Ksv Values Research Articles

Three water-stable luminescent Zn(II) coordination polymers for highly sensitive and selective sensing of acetylacetone and Fe3+ ions

Three water-stable Zn(II) coordination polymers (CPs) including {[Zn2(L)(TBIP)1.5(OH)]·H2O}n (1), [Zn(L)(DBT)]n (2) and [Zn(L)0.5(MIP)]n (3) (L ​= ​1,4-bis(2-methylbenzimidazol-1-yl)-2-butylene, H2TBIP ​= ​5-tert-butyl isophthalic acid, H2DBT ​= ​2,5-dibromoterephthalic acid and H2MIP ​= ​5-methylisophthalic acid) were hydrothermally synthesized and characterized. 1 shows a rarely (3,4,4)-connected framework with point symbol of (3.8.9.102.11)(3.8.9)(3.82.92.10). 2 features a three-fold interpenetrating dia network. 3 possesses a 2D layer structure with a binodal (3,4)-connected 3,4L83 network. Both 1 and 2 present selective and sensitive detection of acetylacetone (acac) with high quenching efficiency (Ksv) values (2651 ​M−1 for 1 and 3923 ​M−1 for 2) and low detection limit (1.43 ​μM for 1 and 0.86 ​μM for 2). 1, 2 and 3 could be treated as efficient probes for sensing of Fe3+ ions.

Synthesis and photophysical properties of A3B-type non-symmetrically substituted anthracene-based zinc(II) phthalocyanine

A novel unsymmetrical zinc(II) phthalocyanine (ZnPc) (3) with an alkynyl functional group was prepared by an efficient mixed statistical condensation of 4-((4-ethynylbenzyl)oxy)phthalonitrile (1) and 4-(4-tertbutylphenoxy)phthalonitrile (2). FTIR, 1H NMR, UV-Vis, elemental analysis, and MALDI-TOF were used to characterize this new compound. Working with different concentrations, the compound’s aggregation properties were investigated and concluded that no aggregation tendency has been observed in the studied concentration range (1.0 x 10-6 M to 1.2 x10-5 M). Fluorescent quantum yields and lifetimes of the compound were studied and found to be 0.09 and 0.57 ns, respectively. As a fluorescent quencher, 1,4-benzoquinone was used in the experiments at differing concentrations in tetrahydrofuran. The kq values showed a close follow-up to the diffusion control limits, around 1011 s-1 and they seem to agree with Einstein-Smoluchowski’s approximation for bimolecular, diffusion-control-including, interactions. For the new compound, the KSV value was calculated as 27.55, which is lower than that of unsubstituted ZnPc. The fluorescence of the studied compound 3 was effectively quenched by 1,4-benzoquinone.

Solvothermal and Ultrasonic Preparation of Two Unique Cluster-Based Lu and Y Coordination Materials: Metal-Organic Framework-Based Ratiometric Fluorescent Biosensor for an Ornidazole and Ronidazole and Sensing Platform for a Biomarker of Amoeba Liver Abscess.

