Remarkable Fluorescence Changes Research Articles

Networked Multicomponent Ensemble as AND Gate with FRET Output.

A networked supramolecular logic AND gate system is accomplished using precise chemical communication within a multicomponent ensemble via metal ion-driven self-sorting processes. The cybernetic AND gate is composed of a copper(I)-loaded nanoswitch, an aza-crown ether and a rhodamine receptor. The modus operandi of the AND gate, from state (0,0), was induced with stoichiometric amounts of two inputs (IN-1= Hg2+,IN-2= Li+) generating copper(I) ions as output only in state (1,1). Generation of state (1,1) from state (0,0) involves selective Cu+ion translocation from the nanoswitch to the aza-crown ether in the first step (IN-1) and then from the aza-crown ether to the rhodamine receptor in the second step (IN-2). The released copper(I) output acts as a messenger that binds to the rhodamine receptor, triggering it's spiro-lactam ring opening, which leads to a diagnostic FRET emission from the copper(I)-loaded Rhodamine scaffold accompanied by a remarkable fluorescence and colour change from pale yellow to pink.

Multi-Stimuli-Responsive Fluorescent Molecule with AIE and TICT Properties Based on 1,8-Naphthalimide.

A multi-stimuli responsive fluorophore, named NBDNI, was developed by constructing a 1,8-naphthalimide derivative in which a rotatable electron-donating N,N-dimethylaniline group attached to its 4-position. This molecular structure endowed NBDNI with aggregate-induced emission (AIE) and twisted intramolecular charge transfer (TICT) properties, enabling remarkable fluorescence changes in response to multiple external stimuli: (i) sensitivity to polarity in various solvent systems and polymer matrix; (ii) significant fluorescence response and excellent linearity towards temperature changes in solution; (iii) distinct switch of fluorescence color upon acid and base treatments; (iv) reversible mechanochromism behavior in the solid state. Moreover, the mechanisms underlying the aforementioned stimuli-responsive phenomena have been proposed based on comprehensive systematic measurements. Furthermore, preliminary applications such as fluorescence thermometry and acid/base test paper have been demonstrated. This research will bring about new opportunities for the development of novel stimuli-responsive luminescent materials.

Highly solvent-dependent naphthalene diimide-based fluorescent polymer sensors for detecting p-xylene

P-xylene (PX), as one of xylenes, is a kind of very important chemical raw material. It is generally fabricated using methanol (MeOH) and toluene (TOL), and serves as a useful intermediary. However, it is difficult to use a simple and convenient tool to distinguish it from TOL and MeOH. Herein, we reported a simple naphthalene diimide-based polycaprolactone polymer (NDI-PCL) as a high-sensitive fluorescent sensor for xylene detection from MeOH and TOL. NDI-PCL was synthesized via ring-opening polymerization (ROP) of ε-caprolactone. NDI-PCL showed a remarkable fluorescence change from blue to green and yellow because of the formation of charge transfer (CT) interaction between naphthalene diimide (NDI) and aromatic solvents. NDI-PCL was successfully applied as the high-sensitive sensor for discriminating binary solvent mixtures such as PX in TOL, MeOH in PX, and MeOH in TOL, and their limit of detection (LOD) were as low as 19 ppm, 16 ppm and 9 ppm. These excellent fluorescence properties ensured that NDI-PCL indicated great potential application in detecting aromatic solvents.

Diminishable solvatochromic emission of a phenothiazine-derived triad for high-performance detection of ClO2

Phenothiazine (PTZ) chromophores have gained extensive attention due to easy modification and unique fluorescence property tuned by oxygen functionalization. Herein, a PTZ-derived triad HDPP-PTZ with strong intramolecular charge transfer (ICT) property is designed. Upon oxidizing the sulfur atom in the PTZ unit into sulfoxide, the polarity sensitive ICT emission of the synthesized fluorophore totally disappears. Inspired by the discovery, a highly selective, sensitive and rapid detection method for a widely used disinfectant chlorine dioxide (ClO2) is established. The detection limit (DL) in THF/water is < 0.052 mg/L, satisfying the setting limit by WHO (1.0 mg/L), and the response time is less than 20 s. Moreover, no significant interference is found. Take advantage of the remarkable fluorescence changes, real samples are visualized and evaluated by RGB analysis. Testing strips are further fabricated for in-situ and at real-time detection of ClO2 both in aqueous solution and gas states. Present study provides significant understanding of the oxidation states of the PTZ derivatives and guides development of fluorescent probes for specific analyte.

