Exhibited Fluorescence Enhancement Research Articles

Eu‐based coordination polymer with fluorescence enhancement for Cu2+/prochloraz and quenching for nitrobenzene/pyrimethanil

The detection of pollutants is an important part of environmental protection. A one‐dimensional Eu(III) coordination polymer (CP1), [Eu2(3‐pyia)2(Ac)2 (H2O)4]·(2,2′‐bipy)0.5·4.25H2O, based on 5‐(pyridin‐3‐ylmethoxy) isophthalic acid (3‐H2pyia) and 2,2′‐bipyridine (2,2′‐bipy) was designed and prepared under hydrothermal condition. The structure was characterized as one‐dimensional ladder‐like structure with water and 2,2′‐bipy guest molecules. The excellent luminescence properties of CP1 prompted us to investigate its fluorescence sensing performance for pollutants. It exhibited fluorescence enhancement for Cu2+ and prochloraz, but quenching for nitrobenzene and pyrimethanil, and the fluorescence sensing mechanism has been further investigated by experimental and density functional theory (DFT) calculations. This work expands the exploitation of rare earth coordination polymers for fluorescence sensing and contributes to pollutant detection.

A comparative study of two thienopyrimidine Schiff base probes for sequential monitoring of Ga3+ and Pd2.

Two Schiff base probes (S1 and S2) were prepared and synthesized by incorporating thienopyrimidine into salicylaldehyde or 3-ethoxysalicylaldehyde individually, with the aim of detecting Ga3+ and Pd2+ sequentially. Upon chelation with Ga3+, S1 and S2 exhibited fluorescence enhancement in DMSO/H2O buffer. Both S1-Ga3+ and S2-Ga3+ were quenched by Pd2+. The limit of detection for S1 in response to Ga3+ and Pd2+ was 2.86 × 10-7 and 4.4 × 10-9M, respectively. For S2, the limit of detection for Ga3+ and Pd2+ was 4.15 × 10-8 and 3.0 × 10-9M, respectively. Furthermore, the complexation ratios of both S1 and S2 with Ga3+ and Pd2+ were determined to be 1:2 through Job's plots, ESI-MS analysis, and theoretical calculations. Two molecular logic gates were constructed, leveraging the response behaviors of S1 and S2. Moreover, the potential utility of S1 and S2 for monitoring Ga3+ and Pd2+ in domestic water was verified.

Rolling Stone Gathers Moss: Rolling Microneedles Generate Meta Microfluidic Microneedles (MMM)

AbstractMicrofluidic chips play crucial roles while lack satisfactory controllability and comprehensive functionality. Inspired by biological systems, this study proposes a method utilizing rolling microneedles (RMNs) to generate muti‐structured templates, realizing photonic crystal membrane (PC) based meta microfluidic microneedle chip (MMM) for efficient wound management. This approach offers advantages in terms of speed and cost‐effectiveness, achieving dual‐sided permeation and patterned design by directly RMNs at desired locations, serving as both template tools for microneedle fabrication. The integration of RMNs with a PC membrane results in the design of 3D multilayer microfluidic channels, effectively addressing issues related to spontaneous fluid flow. As fluid reaches the PC membrane, it generates distinctive structural colors and exhibits fluorescence enhancement, enabling the monitoring of inflammatory factors in mouse wounds and facilitating efficient wound management. In summary, this preparation method involving RMNs paves the way for the design and fluid control of microfluidic chips. This bioinspired patch holds significant potential not only for wound management but also for areas such as clinical drug delivery and point‐of‐care testing (POCT).

Exploring the potential of MIL-53(Fe) as a fluorescent probe for the highly selective and sensitive detection of anti-tuberculosis drug—Isoniazid

Ecosystem and human health can both be catastrophically harmed by overuse of anti-tuberculosis drug, isoniazid. Within this frame of reference, an Fe-based metal organic framework (MIL-53(Fe)) was developed via hydrothermal route to successfully recognise and detect, isoniazid antibiotic, using fluorescence sensing. The structural, morphological and other important property insights of MIL-53(Fe) were gained using various techniques like FT-IR, XRD, FE-SEM, BET, TGA and VSM. The developed fluorescence probe exhibited fluorescence enhancement with the incremental addition of isoniazid antibiotic, in the range of 0.1 to 7.0 µM. The limit of detection (LOD) value was found to be 0.25 µM under optimal sensing conditions. MIL-53(Fe) demonstrated high selectivity and specificity for the detection of isoniazid. In addition, the sensor displayed excellent performance in reproducibility, repeatability and real water studies.

