Monovalent Metal Research Articles

How a range of metal ions influence the interfacial tension of n-decane/carboxylic acid/water systems: The impact of concentration, molecular- and electronic structure

The data from more than 700 pendant droplet interfacial tension (IFT) measurements has been scrutinized to reveal the relation between salinity/surfactant structure and IFT in a brine – decane/carboxylic acid system. The large number of measurements enabled an experimental uncertainty of around 1% in the IFT range around 30 mN/m. Thus, small changes and trends in IFT as a function of salinity and surfactant structure become apparent. Five carboxylic acids are chosen to resemble natural naphthenic acids; individually, they only differ by a CH2-group starting from cyclohexane carboxylic acid and ranging to 5-cyclohexyl pentanoic acid. The salt concentration was varied from 0.01 M to 1.0 M for a range of chlorides of monovalent and divalent metal cations: LiCl, NaCl, KCl, MgCl2, CaCl2, SrCl2, BaCl2, and ZnCl2. For Na+, NaBr, NaI, were also investigated. The variation in IFT with salinity and carboxylic acid is subtle with divalent ions, not surprisingly, inducing larger IFT changes than monovalent ones when the concentration is varied. Zn2+ gives rise to a surprisingly large IFT reduction (up to 7.5 IFT units in the range from 0.01 M to 1.0 M) and clearly stands out as a special case. For the three smallest chain acids the IFT increases as a function of salinity whereas, for the system involving the two largest ones, 4-cyclohexyl butanoic acid and 5-cyclohexyl pentanoic acid, IFT decreases as a function of salinity. The distinct behavior of Zn2+ and the sudden crossover in the variation of IFT as a function of salinity when increasing the chain length of the carboxylic acid is taken to indicate that structure of both the (solvated) electrolyte and the carboxylic acid– particularly with regard to the orientation at the interface - are important factors in determining the magnitude and variation in IFT as a function of physical parameters.

Aqueous Electrolyte Secondary Battery Using Fast Redox Reactions in Single-Walled Carbon Nanotubes

We would like to propose a new concept aqueous electrolyte secondary battery using simultaneous redox reactions of cations and anions in single-walled carbon nanotubes (SWCNTs) that will solve three major problems of Li ion batteries (LIBs): safety, cost and slow-charging problems. Recently we often hear fire and explosion accidents involving LIBs. The accidents were mainly caused by the use of flammable organic electrolytes. The use of organic electrolytes also leads to another problem: the slow-charging problem. Since ion mobility in organic electrolytes is much lower than that in aqueous electrolytes, it is very hard to obtain fast-charging for LIBs. The time-consuming charging process of LIBs hinders the market growth of electric vehicles (EVs). The high cost of LIBs due to the use of rare metals is another problem for the wider distribution of EVs. Therefore, we have to solve the problems of safety, cost and slow-charging. The new concept battery we proposed uses mono-valent or di-valent metal halide (e.g. LiI, NaI, ZnI2) aqueous electrolytes instead of the flammable organic electrolytes used in LIBs. The use of aqueous electrolytes is not only much safer than organic electrolytes, but also advantageous to cost and fast-charging, because alkali metal halides such as LiI, NaI, ZnI2 consist only of abundant elements, and the ion mobilities of both metal ions and halogen ions in water are much faster than those in organic electrolytes. We use SWCNTs as negative and positive electrodes. At positive electrode, iodide ions are oxidized inside the empty SWCNTs and caught as a form of diatomic molecule inside SWCNTs. On the other hand, alkali metal ions are caught by quinone organic molecules encapsulated in SWCNTs and di-valent ions are reduced on the surface of SWCNTs. We used a SWCNT sample purchased from Meijo NanoCarbon Co. The mean tube diameter of the SWCNT sample was determined to be 2.5 nm by XRD analysis. Reagent-grade 9,10-phenanthrenequinone (PhQ) powder sample was also purchased from Wako Pure Chemical Industries. SWCNT and PhQ powder samples were sealed in a vacuum glass tube, and heated at 200ºC for 10 h. The obtained PhQ@SWCNT sample was analyzed by TEM, SEM, Raman and XRD measurements. The electrochemical measurements were performed in a three electrode cell. PhQ@SWCNT sample (anode) was paired with an empty SWCNT electrode (cathode). For CV measurements, we used Ag/AgCl reference electrode. Aqueous electrolytes of 1 mol/L LiI or NaI were used. TEM, FT-IR, XRD, XPS measurements confirmed the encapsulation of PhQ molecules in SWCNTs. The content of encapsulated PhQ molecules per SWCNT weight was determined to be 38.0 wt% by TG measurements. Both in the cases of LiI and NaI aqueous electrolyte cases, PhQ@SWCNT could work as electrode active materials for Li and Na ion charge/discharge. The observed discharge potential for Na ion is about 0.1 V lower than that for Li ion. The cathode reaction of the proposed battery is fixed to the redox reaction of iodide ions, namely to the redox potential of I-/I2 (about +0.45 V vs. Ag/AgCl). Therefore, a lower redox potential of the quinone anode is better to obtain higher EMF from the proposed battery. So, NaI electrolyte is better than LiI electrolyte in terms of the potential. The discharge potential difference between LiI and NaI indicates that PhQ molecule attached to Na ion (PhQ-Na) is chemically more active than PhQ-Li. On the other hand, iodine electrode (cathode) properties have been reported in our previous papers. The molecular structures and phase transformations of the encapsulated iodine molecules were also fully investigated. Therefore, we were convinced that the iodine electrode should work as cathode in the new concept battery. The full cell performance of the proposed cell was also measured. The cathode potential was kept at iodine redox potential as we expected. So, It was also found that PhQ@SWCNT can work as anode electrode. Therefore, basically we have succeeded in demonstrating that the new concept battery, namely, a safe, low-cost and fast charging secondary battery using aqueous electrolyte can work very nicely. However, the amount of the observed charge capacity is quite different from that of the discharge capacity. We should investigate the reason why such a big irreversible capacity was observed in order to improve the proposed new concept aqueous secondary battery. We also would like to talk about di-valent metal cases in the conference.