Through powerful solvothermal and facile ultrasonic synthetic strategies, two unique cluster-based lanthanide Lu and Y nanoporous metal organic frameworks (MOFs) have been successfully prepared, namely, {[Lu2(L)2]·2DMF·H2O}n (Lu-MOF) and [Y(L)(DMF)0.75]n (Y-MOF) (H3L = terphenyl-3,4'',5-tricarboxylic acid). In addition, both the morphologies and nanosizes of Lu-MOF and Y-MOF materials also have been deliberately tuned by adjustable ultrasonic conditions including irradiation time (40, 60, and 80 min) and power (70 w, 100 w). Currently, it is noted that the abuse of antibiotics such as ornidazole and ronidazole leads to great damage to human health, and therefore the development of highly effective and facile detection methods for ornidazole and ronidazole is quite important. Herein, to improve the fluorescent sensing sensitivity of antibiotics, Eu3+ and Tb3+ have been introduced into Lu-MOF (under a solvothermal preparation method) to fabricate a dual-emission hybrid material Eu3+/Tb3+@Lu-MOF through a postsynthesis strategy, which can be successfully applied as a self-calibrated ratiometric fluorescent sensor for ornidazole and ronidazole with high selectivity and sensitivity (the Ksv value for ornidazole is 1.0854 × 106 [M-1], and the Ksv value for ronidazole is 1.0595 × 107 [M-1]) and low detection limit values (2.85 nM for ornidazole and 26.7 nM for ronidazole). On the other hand, amoeba liver abscess (ALA) will easily lead to irregular fever, night sweats, and other tortured symptoms; C-reactive protein autoantibody (CRP Ab) is the important biomarker for the detection of ALA. Given this, Y-MOF (under the solvothermal preparation method) also has been successfully designed to combine FAM-labeled NH-ssDNA to construct the scarcely reported excellent hybrid FAM-labeled NH-ssDNA/Y-MOF sensing platform for the highly effective discrimination of CRP Ab with excellent sensitivity and selectivity in real samples such as human serum solution.

Determination of fluorescence lifetimes of fluorescein from fluorescence quenching data

The fluorescence quenching of fluorescein by 1,4-benzoquinone (BQ) in five solvents – methanol, ethanol, phosphate buffer saline (PBS, pH 7.4), N,N'-dimethylformamide (DMF) and dimethylsulphoxide (DMSO) is hereby investigated. Fluorescein’s fluorescence was effectively quenched by BQ, and the quenching was dynamic (purely collisional) within the BQ’s concentration range (0.001 to 0.004 M) used in this work. Accordingly, the quenching data were in conformity with the Stern-Volmer’s model. Stern-Volmer’s constant (KSV) values range between 17.4 in DMSO and 43.4 in methanol. KSV values, together with the calculated bimolecular rate constants (kD) in the respective solvents, were used to semi-empirically estimate the fluorescence lifetimes (tF) of fluorescein in the individual solvents. Just as for KSV values, tF values are solvent-viscosity dependent, with the lowest values being obtained in methanol and the highest in DMSO, which are the least and most viscous solvents respectively. tF values obtained in this work are 3.55, 3.71, 3.78, 4.13 and 4.51 ns (in methanol, PBS 7.4, ethanol, DMF and DMSO, respectively).  Â

Fluorescent Analogue of Hexa-coordinate Globins to Monitor Accessibility of the Heme Pocket

Neuroglobin (Ngb), cytoglobin (Cygb) and globin X (GbX) belong to the family of vertebrate hexa-coordinate globins. Recent studies have proposed that these globins carry out various function including ROS/RNS scavenger and in vivo studies have indicated the role of Cygb and Ngb in carcinogenesis, cell proliferation, apoptosis and cell survival under hypoxic conditions. Globin X was found to be important for the reduction of nitrite to nitric oxide in fish red blood cells. It was shown that the internal disulfide bond that is unique to hexa-coordinate vertebrate globins modules the heme iron affinity for oxygen in Ngb and Cygb. To probe the mechanism of the ligand migration in Cygb, Ngb and GbX, we replaced the non-fluorescent Fe protoporphyrin IX (FePPIX) with the fluorescent analogue Zn protoporphyrin IX (ZnPPIX) and characterized the ligand migration by monitoring the quenching of the ZnPPIX fluorescent emission by methyl viologen and the quenching of the ZnPPIX triplet state by oxygen. We observed an increase in the Ksv value for methyl viologen quenching in protein variants that are missing the internal disulfide bond, suggesting that the presence of the intraprotein disulfide bond regulates the accessibility of the heme binding pocket. Interestingly the lifetime of the triplet state for ZnPPIX incorporated in hexacoordinate vertebrate globins is not sensitive to changes in the heme environment as the observed lifetime is comparable to that determined previously for myoglobin.

