Presence Of Acetate Ions Research Articles

Anion‐Dependent Outstanding Luminescence Enhancement of Eu(D‐facam)3 Upon Coexistence With the Tetramethylammonium Cation

The effect of a series of tetramethylammonium salts with different counter anions on the photophysical properties of a chiral Eu(III) complex (Eu(D-facam)3 ) was investigated. Anion-dependent luminescence of the Eu(III) complex was observed, and particularly in the presence of acetate ions, an outstanding luminescence enhancement (>300 times) and induced circularly polarized luminescence (glum =-0.63) were obtained. The energy transfer process was then evaluated using key photophysical parameters, and it was found that the sensitisation efficiency of the Eu(III) complex significantly increased in the presence of tetramethylammonium acetate (TMAOAc). The interactions between Eu(D-facam)3 and TMAOAc were confirmed by luminescence analysis, circular dichroism spectroscopy, Fourier transform infrared spectroscopy and mass spectral measurements.

Gallium-binding peptides as a tool for the sustainable treatment of industrial waste streams

Here we provide a proof of principle for an application-oriented concept for the peptide-based recovery of gallium in industrial wastewater, which was supported by biosorption studies with a real wastewater sample. We investigated the interaction of the gallium-binding peptides TMHHAAIAHPPH, NYLPHQSSSPSR, SQALSTSRQDLR, HTQHIQSDDHLA, and NDLQRHRLTAGP with gallium and arsenic through different experimental and computational approaches. Data obtained from isothermal titration microcalorimetry indicated a competitive influence by the presence of acetate ions with an exothermic contribution to the otherwise endothermic peptide gallium interactions. For peptide HTQHIQSDDHLA, a stabilizing influence of acetate ions on the metal peptide interaction was found. Peptide NYLPHQSSSPSR showed the highest affinity for gallium in ITC studies. Computational modeling of peptide NYLPHQSSSPSR was used to determine interaction parameters and to explain a possible binding mechanism. Furthermore, the peptides were immobilized on polystyrene beads. Thus, we created a novel and exceptionally robust peptide-based material for the biosorption of gallium from an aqueous solution. Data obtained from isothermal titration microcalorimetry indicated a competitive influence by the presence of acetate ions with an exothermic contribution to the otherwise endothermic peptide gallium interactions. For peptide HTQHIQSDDHLA, a stabilizing influence of acetate ions on the metal peptide interaction was found. Peptide NYLPHQSSSPSR showed the highest affinity for gallium in ITC studies. Computational modeling of peptide NYLPHQSSSPSR was used to determine interaction parameters and to explain a possible binding mechanism. Furthermore, the peptides were immobilized on polystyrene beads. Thus, we created a novel and exceptionally robust peptide-based material for the biosorption of gallium from an aqueous solution.

The transition from locally excited states to twisted intramolecular charge transfer states for fluorescence methylene blue labeled in biodegradable silica particles

Fluoresce signal is widely used in fields of solid state lasers, optoelectronic devices and medical diagnostic devices. Its brightness and photostability are related to the aggregation state of organic fluorescence dye, such as methylene blue (MB). Herein, silica-MB-ABS powders were synthesized by a modified Stöber method following a treatment with acetate buffer solutions (ABS, pH = 3.60) and characterized by scanning electron microscopy, Fourier transform infrared spectra and Raman spectra. An effective strategy was employed in these fluorescent powders to modulate the aggregation state and fluorescent properties of MB through the hindering effects of Si-O-Si network and acetate ions. The entrancement of acetate ions destroys the π-π stacking of MB monomers, resulting in an increased release of MB monomers from silica-MB-ABS. In comparison with that of free MB particles, fluorescent intensity of silica-MB increases significantly with a blue-shifted emission, indicating that luminogenic MB molecules are assigned to locally excited states during aggregation-induced emission. With the presence of acetate ions, silica-MB-ABS exhibits a red-shifted emission with decreased intensity because MB molecules are aggregated in a twisted intramolecular charge transfer state. This observation is confirmed by calculated values of large twisted angles of MB released from silica-MB-ABS, resulting in a fast rate of charge transfer from excited states though a non-emission decay. Meanwhile, the kinetic release of MB is well described by a Korsmeyer-Peppas' equation and controlled by a combination of diffusion and matrix degradation mechanisms. The simulated release exponents of n decrease for silica-MB-ABS synthesized with increased concentration of acetate ions, indicating the reduction of limitation of matrix degradation on outward diffusion of MB from high-degraded particles. This study could shed light on tiny modification of aggregation state of organic fluorescence dyes and the modulation of fluorescent properties used in solid state lasers, fluorescence diagnostic devices and photochemical sensors.