A lysosome-targetable fluorescent probe for imaging trivalent cations Fe3+, Al3+ and Cr3+ in living cells.

An effective morpholine-type naphthalimide chemsensor, N-p-chlorophenyl-4-(2-aminoethyl)morpholine-1,8-naphthalimide (CMN) has been developed as a lysosome-targeted fluorometric sensor for trivalent metal ions (Fe3+, Al3+ and Cr3+). Upon the addition of Fe3+, Al3+ or Cr3+ ions, the probe CMN showed an evident naked-eye color changes which pale yellow solution of CMN turned deepened and it displayed turn-on fluorescence response in methanol. CMN showed a significant selective and sensitive toward Fe3+, Al3+ or Cr3+ ions, while there was no obvious behavior to other monovalent or divalent metal ions from the UV-vis and fluorescence spectrum. Based on the Job's plot analyses the 1:1 coordination mode of CMN with Fe3+, Al3+ or Cr3+ was proposed. The limit of detection (LOD) observed were 0.65, 0.69 and 0.68 μM for Fe3+, Al3+ and Cr3+ ions, respectively. The N-atom of morpholine directly involved in complex formation, CMN emitted fluorescence through inhibition of photoinduced electron transfer (PET). This probe exhibited excellent imaging ability for Fe3+, Al3+and Cr3+ ions in living cells with low cytotoxicity. Significantly, the cellular confocal microscopic research indicated that the lysosome-targeted group of morpholine moiety was introduced which realized the capability of imaging lysosomal trivalent metal ions in living cells for the first time.

Interfacial properties of sodium para-dimethyl alkylbenzene sulfonate in the presence of monovalent metal counterions at the oil-water interface

The interfacial properties of sodium para-dimethyl alkylbenzene sulfonate surfactant p-S14-41 (formula is) at the oil-water interface in the presence of monovalent metal counterions (Li+, Na+, K+ and Cs+) are investigated by the spinning drop tensiometry. In the presence of monovalent metal counterions (Na+, K+ and Cs+), the interfacial tension (IFT) of oil-water first decreases and then increases with the increase of counterion concentration, while for Li+ concentration in the studied concentration range, the IFT decreases continuously. The reason why the latter (Li+) does not appear the optimum salinity is that the salt concentration is not high enough. The most noteworthy feature is that not only the different counterions affect differently the optimum salinity but also the concentration of p-S14-4 in the studied concentration range for the same counterion has no effect on the optimum salinity. Besides, the optimum salinity is affected by the electrostatic interaction, water-oil ratio (WOR), salting-out effect, and the hydrated radius of counterion, under the synergistic effect of which, the optimum salinity value order under various monovalent metal counterions is as follows: Li+ > Na+ > Cs+ > K+. The influence mechanism of counterions on the adsorption of p-S14-4 at the oil-water interface is also discussed in detail.

