Multifunctional Fluorescent Sensor Research Articles

A multifunctional fluorescence sensor for DNT vapor and Fe3+ based on a conjugated polymer

Due to the molecular wire effect, the fluorescent conjugated polymer (FCP) is always one of the focus of the sensor field. However, the complicated synthesis of FCP usually hinders their further practical application. Meanwhile, the multifunctional fluorescence sensor, which can distinguish multi-analyte only by one sensing material, presents high potential prospect in the real application. Here, a relatively simple benzimidazole-based FCP P1 via Suzuki polymerization was synthesized and further used as a multifunctional fluorescence sensor: P1 can not only efficiently detect Fe3+ in solution with a limit of detection (LOD) of 60 nM, but also monitor 2, 4-dinitrotoluene (DNT) vapor with a low LOD of 3.3 ppb. Furthermore, the simple P1 filter paper sensor was prepared and enable visual detection of Fe3+ and DNT with high performances of portability, flexibility and practicability.

A La-MOF as multi-responsive fluorescence sensor for Fe3+, PO43− and p‑Nitroaniline with high sensitivity and selectivity

Excessive emissions of Fe3+, PO43−, and p-Nitroaniline in the environment pose a major threat to human health and the earth ecology. Hence, a rapid and effective detection method for these pollutants is urgently needed. Here, three kinds of three-dimensional porous lanthanide metal-organic frame materials (Ln-MOFs) have been synthesized by hydrothermal method, namely {[Ln3(NTB)3(bib)0.5(H2O)2]•nH2O}n [H3NTB = Nitrilotrisbenzoic acid, bib = 1,4-bis(1-Imidazoly)benzene, Ln = La(Ⅰ), Ce(Ⅱ), Pr(Ⅲ)]. By single crystal X-ray diffraction analysis, Ⅰ-Ⅲ are homogeneous compounds with monoclinic crystal system and P21/c space group. Peculiarly, La-MOF (Ⅰ) is an excellent multi-response luminescence sensor, which can simultaneously detect Fe3+, PO43− and p-Nitroaniline (LOD values are 1.29 × 10−6 M, 1.59 × 10−6 M, 1.32 × 10−6 M, respectively) with high selectivity, low detection limit and good anti-interference ability. It is a rare multifunctional fluorescence sensor for Fe3+, PO43− and p-Nitroaniline. In addition, La-MOF (I) has excellent chemical and thermal stability, and it can be stable in aqueous solutions with pH = 2–12 and below 240℃, which indicates that La-MOF (I) has the potential to be applied in practical complex environments. The possible mechanisms in the fluorescence sensing process are explored by X-ray powder diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and density functional theory (DFT).

Stable Cd(II)-based coordination polymer as a multifunctional fluorescent sensor for ascorbic acid, acetylacetone and nitrofuran antibiotics

The concentrations of hazardous volatile organic compounds (VOCs), pharmaceutical antibiotics and biomolecules in water systems are closely related with public health and ecological security. Thus, the convenient and accurate detection of these harmful items can not only reflect the state of human health but also evaluate the level of homologous contamination in the environment. To this end, a new Cd(II)-CP ({[Cd3L2(bmoe)]·DMF}n) with excellent luminescence properties was designed by employing the semi-rigid tricarboxylic acid 4-(2′,3′-dicarboxylphenoxy) (H3L) and N-donor ligand 1,1′-bis(1H-benzimidazolyl) oxydiethane (bmoe). The as-prepared Cd-CP features the unique uninodal sql topology. Benefiting from its great stability in the aqueous system, Cd-CP serves as a versatile multifunctional fluorescent sensor for different analytes, ascorbic acid (AA), nitrofuran antibiotics nitrofurantoin (NFT) and nitrofurazone (NFZ) and acetylacetone (ACAC). The established methods are characterized with impressive low detection limits, ultrafast response time, high sensitivity, strong anti-interference ability, as well as reliable reproducibility. Experimental and theoretical calculation reveals that the collaborative effects of Förster resonance energy transfer (FRET), inner-filter effect (IFE) and photoinduced electron transfer (PET) are the most probable causes behind the quenching of the CP's fluorescence signal.

