Fluorescence Switching Properties Research Articles

Hydroxyl-driven construction of dual-emitting CsPbBr3/EuWO4(OH) composite for radiometric thermometer and information encryption applications

Self-assembled inorganic metal halide perovskite composites with high emitting efficiency, tunable multimode emission and stimuli-responsive luminescence demonstrated great potential in diversified luminescence applications. Here, a novel CsPbBr3/EuWO4(OH) composite was successfully prepared through the surface adsorption of Pb2+ ions on hydroxylated EuWO4(OH) microsheets and subsequent nucleation of CsPbBr3 peroviskite quantum dots (PQDs) by the anti-solvent crystallization in CsBr containing N,N-dimethylformamide (DMF) solution. Due to the distinct fluorescent thermochromic switching properties of temperature-insensitive Eu3+ and sensitive CsPbBr3 PQDs emitting centers, the resultant CsPbBr3/EuWO4(OH) composite exhibits excellent ratiometric temperature sensing performance. The CsPbBr3/EuWO4(OH) thermometer based on the fluorescence intensity ratio (FIR) technique originating from emissions of Eu3+ to CsPbBr3 PQDs was then explored with a high temperature sensitivity (Sr) of 5.8 % ℃−1 at 54 ℃. In addition, a high-security-level information encryption scheme was proposed by utilizing the excitation-wavelength-dependent switchable fluorescence of CsPbBr3/EuWO4(OH) composite. This study provides a simple and feasible strategy for assembling dual-emission CsPbBr3/EuWO4(OH) composite, showing potential applications in optical ratiometric thermometry and information encryption fields.

Textile-Based Adsorption Sensor via Mixed Solvent Dyeing with Aggregation-Induced Emission Dyes.

This study demonstrates a novel methodology for developing a textile-based adsorption sensor via mixed solvent dyeing with aggregation-induced emission (AIE) dyes on recycled fabrics. AIE dyes were incorporated into the fabrics using a mixed solvent dyeing method with a co-solvent mixture of H2O and organic solvents. This method imparted unique fluorescence properties to fabrics, altering fluorescence intensity or wavelength based on whether the AIE dye molecules were in an isolated or aggregated state on the fabrics. The precise control of the H2O fraction to organic solvent during dyeing was crucial for influencing fluorescence intensity and sensing characteristics. These dyed fabrics exhibited reactive thermochromic and vaporchromic properties, with changes in fluorescence intensity corresponding to variations in temperature and exposure to volatile organic solvents (VOCs). Their superior characteristics, including a repetitive fluorescence switching property and resistance to photo-bleaching, enhance their practicality across various applications. Consequently, the smart fabrics dyed with AIE dye not only find applications in clothing and fashion design but demonstrate versatility in various fields, extending to sensing temperature, humidity, and hazardous chemicals.

Force-activated ratiometric fluorescence switching of tensile mechano-fluorophoric polyurethane elastomers with enhanced toughnesses improved by mechanically interlocked [c2] daisy chain rotaxanes

The extended and contracted conformations of [c2] daisy chain rotaxanes were introduced in mechano-fluorophoric polyurethane (PU) scaffolds via step-growth polymerizations to obtain distinct mechanical and optical features upon external forces. Particularly, the inherent ductile and stretchable capabilities along with notable toughnesses of PU films containing very low contents of [c2] daisy chain moieties with long-range sliding motions were obviously improved. Furthermore, appealing Förster resonance energy transfer (FRET) behaviors with the optimum energy transfer efficiency ca. 26.02% between blue-emitting tetraphenylethylene (TPE) and yellow-orange-emitting rhodamine derivatives could be acquired in the PU film under tensile conditions, which could be assigned to the incorporation of bi-fluorophoric daisy chain rotaxane into PU frameworks to gain reversible dual fluorescence switching behaviors upon stretching and relaxation processes. Additionally, the stretching deformations of PU films were inspected by X-ray diffraction (XRD) and FTIR techniques for the verification of correlated morphological properties of stretching states in the oriented daisy chain rotaxane-based PU films. Interestingly, impressive shape recovery and reversible ratiometric mechano-fluorophoric fluorescence switching properties of [c2] daisy chain rotaxane-based PU films could be attained upon heating, suggesting potential applications of PU films comprising artificial molecular muscles with glorious mechanical and optical behaviors in advanced polymer networks.

