efficient treatment before progression to vision-threatening complications. A major clinical manifestation of early DR is retinal vascular leakage that may progress from diffuse to more localized focal leakage, leading to increased retinal thickness and diabetic macular edema (DME). In preclinical research, a hallmark of DR in mouse models is diffuse retinal leakage without increased thickness or DME, which limits the utility of optical coherence tomography and fluorescein angiography (FA) for early detection. The Evans blue assay detects diffuse leakage but requires euthanasia, which precludes longitudinal studies in the same animals. We developed a new modality of ratiometric fluorescence angiography with dual fluorescence (FA-DF) to reliably detect and longitudinally quantify diffuse retinal vascular leakage in mouse models of induced and spontaneous DR. These studies demonstrated the feasibility and sensitivity of FA-DF in detecting and quantifying retinal vascular leakage in the same mice over time during DR progression in association with chronic hyperglycemia and age. These proof-of-concept studies demonstrated the promise of FA-DF as a minimally invasive method to quantify DR leakage in preclinical mouse models longitudinally.

Detection of antibiotics at in situ temperature by Rhodamine B encapsulated in terbium-based metal-organic frameworks

Rhodamine B(RhB) was encapsulated in Tb(btc) (btc = 1,2,4-benzene tricarboxylic acid) frameworks by “one-pot” method, and the complex RhB@Tb(btc) with host-guest dual fluorescence emissions was synthesized. Compared with the stability of Tb3+ emission, the characteristic emission of RhB at 620 nm showed a more sensitive response to ambient temperature. By integrating the different temperature dependence of Tb3+ and RhB emissions, the temperature sensing of RhB@Tb(btc) was determined with relative sensitivity ranging from 0.43 to 0.59% K−1 (temperature range 298–353 K). Among several common antibiotics, RhB@Tb(btc) showed fluorescence quenching response to metronidazole (MDZ) and color transition to levofloxacin (LOFX) respectively with stable reusability. The combination of photoinduced electron transfer and internal filtration effect was confirmed as the contributor to MDZ induced fluorescence quenching. Furthermore, hydrogels and milk, which were added antibiotics on purpose for simulating unsafe foods, were detected at in situ temperature by RhB@Tb(btc) test paper, which achieved highly sensitive and highly selective detection to MDZ and LOFX with limit of detection reaching 10−6 M.

Two phenanthro[9,10-d]imidazole-based fluorescence probes for distinguishable detection of Cys and Fe3+ and their applications in food and water as well as living cells monitoring

Accurately designing and developing the dual responsive fluorescence probe with simultaneous recognition of intracellular biothiols and metal ions is of great significance. Here, we reported two phenanthrene[9,10-d]imidazole derivatives (PIP-CHO and NO2-PIP-CHO) modified with aldehyde fragment as chemosensor for synchronous detection of Cys and Fe3+. PIP-CHO and NO2-PIP-CHO performed the hydrophilic nature despite the fact that they possessed the distinct aggregation behavior with the increasing of water contents. In aqueous medium (water/DMF), PIP-CHO predominantly exhibited high sensitivity and selectivity for “on–off” fluorescent recognition of Fe3+ with a limit of detection (LOD) of 213.74 nmol·L–1, and Cys with a LOD of 116.66 nmol·L–1, respectively. Correspondingly, the detection limits of NO2-PIP-CHO toward Fe3+ and Cys were calculated in DMF as 347.68 and 215.64 nmol·L–1, respectively. The fluorescent recognition mechanism of cycloaddition and coordination for PIP-CHO with Cys and Fe3+ was rationally explained by SEM, 1H NMR and ESI-MS, respectively. Noteworthy, the naked-eye strips encompassing PIP-CHO enabled distinguishable visualization of Cys and Fe3+ with the color change under visible or UV light. In addition, PIP-CHO can be successfully applied to detect Cys and Fe3+ in food and water samples by fluorescence method, as well as the living Yeast cells via fluorescence dual channel.

