Solid-state Fluorescence Measurements Research Articles

A 3D printable adapter for solid-state fluorescence measurements: the case of an immobilized enzymatic bioreceptor for organophosphate pesticides detection

The widespread use of pesticides in the last decades and their accumulation into the environment gave rise to major environmental and human health concerns. To address this topic, the scientific community pointed out the need to develop methodologies to detect and measure the presence of pesticides in different matrices. Biosensors have been recently explored as fast, easy, and sensitive methods for direct organophosphate pesticides monitoring. Thus, the present work aimed at designing and testing a 3D printed adapter useful on different equipment, and a membrane support to immobilize the esterase-2 from Alicyclobacillus acidocaldarius (EST2) bioreceptor. The latter is labelled with the IAEDANS, a bright fluorescent probe. EST2 was selected since it shows a high specificity toward paraoxon. Our results showed good stability and replicability, with an increasing linear fluorescent intensity recorded from 15 to 150 pmol of labelled EST2. Linearity of data was also observed when using the immobilized labelled EST2 to detect increasing amounts of paraoxon, with a limit of detection (LOD) of 0.09 pmol. This LOD value reveals the high sensitivity of our membrane support when mounted on the 3D adapter, comparable to modern methods using robotic workstations. Notably, the use of an independent support significantly simplified the manipulation of the membrane during experimental procedures and enabled it to match the specificities of different systems. In sum, this work emphasizes the advantages of using 3D printed accessories adapted to respond to the newest research needs.Graphical abstract

Evaluation of the Molecular State of Piperine in Cyclodextrin Complexes by Near-Infrared Spectroscopy and Solid-State Fluorescence Measurements.

The purpose of this study was to evaluate the physicochemical properties of piperine (PP) in ground mixtures (GMs) of PP with α-, β-, or γ-cyclodextrin (CD) under conditions of humidity, heat, and humidity-heat. In solid-state fluorescence measurements, the fluorescence maxima for GM (PP/αCD = 1/2), GM (PP/βCD = 1/1), and GM (PP/γCD = 1/1) were observed at 463, 472, and 469 nm, respectively. On the other hand, the humidified GMs exhibited maxima at 454, 460, and 465 nm, while the humidified-heated samples displayed fluorescence maxima at 455, 455, and 469 nm, respectively. Therefore, the molecular behavior of PP with α, β, and γCD was concluded to vary upon the coordination of water molecules. NIR and solid-state fluorescence measurements revealed that the molecular behavior of PP inside the α, β, and γCD cavity changed by water and heat factors depends on the mobility of the methylenedioxyphenyl group.

Zinc and cobalt complexes with (2-carboxyphenoxy) acetic acid ligand: syntheses, structures, fluorescent and magnetic properties

Four binary compounds, [Zn(cpa)(H2O)3] (1), [Co(cpa)(H2O)3] (2), [Zn(cpa)(H2O)]n, (3) and [Co(cpa)(H2O)]n (4) (H2cpa = (2-carboxyphenoxy)acetic acid), have been synthesized and structurally characterized. In mononuclear 1 or 2, the metal ion (ZnII for 1 and CoII for 2) is surrounded by three water molecules and one tridentate chelate cpa2− in a distorted octahedral geometry, while in 3 or 4, the central metal ion (ZnII for 3 and CoII for 4) is located in a deformed square–pyramid formed by one water and two cpa2−. Each cpa2− is chelate bridging μ2 coordination and forms a 1-D zigzag chain structure 2 or 3. The different synthesis conditions for 1–4 have been carefully discussed. The solid-state fluorescence measurements for 1 and 3 together with magnetic properties for 4 also have been investigated.

Fluorene–Dithienothiophene-S,S-dioxide Copolymers. Fine-Tuning for OLED Applications