Polymeric assembled nanoparticles through kinetic stabilization by confined impingement jets dilution mixer for fluorescence switching imaging

• Rapidly-assembled nanoparticles prepared by flash nanoprecipitation. • Nanoparticles with controllable size and fluorescence intensity. • Fluorescence switching behavior under visible lights. Traditional fluorescence switching molecules achieving the state change between on and off states commonly based on UV irradiation. However, it is worth noting that UV irradiation is harmful to both the cancer cells and the normal cells. To achieve fluorescence switching under visible wavelength and avoid complicate molecular design, a fluorophore of 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene (4CzIPN) and a quencher of diarylethene (DAE) were physically incorporated within the biocompatible block copolymer poly(lactic-co-glycolic acid)- b -poly(ethylene glycol) (PLGA- b -PEG) to form 4CzIPN-DAE nanoparticles (NPs) through flash nanoprecipitation (FNP). By using the FNP method, the NPs were prepared within milliseconds in a confined impingement jets dilution (CIJ-D) mixer. Quenching and recovery of fluorescence could achieve in the presence of DAE under 475 nm and 560 nm irradiation. Appropriate structure and fluorescent properties of the nanoparticles can be tuned by external conditions for their efficient fluorescence resonance energy transfer (FRET) in a kinetic stabilization process. This NPs formation process was further optimized by varying the dilution ratio, Reynolds number ( Re ) and polymer concentration to modulate the mixing and particle nucleation and growth process. The size and fluorescence switching properties of the NPs were systematically investigated in solution and in cellular uptake experiments. This work is anticipated to provide a simple and highly effective engineering strategy for the modulation of fluorescence switching nanoparticles and beneficial to its engineering application.

Synthesis and photophysical investigation of Schiff base as a Mg2+ and Zn2+ fluorescent chemosensor and its application.

In view of the fluorescent switching properties and anti-fatigue properties of diarylethene, a diarylethene fluorescent chemosensor for the immediate detection of zinc ion (Zn2+ ) and magnesium ion (Mg2+ ) in acetonitrile was synthesized in this article. The structure of 1o was determined by performing spectroscopy and elemental analysis. The presence of Zn2+ or Mg2+ made the chemosensor 1o show an obvious "turn-on" fluorescent signal (bright yellow-green for Mg2+ and bright cyan for Zn2+ ). The fluorescent change caused by the 1:1 binding of 1o and Zn2+ or Mg2+ might be due to hindering the excited-state intramolecular proton transfer (ESIPT) process, which were bolstered by Benesi-Hildebrand analysis, Job's plot curves, proton nuclear magnetic resonance (1 H-NMR) titration and mass spectrometry. The limits of detection were acquired from the standard curve plots for Mg2+ at 44.6nM and for Zn2+ at 14 nM. Based on the fluorescent behaviors, a logic gate was constructed with the emission intensity at 528/518 nm as output signal, the ultraviolet-visible (UV-vis) lights, Mg2+ /Zn2+ and EDTA as input signals. Exogenous Zn2+ and Mg2+ fluorescent bioimaging were performed on Hela cells with 1o, indicating its potential application in biodiagnostic analysis. In particular, 1o was manufactured into test paper, and Zn2+ or Mg2+ can be conveniently, efficiently and qualitatively identified by the fluorescent color variation of the test strips.