A Ratiometric Fluorescent Probe Based on RhB Functionalized Tb-MOFs for the Continuous Visual Detection of Fe3+ and AA.

In this study, a red-green dual-emitting fluorescent composite (RhB@MOFs) was constructed by introducing the red-emitting organic fluorescent dye rhodamine B (RhB) into metal-organic frameworks (Tb-MOFs). The sample can be used as a ratiometric fluorescent probe, which not only avoids errors caused by instrument and environmental instability but also has multiple applications in detection. The results indicated that the RhB@MOFs exhibited a turned-off response toward Fe3+ and a turned-on response for the continuous detection of ascorbic acid (AA). This ratiometric fluorescent probe possessed high sensitivity and excellent selectivity in the continuous determination of Fe3+ and AA. It is worth mentioning that remarkable fluorescence change could be clearly observed by the naked eye under a UV lamp, which is more convenient in applications. In addition, the mechanisms of Fe3+- and AA-induced fluorescence quench and recovery are discussed in detail. This ratiometric probe displayed outstanding recognition of heavy metal ions and biomolecules, providing potential applications for water quality monitoring and biomolecule determination.

Construction of a multifunctional polysaccharide-based aerogel for highly efficient fluorescence detection and removal of formaldehyde

Formaldehyde as an indoor air pollutant poses a serious threat to human health owing to its high toxicity, wide distribution, and long release time. Therefore, the development of methods for the sensitive detection and removal of indoor formaldehyde is crucial. A robust aerogel based on cotton cellulose (CC) and chitosan (CH) with high sensitivity toward formaldehyde was constructed for visual formaldehyde detection and removal. Owing to the presence of a highly sensitive ratiometric fluorescent probe RP, CHCC-RP exhibited up to 600-fold fluorescence enhancement (F540/F450) in a formaldehyde-containing atmosphere. The detection limit was approximately 0.5 × 10−7 M, and the aerogel exhibited a rapid fluorescence response and high selectivity toward formaldehyde. Moreover, the composition of CHCC-RP was optimized, and the physical and formaldehyde-response properties were examined via texture analysis, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). CHCC-RP exhibited excellent formaldehyde adsorption capacity, and over 70% of the NH2 group in the aerogel was consumed by formaldehyde, as indicated by the XPS and Fourier-transform infrared spectra. Additionally, CHCC-RP and RP could successfully detect formaldehyde in live zebrafish with remarkable fluorescence changes.

Acid-base responsive multifunctional poly(formyl sulfide)s through a facile catalyst-free click polymerization of aldehyde-activated internal diynes and dithiols.

Acid-base equilibria play a critical role in biological processes and environmental systems. The development of innovative fluorescent polymeric materials to monitor acid-base equilibria is highly desirable. Herein, a novel catalyst-free click polymerization of aldehyde-activated internal diynes and dithiols was established, and exclusively Markovnikov poly(formyl sulfide)s (PFSs) with high molecular weights and moderate stereoregularity were produced in high yields. Because of the aromatic units and sulfur atoms in their main chains, these polymers possessed high refractive index values. By introducing the fluorene and aldehyde moieties, the resulting PFSs could act as a fluorescent sensor for sensitive hydrazine detection. Taking advantage of the reaction of the aldehyde group and hydrazine, imino-PFSs with remarkable and reversible fluorescence change through alternating fumigation with HCl and NH3 were easily acquired and further applied in multicolor patterning, a rewritable material and quadruple-mode information encryption. Additionally, a test strip of protonated imino-polymer for the tracking of bioamines in situ generated from marine product spoilage was also demonstrated. Collectively, this work not only provides a powerful click polymerization to enrich the multiplicity of sulfur-containing materials, but also opens up enormous opportunities for these functional polysulfides in diverse applications.