Exogenous acetate ion reaches the type II copper centre in CueO through the water-excretion channel and potentially affects the enzymatic activity.

The acetate-bound form of the type II copper was found in the X-ray structure of the multicopper oxidase CueO crystallized in acetate buffer in addition to the conventional OH(-)-bound form as the major resting form. The acetate ion was retained bound to the type II copper even after prolonged exposure of a CueO crystal to X-ray radiation, which led to the stepwise reduction of the Cu centres. However, in this study, when CueO was crystallized in citrate buffer the OH(-)-bound form was present exclusively. This fact shows that an exogenous acetate ion reaches the type II Cu centre through the water channel constructed between domains 1 and 3 in the CueO molecule. It was also found that the enzymatic activity of CueO is enhanced in the presence of acetate ions in the solvent water.

Особливостi електроокиснення Mn<sup>2+</sup> до MnO<sub>2</sub> в ацетатному електролiтi

The results of investigation of Mn 2+ electrooxidation mechanism in the presence of acetate ions have been presented. The kinetic measurements were supplemented by quantum-chemical modeling. The calculated value of the redox potential of [Mn(H 2 O) 5 Ac] + /[Mn(H 2 O) 5 Ac] 2+ system was compared with experimental data obtained at pH 5.2. The similar values have given a reason to assume the direct electrooxidation of ion Mn 2+ to Mn 3+ like complex [Mn(H 2 O) 5 Ac] + . The process occurs according to inner-sphere mechanism due to direct contact of the complex with the electrode through the carboxyl group. The quantum-chemical calculations have shown the impossibility of elimination of second electron without considerable reorganization of the complex [Mn(H 2 O) 5 Ac] 2+ . The final product of electrooxidation of Mn 2+ acetate complex, manganese dioxide, was formed as a result of [Mn(H 2 O) 5 Ac] 2+ disproportionation with subsequent hydrolysis of the [Mn(H 2 O) 5 Ac] 3+ complex. In weakly acidic solution (pH above 4) due to reducing the number of [Mn(H 2 O) 5 Ac] + complexes, electrooxidation of manganese ions were occurred by a similar mechanism to the acid sulphate solution, i. e. by radicals, p roduced by electrooxidation of water molecules.

Influence of anion induced proton abstraction on Cu(II) adsorption by alginic acid

Alginic acid (AA) synthesized by acidification of commercial sodium alginate was investigated for its Cu(II) adsorption efficiency in the presence of different counter ions. The results of batch adsorption studies indicated an adsorption of 169.86mg/g of Cu(II) by AA in the presence of acetate ions, however, it significantly decreased in the presence of chloride (126.36mg/g), sulphate (115.24mg/g) and nitrate (113.28mg/g) as counter ions. This can be accounted to the tendency of conjugate base (anion) to abstract proton from AA, which determines the extent of deprotonation of carboxylic acid. The FTIR and TGA/DTA studies support the difference in the coordination of carboxylate to Cu(II) in the presence of various counter anions. Acetate showed strong chelate coordination between Cu(II) and AA, whereas in the presence of Cl−, NO3− and SO42−, Cu(II) was complexed by weak bridging coordination with AA.

PH-related and site-specific excited-state proton transfer from pterin to acetate.

The pH-related fluorescence quenching mechanism of 2-amino-4-hydroxypteridine (pterin), a biologic functional molecule, in the presence of acetate ion has been fully investigated for the first time. Using a combined experimental and theoretical approach, we discover that the fluorescence quenching observed in acid condition originated from a barrierless excited-state proton-transfer process. The proton on the acid form of pterin is transferred to acetate after photoexcitation. The hydrogen-bonding patterns are found to change with the pH values that govern the occurrence of excited-state proton transfer (ESPT). As revealed by investigating the excitation and relaxation processes of pterin, this ESPT process shows impressive site specificity intrinsically due to the photoinduced acidic center shifting. The experimentally observed fluorescence quenching and lifetime shortening of pterin in acid condition are thus attributed to the site-specific proton transfer from the N5 site. Pterin exists extensively in living organisms and has been found to show favorable proton-donating ability, which may transfer its proton to biofunctional molecules with hydrogen-accepting groups and induce related bioeffects.