2D Zn (II) Metal‐Organic Framework as a Highly Sensitive Luminescent Sensor for Detection of the Cr2O72− and Fe3+

AbstractIn this work, NH2‐containing organic ligand 5‐Aminoisophthalic acid (AIPA), and trans‐1,2‐bis(4‐pyridyl)ethene (bpe) were selected as organic ligands to construct a new two‐dimensional luminescent Zn(II) metal‐organic framework [Zn(AIPA)(bpe)1/2]⋅named MOF‐1. It is worth noting that MOF‐1 exhibited excellent thermal stability and chemical stability in common solvents and different pH aqueous solution. As we expected, the luminescence sensing investigations demonstrated that MOF‐1 could be deemed as a multifunctional fluorescence sensor toward Cr2O72− and Fe3+ via a “turn‐off” effect. Notably, MOF‐1 had high selectivity and sensitivity for Fe3+ and Cr2O72− with low detection limits of 9.72×10−5 M and 1.95×10−5 M, respectively. Furthermore, the possible quenching mechanisms were also explored in detail.

A highly selective multifunctional naphthalene-labeled polymer sensor for Cu2+ and Fe3+ ions in aqueous medium

In this work, the detection of Cu2+ and Fe3+ with naphthalene labeled poly(acrylic acid) (PAA150Np3) was investigated. Other metal ions such as Ag+, Li+, K+, Na+, Ba2+, Mg2+, Ca2+, Zn2+ and Ni2+ were also considered to analyze the sensor performance. The fluorescence quenching of the naphthalene (Np) graft was assessed from the emission spectra and the fluorescence decays of PAA150Np3 in the presence of Cu2+ or Fe3+. The Stern-Volmer and Hill constants, as well as the detection limits of the studied ions were obtained considering the emissions of both the monomer and the excimer of Np. The polymer conformation was investigated by changing the metal ion concentration or the pH. The polymeric sensor showed high selectivity and sensitivity for Cu2+ or Fe3+. A static mechanism of fluorescence quenching was unveiled for the Np graft. A more stable complex formed between PAA150Np3 and Fe3+, as compared to the counterpart system with Cu2+. The sensor’s performance, including detection limit and selectivity of Cu2+ or Fe3+ ions, is higher than of most currently reported sensors. The study shows that the multifunctional fluorescent polymer sensor has the potential to be used in real-life samples, in bio-systems and environmental applications.

Thienopyrimidine-derived multifunctional fluorescence sensor for the detection of Cu2+, Fe3+, and PPi in different solvents.

Hydrazine substituted thienopyrimidine, a new fluorophore, was used to synthesize a novel Schiff base R1 as a chemosensor via the condensation with p-formyltriphenylamine, and the structure was confirmed using nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) analysis. When treated with Cu2+ in dimethylsulfoxide (DMSO)/H2O buffer, R1 showed a phenomenon of fluorescence quenching, which was reversible with the action of ethylenediaminetetraacetic acid (EDTA). When treated with Fe3+ in dimethylformamide (DMF)/H2O buffer, R1 exhibited the same phenomenon, but fluorescence was recovered with inorganic pyrophosphate (PPi) quantitatively. The complexation ratios for R1-Cu2+ and R1-Fe3+ were both 1:2, which were manifested by MS titrations and corresponding Job's plots. The limits of detection of R1 for Cu2+ and Fe3+ were 3.11 × 10-8 and 1.24 × 10-7M, respectively. The sensing mechanism of R1 toward Cu2+ and Fe3+ was confirmed using density functional theory calculations and electrostatic potential analysis. Test strips of R1 were fabricated successfully for on-site detection of Cu2+ and Fe3+. In addition, R1 was applied to recognize Cu2+ and Fe3+ in actual water samples with satisfactory recovery.