Quinoline Derivatives with Fluorescent Switching Properties for Efficient Selective Labeling of Cellular Lipid Droplets

Quinoline Derivatives with Fluorescent Switching Properties for Efficient Selective Labeling of Cellular Lipid Droplets

4-Phenyl-2-(2′-pyridyl) quinoline acts as a highly sensitive fluorescent probe for Fe2+ and Fe3+ ions and exhibits reversible photoelectric stimulation response

4-Phenyl-2-(2′-pyridyl) quinoline (L1) was synthesized by a three-component reaction of aniline, phenylacetylene and pyridine-2-aldehyde catalyzed by trifluoromethanesulfonic acid (TfOH). Its structure was confirmed by FT-IR, MS, NMR and X-ray single crystal diffraction analysis. L1 was investigated as a probe for the detection of Fe3+ and Fe2+ ions, which displayed fluorescence enhancement by Fe3+ and fluorescence quenching by Fe2+. This unique fluorescence switching property of L1 was used to identify Fe2+ and Fe3+ with high selectivity and sensitivity. The detection limit of Fe2+ was 8.772 × 10−9 mol/L and that of Fe3+ was 1.912 × 10−9 mol/L. Mechanism investigation revealed that the fluorescence quenching of probe L1 was caused by ferrous-induced PET process and the fluorescence enhancement was due to the combinational effect of ferric-induced PCT enhancement and PET inhibition. In addition, the cyclic voltammetry curves demonstrated that both the Fe2+ complexes and the Fe3+ complexes displayed reversible redox process, indicating that the Fe2+ and Fe3+ complexes can be reversibly converted into each other upon electrical stimulation. The reversible “On” and “Off” of the fluorescence emission of iron complexes upon electrochemical stimulation could potentially be used in information recording and erasing.

Stimuli-Responsible SNARF Derivatives as a Latent Ratiometric Fluorescent Probe.

Fluorescence imaging is a powerful technique for continuous observation of dynamic intracellular processes of living cells. Fluorescent probes bearing a fluorescence switching property associated with a specific recognition or reaction of target biomolecule, that is, stimuli-responsibility, are important for fluorescence imaging. Thus, fluorescent probes continue to be developed to support approaches with different design strategies. When compared with simple intensity-changing fluorescent probes, ratiometric fluorescent probes typically offer the advantage of less sensitivity to errors associated with probe concentration, photobleaching, and environmental effects. For intracellular usage, ratiometric fluorescent probes based on small molecules must be loaded into the cells. Thus, probes having intrinsic fluorescence may obscure a change in intracellular signal if the background fluorescence of the remaining extracellular probes is high. To overcome such disadvantages, it is necessary to minimize the extracellular background fluorescence of fluorescent probes. Here, the design strategy of the latent ratiometric fluorescent probe for wash-free ratiometric imaging using a xanthene dye seminapthorhodafluor (SNARF) as the scaffold of fluorophore is discussed.

A Highly Selective Hg2+ Fluorescent Chemosensor Based On Photochromic Diarylethene With Quinoline Unit.

A novel diarylethene-based fluorescent chemosensor containing a quinoline unit (1o) had been designed and synthesized. 1o showed good photochromic ability and fluorescence switching properties by alternating UV/vis light irradiation. The chemosensor showed high "Turn-off" fluorescent selectivity for Hg2+ by competitive tests of the fluorescence reaction in the presence other ions in acetonitrile solution. The stoichiometry between the compound 1o and Hg2+ was 1:1 by Job's plot curve and HRMS analysis. In addition, the LOD for Hg2+ was calculated as 60nM. The fluorescence emission can be back to the "Turn-on" state by adding EDTA. Based on these facts, a molecular logic gate that including four input signals (UV/vis and Hg2+/EDTA) and one output signal (fluorescent intensity at 491nm) was designed.

Multicolor fluorescence switching material induced by force and acid

A novel D–A–D chromophore TBQM based on triphenylamine, acylhydrazone and dimethylamino was synthesized, and the emission properties of TBQM was studied in solutions as well as in aggregated state. TBQM showed obvious solvatochromism in different solutions. In addition, the reversible multicolor fluorescence switching properties under the stimulation of external forces and acid were also obtained. The fluorescence of TBQM changed from blue to bright blue, and finally to blue-green as the degree of grinding increased, which would recover after being fumigated by CH2Cl2. Meanwhile, TBQM could undergo twice protonation after fumigated by TFA. The fluorescence color changed from blue to bright blue, blue-green, and yellow-green until the fluorescence was quenched with the increasing of TFA fumigation time, which can be restored automatically or by TEA fumigation. Moreover, TBQM could be used as an advanced fluorescent anti-counterfeiting ink.