Synthesis of large-scale transparent gold nanosheets sandwiched between stabilizers at a solid–liquid interface

Micrometer-sized gold nanosheets (Au-NSs) were directly deposited on a large-scale at a solid–liquid interface using a modified solid matrix (SM) method. The reducing agent and the stabilizer were in the solid phase, and the oxidizing agent (HAuCl4) with an acetate ion as an additional stabilizer was in the aqueous phase. The deposited Au-NSs had either a definite geometric shape or a highly branched 2D dendritic nanosheet-like (Au-DS) morphology. Au-NSs of definite shape were formed on the solid surface from solutions of pH 4 or less. The formation of Au-DSs were observed in solutions of higher pH (5 to 8.4) because of rapid reactions. The deposited Au-NSs were optically transparent and exhibited preferential growth along the {111} crystal facet. The acetate ion acted as a stabilizer and selectively adsorbed onto the Au{111} crystal facet limiting the growth of the Au-NSs in the {111} direction. Hence, the formed Au-NSs were sandwiched between stabilizers in the solid and liquid phases in the presence of acetate ions in the solution phase. However, in the absence of acetate ions, a rapid reaction generates highly branched 3D gold microcrystals with a dendritic morphology. Nano/microcrystals with a highly branched morphology were deposited on a large scale onto the SM without introducing any template or surfactant into the solution phase. A thiol-based epoxy resin immobilized with natural or synthetic tannin was used as the SM.

Adsorption of Chondroitin Sulphate a onto Zirconia Nanoparticles

The adsorption equilibria between chondroitin sulphate A (CSA), a polyanionic biopolymer, and zirconium(IV) dioxide (zirconia) nanoparticles were investigated to characterize the extraction of CSA using the metal oxide. Adsorption isotherms were prepared using sample solutions adjusted to pH values in the range 1.5-7.8, employing various buffer systems, NaCl concentrations and temperatures. The maximum amounts of CSA adsorbed, nam, and the adsorption constants, KL, were calculated from non-linear curve fits to the Langmuir adsorption model. The buffer components suppressed CSA adsorption to varying degrees; however, the reversibility of the adsorption equilibria improved in the presence of the buffers, as indicated by the large values of KL and the small standard deviations. The temperature-dependent adsorption properties showed that a large nam value was obtained at 318 K. The extraction of glycosaminoglycans with zirconia was optimal in the presence of acetate ions and at high temperatures, and subseque...

Photo- and thermal degradation of piroxicam in aqueous solution.

Light and temperature have considerable effect on the degradation of piroxicam in aqueous solutions. The pH and acetate buffer ions also affect the degradation process. The apparent first-order rate constants for the photochemical and thermal degradation of piroxicam have been determined as 2.04–10.01 and 0.86-3.06×10–3 min–1, respectively. The first-order plots for the degradation of piroxicam showed good linearity within a range of 20-50% loss of piroxicam at pH 2.0-12.0. The rate-pH profile for the photodegradation of piroxicam is a U-shaped curve and for the thermal degradation a bell-shaped curve in the pH range of 2.0-12.0. The thermal degradation of piroxicam was maximum around pH 6.0. It is increased in the presence of acetate ions but was not affected by citrate and phosphate ions.

Nickel(II) complexes stabilized by bis[ N-(6-pivalamido-2-pyridylmethyl)]benzylamine: Synthesis and characterization of complexes stabilized by a hydrogen bonding network

Intramolecular hydrogen bonds in metalloproteins are key in directing reactivity yet these effects have been difficult to achieved in synthetic systems. We have been developing a synthetic system that uses hydrogen-bonding interactions to modulate the secondary coordination around a transition metal ion. This was accomplished with the ligand bis[ N-(6-pivalamido-2-pyridylmethyl)]benzylamine (H 2pmb), which contains two carboxyamido units appended from pyridine rings. Several nickel complexes were prepared and structurally characterized. In particular, we found that the appended carboxyamido groups either provide intramolecular H-bond donors or can be converted to bind directly to a metal center. We established that the complex Ni IIH 2pmb(Cl) 2 can be sequentially deprotonated with potassium tert-butoxide, causing coordination of the carboxyamido oxygen atoms and concomitant loss of the chloro ligands. The chloro ligands were also removed with silver(I) salts in the presence of acetate ions and the complex Ni IIH 2pmb(κ 2-OAc)(κ 1-OAc) was isolated, in which an intramolecular H-bonding network occurs between the H 2pmb ligand and the coordinate acetato ligands.