Two Cd(Ⅱ)/Mn(Ⅱ) complexes based on multinuclear metal clusters for Fe(Ⅲ) and Cr(Ⅵ) fluorescence detection and magnetic properties

Two novel complexes, {[Cd3(L)2(H2O)2]·(H2O)4}n (1) and {[Mn(HL)(H2O)2]·(H2O)}n (2), which are synthesized by the reaction of 3-(2, 4-dicarboxyphenyl)-4-carboxypyridine ligand with cadmium and manganese metal ions under the solvothermal method. The complex 1 is a 3D framework based upon trinuclear [Cd3(μ2-COO)4(μ1-COO)4(N)2] SBUs, and the complex 2 is a one-dimensional metal oxygen chain based upon binuclear [Mn2(μ2-COO)2(μ1-COO)2(N)2] SBUs. The solid fluorescence analysis of complex 1 reveals that the emission peak of 451 nm when its excitation peak is 336 nm. The fluorescence detection experiments of complex 1 showed that Fe3+, Cr2O72− and CrO42− can effectively to be detected. Furthermore, their limits of detection are 1.47 × 10−3 M, 1.31 × 10−3 M and 1.25 × 10−3 M, respectively. It has good recovery properties as a potential multifunctional fluorescence sensor. Besides, the quenching mechanism of fluorescence sensing is also discussed. In addition, the magnetic studies of complex 2 show strong antiferromagnetic interactions between its neighboring Mn(II) ions.

A multifunctional fluorescent sensor for Ag+ and Hg2+ detection in seawater.

In order to detect Ag+ and Hg2+ in seawater, we explored a multifunctional fluorescence sensor. A multifunctional Ag+ and Hg2+ sensor was designed by using gold nanoparticles (AuNPs) as quenching agent, PicoGreen dye as fluorescent probe of base pairing double-stranded deoxyribonucleic acid (DNA), and combining the characteristics of Ag+ making C base mismatch and Hg2+ making T base mismatch. Meanwhile, the DNA logic gate was constructed by establishing logic circuit, truth table, and logic formula. The relevant performances of the sensor were investigated. The results revealed that the sensor can detect Ag+ in the range of 100 to 700nM with R2 = 0.98129, and its detection limit is 16.88nM (3σ/slope). The detection range of Hg2+is 100-900nM with R2 = 0.99725, and the detection limit is 5.59nM (3σ/slope). An AND-AND-NOR-AND molecular logic gate has been successfully designed. With the characteristics of high sensitivity, multifunction, and low cost, the recommended detection method has the potential to be applied to the detection of Ag+ and Hg2+ in seawater.

A robust Eu-MOF as a multi-functional fluorescence sensor for detection of benzaldehyde, Hg2+, and Cr2O72-/CrO42-

In this work, a novel Eu-MOF, {[Eu2(L)(phen)2(ox)2(H2O)2]·10H2O·phen}n (H2L = 2,6-bis(4-carboxyphenyl)pyrazine, phen = 1,10-phenanthroline), was assembled under hydrothermal conditions with good water stability and pH stability. The Eu-MOF could be used as a luminescent sensor for detecting gas/liquid benzaldehyde, Hg2+ and Cr2O72-/CrO42- with high sensitivity and selectivity based on luminescence quenching effects. The sensing mechanisms were systematically studied by ICP-AES, PXRD analysis and UV–vis spectroscopy. In addition, the Eu-MOF shows high adsorption of Hg2+ and can be successfully used to quantitatively detect Hg2+ in real samples such as tap water, green tea, and river water. The sensor exhibited a recovery rate in the range of 99.84 %∼102.34 % for detecting Hg2+. The portable fluorescent paper strips based on the Eu-MOF were also successfully fabricated, which can detect benzaldehyde both in gas and liquid phases. The fluorescence sensing system based on Eu-MOF provides a reference for the construction of portable environmental pollutant monitoring sensors.

A novel multifunctional fluorescent capillary-based sensor for simultaneous monitoring of pH, O2 and CO2

A fluorescent capillary sensor for detecting the bioanalytically and biologically relevant analytes pH, O2, and CO2 has been designed. The sensor is based on single capillary tube with 2 mm inner diameter, which is simultaneous doped with emissive O2-sensitive indicator Ru(dpp)3(PF6)2 (RuDP), pH-sensitive and CO2-sensitive indicator 8-hydroxypyrene-1, 3,6-trisulfonic acid trisodium salt (HPTS). The multifunctional sensor can be excited at the same wavelength and realize multi-parameter optical monitoring at the different sensing position. Studies in phosphate-buffered solutions display the excellent feasibility of the capillary sensor for fluorescence detection of pH, O2, and CO2. Overall, the multifunctional capillary sensor exhibits great potential in real-time blood gas analysis, and clinical application of multi-parameter biological detection.