Novel push-pull based phenothiazine-benzothiazole derivatives integrated with molecular logic gate operation for reversible volatile acid detection

• Design and synthesis of push-pull based phenothiazine benzothiazole derivatives. • Positive solvatochromism with large Stokes shifts (113-146 nm). • Naked eye colorimetric and fluorescent acid sensing behavior in solution and solid state. • Fabrication of paper strip sensors for volatile acid. • Development of INHIBIT molecular logic gate with acid and base as inputs. A series of novel push-pull based phenothiazine-benzothiazole derivatives, in which phenothiazine and benzothiazole groups act as donors and acceptors, respectively is designed and synthesized in good yields. These compounds exhibit strong fluorescence in solution and solid state. These derivatives respond to external stimuli such as solvents and acid. A positive solvatochromism with large Stokes shifts (113-146 nm) was observed. In solution state, blue shifted emission wavelengths of compounds containing electron-withdrawing aryl groups indicated reduced Intramolecular Charge Transfer (ICT). However, red shifts in solid state emission spectra of compounds with electron-withdrawing aryl groups indicated more planarity of the excited state. The naked eye detection of reversible acid/base-induced chromogenic and fluorescence switching properties were observed in both solution and the solid state upon subsequent addition of trifluoroacetic acid (TFA) and triethylamine (TEA), thereby making the synthesized derivatives efficient volatile acid-base switches. The reversible acidochromic response was further utilized for the development of inhibit (INH) molecular logic gates using TFA/ (TEA) as the chemical inputs.

A Fluorescence Switching Sensor for Sensitive and Selective Detections of Cyanide and Ferricyanide Using Mercuric Cation-Graphene Quantum Dots.

This study aims to use graphene quantum dots (GQDs) as a fluorescence switching sensor (turn on–off) for the simultaneous detection of cyanide (CN–) and ferricyanide [Fe(CN)6]3– in wastewater samples. The GQDs were synthesized by pyrolyzing solid citric acid. The intrinsic blue color of the solution was observed under ultraviolet irradiation. The fluorescence spectrum was maximized at both excitation and emission wavelengths of 370 and 460 nm, respectively. The fluorescence intensity of GQDs decorated with Hg2+ (turn-off mode as the starting baseline) could be selectively turned on in the presence of CN– and once back to turn-off mode by [Fe(CN)6]3–. The fluorescence switching properties were used to develop a fluorescence turn-on–off sensor that could be used to detect trace amounts of CN– and [Fe(CN)6]3– in water samples. For highly sensitive detection under optimum conditions (Britton–Robinson buffer solution in the pH range of 8.0–9.0, linearity ranges of 5.0–15.0 μM (R2 = 0.9976) and 10.0–50.0 μM (R2 = 0.9994), respectively, and detection limits of 3.10 and 9.48 μM, respectively), good recoveries in the ranges of 85.89–112.66% and 84.88–113.92% for CN– and [Fe(CN)6]3–, respectively, were recorded. The developed methods were successfully used for the simultaneous and selective detection of CN– and [Fe(CN)6]3– in wastewater samples obtained from local municipal water reservoirs.

Force-, heat- and acid-induced fluorescent switching properties of an anthracene-based hydrazide derivative

A novel anthracene-based hydrazide derivative (3,4-ENS) was designed and synthesized, and 3,4-ENS can form stable organogel in dimethyl sulfoxide (DMSO) solvent. Firstly, 3,4-ENS xerogel from DMSO exhibits mechanofluorochromic property and its maximum emission shifts from 433 nm to 484 nm upon grinding. Secondly, DMSO xerogel exhibits thermofluorochromic behavior and its maximum emission shifts from 433 nm to 481 nm upon heating at 110 °C. Thirdly, DMSO xerogel exhibits acidofluorochromic behavior and its maximum emission shifts from 433 nm to 466 nm upon fuming by TFA vapors. The experimental results confirmed that the different luminescent property of 3,4-ENS attributed to the phase transition from well-ordered crystals to metastable disordered aggregation.