A novel fluorescent probe based on a tripeptide-Cu(II) complex system for detection of histidine and its application on test strips and smartphone

Herein, we reported a novel peptide-based fluorescent probe DSSH for highly selective and sensitive detections of both Cu2+ and l-histidine (l-His). DSSH exhibited different color changes and fluorescence “on–off” response toward Cu2+ with a 2:1 binding stoichiometry, and the limit of detection (LOD) for Cu2+ was calculated to be 22.9 nM. The in situ formed DSSH-Cu2+ ensemble showed obvious fluorescence “off–on” response to l-His based on replacement reaction with Cu2+, as well as the discernable color changes under 365 nm UV lamp irradiation with “naked eye”. The specificity of Cu2+/l-His interactions allowed l-His to be determined without interference from other amino acids, and the detection limit of DSSH-Cu2+ ensemble response to l-His was determined as 25.7 nM. Notably, DSSH was successfully applied for detecting Cu2+ and l-His in RKO living cells owing to its remarkable fluorescence behavior and low cytotoxicity. Test strips experiments suggested that DSSH can recognize Cu2+ and l-His together by a remarkable fluorescence change. More importantly, smartphone was combined with l-His solutions of different concentrations and converted into digital values through RGB channels, which was successfully used for semi-quantitative identification of l-His, and the limit of detection (LOD) was 0.97 μM.

Solvatochromic fluorescent styryl pyrene probes for the quantitative determination of water content in organic solvents

A series of D-π-A fluorescent styryl pyrene probes were synthesized through the Wittig reaction. The introduction of an electron-withdrawing substituent on the phenyl ring creates a push-pull system that shows solvent-dependent intramolecular charge transfer (ICT) and solvatochromic properties. Among these, the styryl pyrene probes with nitro (Py-NO2) and aldehyde (Py-CHO) substituents exhibited remarkable sensitivity to environment polarity. They show remarkable fluorescence changes from green to red, and blue to orange in nonpolar to polar organic solvents, respectively. The results were explained by the Lippert-Mataga and ET(30) models, which were supported by theoretical calculations by the density functional theory (DFT). Importantly, the fluorescence emission of Py-NO2 in organic solvents is sensitive to the presence of water in the range of 0–34.2% (v/v) in THF, 0–9.1% (v/v) in DMF, and 0–39.7% (v/v) in CH3CN. The limits of detection of water were established as low as 0.007%, 0.033%, and 0.036% (v/v) in THF, DMF, and CH3CN, respectively. Py-CHO showed somewhat higher limits of detection than Py-NO2 for the same solvents but exhibited a broad linear response to water content in EtOH between 3.3 and 63.6% (v/v) water content with the limit of detection at 2.350% (v/v). Thus, it is possibly useful as a sensor for the wide range detection of alcohol content in beverages. These push-pull styryl pyrene probes not only served as a new supersensitive fluorescent sensor for the quantitative detection of low to medium-level water content in organic solvents but may also be useful in a broad range of applications.

A deep-red emission fluorescent probe for visualization of fluoride anion accumulation in a murine model of acute fluoride toxicity and the roots of Arabidopsis thaliana

Fluorine (F) is a highly reactive and non-biodegradable pollutant widely present in the environment, which has seriously threatened ecosystems and human health. To date, no fluorescent probes have been reported to visually observe the accumulation of excess fluoride ions in living plants and animals, which severely limits the study of the toxic effects of fluoride ions in biological chains. In this work, we designed and synthesized a new deep-red emission fluorescent probe NRF for detecting the accumulation of F− in living animals and plants. Exploiting F-induced cleavage of the silicon-oxygen bond, the probe NRF exhibited remarkable fluorescence changes from weak to strong. In addition, this probe displayed some significant advantages in detecting F−, including excellent selectivity, good photostability, and low biological toxicity. Furthermore, its favorable properties for detecting F− were successfully demonstrated in HeLa cells and zebrafish. Notably, utilizing the robust probe NRF, visualization of F− accumulation in acute F− toxicity model and the roots of Arabidopsis thaliana tissues had been achieved. This study shows that NRF can be used as an effective tool to detect excess F− in living cells, animals and plants, and provides a method for elucidating the toxicity mechanism of fluoride in physiological and pathological processes.