Rational design and synthesis of a stable pillar-layer NaI-organic framework as a multi-responsive luminescent sensor in aqueous solutions

A stable pillar-layer NaI-organic framework, [Na2(DCPB)∙(H2O)2]n (namely 1), was rationally designed and synthesized by the assemble process of NaI and 1,3-di(4'-carboxyl-phenyl)benzene (H2DCPB). Benefiting from the luminescent property and high stability in water, the as-synthesized 1 is a potential multi-responsive luminescent sensor material toward Cr2O72-, Fe3+, and nitrofurazone (NFZ) in water. Ground 1 not only has the excellent detectability and selectivity but also possesses outstanding stability and circularity. The calculated Ksv values of 1 are 8.8×103 for Fe3+, 9.9×103 for Cr2O72-, and 2.7×104 M-1 for NFZ in aqueous solutions, respectively. Furthermore, 1 is able to accurately detect NFZ in real bovine serum samples through luminescence detection technology.

Structural-Dependent N,O-Donor Imine-Appended Cu(II)/Zn(II) Complexes: Synthesis, Spectral, and in Vitro Pharmacological Assessment.

Four mononuclear bioefficient imine-based coordination complexes, [(L1)2Cu], [(L1)2Zn], [(L2)Cu(H2O)], and [(L2)Zn(H2O)], were synthesized using ligands [L1 = 2-(((3-hydroxynaphthalen-2-yl)methylene)amino)-2-methylpropane-1,3-diol and L2 = 4-(1-((1,3-dihydroxy-2-methylpropan-2-yl)imino)ethyl)benzene-1,3-diol]. The formation of the complexes was ascertained by elemental analysis, Fourier transform infrared, 1H NMR, 13C NMR, electrospray ionization–mass spectroscopy, electron paramagnetic resonance, and thermogravimetric analysis. The comparative binding propensity profiles of the above-synthesized complexes with the DNA/human serum albumin (HSA) were investigated via UV absorption, fluorescence, and Förster resonance energy-transfer studies. On the basis of extended conjugation and planarity, L1 complexes exhibited superior bioactivity with greater calculated DNA binding constant values, (Kb) 2.9444 × 103[(L1)2Cu] and 2.2693 × 103[(L1)2Zn], as compared to L2 complexes, 1.793 × 103[(L2)Cu(H2O)] and 9.801 × 102[(L2)Zn(H2O)]. The competitive displacement assay of complexes was performed by means of fluorogenic dyes (EtBr and Hoechst), which corroborates the occurrence of minor groove binding because of the enhanced displacement activity with Hoechst 33258. The minor groove binding of the [(L1)2Cu] complex is further confirmed by the molecular docking study. Moreover, the HSA study demonstrated effective static quenching of complexes with substantial Ksv values. The [(L1)2Cu] complex was found to have pronounced cleavage efficiency as evaluated from sodium dodecyl sulfate polyacrylamide gel electrophoresis electrophoresis. Furthermore, in vitro antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl and superoxide radicals further proclaimed the remarkable bioefficiency of compounds, which make them promising as active chemotherapeutic agents.

Modulated Protein Binding Ability of Anti-Diabetic Drugs in Presence of Monodispersed Gold Nanoparticles and its Inhibitory Potential towards Advanced Glycated End (AGE) Product Formation.