Three groups of fluorene–dithieno[3,2-b;2′,3′-d]thiophene-S,S-dioxides (DTT-S,S-dioxide) copolymers, each having four different ratios of DTT-S,S-dioxide (5, 15, 25, and 50%) were successfully synthesized through Suzuki coupling method. While the first group copolymers P1 had direct connection of fluorene to the peripheral thiophenes of DTT-S,S-dioxide, second group copolymers P2 had a thiophene extension between fluorene and DTT-S,S-dioxide, and in the third group, copolymers P3, fluorene had a connection with DTT-S,S-dioxide through the phenyl moiety of DTT. Absorbance and emission measurements of first two groups P1 and P2 displayed a regular bathochromic shift with increasing content of DTT-S,S-dioxide, which was more clearly observed in their solid state fluorescence measurements. Introduction of thiophene to the peripherals of the DTT-S,S-dioxide in copolymers P2 caused even further bathochromic shift in absorbances and emissions. As the absorbance and emission of P1 went up to 447 and 558 nm in solution, respectively, P2 had them at 472 and 592 nm, respectively. In solid state, emissions of P1 and P2 even went further up to 585 and 646 nm, respectively. The bathochromic trend of P1 and P2 became opposite with absorbance and solid state emission of P3, which had a hypsochromic shift with increasing content of DTT-S,S-dioxide. Solid state emission of P3, particularly the copolymers having 5, 15 and 50% DTT-S,S-dioxide, covered a wide region between 400 and 675 nm. A spread of colors from light blue (border of white) to red through green and yellow was obtained with the OLED applications of the copolymers. Their optical and electronic band gaps varied between 2.17 and 2.99 eV and between 2.68 and 3.57 eV, respectively. While the highest quantum yield was obtained with P2 (5%) as 0.66, the lowest was observed with P2 (50%) as 0.03. Almost all of the polymers displayed good thermal stabilities. No weight loss was observed with the copolymers P2 (5–15%) and P3 up to 400 °C.

Mononuclear lanthanide complexes incorporating an anthracene group: structural modification, slow magnetic relaxation and multicomponent fluorescence emissions in Dy compounds

Four mononuclear lanthanide complexes, [Ln(hfac)3(depma)(H2O)] [Ln(III) = Dy (1), Gd (2)], [Dy(hfac)3(depma)2]2·H2O (3) and [Gd(hfac)3(depma)2]·2H2O (4), have been obtained (hfac = hexafluoroacetylacetonate, depma = 9-diethylphosphonomethyl anthracene) by using one (for 1 and 2) or two (for 3 and 4) depma molecules to substitute coordination water molecules of Ln(hfac)3(H2O)2. It was found that the number of introduced depma ligands can modify the coordination geometry of Ln(iii) ions, showing a distorted biscapped triangular prism geometry in isostructural 1 and 2 and a distorted square-antiprismatic geometry in 3 and 4. Magnetic studies reveal that both 1 and 3 show field-induced slow magnetic relaxation under the applied dc field of 1000 Oe. The solid-state fluorescence measurements indicate the presence of multicomponent emissions in 1 and 3, including ligand-centered (LC) emissions from hfac and depma, and yellow emission from Dy(III) ions and only ligand-centered (LC) emissions in 2 and 4.

Phosphonates containing 8-hydroxyquinoline moiety and their metal complexes: structures, fluorescent and magnetic properties

Two kinds of solid-state structures of 5-phosphonomethyl-8-hydroxyquinoline (5pm8hqH3) have been obtained, namely 1·HCl·H2O and 1·H2O, involving different hydrogen bonds and/or aromatic stacking interactions. As a derivative of 5pm8hqH3, 5-phosphonomethyl-8-(carboxymethoxy)quinoline (5pm8cmoqH3) was synthesized. Based on 5pm8hqH3 and 5pm8cmoqH3, three new metal phosphonates have been hydrothermally prepared, including Zn(5pm8hqH)(H2O)·H2O (2), Cu(5pm8cmoqH)·2H2O (3) and Fe(5pm8cmoqH) (4), exhibiting layered structures for 2 and 4, and a three-dimensional open framework for 3. The 8-hydroxyquinoline moieties in 1·H2O and 2-4 exhibit three kinds of interesting aromatic stacking modes, including pyridine ring-pyridine ring stacking between a pair of moieties, double benzene ring-pyridine ring stacking between a pair of moieties and alternating benzene ring-benzene ring and pyridine ring-pyridine ring stacking among a number of moieties in the layered structure. The solid-state fluorescence measurements indicate the emissions of 1·HCl·H2O and 1·H2O are significantly different due to their distinct packing structures. Compound 2 exhibits both ligand-centered (LC) and ligand-to-metal charge transition (LMCT) emissions. Magnetic studies reveal dominant antiferromagnetic interactions in 3 and 4.

