Absence Of Metal Ions Research Articles

Chromophoric thin film based on cellulose triacetate blends for sensing metal ions

Abstract Chromophoric sensors were made based on 8-hydroxyquinoline immobilized onto a thin film of a polymer blend matrix. The thin films were made by the solution casting method using cellulose triacetate and polyethylene glycol (PEG 600) as plasticizer and pore-forming agent. Different contents of PEG 600 additive were investigated. The prepared films were characterized by FTIR and thermal analysis. The absorption and fluorescence spectra of different films were dependent on the content of PEG 600 with clear quenching of the fluorescence of the film that contains PEG 600 compared to that with zero content. This behavior was attributed to the collective effect of hydrogen bonding (intra- and intermolecular hydrogen bonding) that enhances the process of excited-state proton transfer. This result is favorable to a responsive sensor that shows fluorescence off in the absence of metal ions and fluorescence on upon metal ion chelation. The detection of 5 × 10−5 M of Al3+, Zn2+ and thallium (I) in aqueous solution has been observed with the fluorescence method. The result obtained is consistent with the enhancing effect of PEG 600 in the detectability of metal ions. Compared with the detection of Al3+ and Zn2+, the sensor shows better detection of thallium (I), with clear fluorescence spectra.

A general route to 1,5-disubstituted 1,2,3-triazoles with alkyl/alkyl, alkyl/aryl, aryl/aryl combinations: a metal-free, regioselective, one-pot three component approach

An experimentally simple one-pot reaction, affording 1,5-disubstituted 1H-1,2,3-triazoles in good to excellent yields by combining vinyl sulfones, sodium azide and alkyl bromides, -tosylates, -mesylates or aryl amines, -iodides is reported. The organic azides, generated in situ react with vinyl sulfones in a regioselective fashion in the absence of metal ions. Unlike many of the recently reported strategies, this method is capable of generating alkyl/alkyl, alkyl/aryl and aryl/aryl containing 1,5-disubstituted 1,2,3-triazoles under simple reaction conditions.

Effects of metal ions and pH on the formation and decomposition rates of di- and tri-peptides in aqueous solution

The recent discovery of active deep-sea hydrothermal systems venting high-pH fluids suggests that the prebiotic chemistry of the hydrothermal systems of early Earth may have been more diverse than previously thought. To determine the most favorable conditions for prebiotic oligomerization, the effects of metal ions (Ca2+, Mg2+, Zn2+, Fe2+, Mn2+, and Cu2+) and pH on the formation and decomposition rates of glycylglycine (GlyGly), glycylglycylglycine (GlyGlyGly), and diketopiperazine (DKP) in aqueous solution were investigated. Glycine (Gly) solutions containing metal ions were heated for 1–74 days at 140°C under various pH conditions and the samples were analyzed by high-performance liquid chromatography. GlyGly and DKP were produced in all samples regardless of the presence or absence of metal ions. GlyGly yields were higher under basic conditions (pH 9.8–9.9) than under acidic or neutral conditions. Moreover, GlyGly yields in the presence of Cu2+ and Zn2+ were higher than in the absence of Cu2+ and Zn2+; in the presence of metal ions other than Cu2+ and Zn2+, GlyGly yields were lower. The dimerization rate constant of Gly (k1) increased in the presence of Cu2+. GlyGlyGly was only produced in samples with Cu2+ and the yield was 5 times higher under basic conditions (pH 9.8) than under acidic (pH 3.4) or neutral (pH 7.1) conditions. However, other metal ions inhibited prebiotic peptide synthesis by catalyzing hydrolysis or chelation with amino acids. These results reflect the high stability of Cu2+ complexes with amino acids or peptides in the salt-induced peptide formation reaction, particularly at high pH. Although elongation of oligopeptides was not favored, formation of metal–amino acid or metal–short peptide chelates may have facilitated primitive biological functions and expanded prebiotic reaction fields because of their mobility in the Earth’s early oceans.

