Aqueous Solution In Presence Research Articles

Synthesis, characterization and detection of Concanavalin A based on a mannose-substituted conjugated polymer through aggregation-enhanced FRET

A conjugated polymer (P1) with pendant mannose linkages has been designed and synthesized, which is a highly efficient ratiometric probe for Concanavalin A (Con A) detection. P1 is doped with a low-bandgap fluorophore, porphyrin, which in conjunction with favorable spectral overlap between the poly(fluorene–phenylene) and porphyrin facilitates efficient FRET process in aqueous solutions in presence of Con A. UV/vis spectroscopy and dynamic light scattering studies indicate that P1 and Con A form into nanoparticles by carbohydrate–lectin interactions. Addition of Con A results in the quenching of the poly(fluorene–phenylene) emission at 456nm with simultaneous enhancement of porphyrin emission at 625nm, exhibiting visual emission color change from blue to purple. The intensity ratio of I625/I456 is enhanced 9.3-fold when the concentration of Con A reaches 10μmol/L. Nonspecific proteins including bovine serum albumin (BSA), pepsin (Pep), lysozyme (Lys) show poor fluorescence response, thus highlighting the selectivity and sensitivity of the FRET-based sensing of Con A by P1. Moreover, P1 shows low cytotoxicity by CCK-8 assay, which makes its potential application as fluorescent agent for cellular imaging.

Two unique lanthanide–organic frameworks based on biphenyl-2,3,3′,5′-tetracarboxylic acid: Syntheses, crystal structures and luminescence properties

The reactions in mixtures of lanthanide oxides and biphenyl-2,3,3′,5′-tetracarboxylic acid, in the presence of aqueous solution, result in two interesting lanthanide–organic coordination polymers, formulated as{[Eu(Hbptc)(H2O)4]·H2O}n (1) and [Sm(Hbptc)(H2O)3]}n (2), (H4bptc=biphenyl-2,3,3′,5′-tetracarboxylic acid). The polymers 1 and 2 are built from 2D corrugated layer. The 2D layers are further interconnected to form the 3D framework by hydrogen bonds between water molecules and carboxyl groups. Both the complexes 1 and 2 exhibit efficient sensitized luminescence in the visible region in the solid state based on characterization emission of europium(III) and samarium(III) ions, respectively.

A one-step method to coat polystyrene particles with an organo-silica shell and their functionalization

A facile method of coating polystyrene (PS) particles with organo-silica and their functionalization was presented. By adding the organo-silane precursor into PS aqueous solution in presence of ammonia, an organo-silica shell could be coated on PS particles directly. This method has several characteristics. First, only one process, one precursor and one solvent were used. Second, the organic groups could be varied from methyl, propyl, vinyl, to mercaptopropyl. The third is the tunable shell thickness with a high monodispersity. The organo-silica shells are further functionalized. The PS@vinyl-SiO2 particles were used to assemble colloidal crystals, and further modified with bromine, resulting in tunable photonic band gaps. PS@mercaptopropyl-SiO2 particles allow the encapsulation of Au nanoparticles. The resulting 2.2 nm Au particles were stable at 550 °C and well-distributed in the whole SiO2 shell with a loading up to 20 wt%.

Investigation of Fluorescence Resonance Energy Transfer between Fluorescein and Rhodamine 6G

Fluorescence Resonance Energy Transfer between two organic dyes Fluorescein and Rhodamine 6G was investigated in aqueous solution in presence and absence of synthetic clay laponite. Spectroscopic studies suggest that both the dyes were present mainly as monomer in solution. Fluorescence Resonance Energy Transfer occurred from Fluorescein to Rhodamine 6G in solutions. Energy transfer efficiency increases in presence of laponite and the maximum efficiency was 72.00% in aqueous laponite dispersion. Energy transfer efficiency was found to be pH sensitive. It has been demonstrated that with proper calibration it is possible to use the present system under investigation to sense pH over a wide range from 1.5 to 8.0.