Two-Dimensional Lanthanide Metal-Organic Frameworks as a Platform for Sensing Pollutant and Nitrophenols Reduction.

The discharge of harmful and toxic pollutants in water is destroying the ecosystem balance and human being health at an alarming rate. Therefore, the detection and removal of water pollutants by using stable and efficient materials are significant but challenging. Herein, three novel lanthanide metal-organic frameworks (Ln-MOFs), [La(L)(DMF)2(H2O)2]·H2O (LCUH-104), [Nd(L)(DMF)2(H2O)2]·H2O (LCUH-105), and [Pr(L)(DMF)2(H2O)2]·H2O (LCUH-106) [H3L = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid (H3TZI)] were solvothermally constructed and structurally characterized. In the three Ln-MOFs, dinuclear metallic clusters {Ln2} were connected by deprotonated tetrazol-containing dicarboxylate TZI3- to obtain a 2D layered framework with a point symbol of {42·84}·{46}. Their excellent chemical and thermal stabilities were beneficial to carry out fluorescence sensing and achieve the catalytic nitrophenols (NPs) reduction. Especially, the incorporation of the nitrogen-rich tetrazole ring into their 2D layered frameworks enables the fabrication of Pd nanocatalysts (Pd NPs@LCUH-104/105/106) and have dramatically enhanced catalytic activity by using the unique metal-support interactions between three Ln-MOFs and the encapsulating palladium nanoparticles (Pd NPs). Specifically, the reduction of NPs (2-NP, 3-NP, and 4-NP) in aqueous solution by Pd NPs@LCUH-104 exhibits exceptional conversion efficiency, remarkable rate constants (k), and outstanding cycling stability. The catalytic rate of Pd NPs@LCUH-104 for 4-NP is nearly 8.5 times more than that of Pd/C (wt 5%) and its turnover frequency value is 0.051 s-1, which indicate its excellent catalytic activity. Meanwhile, LCUH-105, as a multifunctional fluorescence sensor, exhibited excellent fluorescence detection of norfloxacin (NFX) (turn on) and Cr2O72- (turn off) with high selectivity and sensitivity at a low concentration, and the corresponding fluorescence enhancement/quenching mechanism has also been systematically investigated through various detection means and theoretical calculations.

An oxazole-derived Schiff base as a multifunctional fluorescence sensor towards Al3+ and Ga3+ in different media

A facile Schiff base derivative N′-(2, 3-dihydroxybenzylidene)-5-(naphthalen-1-yl)oxazole-4-carbohydrazide (G3) was constructed and synthesized through the reaction of 5-(naphthalen-1-yl)oxazole-4-carbohydrazide with 2,3-dihydrobenzaldehyde, which achieved the distinct recognition for two kinds of IIIA group metal ions (Al3+, Ga3+) in different media. G3 performed an enhanced blue luminescence upon addition of Al3+ in CH3OH/H2O buffer solution. As well, G3 exhibited a remarkable fluorescence enhancement toward Ga3+ with a color change from colorless to green in DMSO/H2O buffer solution. Therefore, G3 was applied as a multifunctional fluorescence sensor for Al3+ and Ga3+. The molar ratio for G3 towards Al3+ and Ga3+ was both verified to be 1:2, and the possible sensing mechanism was demonstrated by Job's plot, mass spectrometry titration and theoretical calculation. What’ more, G3 could be used to determinate target ions in real water samples with favorable recovery, which implied a wide prospect for application. And more importantly, the fine difference on microstructure causing the macroscopic performance of sensors in the buffer solution was revealed through the contrastive study of G3 and G1 in previous work.