EP-1531: Stereotactic radiosurgery dose quality assurance: a commercial plastic scintillation versus a diamond detector

A total of 15 patients plans and 79 DCA generated in iPlan RT Dose 4.1.2 (BrainLAB, AG, Germany), with a Pencil Beam algorithm using a kernel resolution of 2.5mm were tested. Mean equivalent MLC field size was of 16.6 mm (range 7.5-32.7mm). Plans were delivered on a Novalis TX, using the 6XSRS energy mode with a D/R of 1000 MU/min and a HDMLC multileaf collimator (2.5 mm leaf size at isocenter). Using a Lucy® 3D QA Phantom (Standard Imaging, Inc., USA), dose distributions were recalculated for each plan and Figure 2. In blue the Lucy phantom with the DD and in grey, bottom, with the PSD, position “tip down”. The water equivalence and absence of metal in the PSD resulted in no change in data for this detector. Both DD and PSD results were within the overall measurements accuracy. Analysis of the measurements performed with the detectors tip up and down, Fig.3, are shown below in Table 3.

Thermal activation of an industrial sludge for a possible valorization

This work fits within the framework of sustainable management of sludge generated from wastewater treatment in industrial network. The studied sludge comes from an industry manufacturing sanitary ware products.Physico-chemical and mineralogical characterization was performed to give an identity card to the sludge. We noted the absence of metal pollution.The industrial sludge has been subjected to thermal activation at various temperatures (650°C to 850°C). The pozzolanic activity was evaluated by physico- chemical and mechanical methods [1]. Pozzolanicity measurement was carried out based on Chapelle test and conductivity revealed the existence of pozzolanic properties of the calcined samples. The best pozzolanic reactivity was obtained for the sample calcined at 800°C. We noticed a decrease in the reactivity of the sample calcined at 850°C. In addition, analysis by means of X-ray diffraction and Fourier transform infrared spectroscopy showed that sludge recrystallization begins at a temperature of 850°C. Pozzolanicity index of the thermally treated samples was determined by measuring the mechanical resistance of mortar specimens previously kept in a saturated lime solution for 28 days (ASTM C618 [2]). The best pozzolanic activity index was obtained for the sample calcined at 800°C (109.1%).This work is a contribution to the research for new supplying sources of raw materials and additives in the field of construction. It presents a proposition of a promising solution for the valorization of waste material as an additive instead of being discharged into open air dumps causing a major environmental problem.

Corrosion Protection of Stainless Steel by Organic Inhibitors in Phosphate Industries in 15% H2SO4

Phosphate industries use sulphuric acid during the manufacturing of fertilizers. This acid interacts with stainless steel to develop corrosion cell and it corrodes metal. Organic inhibitors 2-(aminomethyl) phenol and 2-(aminomethyl) benzenethiol were taken for corrosion control in 15% H2SO4 medium. Inhibitors anticorrosive effect studied at different temperatures and 10 mM concentration. The corrosion rate of metal absence and presence of inhibitors were determined gravimetric methods. The corrosion current density and inhibitors polarization effect was studied by potentiostat. Inhibitors’ corrosion protection activities like physisorption-chemisorption adsorption, thermal stability and surface films formation analysis can be done by activation energy, heat of adsorption, free energy, enthalpy and entropy. The experimental results of inhibitors surface coverage area and inhibition efficiency were exhibited strong bonding between inhibitors and base metal.

Fabrication of Highly Uniform Gel Coatings by the Conversion of Surface-Anchored Metal–Organic Frameworks

We report the fabrication of 3D, highly porous, covalently bound polymer films of homogeneous thickness. These surface-bound gels combine the advantages of metal-organic framework (MOF) materials, namely, the enormous flexibility and the large size of the maximum pore structures and, in particular, the possibility to grow them epitaxially on modified substrates, with those of covalently connected gel materials, namely, the absence of metal ions in the deposited material, a robust framework consisting of covalent bonds, and, most importantly, pronounced stability under biological conditions. The conversion of a SURMOF (surface-mounted MOF) yields a surface-grafted gel. These SURGELs can be loaded with bioactive compounds and applied as bioactive coatings and provide a drug-release platform in in vitro cell culture studies.