Enhanced Photocurrent and Photocatalytic Degradation of Methyl Orange by V-N Codoped TiO2 Nanotube Arrays Cooperated with H2O2

To extend the photo response of TiO2 further into the visible light region, TiO2 nanotube arrays codoped with vanadium and nitrogen were synthesized by anodization process, followed by impregnation and calcination process. X-ray photoelectron spectroscopy (XPS) revealed the existence of interstitial N and V (V4+ and V5+) in V, N codoped TiO2 catalysts, which was beneficial to narrow the bandgap and separating charges. Higher photocurrent density displayed by the V, N codoped TiO2 nanotube arrays showed that more photo-induced electrons were generated, therefore effectively improved the catalytic activity. V, N codoped samples were used for the photodegradation of methyl orange (MO) in aqueous solution in presence of H2O2. H2O2 is used to serve as an electron scavenger and a precursor for •OH radicals, thus significantly accelerating the photodegradation of MO under visible light irradiation. A synergistic effect between V, N codoped TiO2 catalyst and H2O2 contributed to the high degradation activity toward MO.

ОПРЕДЕЛЕНИЕ МЕДИ, ЦИНКА, КАДМИЯ И СВИНЦА В ВОДЕ МЕТОДОМ СПЕКТРОСКОПИИ ДИФФУЗНОГО ОТРАЖЕНИЯ

Found the concentration conditions of copper, zinc, cadmium and lead from aqueous solutions using clay mineral modified with rhodamine B. It is established that colorimetric characteristics of colored complexes Cu 2+ , Zn 2+ , Cd 2+ , and Pb 2+ with rhodamine B, immobilized on montmorillonite containing clay, depend on the pH and heavy metalsconcentration in the aqueous phase. The distribution coefficients of metals were obtained. Determined the maximum allowable concentrations of macro components of water that do not hinder the formation of complexes of heavy metals with rhodamine B immobilized on clay. To eliminate the interfering effect of metals at their joint presence in aqueous solutions the appropriate masking agents were proposed. On the basis of the obtained dependences the highly sensitive technique for determination of copper, zinc, cadmium and lead in drinking water by diffuse reflectance spectroscopy was developed. Estimated metrological characteristics of the proposed methods: the relative standard deviation (sr) analysis of water samples was 0.01-0.08; detection limit and the linearity range of the determination of heavy metals in drinking water was, mcg/l: Cu 2+ – 0.6, 1.8-100; Zn 2+ – 1.6, 4.8-100; Cd 2+ – 0.5, 1.5-100; Pb 2+ – 5.0, 15-600, respectively. The method was tested using the real samples of natural water. Keywords: clay mineral, rhodamine B, modification, heavy metals, sorption, method of determination, drinking water (Russian) DOI: http://dx.doi.org/10.15826/analitika.2015.19.3.002 A.Sh. Ramazanov, Esmail Gameel Qasim Daghestan State University, Makhachkala, Republic Daghestan,Russian Federation

The Inhibition Effect of Cinnamon Extract on Leaching of Aluminum Cook Wares in NaCl Solutions at Quasi-Cooking Condition

The contribution of cinnamon extract on leaching of aluminum (Al) cook wares was investigated using two aluminum alloys (Indian and Egyptian) and pure Al. The cinnamon (Cin) was extracted by heating the Cin sticks at 90&degC in distilled water for an hour to make the 10% stock solution. This study was done in aqueous solutions in presence and absence of 1% NaCl using weight loss at 90&degC. Moreover surface study (SEM and EDX) and electrochemical methods (Open Circuit Potential and Tafel plot) were applied. The addition of Cin solutions to 1% NaCl decreased the corrosion rates in weight loss and electrochemical method compared to 1% NaCl solutions which showed an inhibitive property of Cin solution. The inhibition was found to obey the modified Langmuir isotherm with a negative Langmuir ΔGads indicating the spontaneous nature of adsorption even at 90&degC. The EDX surface analysis of the Al surface immersed in Cin + NaCl revealed the composition of the pits formed. From Tafel method, it was found that the corrosion current density of pure Al was more than that of the Egyptian alloy. The apparent activation energy values for Cin, Cin + NaCl and NaCl solution were evaluated and discussed.