Zn-based metal-organic-framework as a multifunctional fluorescent sensor for HSO4−, acidic and basic amino acids

A multifunctional fluorescent sensor Zn-MOF was successfully prepared by hydrothermal reaction, Zn2+ as node, 1,3,5-tris(1-imidazolyl)-benzene (L) and chiral ligands D(+)-camphoric acid (D-H2cam) as linkers. It had been characterized by single crystal X-ray diffraction (XRD), powder X-ray diffraction (PXRD), circular dichroism (CD), chromaticity coordinates (CIE) and thermogravimetric analysis (TGA). The study of fluorescence properties revealed that the multifunctional fluorescent sensor Zn-MOF exhibited high selectivity and sensitivity to detect HSO4− or glutamate (Glu)/aspartic (Asp) by “Turn Off” the emission. Furthermore, the in situ generated [Zn-MOF + Glu/Asp] system was used for the relay detection of arginine (Arg)/lysine (Lys) without separation and purification and exhibited a new fluorescence “Turn On” signal under the same conditions. In addition, the sensing process possessed out-standing cost-saving, rapid responsiveness as well as recyclability in aqueous solution.

Multiple Stimulus Response 2D Framework Constructed by a Flexible Cyclotriphosphazene-Derived Carboxylic Acid Linker: Synthesis, Characterization, and Fluorescence Sensing to Phenolic Pollutants and Small-Molecule Drugs.

Hexachlorocyclotriphosphazene is one of the most representative phosphazene compounds which have been proved to have broad application prospects in many fields. However, it is an emerging research perspective to combine cyclotriphosphazene-derived polycarboxylic acid compounds with lanthanides for the construction of Tb-DPCP metal-organic framework (MOF) materials. Herein, a Tb-DPCP MOF, (CH3)2NH2[Tb3(HDPCP)(DMF)(H2O)3]·6DMF (1), was successfully prepared via the reaction of H12HDPCP [hexa(4-carboxyphenoxy) cyclotriphosphazene] and Tb(NO3)3·6H2O under the solvothermal condition. Through fluorescence sensing experiments, it was found that both nitrophenols and chlorophenols could cause the fluorescence quenching of compound 1. At the same time, the compound also exhibited nice trace detection ability for small-molecule drugs (moxifloxacin hydrochloride, balsalazide disodium, and colchicine); the limits of detection were all lower than 0.2 μM. These experimental results fully demonstrated the potential application value of 1 as a multifunctional fluorescent sensor.

Four Novel Cobalt(II) Coordination Polymers Based on Anthracene-Derived Dicarboxylic Acid as Multi-functional Fluorescent Sensors toward Different Inorganic Ions

A series of Co(II)–H2L coordination polymers were prepared with different auxiliary ligands, namely {[Co(L)(bibp)]}n 1, {[Co(L) (bpy)(H2O)]2·2H2O}n 2, {[Co(L)(bipd)]}n 3, and {[Co(L)(bbibp)]·H2O}n 4 (H2L = 5-{(anthracene-9-ylmethyl)amino}isophthalic acid, bibp = 4,4′-bis(imidazolyl)biphenyl, bpy = 2,2′-bipyridine, bipd = 3,5-bis(1-imidazoly)pyridine, and bbibp = 4,4′-bis(benzoimidazo-1-yl)biphenyl), by a similar solvothermal method. X-ray diffraction analyses revealed that 1, 3, and 4 exhibit a two-dimensional (2D) structure, which further builds the three-dimensional (3D) supramolecular architecture via the weakly interacting hydrogen bonds of C–H···O, while 2 displayed a one-dimensional (1D) double-chain architecture extended from two 1D zigzag chains by intermolecular hydrogen bonding interactions. The sensing experiments revealed that 1 and 2 can serve as either individual- and/or multi-responsive sensors to selectively detect Cr3+, Al3+, and Pb2+ ions through the fluorescence turn-on effect, while 3–4 exhibited fluorescence turn-off sensing behavior for Fe3+ ions. Moreover, 1–4 can effectively detect and recognize Cr2O72– and CrO42– due to their high selectivity and sensitivity for fluorescence quenching in aqueous solutions, and the sensing mechanism for various ions has been discussed.