Isostructural lanthanide oxalatophosphonates Ln(5pm8hqH3)(C2O4)1.5(H2O)·2H2O [Ln(iii) = Eu, Gd, Tb, Dy] (5pm8hqH3 = 5-phosphonomethyl-8-hydroxyquinoline): structures, magnetic and fluorescent properties

Isostructural lanthanide oxalatophosphonates Ln(5pm8hqH3)(C2O4)1.5(H2O)·2H2O [Ln(III) = Eu(1), Gd(2), Tb(3), Dy(4)] have been obtained through hydrothermal reactions of 5-phosphonomethyl-8-hydroxyquinoline (5pm8hqH3), oxalate, and Ln(NO3)3·6H2O. Four compounds reveal layer structures, in which {LnO8} polyhedra are linked through oxalate units into a netlike {Ln(C2O4)1.5}n layer containing 24-member ring composed of six Ln(III) ions and six oxalate anions. The noncoordinated 8-hydroxyquinoline groups protrude from two sides of the layer. Neighboring layers are further connected to each other through hydrogen bonds and aromatic stacking of the 8-hydroxyquinoline rings, forming a supramolecular 3D structure. In magnetic measurements, compound 2 shows weak antiferromagnetic interactions. The magnetic behaviors of 1, 3 and 4 are ascribed to the depopulation of the Stark levels and weak antiferromagnetic interactions. In the solid-state fluorescent measurements, strong ligand-centered emissions and weak Ln(III)-centered emissions can be observed for 1 and 4, while only ligand-centered emissions for 2 and 3.

Zinc and manganese coordination polymers constructed by a new coordination mode of 4, 5-dicyanoimidazolate ligand: Syntheses, crystal structures, fluorescent and magnetic properties

Abstract Two isostructural coordination polymers, [Zn(dci)2(H2O)2]n (1) and [Mn(dci)2(H2O)2]n (2) (Hdci = 4, 5-dicyanoimidazole), have been synthesized by conventional solution reactions and characterized by IR spectra, elemental analyses and single-crystal X-ray diffractions. In both complexes, the metal ion (ZnII for 1 and MnII for 2) is surrounded by four dciˉ ligands and two coordinated aqua in a distorted N4O2 octahedral geometry. The dciˉ anion adopts a new coordination mode of μ2-(N, Nʺ) through its neighbouring imidazole nitrogen and cyano nitrogen atoms, and connects adjacent metal ions together, thus forming the 1D double-stranded chain structures 1 and 2. The solid-state fluorescence measurements for 1 and magnetic properties for 2 have been discussed.

Molecular States of p-Dimethylaminobenzonitrile Coground with .BETA.-Cyclodextrin Investigated Using Solid-State Fluorescence Spectroscopy

Changes in molecular states of p-dimethylaminobenzonitrile (DMABN) coground with β-cyclodextrin (β-CD) were examined using solid-state fluorescence measurements. Formation of a DMABN/β-CD inclusion complex by coprecipitation was confirmed by powder X-ray diffraction measurement. The powder X-ray diffraction pattern of the ground mixture was a halo pattern and differed from the pattern of the mixture prepared by coprecipitation. Solid-state fluorescence measurements revealed emission by DMABN crystals in a twisted intermolecular charge-transfer state at 473 nm. DMABN in the DMABN/β-CD coprecipitate had a fluorescence emission peak at 393 nm due to its planar structure. In contrast, DMABN in a DMABN/β-CD ground mixture had an emission peak at 473 nm due to its twisted structure. Grinding time-dependent structural changes in DMABN were evaluated using fluorescence lifetime and relative quantum yield measurements. Structural changes in DMABN in the DMABN/β-CD coprecipitate from a planar to a twisted structure were observed with grinding. DMABN, dispersed in microcrystalline cellulose (CC) molecules in a DMABN/CC ground mixture, had a fluorescence emission peak at 473 nm. However, the excitation spectrum of a DMABN/β-CD ground mixture differed from that of DMABN in CC. These results indicated that the molecular state of DMABN accommodated in the β-CD cavity differs between the coprecipitate and the ground mixture.

A potassium and cadmium coordination polymer connected by two kinds of coordination modes of 4,5-dicyanoimidazole ligands: Synthesis, crystal structure and fluorescent properties of {[K[Cd(dci)2(H2O)2]6]Cl}n

Abstract A novel heteronuclear cooordination polymer containing potassium and cadmium, {[K[Cd(dci)2(H2O)2]6]Cl}n (1) (Hdci = 4,5-dicyanoimidazole), has been synthesized and characterized with the aid of elemental analysis, fluorescence spectroscopic studies and single-crystal X-ray diffraction. In compound 1, half of dci− anions act as bidentate bridging ligands and the other half act as tridentate bridging ligands. It is through the bridging function of dci− ligands that K(I) and Cd(II) ions are connected and 3D coordination polymer of 1 forms. Solid-state fluorescence measurements reveal that complex 1 can emits strong purple emission band.