Synthesis, Characterization and Evaluation of the Cytotoxicity of Ni‐Doped Zn(Se,S) Quantum Dots

Quantum dots (QDs) are semiconductor nanocrystals with desirable optical properties for biological applications, such as bioimaging and drug delivery. However, the potential toxicity of these nanostructures in biological systems limits their application. The present work is focused on the synthesis, characterization, and evaluation of the toxicity of water‐stable Ni‐doped Zn(Se,S) QDs. Also, the study of nondoped nanostructures was included for comparison purposes. Ni‐doped nanostructures were produced from zinc chloride and selenide aqueous solutions in presence of 3‐mercaptopropionic acid and Ni molar concentration of 0.001 M. In order to evaluate the potential cytoxicity of these doped nanostructures, human pancreatic carcinoma cells (PANC‐1) were used as model. The cell viability was monitored in presence of Ni‐doped Zn(Se,S) QDs at concentrations ranging from 0 μg/mL to 500 μg/mL and light excited Ni‐doped Zn(Se,S) nanostructures were evaluated at 50 μg/mL. Results suggested that Ni‐doped Zn(Se,S) nanostructures were completely safe to PANC‐1 when concentrations from 0 μg/mL to 500 μg/mL were used, whereas non‐doped nanostructures evidenced toxicity at concentrations higher than 200 μg/mL. Also, Ni‐doped Zn(Se,S) QDs under light excitation do not evidence toxicity to PANC‐1. These findings suggest strongly that Zn(Se,S) nanostructures doped with nickel could be used in a safe manner in light‐driving biological applications and drug delivery.

Physicochemical behaviour of poly(acrylamide-co-(4-vinylpyridine))

A new copolymer poly(AM-co-4VP ) of acrylamide (AM) and 4-vinylpyridine (4VP) was synthesized by radical adiabatic copolymerization in aqueous solution. The structure and composition of the copolymer were characterized by their 1 H NMR, 13 C NMR, UV-visible spectra and conductimetry. The molecular weights are obtained by GPC and viscosity. The variation of the reduced viscosity of aqueous copolymer solutions with copolymer concentration revealed a strong intermolecular macromolecular interaction (microdomaines). It’s showed an anti-polyelectrolyte behaviour in aqueous solution in presence of NaCl salt. On the order hand the anti-polyelectrolyte behaviour, that reduces viscosity (η red ) increases remarkably in dilute regime with the added of NaCl salt to the aqueous copolymer solutions. This phenomenon depended on the pH of the aqueous medium. The viscosimetric macromolecular (Mv) was determined using Mark Howink equation of polyacrylamide which is compared with macromolecular weight (M W ) obtained by GPC.

Conformational switch of insulin-binding aptamer into G-quadruplex induced by K+ and Na+: an experimental and theoretical approach

Guanine-rich sequences can form the G-quadruplex structure in the presence of specific metal ions. Here, circular dichroism, UV–vis absorption, fluorescence, and molecular dynamics simulation studies revealed that insulin-binding aptamer (IBA) could form an intramolecular G-quadruplex structure after binding K+. Circular dichroism (CD) spectra demonstrated that IBA could fold into a parallel G-quadruplex with a strong positive peak at 263 nm. Analysis of equilibrium titration data revealed that cation binding was cooperative with the Hill coefficient of 2.01 in K+ and 1.90 in Na+. Thermal denaturation assays indicated that K+-induced G-quadruplex is more stable than Na+-induced structure. Folding of IBA into G-quadruplex leading to the contact quenching occurs as a result of the formation of a nonfluorescent complex between donor and acceptor. Based on fluorescence quenching of IBA folding, a potassium-sensing aptasensor in the range of 0–1.4 mM was proposed. Since the quenching process was predominantly static, the binding constant and the number of binding sites were determined. In this research, based on the experimental data, the initial model of IBA G-quadruplex was constructed by molecular modeling method. The modeling structure of IBA is an intramolecular parallel-strand quadruplex conformation with two guanine tetrads. The extended molecular dynamics simulation for the model indicated that the G-quadruplex maintains its structure very well in aqueous solution in presence of K+ in the central cavity. In contrast, it was demonstrated that the G-quadruplex structure of model in the water collapses in absence of this cation.

Formation of bromate in sulfate radical based oxidation: Mechanistic aspects and suppression by dissolved organic matter

Sulfate radical based oxidation is discussed being a potential alternative to hydroxyl radical based oxidation for pollutant control in water treatment. However, formation of undesired by-products, has hardly been addressed in the current literature, which is an issue in other oxidative processes such as bromate formation in ozonation of bromide containing water (US-EPA and EU drinking water standard of bromate: 10 μg L−1). Sulfate radicals react fast with bromide (k = 3.5 × 109 M−1 s−1) which could also yield bromate as final product. The mechanism of bromate formation in aqueous solution in presence of sulfate radicals has been investigated in the present paper. Further experiments were performed in presence of humic acids and in surface water for investigating the relevance of bromate formation in context of pollutant control. The formation of bromate by sulfate radicals resembles the well described mechanism of the hydroxyl radical based bromate formation. In both cases hypobromous acid is a requisite intermediate. In presence of organic matter formation of bromate is effectively suppressed. That can be explained by formation of superoxide formed in the reaction of sulfate radicals plus aromatic moieties of organic matter, since superoxide reduces hypobromous acid yielding bromine atoms and bromide. Hence formation of bromate can be neglected in sulfate radical based oxidation at typical conditions of water treatment.