A highly selective naked-eye colorimetric sensor for acetate ion based on 1,10-phenanthroline-2,9-dicarboxyaldehyde-di-(p-substitutedphenyl-hydrazone)

A new and simple colorimetric sensor with high selectivity for acetate ion based on 1,10-phenanthroline-2,9-dicarboxyaldehyde-di-(p-substitutedphenylhydrazone) receptor 2 has been synthesized. The selectively binding ability of receptor 2 to acetate ion over other anions tested was demonstrated by UV–vis absorption spectroscopy in DMSO. Comparing with other anions studied, the UV–vis absorption spectrum in dimethyl sulfoxide shows significant response toward acetate ion with high selectivity, and meanwhile dramatic color change is observed from yellow to green in the presence of acetate ion (5 × 10 −6 mol/L). Little UV–vis absorption spectrum change has occurred when receptor 2 was titrated with other different guest (F −, Cl −, Br −, I −, H 2PO 4 − and OH −). In addition, the 1H NMR spectrum titration shows deprotonation of the receptor in the presence of acetate ion.

The effects of acetate ions on electrochemical behaviour of brass in chloride solutions

The corrosion behaviour of brass (67% Cu, 33% Zn) was investigated in chloride solutions, in the presence of acetate ions. For this aim, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements were utilized. The pH of solution was adjusted to 8.5. It was shown that, CH 3COO − ions could inhibit anodic dissolution of brass in aggressive chloride media. The effect of temperature was also studied in a range between 298 and 328 K. The inhibition effect of acetate ions was resulted from complex formations (between acetate ions and corrosion products) which physically adsorbed on the surface. The inhibition efficiency decreased with the temperature. The results obtained at different temperatures were used to evaluate various thermodynamical properties.

The effects of acetate ions (CH 3COO −) on electrochemical behavior of copper in chloride solutions

The corrosion behavior of copper has been investigated in presence of acetate ions, at various temperatures in highly corrosive chloride solution. For this aim, potentiodynamic and EIS (electrochemical impedance spectroscopy) measurements were used. Corrosion rates have been determined by extrapolating the polarization curves. The role of temperature, ionic species and the effect of oxide film formation have been interpreted in aspect of anodic and cathodic processes rate. Thermodynamical properties Δ G (free enthalpy), Δ H (enthalpy), Δ S (entropy) and E a (activation energy) values have been evaluated with help of current–potential measurement results. The experimental results showed that acetate ions have decreased the corrosion rate of copper in chloride containing solutions of pH 8.5. It was also shown that the acetate ions could provide protection behavior at elevated temperatures. The changes in thermodynamic properties showed that acetate ions formed stable and protective complex which physically adsorbed on the surface. The Δ G value decreased and E a values increased in presence of acetate ions.

A Novel Acetate Selective UV‐Vis Chemosensor Containing a Tripodal Benzaldehydic‐phenylhydrazone

AbstractA new colorimetric chemosensor 1 based on a tripodal benzaldehydic‐phenylhydrazone selectively sensing acetate ion has been synthesized. The highly selective binding ability of receptor 1 to acetate ion over other studied anions was demonstrated by UV‐Vis absorption spectroscopy in DMSO. Compared with other anions studied, its UV/Vis absorption spectrum in DMSO shows response towards the presence of acetate ion with high selectivity, and also color change from yellow to blue in the presence of acetate ion (2×10−5 mol·dm−3). Little UV/Vis absorption spectrum change has occurred when receptor 1 was treated with other different guest anions (F−, Cl−, Br−, I−, H2PO4− and OH−). The Kass of receptor 1 binding with acetate ion is 1.69×104.

Facile Synthesis and Characterization of Potassium-Doped MnO2 Nanowires

A new type of potassium doped manganese oxide nanowires were synthesized using a simple hydrothermal route. The reduction of MnO4- in the presence of acetate species led to the formation of the Multi-filamentous nanowire structure. Detailed TEM and chemical characterizations indicated that potassium ions were homogeneously distributed in the nanowires. XPS results show a clear binding energy shift (1 eV) for K(2p) peak in nanowires compared with its starting material of KMnO4. Detailed synthetic condition investigation indicated that the presence of acetate ions played an important role in the formation of such a type of nanowires other than layered structures.