Mn2+and Mg2+synergistically enhanced lactic acid production byLactobacillus rhamnosusFTDC 8313 via affecting different stages of the hexose monophosphate pathway

The study aimed to evaluate the effects of Mn(2+) and Mg(2+) on lactic acid production using response surface methodology and to further study their effects on interactions between the enzymes and substrates along the hexose monophosphate pathway using a molecular modelling approach. A rotatable central composite design matrix for lactic acid production was generated with two independent factors namely, manganese sulfate and magnesium sulfate. The second-order regression model indicated that the quadratic model was significant (P<0·05), suggesting that the model accurately represented the data in the experimental region. Three-dimensional response surface showed that lactic acid production was high along the region where the ratio of MnSO4 to MgSO4 was almost 1:1, justifying the need for both Mg(2+) and Mn(2+) to be present simultaneously in stimulating the production of lactic acid. Molecular docking simulation was performed on a total of 13 essential enzymes involved in the hexose monophosphate pathway for the production of lactic acid with four different conditions namely in the presence of Mg(2+) , Mn(2+) , both Mg(2+) and Mn(2+) and in the absence of metal ions. Results showed that the presence of both Mg(2+) and Mn(2+) within the binding site improved the binding affinity for substrates in five enzymes namely, glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, phosphopyruvate hydratase and pyruvate kinase. Using response surface methodology and molecular modelling approach, we illustrated that Mg(2+) and Mn(2+) synergistically enhanced lactic acid production by Lactobacillus rhamnosus FTDC 8313 via affecting different stages of the hexose monophosphate pathway. Mg(2+) and Mn(2+) synergistically improved lactic acid production of Lact.rhamnosus via improved binding affinity of the enzyme-substrate along the hexose monophosphate pathway, instead of purely affecting growth as previously understood.

Theoretical Aspects of Hydrolysis of Peptide Bonds by Zinc Metalloenzymes

Activation and reaction energies for four model systems capturing the essential physicochemical features of the hydrolysis of the peptide bond have been calculated at various level of theory, including the presumably accurate CCSD(T) calculations. The models studied covered a part of the spectrum encountered in biological systems: the hydrolysis in the absence of metal ions (represented by formamide and Ala-Ala) and the hydrolysis in the presence of one and two zinc(II) ions, mimicking the active sites of mono- and dizinc metallopeptidases, respectively (by using thermolysin and glutamate carboxypeptidase II as the model catalytic systems and formamide as the model substrate). The results obtained using CCSD(T)/def2-TZVP and CCSD(T)/aug-cc-pVTZ calculations were used as the benchmark values to which the set of cheaper methods, such as (RI-)DFT, (RI-)MP2, and SCS-MP2, were referenced. It was shown that deviations of 3-5 kcal mol(-1) (translating to 2-3 orders in reaction constants) with respect to the reference CCSD(T) barriers are frequently encountered for many correlated methods and most of studied DFT functionals. It has been concluded that from the set of wave-function methods, both MP2 and SCS-MP2 methods can be recommended for smaller models (measured by the mean absolute deviation of the activation barriers over the four systems studied), whereas among the popular DFT functionals, B3LYP and especially M06-2X are likely to be reasonable choices for calculating the activation barriers of zinc metallopeptidases. Finally, with the model of glutamate carboxypeptidase II, issues related to the convergence of the calculated barriers with the size of the model system used as the representative of the enzyme active site were addressed. The intricacies related to system truncation are demonstrated, and suggest that the correlated wave-function methods may suffer from problems, such as intramolecular BSSE, which make their usage for the larger system questionable. Altogether, the presented data should contribute to efforts to understand enzymatic catalysis more deeply and to gain control of the accuracy and deficiencies of the available theoretical methods and computational approaches.