Machine learning-based classification of dual fluorescence signals reveals muscle stem cell fate transitions in response to regenerative niche factors

The proper regulation of muscle stem cell (MuSC) fate by cues from the niche is essential for regeneration of skeletal muscle. How pro-regenerative niche factors control the dynamics of MuSC fate decisions remains unknown due to limitations of population-level endpoint assays. To address this knowledge gap, we developed a dual fluorescence imaging time lapse (Dual-FLIT) microscopy approach that leverages machine learning classification strategies to track single cell fate decisions with high temporal resolution. Using two fluorescent reporters that read out maintenance of stemness and myogenic commitment, we constructed detailed lineage trees for individual MuSCs and their progeny, classifying each division event as symmetric self-renewing, asymmetric, or symmetric committed. Our analysis reveals that treatment with the lipid metabolite, prostaglandin E2 (PGE2), accelerates the rate of MuSC proliferation over time, while biasing division events toward symmetric self-renewal. In contrast, the IL6 family member, Oncostatin M (OSM), decreases the proliferation rate after the first generation, while blocking myogenic commitment. These insights into the dynamics of MuSC regulation by niche cues were uniquely enabled by our Dual-FLIT approach. We anticipate that similar binary live cell readouts derived from Dual-FLIT will markedly expand our understanding of how niche factors control tissue regeneration in real time.

Synthesis of Multifunctional Eu(III) Complex Doped Fe3O4/Au Nanocomposite for Dual Photo-Magnetic Hyperthermia and Fluorescence Bioimaging

In this paper, the luminescent complex Eu(3-thenoyltrifluoroacetonate)3 was integrated with Fe3O4 and gold (Au) nanoparticles to form a multifunctional nanocomposite, Fe3O4/Au/Eu(TTA)3 (FOASET NC), for dual magnetic-photothermal therapy and biomedical imaging. Upon functionalization with amine-NH2, the FOASET NC exhibits a small size of 60-70 nm and strong, sharp emission at λmax = 614 nm, enhanced by surface plasmon resonance (SPR) of Au nanoparticles that provided an effective label for HT29 colorectal cancer cells by fluorescence microscopy imaging. In addition, a hyperthermia temperature (42-46 °C) was completely achieved by using these FOASET NCs in an aqueous solution with three heating modes for (i) Magnetic therapy (MT), (ii) Photothermal therapy (PT), and (iii) Dual magnetic-photothermal therapy (MPT). The heating efficiency was improved in the dual magnetic-photothermal heating mode.

Dual-template molecularly surface imprinted polymer on fluorescent metal-organic frameworks functionalized with carbon dots for ascorbic acid and uric acid detection

In this work, dual-template molecularly imprinted polymer surfaces imprinted on blue fluorescent Cr-based MOF (Cr-MOF) functionalized with yellow emissive carbon dots (Y-CDs) were prepared using l-ascorbic acid (AA) and uric acid (UA) as templates for simultaneous selective recognition of AA and UA. The as-prepared nanocomposite probe (Y-CDs/Cr-MOF@MIP) contains two recognition site cavities and emits a dual well-resolved fluorescence spectra when excited at 390 nm; blue emission (λem 450 nm) is due to Cr-MOF, and yellow emission (λem 560 nm) is due to Y-CDs. The yellow fluorescence emission of Y-CDs was quenched upon the addition of ascorbic acid, while Cr-MOF’s emission remained unaffected. In the same way, the blue fluorescence emission of the Cr-MOFs was quenched in the presence of uric acid, while the yellow emission remained constant. Both emissions were quenched in a sample containing both AA and UA. This can be exploited to design a dual-template biosensor to detect UA and AA simultaneously. The Y-CDs/Cr-MOF@MIP sensor displayed a dynamic linear response for AA in the range 25.0 µM – 425.0 µM with a detection limit of 1.30 µM, and for UA in the range 25.0 µM – 425.0 µM with a detection limit of 1.10 µM. The dual-target probe Y-CDs/Cr-MOF@MIP was highly selective and sensitive for the detection of UA and AA in human urine samples due to the selectivity of the two recognition sites.