Microwave Assisted Degradation of Lignin to Monolignols

Objective: To carry out lignin degradation under very mild conditions using microwave technique. Methods: Lignin salt purchased from HiMedia laboratories was dissolved in distilled water and the solution was introduced to Biotage Initiator microwave. The reaction temperature was varied between 100-150°C with average power 85-90 W. Mass spectra were recorded in ACN-H2O (3:7) solution on BrukermicroTOF QII mass spectrometer in +ve ESI mode. Acetonitrile and water were HPLC grade and were bought from Sigma Aldrich while Sodium fluoride was purchased from Spectrochem. SEM images were recorded on ZEISS EVO LS10 scanning electron microscope with prior coating of silver using Quorum Q150R ES coating machine. Results: 1 g of lignin dissolved in 10 ml distilled water was irradiated under microwaves. Aliquots of samples were withdrawn and mass spectra were recorded after every 10 min. Maximum conversion of lignin to monolignols was observed after 90 min. Effect of NaF was also observed when catalytic amount of NaF (10 mg) was used in each reaction. Surprisingly, the results obtained in the previous conditions after 90 min were achieved only after 30 min in the presence of NaF. Conclusion: Lignin was degraded to its monomeric units when its aqueous solution in presence of catalytic amount of NaF was irradiated under microwaves at 150°C for 30 min. Hence, this technique could be used to degrade lignin into various lower lignols along with monolignols. Using this technique, revolutionary change could be made in paper, pulp and leather industry. Above all, several pharmaceutical raw materials could be synthesized efficiently from important monolignols produced from lignin degradation.

Membrane Integrity of Two Human Erythrocyte Genotypes in The Presence of Aqueous Solution of Sodium Metabisulphite and Their Correlations In Vitro.

Erythrocyte membrane integrity is a pre-requisite for cellular functionality. The present study sought to investigate the capacity of normal adult haemoglobin (HbAA) and homozygote haemoglobin S (HbSS) erythrocytes to withstand osmotic stress when incubated over time (0 h ≤ t ≤ 8 h) in relatively low concentrations of Na2S2O5

Fluoride-responsive hydrogel of cholesterol appended pyridinium urea and its metal detecting ability and semi-conducting behaviour

Cholesterol appended pyridinium urea 1 acts as low molecular weight gelator in DMSO:H2O (1:1, v/v) showing distinct colour change in the presence of aqueous solution of KF as well as tetrabutylammonium fluoride and recognises F− specifically. In addition, this hydrogel is noted to detect aqueous solution of Cu2+ and Pb2+ ions over a series of other metal ions and exhibits good semi-conducting property.

Photodecomposition of dodecyltrimethylammonium bromide in aqueous solutions in presence of hydrogen peroxide

It is established that the cationic surfactant (dodecyltrimethylammonium bromide, DTAB) efficiently decomposes in an aqueous solution in the presence of H2O2 upon exposure to UV radiation. The presence of bicarbonate ions decreases the rate of photodecomposition, which is due to the acceptance of OH radicals generated in the photochemical reaction. The rate constant of OH radicals and DTAB reaction equals ∼109 L mol−1 s−1. The kinetics of DTAB decomposition are described by the first-order reaction equation, and the effective rate constant is proportional to the H2O2 content in the solution.