Synthesis, crystal structure and properties of a silver(I) complex with 2-(1H-1,2,4-triazol-1-yl) acetic acid

The treatment of 2-(1H-1,2,4-triazol-1-yl) acetic acid (Htza) with AgClO4 resulted in [Ag3(tza)2(ClO4)] n . Its crystal structure was characterized by X-ray crystallography. Each pair of adjacent Ag1 atoms, separated at 2.954 Å, is bridged by the bidentate carboxylate. Each Ag2 is coordinated in an exactly linear geometry by two triazole nitrogens from two tza− ligands. Solid state fluorescent measurements have a ligand-based emission at 415 nm. Thermal properties were also investigated.

Solid States Fluorescence Study of <i>p</i>-Dimethylaminobenzonitrile by Co-grinding with Cyclodextrins

The molecular status of a freeze-dried sample or a ground mixture of p-dimethylaminobenzonitrile (DMABN) with alpha-, beta-, or gamma-cyclodextrins (CDs) was examined using solid-state fluorescence measurements. A twisted intramolecular charge transfer (TICT) emission of DMABN crystals was shown at 475 nm. Emission peaks of freeze-dried samples were observed at 450, 380, and 393 nm in alpha-CD/DMABN, beta-CD/DMABN, and gamma-CD/DMABN systems, respectively. It was speculated that DMABN molecules existed as a twisted form in the cavity of alpha-CD, and as a plane structure in that of beta-CD or gamma-CD. On the other hand, fluorescence emission peaks of ground mixtures of DMABN with alpha-, beta-, or gamma-CD were observed at around 450 nm. When DMABN was ground together with microcrystalline cellulose, which cannot form an inclusion complex, only TICT emission was detected. These results suggest that the observed shift in the fluorescence peak could be due to inclusion phenomena. When the ground mixtures were crystallized under humid conditions, fluorescence emission peaks were observed at 450 nm in alpha-CD and of around 400 nm in beta- and gamma-CD systems. It is concluded that the conformation of the DMABN molecules in a crystalline CD/DMABN inclusion complex change depending on the size of the CD cavity.

Structures, Fluorescent Properties of the d 10 Metal Ions Compounds Based on Molecular Clips

Two closed-shell d 10 metal ions complexes Cd 2 (L) 2 (I) 4 (1) and Zn 2 (L) 2 (Cl) 4 (DMF) 2 (2) were prepared from molecular clips, 2,2′-bis(benimidazol-1-ylmethyl)-biphenyl (L), and structurally characterized to investigate the structures. Both compounds 1 and 2 are bimetallic supramolecular rectangles in which two L ligands are connected by two tetrahedral coordinated metal ions. These units are connected together through weak π < eqid1 > π interaction, and 1 and 2 are crystallized in P2(1)/c and P-1 space group, respectively. Solid state fluorescent measurements exhibit the presence of ligand-based emission at 407 and 370 nm of compounds 1 and 2, respectively.

Solid-Phase Extraction and Solid-State Spectroscopy for Monitoring Water Pollution

Abstract Research results are described which bring out the potential of using commercially available solid-phase extraction membranes and solid-state spectroscopy for monitoring water pollution. The membranes are used to preconcentrate pollutants by sorption from aqueous solution followed by nondestructive spectroscopic measurements. Solid-state fluorescence measurements using EmporeTM C18 membranes were employed in the laboratory for concept validation studies. Tabs from the membranes were suspended in solutions containing parts per billion (ppb) concentrations of anthracene for specific periods of time. The tabs were withdrawn, allowed to dry briefly in air, and then examined for fluorescence. The potential exists for at least semiquantitative analysis. The method is relatively simple. Use of extraction membranes in B dip-stick mode is new, as is the use of the membranes with solid-state fluorescence spectroscopy. Limitations are being defined.

Fluorodensitometric Measurements of Afiatoxins on TLC Plates

Abstract Eight collaborators analyzed a cottonseed meal extract spiked with known amounts of afiatoxins B1, B2, G1 and G2. Afiatoxins were resolved by TLC on silica gel-coated plates and estimated by solid state fluorescence measurements on the plates. Average recovery values were 93—99% for individual afiatoxins and 97.8% for the total amount added. Coefficients of variation ranged from 3.6 to 15.7% for individual afiatoxins and 4.9% for total afiatoxins. The technique appears to be accurate and precise. It is proposed that collaborative study be initiated