Carbon quantum dots@metal–organic framework based catalytic nucleic acid fluorescent system for highly sensitive and selective detection of Pb2+ in aqueous solutions

Accumulation of heavy metal ions in the ecosystem has become a major concern due to their adverse impacts on animals, humans, and aquatic habitats. The development of a rapid and portable sensing system is important for the prompt detection and proper management of such pollutants. Herein, we have designed a fluorescence-based biosensor for the selective and sensitive detection of Pb2+ ions using a DNAzyme system that is active only in the presence of lead (II) ions (Pb2+). The developed nanoprobe relies on two major components: (i) boron and nitrogen carbon dots (BNCDs)-doped carboxyl functionalized-terbium metal-organic framework (COOH-Tb MOF) as a fluorescent tag and (ii) quencher-modified catalytic NH3-GR5 DNAzyme as a bioreceptor molecule. The fluorescent tag (BNCDs/MOF) exhibits dual fluorescence with emission peaks located in the regions of blue and green. In the absence of Pb2+ ions, this hybridization undergoes reduced emission intensity because of the overlap in fluorescence emission between BNCDs@Tb-MOF and quenchers. However, as the catalytic core of the DNAzyme strand is activated in the presence of Pb2+ ions, the fluorescent emission of BNCDs/Tb-MOF resumes with the cleavage of quencher-tagged substrate strand. Here, the release of a shorter oligo sequence effectively increases the intensity of the proposed novel biosensor to realize low level detection of Pb2+ (e.g., to 0.96 ppb in a wide detection range from 2 to 1000 nM). The establishment of this novel biosensing approach is expected to offer new insights into rapid, selective, and sensitive detection of major pollutants for food and environmental safety.

Novel metal enhanced dual-mode fluorometric and SERS aptasensor incorporating a heterostructure nanoassembly for ultrasensitive T-2 toxin detection.

Fluorescent gold (Au) nanostructures have emerged as burgeoning materials to fabricate nanomaterial assemblies which play a vital role in improving the detection sensitivity and specificity for various biomolecules. In this work, a fluorescence labelled (Rhodamine-B-Isothiocyanate) silica shell with Au metal core (AuNPs@PVP@RITC@SiO2) and a graphene-Au nanostar nanocomposite (rGO-AuNS) are presented as a metal enhanced fluorescence (MEF) material and Raman signal enhancer, respectively. Their composite (AuNPs@PVP@RITC@SiO2NPs/rGO-AuNS) was employed as a dual-mode fluorescence (FL) and surface-enhanced Raman scattering (SERS) nanoprobe for selective and sensitive detection of T-2 toxin. To comprehend the dual-modality, a core-shell nanostructure, AuNPs@PVP@RITC@SiO2, was functionalized with an aptamer (donor) and adsorbed on the surface of rGO-AuNS through electrostatic forces and π-π stacking which act as a FL quencher and SERS signal enhancer. When exposed to T-2 toxin, the apt-AuNPs@PVP@RITC@SiO2NPs move away from the surface of rGO-AuNS, resulting in the restoration of FL and reduction of the SERS signal. There was distinct linearity between the T-2 toxin concentration and the dual FL and SERS signals with lower limits of detection (LOD) of 85 pM and 12 pM, as compared to the previous methods, respectively. The developed FL and SERS aptasensor presented excellent recovery ratio and RSD in wheat and maize, respectively, as compared with the standard ELISA method. The complementary performances of the developed stratagem revealed a high correlation between the FL and SERS sensing modes with exquisite detection properties.

An optical keypad lock with high resettability based on a quantum dot-porphyrin FRET nanodevice.