High-efficient luminescence induced by the restriction of benzothiazole group torsion for the HBT-H-H molecule in the aggregate state

The aggregation-induced emission (AIE) effect has been demonstrated to have great potential application in different areas, from organic electronics to biomedical research and physical process monitoring. In general, molecules with AIE characteristic exhibit fluorescence enhancement in the aggregated state by restricting intramolecular motion consumption. The combination of AIE and excited-state intramolecular proton transfer (ESIPT) is meaningful for promoting luminescence. Recently, HBT-H-H molecule, as a derivative of 2-(2-Hydroxyphenyl)benzothiazole (HBT), has drawn extensive attention from researchers. The molecule possesses the intramolecular hydrogen bonding structure which has the potential for ESIPT. Moreover, the fluorescence quantum yield of HBT-H-H in the aggregation state is 35 times higher than that in Toluene. However, the interplay between excited state dynamics and the AIE effect for this molecule is not clear. Especially, how does AIE effect beat non-radiative transition channel by affecting motions of molecular structure. Herein, we investigated the excited state dynamics of HBT-H-H molecule by the spin-flip time-dependent density functional theory and QM/MM method. We found that the molecule relaxes to the conical intersection region through the twisting motion of the benzothiazole group in Toluene solvent. While the AIE effect effectively inhibits this process by preventing the torsion of benzothiazole group, which induces the emission enhancement. The interplay between the excited-state dynamics and AIE effect for the HBT-H-H molecule delineated in this work not only benefits the deep understanding of molecular behavior to the aggregate level, but also provides a guide for the synthesis of AIE materials with favorable performance.

Fluorescent probes based on a tetrad BODIPY structure for detection of a wide range of water contents in organic solvents

A series of tetrad Boron dipyrromethene (BODIPY) derivatives containing a variety of nitrogen-heterocyclic meso-substituents were synthesized. All exhibited fluorescence enhancement in the presence of water in organic solvents. Water-soluble tetrad BODIPY derivatives were obtained by displacement of fluoride at the boron atom by a bicyclic structure, and their fluorescence response was observed over a wide range of water contents in various organic solvents. The presence of acids or metal ions induced only a fluorescence shift and retained the fluorescence efficiency.

Synthesis and ESIPT Phenomena of A New -Naphthol Derivative, An Experimental and In Silico Study

A new derivative based on -naphthol skeleton was successfully synthesized through Knoevenagel condensation as a yellow solid with an overall chemical yield of 28% in two steps. The compound showed maxima of UV/Visible and emission spectra in acetonitrile at 404 nm and 521 nm respectively. Based on spectroscopy data of FTIR, ToF-HRMS, 1H-NMR and 13C-NMR, the product was characterized as 4-((2-hydroxynaphthalene-1-yl)methylene)pyrazolidine-3,5-dion. Chelation experimental study of the compound against various metal ions in acetonitrile exhibited fluorescence enhancement by three folds of magnitude, especially against Al3+ and Mg2+ at emission maxima of 521 nm. The LoD and LoQ of the compound were respectively calculated to be 0.004 mg L-1 and 0.013 mg L-1 for Al3+ and 0.002 mg L-1 and 0.008 mg L-1 for Mg2+. DFT and TD/DFT calculations revealed that the interaction mechanism of the compound with the metal ions was through inhibition of excited-state intramolecular proton transfer (ESIPT).

Simple and Rapid Endotoxin Recognition Using a Dipicolylamine-Modified Fluorescent Probe with Picomolar-Order Sensitivity.

Endotoxin is a lipopolysaccharide (LPS) that is found in the outer membrane of the cell wall of Gram-negative bacteria. Due to its high toxicity, the allowable endotoxin limit for water for injection is set at a very low value. Conventional methods for endotoxin detection are time-consuming and expensive and have low reproducibility. A previous study has shown that dipicolylamine (dpa)-modified pyrene-based probes exhibit fluorescence enhancement in response to LPS; however, the application of such probes to the sensing of LPS is not discussed. Against this backdrop, we have developed a simple and rapid endotoxin detection method using a dpa-modified pyrenyl probe having a zinc(II) center (Zn-dpa-C4Py). When LPS was added into Zn-dpa-C4Py solution, excimer emission of the pyrene moiety emerged at 470 nm. This probe can detect picomolar concentrations of LPS (limit of detection = 41 pM). The high sensitivity of the probe is ascribed to the electrostatic and hydrophobic interactions between the probe and LPS, which result in the dimer formation of the pyrene moieties. We also found that Zn-dpa-C4Py has the highest selectivity for LPS compared with other phosphate derivatives, which is probably caused by the co-aggregation of the probe with LPS. We propose that Zn-dpa-C4Py is a promising chemical sensor for the detection of endotoxin in medical and pharmaceutical applications.