Binding strength of the anti-diabetic drugs chlorpropamide (CPM) and tolbutamide (TBM) with model protein bovine serum albumin (BSA) shows strong modulation in presence of colloidal gold nanoparticles (AuNP). Intrinsic tryptophan fluorescence of both the native BSA and BSA-AuNP conjugate quenched in presence of the drugs. Stern-Volmer quenching constant (KSV) of CPM binding to BSA-AuNP conjugate at different temperatures is almost twice (6.76~14.76 × 103M-1) than the corresponding values in native BSA (3.21~5.72 × 103M-1). However, the calculated KSV values with TBM show certain degree of reduction in presence of AuNP (6.46× 103M-1), while comparing with native BSA (8.83 × 103M-1). The binding mode of CPM towards BSA-AuNP conjugate is mainly through hydrophobic forces; whereas, TBM binding is identified to be Van der Waal's and hydrogen bonding type of interaction. Fluorescence lifetime analysis confirms static type of quenching for the intrinsic tryptophan fluorescence of BSA as well as BSA-AuNP conjugate with addition of CPM and TBM at different concentrations. The α-helical content in the secondary structure of BSA is decreased to 48.32% and 45. 28% in presence of AuNP, when the concentration of CPM is 0.08mM and 0.16mM in comparison with that of native protein (50.13%). On the other hand, the intensity of sugar induced advanced glycated end (AGE) product fluorescence is decreased by 55% and 80% at 0.13nM and 0.68nM AuNP, respectively. Change in the binding strength of the drugs with transport protein and reduced AGE product formation in presence of AuNP could lead to a major development in the field of nanomedicine and associated drug delivery techniques. Graphical Abstract Modulated drug binding ability and AGE product formation of serum proteins in presence of AuNP.

Design of a pillar-layered metal-organic framework as high-performance fluorescence sensor for nitroaromatic compounds

A ternary luminescent cadmium-triazolate-carboxylate framework, [(CH3)2NH2][Cd(1245-BTC)0.5(3S-TRZ)] (SNNU-111, 1245-BTC ​= ​1245-benzenetetra- carboxylic acid, 3S-TRZ ​= ​3-mercaptotriazole) was successfully designed in this work. X-ray single crystal diffraction results show that Cd atoms are connected by 3S-TRZ ligands to form 2D wave-like layers, which are further extended by 1245-BTC linkers to generate the 3D pillar-layered architecture of SNNU-111. Solid-state and solution photoluminescence both showed that the emissions of SNNU-111 was ascribed to the intraligand charge transfer in 1245-BTC. Benefited from this process, SNNU-111 MOF can act as excellent fluorescence sensor to quantitatively detect involved nitroaromatics including nitrobenzene (NB), 1,2-dinitrobenzene (1,2-DNB), 1,3-dinitrobenzene (1,3-DNB), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and 2,4,6-trinitrophenol (PA) through the fluorescence quenching. The corresponding quenching coefficient (Ksv) values are of 1.0 ​× ​104-1.7 ​× ​104 ​M−1, which surpass the performance of many reported sensors. Specially, the Ksv value of 1.2 ​× ​104 ​M−1 for NB is nearly the highest one among all MOF sensors up to now. On the other hand, SNNU-111 sensor also exhibits good sensitivity to nitroaromatics with the detection limits as low as 1.61–5.77 ​ppm. Overall, the definite pillar-layered structure, fast response and high sensitivity make SNNU-111 a promising fluorescent sensor to detect nitroaromatic compounds.

One luminescence probe and the impact of dye-adsorption on the luminescent property

In this work, one new coordination polymer (CP) {[Cd2(bibp)2.5(NO3)2(NO2)2]}n (1) (bibp = 4,4′-bis(imidazolyl)biphenyl) was synthesized under solvothermal conditions. Considering that there are some coordinated NO3− and NO2− in the structure, it is hypothesized that compound 1 can be used for luminescence sensing and dye uptake. The results shown that compound 1 has a selective and sensitive recognition ability for Fe3+ (Ksv value = 1.42 × 104 M−1) and the recognition ability is not affected by other metal ions. At the same time, compound 1 show a good adsorption capacity for methyl orange. Then, we investigated the impact of dye-adsorption on the luminescent properties of the compound 1.