Anomalies in Solution Behavior of an Alkyl Aminopolycarboxylic Chelating Surfactant

The solution behavior of a DTPA (diethylenetriamine pentaacetic acid)-based chelating surfactant, 4-C12-DTPA, has been studied by tensiometry and NMR diffusometry. In the absence of metal ions, the eight donor atoms in the headgroup are titrating, and the charge of the headgroup can thus be tuned by altering the pH. 4-C12-DTPA changes from cationic at very low pH, over a number of zwitterionic species as the pH is increased, and eventually becomes anionic at high pH. Around the isoelectric point, the chelating surfactant precipitated. The solution properties, studied above the solubility gap, were found strongly pH dependent. When increasing the amount of negative charges in the headgroup, by increasing the pH, the adsorption efficiency was reduced and the cmc was increased. An optimum in surface tension reduction was found at pH 5, due to a proper balance between protonated and dissociated groups. Anomalies between surface tension measurements and NMR diffusometry in determination of cmc revealed a more complex relation between surface tension, surface coverage, and cmc than usually considered, which is not in line with the common interpretation of the Gibbs adsorption equation. At some of the investigated pH levels, measurements of bulk pH could confirm the location of cmc, due to the increased protonation of micelles compared to monomers in solution. The adsorption of monomers to the air-water interface showed unusually slow time dependence, evident from decreasing surface tension for several hours. This is explained by rearrangements of the large head groups to reduce the headgroup area and increase the packing parameter.

Potentiating toxicological interaction of single‐walled carbon nanotubes with dissolved metals

The present study explored the ecotoxicology of single-walled carbon nanotubes (SWCNTs) and their likely interaction with dissolved metals, with a focus on the effect of in vivo exposure in marine mussels. Any nano-scale effects were negated by the tendency of uncoated SWCNTs to agglomerate in water, particularly with high ionic strength as is the case in estuarine and full-strength seawater. However, SWCNTs, in combination with natural organic matter, remained suspended in seawater for long enough to become available to filter-feeding mussels, leading to their concentration on and increased contact with gill epithelia during exposure. For the first time, the authors describe a potentiating toxicological effect, expressed as DNA strand breaks obtained using the comet assay, on divalent metals afforded by negatively charged SWCNT agglomerates in seawater at concentrations as low as 5 µg L⁻¹. This is supported by the observation that SWCNTs alone were only toxic at concentrations ≥100 µg L⁻¹ and that the SWCNT-induced DNA damage was correlated with oxidative stress only in the absence of metals. If these laboratory experiments are confirmed in the natural environment, the present results will have implications for the understanding of the role of carbon nanotubes in environmental metal dynamics, toxicology, and consequently, regulatory requirements.

Disproportionation of elemental sulfur by haloalkaliphilic bacteria from soda lakes

Microbial disproportionation of elemental sulfur to sulfide and sulfate is a poorly characterized part of the anoxic sulfur cycle. So far, only a few bacterial strains have been described that can couple this reaction to cell growth. Continuous removal of the produced sulfide, for instance by oxidation and/or precipitation with metal ions such as iron, is essential to keep the reaction exergonic. Hitherto, the process has exclusively been reported for neutrophilic anaerobic bacteria. Here, we report for the first time disproportionation of elemental sulfur by three pure cultures of haloalkaliphilic bacteria isolated from soda lakes: the Deltaproteobacteria Desulfurivibrio alkaliphilus and Desulfurivibrio sp. AMeS2, and a member of the Clostridia, Dethiobacter alkaliphilus. All cultures grew in saline media at pH 10 by sulfur disproportionation in the absence of metals as sulfide scavengers. Our data indicate that polysulfides are the dominant sulfur species under highly alkaline conditions and that they might be disproportionated. Furthermore, we report the first organism (Dt. alkaliphilus) from the class Clostridia that is able to grow by sulfur disproportionation.