Due to their appealing properties, nanomaterials have become ideal candidates for the implementation of computing systems. Herein, an optical keypad lock based on a Förster resonance energy transfer (FRET) nanodevice is developed. The nanodevice is composed of a green-emission quantum dot with a thick silica shell (gQD@SiO2) and peripheric blue-emission quantum dots with ultrathin silica spacer (bQD@SiO2), on which 5,10,15,20-tetrakis(4-sulfophenyl)porphyrin (TSPP) is covalently linked. The nanodevice outputs dual emission-based ratiometric fluorescence, depending on the FRET efficiency of bQD-porphyrin pairs, which is highly sensitive to the metalation of TSPP: values are 59.7%, 44.8%, and 10.1% for bQD-Zn(ii)TSPP, bQD-TSPP, and bQD-Fe(iii)TSPP pairs, respectively. As such, by using the competitive chelation-induced transmetalation of TSPP, the nanodevice is capable of implementing a 3-input keypad lock that is unlocked only by the correct input order of Zn(ii) chelator, iron ions, and UV light. Interestingly, the reversible transmetalation of TSPP permits the reset (lock) operation of the keypad lock with the correct input order of ascorbic acid, Zn(ii), and UV light. Application of the nanodevice is exemplified by the construction of paper and cellular keypad locks, respectively, both of which feature signal readability and/or high resettability, showing high potential for personal information identification and bio-encryption applications.

A dual channel fluorescence tongue for catechin recognition based on the MnO2 nanorods-Amplex Red-o-phenylenediamine reaction system.

Here, we report a dual-channel fluorescence sensor array for catechin discrimination based on the MnO2 nanorods (NRs)-Amplex Red (AR)-o-phenylenediamine (OPD) catalytic reaction system. MnO2 catalyzes both OPD and AR oxidation, and the fluorescence intensity values generated at 550 nm and 590 nm provide "fingerprints" for the sensor array. Different catechins have varying degrees of inhibitory effects on the MnO2 NRs-AR-OPD catalytic reaction system, thus obtaining unique fluorescence response fingerprints. Through linear discriminant analysis (LDA), the sensor array can not only successfully distinguish 5 catechins with concentrations as low as 500 nM and different concentrations of catechins, but also realize the identification of catechin mixtures. Notably, this method only requires the preparation of a single nanomaterial that catalyzes two substrates simultaneously and can generate two different fluorescence signal outputs, greatly facilitating the design of the sensor array.

AIEgens for dual second harmonic generation and fluorescence “turn-on” imaging of membrane and photodynamic therapy in cancer cells

The integration of second harmonic generation (SHG) microscopic imaging and aggregation-induced emission fluorescence imaging would greatly boost the imaging outcomes because of the combination of merits in each imaging modality.

A dual response UV-vis and fluorescence receptor based on acetylenic-indole conjoined silatrane for selective recognition of Co2+ and Cu2+ ions and in silico antidiabetic activity

This work involves the UV-vis and fluorescence study of a newly synthesized acetylenic-indole cojoined silatrane receptor for the selective recognition of Co2+ and Cu2+ ions and its molecular docking interaction with the α-glucosidase enzyme.

Long-range hydrogen-bond relay catalyses the excited-state proton transfer reaction.