Exploring the interaction mechanism of a dicarboxamide fungicide, iprodione with bovine serum albumin

Binding of iprodione (IPR), a dicarboxamide fungicide, to the carrier protein in bovine circulation, bovine serum albumin (BSA) was characterized with the help of fluorescence, absorption, circular dichroism and Fourier transform infrared (FTIR) spectral measurements in combination with computational analysis. The increase in the KSV (Stern–Volmer constant) value with temperature and absorption spectral results characterized the IPR-induced quenching of BSA fluorescence as dynamic quenching. On the other hand, higher value (> 1011 M−1 s−1) of the bimolecular quenching rate constant (kq) suggested complex formation between IPR and BSA. In view of it, increase in KSV value with temperature can be considered as an indication of the involvement of endothermic apolar (hydrophobic) interactions in stabilizing the IPR–BSA complex, as these forces are maximized at higher temperature. A weak binding affinity was anticipated from the values of the binding constant (Ka = 0.83–2.69 × 103 M−1) for IPR–BSA association. Thermodynamic analysis of the binding data further supported contribution of hydrophobic interactions in the IPR–BSA association process. This result was validated by the computational docking analysis. Spectral results from three-dimensional fluorescence and circular dichroism demonstrated microenvironmental changes around BSA fluorophores and protein’s structural (secondary and tertiary) alterations, respectively, upon IPR binding to the protein. Slight variation in the secondary structures of BSA in the presence of IPR was also verified from FTIR spectral results. IPR was found to bind to both site I (subdomain IIA) and site II (subdomain IIIA) of BSA, showing more preference toward site II, as identified by the competitive drug displacement results and supported by the computational analysis.

Water-stable CdII-based metal–organic framework as a reversible luminescent sensor for NFT with excellent recyclability and selectivity

A 3D CdII-based metal–organic framework, [CdLeneN3]n (namely complex 1), was prepared by heating CdCl2, NaN3, and 4-(4-cyanostyryl)pyridine (L) in a mixed solution of i-PrOH and H2O at 165 °C for 72 h. Interestingly, cyano and azide groups can react with each other in suit to generate tetrazolate groups during the synthetic process, which can be confirmed by the single crystal X-ray diffraction analysis. On account of its excellent stability and luminescent property, the as-synthesized 1 is an outstanding luminescent sensor material for nitrofurantoin (NFT) in water. The Ksv value of complex 1 toward NFT is ~1.4 × 104 M−1 with a good R2 value of 0.9983. More importantly, the resultant crystals are easily recollected and reused at least five cycles.

A water-stable luminescent Co(II) coordination polymer as probe for efficient detection of Cr(VI)-anions (Cr2O72– and CrO42–) in aqueous solution

A new 2D Co(II)-based coordination polymer (CP), {[Co(TCPA)(L)]·H2O}n (1) (L = 1,3-bis(5,6-dimethylbenzimidazol-1-yl)propane, and H2TCPA = 2,3,5,6-tetrachloroterephthalic acid), was successfully constructed under hydrothermal condition. 1 features a 2D (4,4)-connected layered structure. Adjacent sheets of 1 are interconnected via π···π stacking interactions generating a 3D supramolecular framework. Further, 1 exhibits the high sensing ability for Cr2O72– (pH = 4.0) and CrO42– (pH = 11.0) in aqueous systems through luminescence quenching effects. The Ksv values are 1.43 × 104 M−1, and 1.24 × 104 M−1 for Cr2O72–, and CrO42–, respectively. Besides, the possible selective fluorescence sensing mechanism was speculated.

A dual luminescent chemosensor derived from a europium(III) metal-organic framework for quantitative detection of phosphate anions and acetylacetone in aqueous solution

A luminescent europium(III) metal-organic framework (MOF) {[Eu(bcpt)(HCOO)]·0.5H2O}n (1) has been synthesized under solvothermal conditions by adopting a elongated ligand encompassing three aromatic rings groups, 3,5-bis(4′-carboxy-phenyl)-1,2,4-triazole (H2bcpt). This MOF demonstrates a binodal (4,10)-connected framework with a Schläfli symbol of {34·42}{38·414·516·67}, in which the adjacent Eu(III) ions can be bridged by HCOO− anions to form a 2D layer and further connected by H2bcpt as a pillar to generate a 3D pillared-layer structure. Notably, such a binodal (4, 10)-connected topological structure is rarely explored in MOF family, particular of lanthanide(III) MOF chemistry. Furthermore, 1 could be exploited as a dual luminescent chemosensor to probe PO43− anions and acetylacetone in aqueous solution with the average quenching Ksv values of 1.27 × 104 L mol−1 and 322 L mol−1, and the detection limits of 2.74 × 10−4 mol L−1 and 1.21 × 10−4 mol L−1, respectively.