Sensitively liquid and gaseous detection of formaldehyde based on a supramolecular organic framework

Because of the serious threat to human health, the development of fluorescent sensor for detection of formaldehyde (FA) has attracted great concern. Herein, a 4,4′-(1,2-diphenylethene-1,2-diyl)dibenzoic acid-based SOF (HNU-44), has been assembled, which can be used to detect FA by quite different fluorescent response in liquid and gas. In liquid phase, HNU-44 exhibits fluorescence enhancement with the limit of detection (LOD) 27.41 ppb. On the contrary, fluorescence quenching happens when HNU-44 is exposed in the FA atmosphere with the LOD of 2.61 ppb. The LOD in gas is even lower than the air quality criterion of gaseous FA (80 ppb) recommended by World Health Organization (WHO). Furthermore, sensing tests were performed on fish samples, which means that HNU-44 can be used in actual sample. This work expands promising approach for effective FA detection both in the experiment test and actual application.

Azulene-based fluorescent chemosensor for adenosine diphosphate.

AzuFluor® 435-DPA-Zn, an azulene fluorophore bearing two zinc(II)-dipicolylamine receptor motifs, exhibits fluorescence enhancement in the presence of adenosine diphosphate. Selectivity for ADP over ATP, AMP and PPi results from appropriate positioning of the receptor motifs, since an isomeric sensor cannot discriminate between ADP and ATP.

Effect of Nanostructure and Europium Doping on Fluorescence Properties of YbxMnyOz:Eu3+ Nanotube Arrays

YbxMnyOz:Eu3+ nanotube arrays have been synthesized in anodic aluminum oxide (AAO) templates with negative pressure filtration. The morphology, structure, and composition have been characterized by SEM, TEM, HRTEM, XRD and EDS, respectively. Compared with nanoparticles and nanowire arrays excited by 394 nm light wave, YbxMnyOz:Eu3+ nanotube arrays exhibit fluorescence enhancement and are accompanied by red and blue shift, and there are three fluorescence emission peaks at 480 nm, 590 nm and 702 nm, respectively. The peaks at 590 and 702 nm correspond to the 5D0–7F1 and 5D0–7F4 energy level transition of Eu3+, and the peak of 480 nm is from the “cooperative fluorescence” due to two-photon excitation. The fluorescence intensity of YbxMnyOz:Eu3+ nanotube arrays increases with the doping concentration of Eu3+, which reaches a maximum at 5 vol %, and remarkably decreases at higher concentrations.

Perylene bisimide anchored palygorskite nanofibers as a solid-state fluorescence sensor for detection of volatile organic compounds

A novel palygorskite (Pal) based fluorescence sensor (Pal-PBS-C12) was developed for the vapor probing of volatile organic compounds. Pal is a naturally occurred fibrous phyllosilicate mineral and it acts as a supporting substrate in the fluorescence sensory material. Perylene-3,4,9,10-tetracarboxylic dianhydride (PBS), playing the role of fluorescence probe, was grafted to Pal. With further introduction of the hydrophobic n-dodecylamine group, the organic affinity of the sensory material was dramatically improved. The PAL-PBS-C12 material exhibited good sensitivity, photostability, and selectivity in solid-state fluorescence probing performance tests for organic vapors. Different from the traditional sensors, which show fluorescence diminishment upon contact with target molecules, the reported material exhibited fluorescence enhancement after contact with polar organic vapors. The mechanism of the fluorescence enhancement was proposed.