Luminescence from cerium(iii) acetate complexes in aqueous solution: considerations on the nature of carboxylate binding to trivalent lanthanides

The luminescence of cerium(III) has been studied in aqueous solutions in the presence of acetate ion. In contrast to previous reports that cerium(III) carboxylate complexes do not luminesce, a weak emission is observed, which has a similar spectrum to the aquo cerium(III) species but a much shorter lifetime. Results from a variety of studies on complexation of various trivalent lanthanide ions with carboxylates, including NMR spectral and relaxation measurements, molecular mechanics calculations, deuterium isotope effects on Tb(III) luminescence lifetimes, together with literature data strongly suggest that the dominant mode of complexation between carboxylates and trivalent lanthanides involves a weak, predominantly bidentate, binding to the metal cation. We suggest that the observed emission arises from a 1 : 1 cerium acetate species involving such bidentate coordination.

Synthesis and crystal structure of a homotrinuclear Ni(II) complex

Abstract A tetradentate ONNO type Schiff base was synthesized from salicyaldehyde and 1,4-diaminobutane. Thermogravimetric analysis, elemental analysis and X-ray diffraction results showed this Schiff base to give a trinuclear complex with Ni(II) ions in presence of acetate ions. The complex crystallizes in the triclinic P-1 space group with a = 9.7510(2), b = 10.6854(2), c = 12.4781(4) Å, α = 112.101(3), β = 100.621(4) and γ = 91.733(3)°. Similar to those found in the literature the terminal Ni(II) ions are coordinated to the Schiff base and have a N2O4 coordination sphere. The central Ni(II) ion has a O6 coordination sphere formed by the phenolic oxygens and the acetate bridges. The conformation of the chelate ring formed between the Ni(II) ions and the iminic nitrogens were examined.

Synthesis and characterisation of morin-functionalised silica gel for the enrichment of some precious metal ions

Silica gel was firstly functionalised with aminopropyltrimethoxysilane obtaining the aminopropylsilica gel (APSG). The APSG was reacted subsequently with morin yielding morin-bonded silica gel (morin-APSG). The structure was investigated and confirmed by elemental and thermogravimetric analyses, IR and 13C NMR spectral studies. Morin-APSG was found to be highly stable in common organic solvents, acidic medium (<2 mol L −1 HCl, HNO 3) or alkaline medium up to pH 8. The separation and preconcentration of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) from aqueous medium using morin-APSG was studied. The optimum pH values for the separation of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) on the sorbent are 5.7, 2.2, 3.7, 3.7 and 6.8, giving rise to separation efficiencies of 43.9, 85.9, 97.7, 60.9 and 91.0%, respectively, where the activity was found to be >90% in the presence of acetate ion. The ion sorption capacity of morin-APSG towards Cu(II) at pH 5.5 was found to be 0.249 mmol g −1 where the sorption capacities of Ag(I) and Pd(II) were 0.087 and 0.121 mmol g −1 and 0.222 and 0.241 mmol g −1 at pH 2.2 and 5.7, respectively. This indicates a 1:1 and 1:2 morin/metal ratios at pH 2.2 and 5.7, respectively. Complete elution of the sorbed metal ions was carried out using 10 mL (0.5 mol L −1 HCl + 0.01 mol L −1 thiourea) in case of Au(III), Pd(II), Pt(II) and Rh(III) and 10 mL 0.5 mol L −1 HNO 3 in case of Ag(I). Morin-APSG was successfully employed in the separation and preconcentration of the investigated precious metal ions from some spiking water samples yielding 100-folds concentration factor. The relative standard deviation (R.S.D.) and the T-test ( | t | 1 ) were calculated.

Tafel and Electron Paramagnetic Resonance Studies of the Anodic Deposition of Hydrous Manganese Oxides with the Presence of Acetate Ions

The Tafel responses [i.e., ] of the anodic deposition for hydrous manganese oxide (denoted as ) from with the presence of acetate ions are systematically examined. Variables studied in this work include the concentration of and as well as the temperature and pH of the plating solution. The decrease in the Tafel slope for this anodic deposition, defined as , indicates that is monotonously increased from 0.18 to 0.4 with increasing the concentration of . The average reaction orders of and are about and , respectively. The pseudo-equilibrium potential of the anodic deposition of , obtained from the responses, is linearly decreased with increasing pH of the plating solution . The onset potential for the anodic deposition of , examined by linear sweep voltammetry (LSV), is negatively shifted with the continuous addition of acetate ions into the solution. This reduction in the deposition potential is attributed to the formation of Mn–AcO complexes [presumably denoted as ], revealed by the electron paramagnetic resonance (EPR) analyses and the molecular orbital∕ligand field stabilization energy theory. The influence of deposition potentials on the mean oxidation state of is also investigated by the EPR analyses. Finally, a scheme corresponding to the anodic deposition of from with the presence of is proposed.