Solvo‐thermal Preparation of One Novel Cadmium(II) Coordination Polymer with 1‐(4‐Aminobenzyl)‐1,2,4‐Triazole and Bi‐functional Photo‐Luminescent Sensing for Acetone and Dichromate

In this work a 1,2,4‐triazole derivative 1‐(4‐aminobenzyl)‐1,2,4‐triazole (abtz) was utilized, one new cadmium(II) coordination polymer, namely [Cd(abtz)I2]n (1) was prepared through the powerful solvo‐thermal synthetic strategy. In compound 1, the abtz building blocks are interlinked through the central CdII ions forming the two‐dimensional (2D) layer coordination framework. Powder X‐ray diffraction (PXRD) characterization also reveals that we have prepared the pure phases of coordination polymer 1. Optical properties have been determined, which can behave the excellent photo‐luminescent emission of coordination polymer 1. Photo‐luminescent experiment also reveals that coordination polymer 1 can behave the highly sensitive detection for acetone molecules with high Ksv value (Ksv = 4.12 ×104 L·mol–1) in the recyclable detection fashion. Additionally, coordination polymer 1 also can behave the highly sensitive detection for pollutant dichromate with excellent quenching efficiency Ksv (Ksv = 2.12 × 104 L·mol–1) and low detection limit [38 × 10–3 mM (S/N = 3)]. UV/Vis, photo‐luminescent lifetime, and PXRD patterns also have been determined to analyze the detection mechanism.

Synthesis and photophysical properties of usymmetrically substituted phthalocyanine-pyrene conjugate

Unsymmetrical zinc phthalocyanine (Pc) bearing one pyrene (Py) and six tert-butylphenoxy units was synthesized in 3 steps. The unsymmetric zinc phthalocyanine carrying the protecting group was synthesized in the first step. In the second stage, the protecting group was removed and in the final stage pyrene structure was introduced under the condition of the Sonagashira coupling reaction. The new compound was characterized by using spectroscopic techniques. The photophysical measurements of the conjugated structure were performed to determine the effect of the pyrene group on the fluorescence of Pc. It was determined that the absorption of the pyrene structure around 350 nm was overlapping with the B-band of phthalocyanine after conjugation. Fluorescence quantum yield and lifetime were calculated. The fluorescence quenching examinations were performed by adding the different concentration of benzoquinone in DMF and the Ksv and kq values of unsymmetrical zinc phthalocyanine (5) were determined.

A Dye@MOF composite as luminescent sensory material for selective and sensitive recognition of Fe(III) ions in water

Dye encapsulated metal-organic framework (MOF) composites have emerged as one of the promising platforms toward chemical recognition. Herein, a highly potent hydrolytically stable luminescent sensory probe was crafted exhibiting selective fluorescence response for Fe3+ ions in water medium. Encapsulation of a cationic dye inside a porous anionic MOF was successfully achieved via an ion-exchange process. Confinement of dye molecules inside the MOF serving as a crystalline flask prohibits the aggregation-induced quenching of dye molecules thereby manifesting a Dye@MOF luminescent composite material. The Dye@MOF composite shows selective response toward Fe3+ ions with remarkable luminescence quenching even in presence of other metal ions. Additionally, a high Ksv (quenching coefficient) value of 5.5 × 104 M−1 and low limit of detection (LOD) of 1.1 ppm was observed for Fe3+ ions.