An aldimine condensation reaction based fluorescence enhancement probe for detection of gaseous formaldehyde

Formaldehyde, a volatile organic compound that is ubiquitous in gas pollutants, has an indelible hazard to the health system of humans. Development of simple and convenient ways for the visual detection of formaldehyde in air is still of importance and challenging. In this paper, we report a new type of fluorescence enhancement probe (FAP), which directly exhibited fluorescence enhancement response to formaldehyde with high sensitivity and selectivity. The FAP was synthesized through the substitution reaction between hydrazine and NBD (7-nitrobenzo-2-oxa-1, 3-diazolyl) chloride, that the hydrazine group acted as both fluorescence quencher based on the photo-induced electron transfer (PET) pathway and reaction triggering factor for selectively recognizing formaldehyde. When the FAP was incubated with a formaldehyde-containing circumstance, Schiff base compound was produced by means of the aldimine condensation reaction which inhibited the PET pathway from hydrazine group to NBD, and thus turned on the fluorescence of the FAP significantly. It is worth mentioning that the FAP showed more remarkable response to formaldehyde under acid conditions. Under the optimal experimental conditions, the FAP responded linearly toward formaldehyde in a wide range of 0.015–0.8 mg•L−1, while the fluorescence enhancement was close to 30 times. This FAP was successfully used to detect gaseous formaldehyde in indoor air.

A Tetrakisquinoline Analog of Calcium Indicator Quin2 for Fluorescence Detection of Cd2+

Quin2 (2‐{2‐[bis(carboxymethyl)amino‐5‐methylphenoxy]methyl}‐6‐methoxy‐8‐[bis(carboxymethyl)amino]quinoline) is a well‐known fluorescent Ca2+ indicator. In this study, we replaced its four carboxy groups with quinolines and deleted a methyl group on the benzene ring to afford TQquin2 [N,N,N',N'‐tetrakis(2‐quinolylmethyl)‐8‐amino‐2‐(2‐aminophenoxy)methyl‐6‐methoxyquinoline]. In methanol solution, TQquin2 exhibited fluorescence enhancement toward Cd2+ with excellent selectivity.

Switching of Fluorescent Zn/Cd Selectivity in N,N,N',N'-Tetrakis(6-methoxy-2-quinolylmethyl)-1,2-diphenylethylenediamine by One Asymmetric Carbon Atom Inversion.

A quinoline-based hexadentate ligand, (S,S)-N,N,N',N'-tetrakis(6-methoxy-2-quinolylmethyl)-1,2-diphenylethylenediamine ((S,S)-6-MeOTQPh2EN), exhibits fluorescence enhancement at 498 nm upon addition of 1 equiv of Zn2+ (IZn/I0 = 12, φZn = 0.047) in aqueous DMF solution (DMF/H2O = 2:1). Addition of 1 equiv of Cd2+ affords a much smaller fluorescence increase at the same wavelength (ICd/I0 = 2.5, ICd/IZn = 21%). The trivalent metal ions such as Al3+, Cr3+, and Fe3+ also exhibit fluorescence enhancement at 395 nm (IAl/I0 = 22, ICr/I0 = 6 and IFe3+/I0 = 13). In contrast, meso-6-MeOTQPh2EN exhibits a Cd2+-selective fluorescence increase at 405 nm in the presence of 1 equiv of metal ion (ICd/I0 = 11.5, φCd = 0.022), while Zn2+ induces a smaller fluorescent response under the same experimental conditions (IZn/I0 = 3.3, IZn/ICd = 29%). In this case, the fluorescence intensities of meso-6-MeOTQPh2EN in the presence of a large amount of Zn2+ and Cd2+ become similar. This diastereomer-dependent, fluorescent metal ion specificity is derived from the Zn2+-specific intramolecular excimer formation in (S,S)-6-MeOTQPh2EN-Zn2+ complex and higher binding affinity of meso-6-MeOTQPh2EN with Cd2+ in comparison to Zn2+. The more conformationally restricted diastereomeric pair, namely, cis- and trans-TQDACHs (cis- and trans-N,N,N',N'-tetrakis(2-quinolylmethyl)-1,2-diaminocyclohexanes), both exhibit Zn2+-specific fluorescence enhancement because of the high metal binding affinity and intramolecular excimer forming property derived from the rigid DACH backbone.

A novel schiff base fluorescent probe based on coumarin and benzothiazole for sequential detection of Al3+ and PPi and its applicability in live cell imaging

In this study, a novel schiff base fluorescent probe (E)-N'-(3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzylidene)-7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide (CHS) was synthesized for sequential detection of Al3+ and pyrophosphate ions (PPi) in a DMSO/HEPES (4:1 v/v, pH = 7.4) buffer system and characterized by 1H NMR, 13C NMR, ESI-HR-MS and DFT calculation. Its detection limit was determined to be 0.16 μM for Al3+ and 0.18 μM for PPi in a pH range of 4∼8, respectively. The Job’ s plot showed that the stoichiometric ratio to Al3+ was 1:1, and CHS-Al3+ showed highly selective recognition of PPi. The sensor CHS could also recognize Al3+ and PPi and exhibited fluorescence enhancement and quenching properties in HeLa cells.