Rationally designed porous polystyrene encapsulated zirconium phosphate nanocomposite for highly efficient fluoride uptake in waters

Fluoride pollution in waters has engulfed worldwide regions and an excess of fluoride intake always causes skeletal fluorosis. Herein, a novel hybrid nanomaterial ZrP-MPN was fabricated for fluoride retention by encapsulating nano-ZrP onto macroporous polystyrene materials modified with quaternary ammonium groups. The as-obtained materials exhibited favorable removal of fluoride ions from aqueous solution in presence of common anions (SO42−/NO3−/Cl−) at high contents. Moreover outstanding sorption properties were also detected by involving series of commercial adsorbents (AA/magnetite/GFH/manganese sands) as references. Such satisfactory performances might be ascribed to the structural design of nanocomposite. (1) the CH2N+(CH3)3Cl groups enhances sorption diffusion and preconcentration in sorbent phase theoretically based on Donnan membrane principle; (2) the embedded ZrP nanoparticles also devotes to the efficient adsorption capacities due to its size-dependent specific properties. Additionally, the exhausted ZrP-MPN could be regenerated readily by alkaline solution. Thus, ZrP-MPN was a promising material for fluoride retention in waters.

Low concentrated hydroxyectoine solutions in presence of DPPC lipid bilayers: A computer simulation study

The influence of hydroxyectoine on the properties of the aqueous solution in presence of DPPC lipid bilayers is studied via semi-isotropic constant pressure (NPT) Molecular Dynamics simulations. We investigate the solvent–co-solute behavior in terms of Kirkwood–Buff integrals as well as hydrogen bond life times for an increasing hydroxyectoine concentration up to 0.15mol/L. The observed preferential exclusion mechanism identifies hydroxyectoine as a kosmotropic osmolyte. Our findings with regard to the DPPC lipid bilayer indicate an increase of the surface pressure as well as the solvent accessible surface area in presence of higher hydroxyectoine concentrations. The results are in agreement to the outcome of recent experiments. With this study, we are able to validate the visibility of co-solute–solute–solvent effects for low and physiologically relevant osmolyte concentrations.

Cationic surfactant hemimicelle on alginate gel for removing bisphenol A from aqueous solution

In this paper, alginate gel (AG) was prepared by cross-linking sodium alginate with calcium ion. By adding cationic surfactant cetyl trimethyl ammonium bromide (CTAB) as sorption medium, the bisphenol A (BPA) sorption from aqueous solution onto AG was investigated. The BPA removal was found to be dependent on initial pH, AG dose, CTAB concentration, BPA concentration, contact time, and temperature. The isothermal data of BPA sorption on AG conformed well to the Langmuir model, and the maximum sorption capacity (Qm) of AG for BPA was 30.96 mg/g. The BPA sorption process could be described by the pseudo-second-order rate kinetic model. The thermodynamic study indicated that the BPA sorption process was spontaneous and exothermic. The results in this research confirmed that the AG could effectively remove BPA from aqueous solution in presence of the CTAB. The following sorption mechanism was proposed. Firstly, the negatively charged AG sorbed CTAB to form hemimicelle, then BPA was sorbed on hemimicelle by hydrophobic interaction.

Chitin-natural clay nanotubes hybrid hydrogel

Novel hybrid hydrogel was synthesized from chitin NaOH/urea aqueous solution in presence of halloysite nanotubes (HNTs) via crosslinking with epichlorohydrin. Fourier transform infrared (FT-IR) spectra and atomic force microscopy (AFM) results confirmed the interfacial interactions in the chitin–HNTs hybrid hydrogel. The compressive strength and shear modulus of chitin hydrogel were significantly increased by HNTs as shown in the static compressive experiment and rheology measurement. The hybrid hydrogels showed highly porous microstructures by scanning electron microscopy (SEM). The swelling ratio of chitin hydrogel decreased because of the addition of HNTs. The malachite green's absorption experiment result showed that the hybrid hydrogel exhibited much higher absorption rate than the pure chitin hydrogel. The prepared hybrid hydrogel had potential applications in waste treatment and biomedical areas.

Analytical model for zeta potential of asphaltene

In this paper, we provide for the first time an analytical framework for calculating the zeta (ζ) potential of asphaltene in aqueous solution in presence and in absence of an electrolyte salt. The analytical model is based on the assumption that the ionizable (in aqueous solution) carboxylic and hydroxyl groups present on the asphaltene molecule lead to its charging. The model predicts the ζ potential as a function of parameters such as buffer pH and electrolyte salt concentration. For the case with the added salt, ζ potential decreases with pH monotonically, and we obtain quantitative match with the experimental results. For the case without the added salt, the variation with pH is non-monotonic, represented by presence of two distinct extrema, and can be attributed to the role of the corresponding Electric Double Layer (EDL) thickness, which (in absence of any added salt) is a sole function of the pH.