Novel Aggregation-Induced Emission Fluorescent Molecule for Platinum(IV) Ion-Selective Recognition and Imaging of Controlled Release in Cells.

The loading, delivery, and release of Pt(IV) precursors in living organisms are important aspects of exploring the development of platinum drugs. In recent years, the biological application of the fluorescent sensors to platinum drugs has been insufficient to meet the study of Pt(IV) precursors. It is urgent to design and develop a biocompatible, multifunctional fluorescent sensor for the study of loading, transport, and release of Pt(IV) ions. Herein, we report a fluorescent molecule (E)-6-(diethylamino)-N'-(4-(diphenylamino) benzylidene)-2-oxo-2H-chromene-3 carbohydrazide (CHTPA). CHTPA has good sensitivity and selectivity to Pt(IV) when the water content is 5%, and significant increase of the fluorescence emission intensity of CHTPA is observed with Pt(IV) concentration. The sensing mechanism is attributed to photo-induced electron transfer, which is verified by X-ray absorption near edge spectroscopy spectra, UV-vis absorption spectroscopy, 1H NMR spectra, and Fourier transform infrared spectra. Furthermore, the CHTPA-Pt(IV) complex is able to release Pt(IV) in aqueous solution, and the green fluorescence of CHTPA based on the aggregation-induced emission effect can be observed. Inspired by these, the amphiphilic block copolymer poly(ethyloxide)-block-polystyrene (PEO-b-PS) is used to prepare the nonconjugated polymer dots (Pdots). The experimental results show that Pdots can effectively slow down the release speed of Pt(IV) in aqueous solution and it has a great monodispersity in aqueous solution. Meanwhile, Pdots show low cytotoxicity, and this is favorable for intracellular applications. The investigation of cellular imaging indicates that these Pdots can act as a carrier to deliver Pt(IV) into MCF-7 cells for visualized delivery and sustained release of platinum(IV) ions. Therefore, this study provides a new avenue to design and develop a biocompatible multifunctional fluorescent sensor for studying the loading, delivery, and release of Pt(IV) in cells.

Fluorophore molecule loaded in Tb-MOF for dual-channel fluorescence chemosensor for consecutive visual detection of bacterial spores and dichromate anion

Developing multifunctional luminescent switches for detecting various poisons are urgent given the continuous deterioration of the environment. Herein, a new porous fluorescent metal–organic framework [Tb2(TPTC)(DMA)4(NO3)2]n(HPU-25) was initially designed. Then, fluorophore molecule tris(2,2′-bipyridine) dichlororuthenium(II) hexahydrate (Ru(bpy)32+) was loaded onto HPU-25 by a simple post-synthesis strategy to prepare a new ratio fluorescence sensor Ru(II)@HPU-25. As a sensor, it can detect 2,6-pyridinedicarboxylic acid (DPA) content in real-time, with high sensitivity and selectivity, without being disturbed by probe concentration and environment. Evident changes in fluorescence color and intensity are observed in distinguishing DPA contents. In addition, after detecting DPA, it can be used for consecutive visual detection of dichromate anion (Cr2O72−) in water. This multifunctional fluorescence sensor could make up for the defects of single fluorescence and single function of the traditional fluorescence sensor by using the dual strategies of ratio sensing and cascade sensing. Interestingly, DPA and Cr2O72− in samples can be visually detected rapidly in real-time through the chroma acquisition APP on smartphone. More importantly, we also designed the combination of two logic gate operations for sensing the two targets. In the poison detection in daily life, these intelligent applications of fluorescence sensors have a broad development space.

Highly sensitive fluorescent sensing and photocatalytic degradation performance of two-dimensional Tb-organic network