Chiral separation of racemic mandelic acids by use of an ionic liquid-mediated imprinted monolith with a metal ion as self-assembly pivot

A new chiral stationary phase based on molecularly imprinted polymers (MIP) was prepared in ionic liquid by use of the metal pivot concept. Imprinted monoliths were synthesized by use of a mixture of R-mandelic acid (template), 4-vinylpyridine, ethylene glycol dimethacrylate, and several metal ions as pivot between the template and functional monomer. A ternary mixture of dimethyl sulfoxide-dimethylformamide-[BMIM]BF4 containing metal ions was used as the porogenic system. Separation of the enantiomers of rac-mandelic acid was successfully achieved on the MIP thus obtained, with resolution of 1.87, whereas no enantiomer separation was observed on the imprinted monolithic column in the absence of metal ions. The effects of polymerization conditions, including the nature of the metal ion and the ratios of template to metal ions and template to functional monomer, on the chiral separation of mandelic acid were investigated. The results reveal that use of metal ions as a pivot, in combination with ionic liquid, is an effective method for preparation of a highly efficient MIP stationary phase for chiral separation.

Different recycle behavior of Cu2+ and Fe3+ ions for phenol photodegradation over TiO2 and WO3

Photocatalytic degradation of organic pollutants on TiO2 and WO3 have been widely studied, but the effects of Cu2+ and Fe3+ ions still remain unclear. In this work, we have found that the recycle behavior of Cu2+ and Fe3+ are greatly dependent on the photocatalytic activity of metal oxide used. With TiO2 (P25, anatase, and rutile), all the time profiles of phenol degradation in water under UV light well fitted to the apparent first-order rate equation. On the addition of Cu2+, phenol degradation on anatase, rutile and WO3 also followed the first-order kinetics. On the addition of Fe3+, the initial rate of phenol degradation on each oxide was increased, but only the reactions on three TiO2 became to follow the first order kinetics after half an hour. The relevant rate constants for phenol degradation in the presence of Cu2+ or Fe3+ were larger than those in the absence of metal ions. Under visible light, phenol degradation on WO3 was also accelerated on the addition of Fe3+ or Cu2+. Moreover, several influencing factors were examined, including the metal ion photolysis in solution. It becomes clear that as electron scavengers of TiO2 and WO3, Fe3+ is better than Cu2+, while they are better than O2. We propose that Fe3+ recycle occurs through H2O2, photogenerated from TiO2, not from WO3, while Cu2+ regeneration on a moderate photocatalyst is through the dissolved O2 in water.

Identification tag in the terahertz frequency domain using low-cost and tunable refractive index materials

In the present paper, we propose a new structure of chipless and low-cost tag for data encoding in the terahertz frequency range. The device is based on a multilayer structure in which the thicknesses of the different layers are of the order of the wavelength, i.e., in the submillimeter range. In this device, the information is encoded in the volume of the tag thanks to the adjustable refractive index and low-cost materials, leading to a high level of security. The two main advantages compared to classical radiofrequency identification tags are the absence of metal and the encoding of the information in the volume of the structure, thus limiting the risk of damage during handling and preventing from reverse engineering, for example.

Ultrathin Graphitic Carbon Nitride Nanosheet: A Highly Efficient Fluorosensor for Rapid, Ultrasensitive Detection of Cu2+

A highly efficient fluorosensor based on ultrathin graphitic carbon nitride (g-C₃N₄) nanosheets for Cu(2+) was developed. In the absence of metal ions, the nanosheets exhibit high fluorescence; the strong coordination of the Lewis basic sites on them to metal ions, however, causes fluorescence quenching via photoinduced electron transfer leading to the qualitative and semiquantitative detection of metal ions. This fluorosensor exhibits high selectivity toward Cu(2+). The whole detection process can be completed within 10 min with a detection limit as low as 0.5 nM. The use of test paper enables the naked-eye detection of Cu(2+) with a detection limit of 0.1 nmol. The practical use of this sensor for Cu(2+) determination in real water samples was also demonstrated.

Survivability and abiotic reactions of selected amino acids in different hydrothermal system simulators.

We tested the stability and reaction of several amino acids using hydrothermal system simulators: an autoclave and two kinds of flow reactors at 200-250 °C. This study generally showed that there is a variation in the individual amino acids survivability in the simulators. This is mainly attributed to the following factors; heat time, cold quenching exposure, metal ions and also silica. We observed that, in a rapid heating flow reactor, high aggregation and/or condensation of amino acids could occur even during a heat exposure of 2 min. We also monitored their stability in a reflow-type of simulator for 120 min at 20 min intervals. The non-hydrolyzed and hydrolyzed samples for this system showed a similar degradation only in the absence of metal ions.