Crystallographic Visualization of a Guest-Induced Solar-Driven Cycloaddition Reaction Based on a Recyclable Nonporous Coordination Polymer.

Stimuli-responsive solids with adjustable photophysical properties are particularly attractive because they can be used as smart materials in anticounterfeiting, information storage, holographic imaging, and other fields. Herein, we report a unique nonporous coordination polymer, {[Ag(3,3'-dpe)](2,2'-Hbpdc)}n (1; 3,3'-dpe = 1,2-dipyridin-3-ylethene and 2,2'-H2bpdc = 2,2'-biphenyldicarboxylic acid), that can convert to an extremely photoreactive compound, 1·H2O·MeCN (MeCN = acetonitrile), through guest capture. Upon irradiation of sunlight, 1·H2O·MeCN can transform to {[Ag(3,3'-tpcb)0.5](2,2'-Hbpdc)(H2O)(MeCN)}n (2·H2O·MeCN; 3,3'-tpcb = 1,2,3,4-tetrapyridin-3-ylcyclobutane). 2·H2O·MeCN can lose its solvent molecules to form 2 and further return to 1 at high temperature. Accompanied by direct visualization based on multistep single-crystal-to-single-crystal conversions, the recyclable crystalline solid exhibits remarkable fluorescence changes, which makes it a supramolecular switch for application in multiple anticounterfeiting.

Construction of a Rational-Designed Multifunctional Platform Based on a Fluorescence Resonance Energy Transfer Process for Simultaneous Detection of pH and Endogenous Peroxynitrite.

Peroxynitrite (ONOO-), a kind of reactive oxygen species, plays an indispensable role in many physiological processes. The stability and reactivity of ONOO- are significantly affected by the pH of the environment. A novel fluorescent probe RN-NA that can simultaneously respond to ONOO- and pH was proposed and constructed based on a rational-designed multifunctional fluorescence resonance energy transfer (FRET) platform. The RN-NA probe exhibited a remarkably different fluorescence change in response to ONOO- and pH. The fluorescence signals at 525 and 710 nm increased about 4-fold with a pH change from 8.0 to 3.0. The changes in fluorescence at 525 nm are mainly attributed to photo-induced electron transfer, and the fluorescence enhancement at 710 nm was mainly due to acid-induced open-closed circulation. In the presence of ONOO-, the fluorescence at 525 nm increased 5-fold, while the fluorescence at 710 nm was almost completely diminished. Up to 70-fold fluorescence enhancement was observed in the ratiometric channel F525/F710. In the cell imaging experiment, the intracellular pH was adjusted using H+/K+ ionophore and nigericin, and the endogenous ONOO- was generated by lipopolysaccharide (LPS) and γ-interferon (IFN-γ). The RN-NA probe can respond to cellular pH and endogenous ONOO- with remarkable fluorescence changes in both red/green and ratiometric channels.

A near-infrared-emission aza-BODIPY-based fluorescent probe for fast, selective, and “turn-on” detection of HClO/ClO−

A novel near-infrared-emitting aza-BODIPY-based fluorescent probe with two tellurium atoms at two upper benzyl rings has been prepared and explored for its fluorescent sensing properties towards hypochlorous acid/hypochorite (HClO/ClO−), which showed high selectivity and absolutely fluorescent “turn-on” phenomenon at 738 nm. The fluorescence of this probe was sufficiently quenched due to photoindued electron transfer by two tellurium atoms. Upon exposure to HClO/ClO−, a strong near-infrared emission at 738 nm appeared with fluorescence quantum yields changing from 0 to 0.11. This remarkable fluorescence change was ascribed to the oxidation of both electron-rich tellurium atoms. The detection limit of this probe towards HClO/ClO− was calculated to 0.09 μM in acetonitrile aqueous solution by the linear fluorescence change at 738 nm in the HClO/ClO−-concentration range of 0–30 μM. Interestingly, this probe was found to be applicable in a broad pH range (2–10). Meanwhile, the oxidized probe could be further responsive to biothiols with substantial fluorescence disappearance. The bioimaging experiments in RAW264.7 cells showed the appearance of intracellular near-infrared fluorescence after addition of HClO/ClO− and PMA, and the fluorescence could also be reversed to be silenced by further introduction of GSH, confirming its potential application for exogenous and endogenous detection of HClO/ClO− in living cells.