A novel tetra-nuclear Tb-organic network, named as [Tb4(2-pyia)6(HAc)0.5(2,2′-bipy) (H2O)4.5]·2,2′-bipy·H2O (1), was synthesized hydrothermally based on 5-(pyridin-2-ylmethoxy) isophthalic acid (H2pyia) and 2,2′-bipyridine (2,2′-bipy) ligands, and characterized by single crystal X-ray diffraction, thermogravimetric (TG) analyses, powder X-ray diffraction (PXRD) and infrared (IR) technology. 1 possesses a two-dimensional network based on the tetra-nuclear inorganic building units, and the π-π stacking interactions between the pyia2− ligands and the guest 2,2′-bipy molecules play an important role in the forming of 3D supramolecular structure. 1 exhibits excellent fluorescent sensing performance for Fe3+ (1.26 × 10−8 mol/L), Cr2O72− (8.1 × 10−7 mol/L), 2,4,6-trinitrophenol (TNP) (2.71 × 10−8 mol/L) and tetracycline (TCT) (2.76 × 10−7 mol/L) in aqueous solution with lower detection concentrations. The sensing mechanisms of 1 were investigated by density functional theory (DFT) calculations, ultraviolet–visible (UV-Vis) diffuse reflectance spectroscopy, PXRD and fluorescent lifetime analyses. The activated product of 1 was prepared by heating at 255 °C under constant pressure and used to photo-catalytically degrade TCT. Both 1 and the activated one have good photocatalytic degradation performance for TCT with degradation rates of 84.29% and 96.07%, respectively. The photocatalytic mechanisms were discovered by UV–Vis diffuse reflectance spectroscopy and radical trap experiments. The Tb-organic framework might be an excellent multifunctional fluorescent sensor and a good photocatalytic agent for TCT degradation in the future.

Effective detection of Ag+, Hg2+ and dye adsorption properties studies of Ln-MOFs based on a benzimidazole carboxylic acid ligand.

Five new lanthanide metal-organic frameworks (Ln-MOFs), namely {[Ln(L)]·Cl}n, [Ln = Pr(1), Nd(2), Eu(3), Ho(4), Ce(5)], based on a benzimidazole carboxylic acid ligand [H2L = 2-(2-carboxyphenyl)-1H-benzo[d]imidazole-6-carboxylic acid] were synthesized by a solvothermal method. Ln-MOFs 1-5 have the same two-dimensional layered structures. Interestingly, 1-5 exhibit excellent adsorption performance to anionic dye Congo red (CR), with adsorption capacities of 2724 mg g-1, 2719 mg g-1, 2718 mg g-1, 327 mg g-1, and 2273 mg g-1, respectively. Adsorption kinetics experiments showed that this kind of adsorption belonged to chemisorption; the hydrogen bonding and π-π interactions between the 1-5 host and CR guest molecules resulted in a high adsorption capacity. Luminescence and sensing experiments showed that 5 can be considered a promising multifunctional fluorescent sensor with good reusability and a high sensitivity toward Ag+ and Hg2+ ions, with detection limits of 1.7 × 10-7 and 2.5 × 10-6 M, respectively.

Dual-Fluorophore and Dual-Site Multifunctional Fluorescence Sensor for Visualizing the Metabolic Process of GHS to SO2 and the SO2 Toxicological Mechanism by Two-Photon Imaging

As a momentous gas signal molecule, sulfur dioxide (SO2) participates in diverse physiological activities. Excess SO2 will cause an apparent decrease in the level of intracellular glutathione (GSH), thereby damaging the body's antioxidant defense system. In addition, endogenous SO2 can be generated from GSH by reacting with thiosulfate (S2O32-) and enzymatically reduced to cysteine (Cys), a synthetic precursor of GSH. In view of their close correlation, a two-photon (TP) mitochondria-targeted multifunctional fluorescence sensor Mito-Na-BP was rationally designed and synthesized for detecting SO2 and GSH simultaneously. Under single-wavelength excitation, the sensor responded to GSH-SO2 and SO2-GSH continuously with blue-shifted and green fluorescence-enhanced signal modes, respectively, not just to GSH (enhanced) and SO2 (quenched) at 638 nm with a completely converse response tendency. Given its favorable spectral performance (high sensitivity, superior selectivity, and fast response rate) at physiological pH, Mito-Na-BP has been successfully applied in monitoring the level fluctuation of GSH affected from high-dose SO2 and visualizing in real time the metabolic process of GSH to SO2 by TP imaging. It is expected that this research will provide a convenient and efficient tool for elucidating intricate relationships of GSH and SO2 and facilitate further exploration of their functions in biomedicine.