Texture and trace element geochemistry of quartz in skarn system: Perspective from Jiguanzui Cu–Au skarn deposit, Eastern China

The Jiguanzui Cu–Au deposit is an important skarn deposit in the Edong ore district of the Middle–Lower Yangtze River Valley Metallogenic Belt (MLYRB), Eastern China. The skarn mineralization occurs dominantly in the intrusive contact between quartz diorite and marble of the Lower-Middle Triassic Jialingjiang Formation. The main mineralization stage (quartz-sericite-pyrite-chalcopyrite) is characterized by abundant quartz, which can be grouped as quartz in orebodies (Qtz1), quartz in quartz-pyrite hydrothermal veins in hornfels of the Middle Triassic Puqi Formation and quartz diorite (Qtz2 and Qtz3, respectively). Cathodoluminescent (CL) imaging reveals core-rim texture in Qtz1 and oscillatory zoning in Qtz2 and Qtz3, suggesting that Qtz1 was formed under low crystallization rate, in a relatively stable closed system, whereas Qtz2 and Qtz3 were formed under high crystallization rate, in an open system with oscillatory physicochemical fluctuations. As the main trace element in the Jiguanzui quartz, aluminum is incorporated into quartz as trivalent Al3+ to substitute Si4+. Monovalent alkali metal (esp. Li+) and divalent cations (Ge2+, Sr2+) act as charge compensators for the Al3+ substitution. Titanium concentrations (mostly <10 ppm) and the clear positive Al vs. Li correlation indicate the main mineralization at Jiguanzui formed under low temperature (<350 °C). Additionally, CL reflectivity of Qtz1 increases from core to rim, suggesting neutralization of the acidic ore fluids, which is interpreted to be an important cause of metal sulfide precipitation at Jiguanzui.

Effect of Activity Coefficient of Polyvalent Ionic Salt Solution on Demulsification of Soy Lecithin Based Oil-in-Water Emulsion

Lecithin based Oil-in-Water (O/W) emulsion finds a lot of applications in food and cosmetic industries. The stability of O/W emulsion depends on properties of the emulsifying solution and the ionic impurities present. The present experiment well explained the role of polyvalent Lewis acid salt solution in establishing the stability of emulsion. Lewis acid salts solutions of NaCl, KNO3 BaCl2 MgCl2, Al2(SO4)3 and FeCl3 were used in the preparation of lecithin based O/W emulsion. The ionic activity coefficient calculated from Debye-Hückel limiting law (DHLL) for Lewis metal ions Na+, K+, Ba2+, Mg2+, Al3+ and Fe3+ were found to be 0.955, 0.965,0.869,0.872, 0.737 and 0.737 which directly decrease the pH value of the ionic solutions to 6.9,7.0,7.14,7.04, 2.2 and 2.5 respectively. The conductance of ionic solution increases with decrease in ionic activity coefficient. These trends very strongly destabilize the lecithin O/W emulsion showing a significant order of breakup time of different emulsion systems as 3.5, 2.0,1.4,1.0, 0.5 and 0.25 minutes. The effect of ionic activity coefficient on emulsion destabilization was well projected by microscopic view. Measurement of droplet diameter was conspicuous for monovalent and divalent metal ions ranging from 14-156 micrometer and number of larger droplets increases with increasing in the valence. However, the higher valence Al3+ and Fe3+ ionic solutions totally break the emulsion with immediate separation of oil and water layer having lower activity coefficients. Thus, the increased valence and conductance, decreased ionic activity coefficient and pH value of the emulsifying solution destabilize the soy lecithin based O/W emulsion significantly by increasing the interfacial tension and retarding the binding ability of the emulsifier.