Fulgide Derivative-Based Solid-State Reversible Fluorescent Switches for Advanced Optical Memory

Fulgide Derivative-Based Solid-State Reversible Fluorescent Switches for Advanced Optical Memory

CO2-Responsive Water-Soluble Conjugated Polymers for In Vitro and In Vivo Biological Imaging.

Water-soluble conjugated polymers (WCPs) composed of a hydrophobic polythiophene main chain with hydrophilic tertiary amine side-chains can directly self-assemble into sphere-like nano-objects in an aqueous solution due to phase separation between the hydrophilic and hydrophobic segments of the polymeric structure. Due to the presence of gas-responsive tertiary amine moieties in the spherical structure, the resulting polymers rapidly and reversibly tune their structural features, surface charge, and fluorescence performance in response to alternating carbon dioxide (CO2) and nitrogen (N2) bubbling, which leads to significantly enhanced fluorescence and surface charge switching properties and a stable cycle of on and off switching response. In vitro studies confirmed that the CO2-treated polymers exhibited extremely low cytotoxicity and enhanced cellular uptake ability in normal and tumor cells, and thus possess significantly improved fluorescence stability, distribution, and endocytic uptake efficiency within cellular organisms compared to the pristine polymer. More importantly, in vivo assays demonstrated that the CO2-treated polymers displayed excellent biocompatibility and high fluorescence enhancement in living zebrafish, whereas the fluorescence intensity and stability of zebrafish incubated with the pristine polymer decreased linearly over time. Thus, these CO2 and N2-responsive WCPs could potentially be applied as multifunctional fluorescent probes for in vivo biological imaging.

A novel diarylethene‐based fluorescence sensor with a benzohydrazide unit for the detection of Zn2+

AbstractA novel fluorescent sensor on the basis of diarylethene and benzohydrazide unit was successfully synthesized. Its photochromic and fluorescent switching properties have been studied in detail by the irradiation of UV‐visible (UV‐Vis) lights and the stimulus of Zn2+/EDTA. The sensor exhibited high sensitivity and selectivity toward Zn2+ in tetrahydrofuran, which is not interfered by other cations, especially of congener Cd2+. The fluorescence intensity enhanced 84 times along with a 44‐nm blue shift of the emission peak after adding Zn2+. The stoichiometric ratio between the sensor and Zn2+ was 1:1, and the limit of detection (LOD) was calculated as 5.60 × 10−9 mol L−1. Besides, the sensor was applied in the detection of practical water samples with high accuracy.

"Plug and Play" logic gate construction based on chemically triggered fluorescence switching of gold nanoparticles conjugated with Cy3-tagged aptamer.

Gold nanoparticles (AuNPs) conjugated with Cy3-tagged aptamer which can specifically recognize chloramphenicol (CAP) (referred to as AuNPs-AptCAP) are described. CAP can trigger the configuration change of CAP binding aptamer, and thus switching the fluorescence of AuNPs-AptCAP through changing the efficiency of the fluorescence resonance energy transfer (FRET) system with Cy3 as donors and AuNPs as recipients. AuNPs-AptCAP exhibits a linear range of CAP concentrations from 26.0 to 277μgL-1 with a limit of detection of 8.1μgL-1 when Cy3 was excited at 530nm and emission was measured at 570nm. More importantly, AuNPs-AptCAP can be utilized as signal transducers for the build-up of a series of logic gates including YES, PASS 0, INH, NOT, PASS 1, and NAND. Utilizing the principle of ametal ion-mediated fluorescence switch together with astrong metal ion chelator, the fluorescence of AuNPs-AptCAP could be modulated by adding metal ions and EDTA sequentially. Therefore, a "Plug and Play" logic system based on AuNPs-AptCAP has been realized by simply adding other components to create new logic functions. This work highlights theadvantages of simple synthesis and facile fluorescence switching properties, which will provide useful knowledge for the establishment of molecular logic systems. Graphical abstract.