Rational design of a unique palladium coordination polymer with distinctive fluorescence and its application for CO sensing in living zebrafish

Carbon monoxide (CO) is known as a highly toxic gaseous air pollution, and also act as a key small signaling molecule that plays an important role in living organisms. Therefore, the real-time tracking of CO is of great significance for further research on the role of CO in physiological activity. To this end, a unique Palladium coordination polymer (Pd-NA) based on fluorescent naphthalene derivatives is constructed and applied for imaging CO. Morphology study indicates that Pd-NA assembles into large stacked planar structure. Spectroscopic experiments show that Pd-NA can response to CO with remarkable fluorescence change, significant fluorescence enhancement is obtained at 510 nm with the addition of CO. Similar with spectral change, Pd-NA can response to exogenous and endogenous generated CO in HeLa cells with up to 10-fold florescence enhancement. Furthermore, Pd-NA exhibits excellent one-photon and two-photon fluorescence imaging capability of sensing CO in living zebrafish. Overall, the present work has afforded a new paradigm and demonstrated the feasibility of CO sensing in living organisms by a rational designed Palladium coordination polymer for the first time.

A Single Fluorescent pH Probe for Simultaneous Two-Color Visualization of Nuclei and Mitochondria and Monitoring Cell Apoptosis

Subcellular organelles play indispensable roles in diverse biological processes by their precise mutual cooperation. Thus, the development of a single fluorescent probe (SF-probe) for simultaneous and discriminable visualization of different organelles and their dynamics during certain bioprocess is significant, yet remains greatly challenging. Herein, for the first time, we rationally prepared a pH-sensitive SF-probe (named HMBI) for the simultaneous two-color visualization of nuclei and mitochondria and monitoring cell apoptosis. HMBI shows remarkable ratiometric fluorescence changes toward pH changes. Due to different pH environments in subcellular organelles, HMBI can image nuclei and mitochondria with green and red emission, respectively. HMBI can monitor drug-induced cell apoptosis with dramatically decreased red emission in mitochondria but almost unchanged green emission in nuclei, and the shrinking and pyknotic nuclei are also observed during cell apoptosis. HMBI possesses tremendous potential in two-color biomedical imaging of the dynamic changes of nuclei and mitochondria in many physiological processes.

A rhodamine-based chemosensor and functionalized gel ball for detecting and adsorbing copper ions

Abstract The development of sensitive colorimetric and fluorescent chemosensors for Cu2+ sensing has gained much attention in recent years because of their potential application in clinical biochemistry and environmental studies. Herein, a novel rhodamine-based chemosensor NRG was constructed, which exhibited high sensitivity and selectivity and a quick response for Cu2+, accompanied by remarkable color and fluorescence changes. Moreover, besides sensing Cu2+, NRG can capture Cu2+ effectively and quickly in aqueous solution. Based on the results, NRG-functionalized gel balls were fabricated and exhibited strong adsorbability and a high adsorption capacity for Cu2+, accompanied by an obvious color change. More interestingly, the gel balls can be recycled after treatment with an EDTA solution. These excellent properties make the gel ball a promising candidate for copper ion purification.

An ICT-based fluorescent probe for ratiometric monitoring the fluctuations of peroxynitrite in mitochondria

Peroxynitrite (ONOO−) is a well-known reactive oxygen species (ROS) which closely involves in various physiological and pathological processes. It is reported that mitochondria are the major site of ONOO− production. Normal level of ONOO− benefits mitochondria biological functions, while its overproduction will induce oxidative stress, resulting in an imbalance of mitochondria homeostasis. Therefore, accurate monitoring of ONOO− in mitochondria will be beneficial for elucidating the physiological metabolism and fluctuations of ONOO−. Herein, a novel mitochondria-targeted ratiometric fluorescent probe Mito-NA for ONOO− was designed rationally by regulating its intramolecular charge transfer (ICT) effect. Once reaction with ONOO−, Mito-NA manifested remarkable ratiometric fluorescence changes (18-fold) with a large red-shift (∼104 nm) emission, which was ascribed to the enhanced ICT process caused by the elimination of the electron-withdrawing recognition group 3-(trifluoromethyl) cinnamic acid and the exposure of electron-donating hydroxyl on Mito-NA structure. Furthermore, Mito-NA exhibited satisfactory performances for ONOO− such as good sensitivity (LOD =0.12 μM), high selectivity to ONOO− over other ROS, fast response and good mitochondrial targeting. More importantly, Mito-NA was successfully applied for ratiometric imaging and monitoring the fluctuations of mitochondrial ONOO− in living cells.