Solvent (e.g., water)-catalyzed proton transfer (SCPT) via the relay of hydrogen (H)-bonds plays a key role in proton migration. In this study, a new class of 1H-pyrrolo[3,2-g]quinolines (PyrQs) and their derivatives were synthesized, with sufficient separation of the pyrrolic proton donating and pyridinic proton accepting sites to probe excited-state SCPT. There was dual fluorescence for all PyrQs in methanol, i.e., normal (PyrQ) and tautomer 8H-pyrrolo[3,2-g]quinoline (8H-PyrQ) emissions. The fluorescence dynamics unveiled a precursor (PyrQ) and successor (8H-PyrQ) relationship and the correlation of an increasing overall excited-state SCPT rate (kSCPT) upon increasing the N(8)-site basicity. kSCPT can be expressed by the coupling reaction kSCPT = Keq × kPT, where kPT denotes the intrinsic proton tunneling rate in the relay and Keq denotes the pre-equilibrium between randomly and cyclically H-bonded solvated PyrQs. Molecular dynamics (MD) simulation defined the cyclic PyrQs and analyzed the H-bond and molecular arrangement over time, which showed the cyclic PyrQs incorporating ≧3 methanol molecules. These cyclic H-bonded PyrQs are endowed with a relay-like proton transfer rate, kPT. MD simulation estimated an upper-limited Keq value of 0.02-0.03 for all studied PyrQs. When there was little change in Keq, the distinct kSCPT values for PyrQs were at different kPT values, which increased as the N(8) basicity increased, which was induced by the C(3)-substituent. kSCPT was subject to a deuterium isotope effect, where the kSCPT of 1.35 × 1010 s-1 for PyrQ-D in CH3OD was 1.68 times slower than that (2.27 × 1010 s-1) of PyrQ in CH3OH. MD simulation provided a similar Keq for PyrQ and PyrQ-D, leading to different proton tunneling rates (kPT) between PyrQ and PyrQ-D.

1,6-Naphthyridin-7(6H)-ones: synthesis and optical properties.

Efficient synthesis of original 1,6-naphthyridin-7(6H)-ones and their optical properties are described. Their powerful fluorescence properties including dual fluorescence, solvatochromism, acidochromism, large Stokes shifts and high quantum yields, suitable for biological applications or as luminescent devices in materials science, are evidenced.

Circularly polarized luminescence of natural products lycorine and narciclasine: role of excited-state intramolecular proton-transfer and test of pH sensitivity.

Circularly polarized luminescence (CPL) is increasingly gaining interest not only for its applicative potentialities but also for providing an understanding of the excited state properties of chiral molecules. However, applications of CPL are mainly in the field of materials science: special organic molecules and polymers, metal (lanthanide) complexes, and organic dyes are actively and intensely studied. So far natural compounds have not been investigated much. We fill the gap here by measuring circular dichroism (CD) and CPL of lycorine and narciclasine, the most abundant known alkaloid and isocarbostyril from Amaryllidaceae, which exhibit a large spectrum of biological activities and are promising anticancer compounds. Dual fluorescence detection in narciclasine led us to unveil an occurring excited-state intramolecular proton transfer (ESIPT) process, this mechanism well accounts for the Stokes shift and CPL spectra observed in narciclasine. The same molecule is interesting also as a pH chiroptical switch. Both in absorption and emission, lycorine and narciclasine are also studied computationally via density functional theory (DFT) calculations further shedding light on their properties.

Dual fluorescence properties and enhanced thermal stability of SrSi2O2N2:Eu2+ phosphors by coupling with g-C3N4.

Nowadays, considerable efforts have been extensively devoted to explore a general strategy for improving the color uniformity and thermal stability of phosphors, which is vital for its applications in health and comfort lighting. In this study, the SrSi2O2N2:Eu2+/g-C3N4 composites were successfully prepared via a facile and effective solid-state method to improve their photoluminescence properties and thermal stability. The coupling microstructure and chemical composition of the composites were demonstrated by high-resolution transmission electron microscopy (HRTEM) and EDS line-scanning analyses. Notably, the dual emissions at ∼460 nm (blue) and ∼520 nm (green) were observed for the SrSi2O2N2:Eu2+/g-C3N4 composite under near-ultraviolet (NUV) excitation, attributed to the g-C3N4 and 5d-4f transition of Eu2+ ions, respectively. The coupling structure will be beneficial to the color uniformity of the blue/green emitting light. Further, SrSi2O2N2:Eu2+/g-C3N4 composites exhibited a similar photoluminescence intensity compared with the SrSi2O2N2:Eu2+ phosphor even after thermal treatment at 500 °C for 2 h due to the protection of g-C3N4. The decreased decay time (1798.3 ns) of green emission for SSON/CN compared with SSON phosphor (1835.5 ns) indicated that the coupling structure suppressed the non-radiative transition and improved photoluminescence properties and thermal stability. This work provides a facile strategy to construct SrSi2O2N2:Eu2+/g-C3N4 composites with coupling structure for improved color uniformity and thermal stability.