Reversible fluorescent switching properties of pyrene-substituted acylhydrazone derivatives toward mechanical force and acid vapor with aggregation-induced emission

Four pyrene-substituted acylhydrazone derivatives named PMBH ((E)-N'-(pyren-1-ylmethylene)benzohydrazide), PMPH ((E)-N'-(pyren-1-ylmethylene)picolinohydrazide), PMNH ((E)-N'-(pyren-1-ylmethylene)nicotinohydrazide) and PMIH ((E)-N'-(pyren-1-ylmethylene)isonicotinohydrazide) by functionalizing the phenyl ring and pyridyl ring with pyrene-substituted acylhydrazone moiety have been designed and synthesized, whose properties were investigated. All the four synthesized compounds exhibited favorable aggregation induced emission (AIE) features and reversible mechanofluorochromism (MFC) behaviour. Especially, the intense cyan emission of PMIH changed into orange-yellow emission with a 101 nm red-shift upon grinding. The MFC behavior was associated with the crystalline-amorphous phase transformation between the pristine and ground states, which was confirmed by the investigations of the power X-ray diffraction (PXRD), the differential scanning calorimetry (DSC) and field emission scanning electron microscopy (FESEM). Specifically, PMPH, PMNH and PMIH demonstrated remarkable and reversible acidofluorochromic response due to the presence of free nitrogen atom of pyridyl groups at the terminal position. The chosen approaches showed a new possibility for generating multi-stimuli responsive materials with modulated solid state properties.

Visible light responsive donor-acceptor stenhouse adducts with indoline-tri/tetra-phenylethylene chromophore: Synthesis, aggregation-induced emission, photochromism and solvent dependence effect

We designed and synthesized two new visible light triggered photochromic and aggregation-induced emission compound derived from the third generation donor−acceptor Stenhouse adducts (DASAs) with indoline-tri/tetra-phenylethylene moiety (abbreviation: SPE-IF/TPE-IF). The chemical structures of these compounds are identified by NMR, MS and so on. The key intermediate SPE-ID/TPE-ID as donor showed excellent AIE properties in water-THF (v/v) solutions. The absorption and emission of SPE-IF/TPE-IF were investigated by UV–Vis and fluorescence spectroscopy, respectively. The results shown they exhibited photochromic with fatigue resistance and fluorescent switching properties with visible light regulation. The open/colored triene and closed/colorless cyclopentenone isomers of SPE-IF/TPE-IF were equipped with high photo bleaching and fluorescence effect upon alternating visible light irradiation and heating both in solution and in PMMA doped solid state. And the solvent dependence effect of TPE-IF was studied. The photochromic mechanism of SPE-IF/TPE-IF was also basically investigated by computational method. These results indicate SPE-IF or TPE-IF is a promising candidate for visible light-responsive smart materials.

Stimuli-Responsive Naphthalene Diimide as Invisible Ink: A Rewritable Fluorescent Platform for Anti-Counterfeiting.

Herein, we report an approach to combat counterfeiting and storage of valuable information based on the solid-state fluorescence switching behavior of isoniazid functionalized naphthalene diimide (ISO_NDI) in response to an external stimuli (i. e., HCl vapor). The unique feature of ISO_NDI is further utilized to develop an invisible ink (ISO_NDI-PVA) with commercial polymer polyvinyl alcohol (PVA). A solid-state fluorescence recovery was observed while loading with HCl vapors. This exclusive property of the material could be applied directly as a security ink for confidential data storage purpose. Based on above strategy, we successfully realized the rewritable application by using ISO_NDI-PVA ink and confirm its practical efficacy on various substrates by creating different patterns. The solid-state fluorescence switching behavior of ISO_NDI-PVA ink exhibited reversible on/off signal for multiple cycles under the influence of HCl/NH3 vapors. Mechanistic investigation supports a clear participation of intermolecular charge transfer (ICT) phenomenon in the solid-state fluorescence switching property. The ease of fabricating the ink with invisible to visible characteristics in response to HCl vapors provides new opportunities for exploring the application of ISO_NDI-PVA as invisible ink for targeted security applications.