Antimonene Quantum Dots as an Emerging Fluorescent Nanoprobe for the pH-Mediated Dual-Channel Detection of Tetracyclines.

Antimonene quantum dots (AMQDs) are attracting considerable attention due to their fascinating physicochemical properties. However, research on their semiconductor characteristics, especially the photoluminescence performance, is still in a preliminary stage and the experimental verification is scarcely reported, significantly restricting their further applications. Herein, the photoluminescence property of AMQDs is experimentally verified. The AMQDs are prepared by probe sonication-assisted liquid-phase exfoliation and show robust blue fluorescence, and the photoluminescence is hardly affected by pH. In view of the derivatization reaction of tetracyclines (TET) at different pHs, AMQDs are developed as a pH-mediated dual-channel ratiometric fluorescent probe for TET detection. Under acidic conditions, the AMQDs' probe exhibits unique recognition behavior due to the inherent fluorescence of TET and the solvent-enhancing effect, that is, the fluorescence changes from blue to red. Under alkaline conditions, this fluorescent probe realizes the transition from blue to yellow-green because of the decomposition of TET. The limits of detection are 27 × 10-9 and 74 × 10-9 m, respectively. The high sensitivity and remarkable fluorescence changes make AMQDs ideal probes for TET sensing. Additionally, this is the first report on the photoluminescence property of AMQDs. It is believed that this work will open a new avenue for AMQDs in optical sensing fields.

Ratiometric Fluorescent Mapping of pH and Glutathione Dictates Intracellular Transport Pathways of Micellar Nanoparticles.

Visualization of intracellular transport pathways is crucial to investigate the internalization mechanism and understand the intracellular behavior of nanomaterials. Herein, we rationalized the design of micellar nanoparticles (NPs) for ratiometric fluorescent mapping of intracellular pH and glutathione (GSH), two essential parameters for maintaining normal cellular functions. Specifically, pH-sensitive naphthalimide-based probe (NPI) and pH-inert rhodamine B (RhB) were covalently labeled to double hydrophilic block copolymers (DHBCs) using the thiolactone chemistry, enabling the covalent attachment of NPI and RhB to one molecule with a redox-responsive disulfide linkage. The dually labeled DHBCs exhibited blue/orange dual emissions in acidic pH, which was further converted into green/orange dual emissions in neutral pH because of the deprotonation of NPI moieties and the sole green emission in the presence of GSH at neutral pH because of the decreased Förster resonance energy transfer efficiency between an NPI donor and an RhB acceptor as a result of GSH-mediated cleavage of disulfide bonds. These remarkable ratiometric fluorescence changes allowed for not only the simultaneous mapping of the intracellular pH and GSH but also the intracellular transport pathways of internalized NPs.

A ratiometric fluorescent probe with high sensitivity and selectivity for phosgene sensing in solution and gas

AbstractPhosgene has attracted wide attention because of its important applications and value in modern industry, agriculture, and other fields, though it easily leaks and is difficult to detect. In this work, we designed and synthesized a naphthalimide‐based fluorescent probe, which is easy to prepare, stable, and able to discriminate between phosgene, acetyl chloride, oxalyl chloride, thionyl chloride, phosphorus oxychloride, and tosyl chloride. Our results indicate that the probe can react with phosgene selectively and sensitively, showing remarkable ratiometric fluorescence changes. Furthermore, the probe can be made into test strips, which can determine phosgene in air effectively. The present work provides a novel class of naphthalimide‐based derivatives with potential application in phosgene sensing in real time simply and safely with further optimization.