Formation of the inclusion complex of water soluble fluorescent calix[4]arene and naringenin: solubility, cytotoxic effect and molecular modeling studies

Naringenin is considered as an important flavonoid in phytochemistry because of its important effect on cancer chemoprevention. Unfortunately its poor solubility has restricted its therapeutic applications. In this study, an efficient water-soluble fluorescent calix[4]arene (compound 5) was synthesized as host macromolecule to increase solubility and cytotoxicity in cancer cells of water-insoluble naringenin as well as to clarify localization of naringenin into the cells. Complex formed by host–guest interaction between compound 5 and naringenin was analyzed with UV–visible, fluorescence, FTIR spectroscopic techniques and molecular modeling studies. Stern–Volmer analysis showed binding constant value of Ksv 3.5 × 107 M−1 suggesting strong interaction between host and guest. Binding capacity shows 77% of naringenin was loaded on compound 5. Anticarcinogenic effects of naringenin complex were evaluated on human colorectal carcinoma cells (DLD-1) and it was found that 5-naringenin complex inhibits proliferation of DLD-1 cells 3.4-fold more compared to free naringenin. Fluorescence imaging studies show 5-naringenin complex was accumulated into the cytoplasm instead of the nucleus. Increased solubility and cytotoxicity of naringenin with fluorescent calix[4]arene makes it one of the potential candidates as a therapeutic enhancer. For deep understanding of host–guest interaction mechanisms, complementary multiscale molecular modeling studies were also carried out.Communicated by Ramaswamy H. Sarma

ENHANCEMENT OF OPTICAL OXYGEN SENSING PROPERTIES OF [RU(BPY)3]2+- BASED COMPOSITES ALONG WITH MAGHEMITE AND IONIC LIQUID

In this study, we measured oxygen-induced emission and decay-time data of tris( 2,2′ -bipyridyl)ruthenium(II) chloride dye in the presence of additives, maghemite and ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate. The fluorescent dye along with the additives was embedded in ethylcellulose matrix that was used as supporting material in form of thin-film and electrospun mat. The synthesized maghemite was used to enhance the oxygen sensitivity and linear working range of the dye. Ionic liquid (IL) was used to increase the stability and sensitivity of the sensing fluorophore. Together with the additives ruthenium dye-based composites exhibited higher Stern-Volmer constant ( K SV) , relative signal change and larger linear response. High relative signal change and KSV values mean that fluorophore has a better oxygen gas sensitivity.Stern-Volmer values of thin-film and microporous mats were found 1.64×10 −2 and 2.21×10 −2 , the relative signal changes (I 0 /I) were calculated as 2.64 and 3.21, respectively. There is no previous work about the utilization of both maghemite and ionic liquid additives together for the enhancement of oxygen sensitivity of the ruthenium.

A highly stable, luminescent and layered zinc(II)-MOF: Iron(III)/copper(II) dual sensing and guest-assisted exfoliation

A highly stable and luminescent metal-organic framework (LMOF) with layered structure, namely, C6H4N5OZn (1) has been successfully achieved and fully characterized by single crystal X-ray diffraction, powder X-ray diffractions, fluorescence titration and thermogravimetry. This blue-light emitting compound 1 exhibit outstanding stability and can detect Fe3+ and Cu2+ in water specifically, presenting potential application in the field of fluorescent probe technology. Fluorescence titration experiments indicate that the detection of Fe3+ ions by 1 is more significant than that of Cu2+ ions in terms of Ksv value. Furthermore, guest-assisted exfoliation of layered MOF 1 is efficiently carried out through ether OH hydrogen bond or π···π interactions between the layered host structure and intercalated guest molecules (4,4′-oxybisbenzoic acid and triphenylamine). Tyndal scattering was observed in the suspensions of obtained MOF nanosheets. This study shows that the compound 1 with unique metal ion sensing properties can be applied as a probe material in water pollution treatment field, but also opens up the opportunity for synthesizing luminescent MONs through the “bottom-up” guest intercalation methodology.