Design and synthesis of malonohydrazide based colorimetric receptors for discrimination of maleate over fumarate and detection of F-, AcO- and AsO2- ions.

In this study, we have designed and synthesized two new organic receptors R1 and R2 based on malonohydrazide for the recognition of biologically important anions. The receptor R1 capable of colorimetric discrimination of maleate over fumarate ion, exhibit significant color change from pale yellow to wine red due to intermolecular hydrogen bond between the R1 and maleate ion, supported by 1HNMR titration, where the peak at δ12.0ppm attributed to the NH proton experiences a downfield shift upon binding with maleate ion. Receptor R1, equipped with two electron-withdrawing NO2 moieties as the chromogenic signaling unit enhance the hydrogen bonding tendency and acidity, and thus when comparing with receptor R2, R1 displayed substantial higher redshift (∆λmax) of 148nm, 143nm, and 140nm towards F-, AcO-, and maleate anion in the DMSO. In addition, the synthesized receptors R1 and R2 are able to detect F-, AcO-, and AsO2- ions as their sodium salts in an aqueous solution with visual color change. Receptor R1 exhibit electrochemical response towards F- and AcO- ions. The receptors R1 and R2 are successfully applied for quantitative detection of F- ion in the toothpaste solution in an aqueous medium. Additionally, R1 and R2 exhibit fluorescence enhancement towards F- and AcO- ions in the DMSO. As well, R1 and R2 demonstrate to be potentially useful colorimetric chemosensor for sensing maleate ion using the test strip. The theoretical calculation based on TD-DFT corroborates well with the experimental results of the receptors R1 and R2 with fluoride, acetate and maleate.

Modified CdS quantum dots as selective turn-on fluorescent nanosensor for detection and determination of methamphetamine

Surface modification of cadmium sulfide quantum dots (CdS-QDs) with anti-methamphetamine (anti-METH) antibody produced a new turn-on fluorescent nanosensor, anti-METH-CdS-QDs, for detection of methamphetamine. The anti-METH-CdS-QDs nanosensor was obtained readily via the covalent conjugation of mercaptoacetic acid capped CdS-QDs with anti-METH in the presence of N-ethyl-N′-(3-dimethylaminopropyl carbodiimide) (EDC) and Sulfo-N-hydroxysuccinimide (Sulfo-NHS) as coupling agents. The results of FT-IR and energy dispersive X-ray (EDX) spectroscopies confirmed the functionalization of CdS-QDs with anti-METH species. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses revealed the crystal phase and microstructure of CdS-QDs in the anti-METH-CdS-QDs. The obtained anti-METH-CdS-QDs exhibited fluorescence enhancement upon addition of methamphetamine molecules which allowed the highly sensitive and selective determination of methamphetamine with detection limit of 0.006 mg/L. Further studies disclosed that this nanosensor has little interaction with other drugs such as codeine and ibuprofen. Hence, it can be utilized as simple, inexpensive, and selective nanosensor for determination of methamphetamine in low concentrations.

Fluorescent enhancement sensing of cadmium (II) ion based on a perylene bisimide derivative

A perylene bisimide derivative (PBI-Lac-DPA) with lactose and DPA moiety conjugates was synthesized, and this compound exhibited fluorescence turn-on sensing for Cd2+ ions in an aqueous solution with a binding constant of (6.0 ± 0.3) × 104 M−1, and detection limit of 5.2 × 10-7 M. PBI-Lac-DPA exhibited high selectivity for the Cd2+ ion with a 2:1 binding stoichiometry between PBI-Lac-DPA and Cd2+ ions due to the additional coordinating sites in the self-assembly process of PBI-Lac-DPA itself. Furthermore, PBI-Lac-DPA exhibited fluorescence enhancement upon complexation with the Cd2+ ion in living cells. This work explored a new method for increasing the selectivity for Cd2+ ions via the enhanced additional complex sites of the DPA moiety from self-assembly process.

A novel ratiometric and turn-on fluorescent coumarin-based probe for Fe(iii)

6-Methoxy-3-(pyridin-2-yl)-2H-chromen-2-one exhibited fluorescence enhancement in the presence of Fe(iii). This molecule was a selective fluorescent chemosensor for Fe(iii).