Micellization Turned on Dual Fluorescence and Room Temperature Phosphorescence by Pseudo-ESIPT in Thiadiazole Derivatives

Some luminophores cannot fluoresce from dilute solution, especially those that are highly flexible. By aggregation, the rigidity of these molecules increases allowing for photoluminescence. However, the enhanced rigidity and the intermolecular interactions can give rise to several high-energy excited states, and since they can fluoresce only from the lowest energy excited state, known as the Kasha rule, the energy surplus is lost to the surroundings. In the pursuit of developing efficient light harvesting strategies from the higher energy excited states, it is necessary to look upon the effects not only at the level of nanometric molecules themselves but also of their supramolecular assemblies. Herein, we pinpoint the impact of poor conjugated moieties over the chromophore units, as well as the optical phenomena emerging at the supramolecular level. The molecular design consists of the S-alkylation of 5-amino-1,3,4-thiadiazole-2-thiol with permethylated silicone or hydrocarbons. The synthesized compounds display excited state intermolecular proton transfer (pseudo-ESIPT), blue and green fluorescence, and near-infrared phosphorescence at room temperature.

Facile Preparation Strategy of Novel Carbon Dots with Aggregation‐Induced Emission and Room‐Temperature Phosphorescence Characteristics

AbstractAs one of the most promising fluorescent nanomaterials, carbon dots (CDs) are extensively studied. Nevertheless, one‐pot synthesis methods for CDs with both dual emission aggregation‐induced emission (AIE) and room‐temperature phosphorescence (RTP) could lead to significant breakthrough in extensive application fields. Herein, a new class of CDs (E‐CCDs) with reversible luminescence (blue dissolved fluorescence and red AIE) and RTP behavior is obtained with an eco‐friendly, low‐cost one‐pot solvothermal method. E‐CCDs exhibit dual fluorescence emission at 460 (Em‐1) and 600 nm (Em‐2), which is related to different emission centers. The addition of cyanic acid enhances the RTP behavior with a lifetime of 1.17 s, which lasts for ≈9 s to the naked eye. Based on the unique fluorescence and phosphorescence characteristics of CDs, E‐CCDs can be potentially used for fingerprint detection and information encryption.

Spectroscopic characterization and assessment of microbiological potential of 1,3,4-thiadiazole derivative showing ESIPT dual fluorescence enhanced by aggregation effects

In the presented study, advanced experimental techniques, including electronic absorption and fluorescence spectroscopies [with Resonance Light Scattering (RLS)], measurements of fluorescence lifetimes in the frequency domain, calculations of dipole moment fluctuations, quantum yields, and radiative and non-radiative transfer constants, were used to characterize a selected analogue from the group of 1,3,4-thiadiazole, namely: 4-[5-(naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl]benzene-1,3-diol (NTBD), intrinsically capable to demonstrate enol → keto excited-states intramolecular proton transfer (ESIPT) effects. The results of spectroscopic analyses conducted in solvent media as well as selected mixtures were complemented by considering biological properties of the derivative in question, particularly in terms of its potential microbiological activity. The compound demonstrated a dual fluorescence effect in non-polar solvents, e.g. chloroform and DMSO/H2O mixtures, while in polar solvents only a single emission maximum was detected. In the studied systems, ESIPT effects were indeed observed, as was the associated phenomenon of dual fluorescence, and, as demonstrated for the DMSO: H2O mixtures, the same could be relatively easily induced by aggregation effects related to aggregation-induced emission (AIE). Subsequently conducted quantum-chemical (TD-)DFT calculations supported further possibility of ESIPT effects. The following article provides a comprehensive description of the spectroscopic and biological properties of the analyzed 1,3,4-thiadiazole derivatives, highlighting its potential applicability as a very good fluorescence probes as well as a compound capable of high microbiological activity.