A modified cyclen azaxanthone ligand as a new fluorescent probe for Zn2+

A new cyclen derivative L, bearing a methyl-chromeno-pyridinylidene hydrazone moiety, was synthesized and studied in MeOH, as potential fluorescent "OFF-on-ON" sensors for Zn(ii). Photophysical properties of this ligand being PET regulated, L was only weakly emissive in the absence of metal ions (OFF). L fluorescence was increased modestly upon addition of one equivalent of Zn(II), and further increased upon addition of a second equivalent. Therefore, Zn : L behaved as a highly sensitive ON sensor for zinc. This efficiency was correlated to Zn(II) coordination via the hydrazone moiety of the fluorophore, producing an efficient CHelation-Enhanced Fluorescence (CHEF) effect. A complementary theoretical study carried out with DFT calculations further elucidated the optical properties.

Non-specific clustering of histidine tagged green fluorescent protein mediated by surface interactions: the collective effect in the protein-adsorption behaviour

The chemically programmed non-fouling surfaces were used to observe the surface assembly behaviour of hexahistidine tagged Green Fluorescent Protein (His-GFP) as a model protein. In this particular case, site-selective physisorption of His-GFP was achieved in the absence of metal ions. This preference does not arise from surface charge, wettability or topographic differences between regions. We found that His-GFP has a tendency to centre into an array of marked squares and acquires a template shape on the entire non-fouling surface when both the internal and surrounding areas present carboxylate groups. This surface-directed organization of protein in assemblies is an unusual example of non-specific molecular interactions transfer to a higher scale objects organization. Furthermore, we performed a proof-of-concept study for the autonomous formation of protein microarrays with uniform orientation of the tagged protein molecules on the surface. Periodic protein microarrays were formed spontaneously within about one minute after the deposition of a few drops of protein solutions on the substrate. We propose a simple, gentle and cost-effective approach to fabrication of protein microarrays, which can be done by the end-user. This phenomenon of collective protein clustering into large scale patterns may help to assess experimentally how the peripheral proteins arrange into separate domains of the cell membrane.

Low symmetry pyrazole-based tripodal tetraamineligands: metal complexes and ligand decomposition reactions

The new low symmetry pyrazole-based tripodal tetraamine ligands 2-(1H-pyrazol-1-yl)-N,N-bis(1H-pyrazol-1-ylmethyl)ethanamine (bmpz) and 2-(1H-pyrazol-1-yl)-N-[2-(1H-pyrazol-1-yl)ethyl]-N-(1H-pyrazol-1-ylmethyl)ethanamine (bepz) have been prepared and characterised, as have metal complexes containing these ligands. X-ray crystal structures of [Co(bmpz)Cl](2)[CoCl(4)]·H(2)O, [Co(bmpz)MeCN](ClO(4))(2)·0.13H(2)O, [Zn(bmpz)MeCN](ClO(4))(2)·0.15H(2)O, [Zn(bepz)OH(2)](ClO(4))(2)·0.5H(2)O and [(Co(bepz)Cl)(2)]Cl(2)·6H(2)O confirm coordination of the intact tripodal ligands to the metal ions through all four N atoms. However, attempts to make Cu(2+) complexes containing bmpz and bepz gave, respectively, [Cu(7)Cl(2)]·0.2H(2)O and [Cu(8)Cl(2)] (7 = 1-(1H-pyrazol-1-yl)-N-(1H-pyrazol-1-ylmethyl)ethanamine, 8 = 2-(1H-pyrazol-1-yl)-N-[2-(1H-pyrazol-1-yl)ethyl]ethanamine), complexes containing the tridentate ligands 7 and 8 which are formed by loss of a pyrazolylmethyl arm from the appropriate tripodal ligand. This decomposition reaction occurs in protic solvents both in the presence and absence of metal ions, and is ascribed to the presence of an aminal functionality in the tripodal ligands. A possible mechanism for the decomposition, based on NMR and ESMS data, is suggested.