Phase equilibria in LaBr3-TlBr pseudobinary system. Thermodynamic assessment of LaBr3-MBr (M = Li, Na, K, Rb, Cs, Tl) pseudobinary systems

The phase equilibria in the lanthanum(III) bromide-thallium bromide pseudobinary system was established by means of differential scanning calorimetry (DSC). The DSC investigations were performed on samples with different compositions in the whole mole fraction x(LaBr3) range. This system includes one intermediate compound Tl2LaBr5. It melts congruently at 829 K. The compositions of TlBr-Tl2LaBr5 and Tl2LaBr5-LaBr3 eutectics, corresponding to LaBr3 mole fraction x = 0.088 (T = 687 K) and x = 0.491 (T = 788 K) respectively, was found from Tammann's plot. The LaBr3-TlBr pseudobinary system was also optimized by CALPHAD method using the available experimental data. Experimental and calculated data concerning LaBr3-TlBr system were compared with data for LaBr3-MBr (M = Li-Cs) systems, which have also been optimized by CALPHAD method. The thermodynamic properties of the liquid phase in the systems were modelled using the Associated Solution Model with {3 M+ + LaBr63−} (M = Li-Cs, Tl) associate. The dependencies of mixing enthalpy and mixing entropy on mole fraction x(LaBr3) were estimated for all investigated systems. The dependencies of formation Gibbs energy on temperature and temperature range of existence of intermediate compounds have been calculated and discussed. The CALPHAD optimization indicates that the participation of the associate in the liquid phase in the LaBr3-MBr (M = K⋯Cs, Tl) systems increases with the increase of the ionic radius of the monovalent metal.

Effect of alkali metal Na on the formation and superconductivity of Tl-1212-type phase (Tl0.85Cr0.15)Sr2−xNaxCaCu2O7

The effect of Na substitution on the formation and superconductivity of Tl-1212-type phase (Tl0.85Cr0.15)Sr2−xNaxCaCu2O7 (x = 0–0.30) is reported. The samples were prepared via the solid-state reaction method. X-ray diffraction patterns showed the presence of Tl-1212-type phase or Ca0.3Sr0.7CuO2 (CSCO) as a major or minor phase in the samples. The resistance versus temperature curves showed onset transition temperature, Tc-onset between 97 and 106 K and zero-resistance temperature, Tc-zero between 88 and 99 K. AC susceptibility measurement showed superconducting transition $${T_{{\text{c}}{\chi ^\prime }}}$$ between 89 and 98 K. The peak temperature, Tp, of the imaginary part of the susceptibility, χ″, was the highest for x = 0.02 sample (Tp = 96 K). The inter-grain critical current density, Jc, at Tp for x = 0 sample was Jc (Tp = 68 K) = 14 A cm−2 and for x = 0.02, 0.20 and 0.30 Jc (Tp) at 96, 96, and 88 K, respectively, is 19 A cm−2. Na substitution increased the grain size of the Tl-1212 samples. All Na-substituted samples showed higher transition temperature, enhanced critical current density, and improved inter-grain coupling compared with the non-substituted sample. This work showed that other than rare-earth elements, monovalent alkali metal such as Na could also be used to enhance the superconducting properties of the Tl-1212 phase.

A study of possible extra-framework cation ordering in Pbca leucite structures with stoichiometry RbCsX2+Si5O12 (X = Mg, Ni, Cd)

Leucites are silicate framework structures with some of the silicon framework cations partially replaced by divalent or trivalent cations. A monovalent extraframework alkali metal cation is also incorporated to balance the charges. We have previously reported Pbca leucite structures with the stoichiometries Cs2X2+Si5O12 (X = Mg, Mn, Co, Ni, Cu, Zn, Cd) and Rb2X2+Si5O12 (X = Mg, Mn, Ni, Cd). These orthorhombic leucite structures have all the silicon and non-silicon framework cations completely ordered onto separate crystallographic sites. This structure has five distinct Si sites and 1 X site; there are also two distinct sites for the extra-framework Cs or Rb. We have recently synthesised leucite analogues with two different extra-framework cations, these have the stoichiometry RbCsX2+Si5O12 (X = Mg, Ni, Cd). The initial Rietveld refinements assumed 50% Cs and 50% Rb on each of the two extra-framework cation sites. The refined structures for X = Ni and Cd have (within error limits) complete extra-framework cation site disorder. However, for X = Mg there is partial ordering of the extra-framework cation sites, the site occupancies are:- Cs1 0.37(3), Rb1 0.63(3), Cs2 0.63(3), Rb2 0.37(3).

Superlubricity and Antiwear Properties of In Situ-Formed Ionic Liquids at Ceramic Interfaces Induced by Tribochemical Reactions.

Several ionic liquids (ILs) are formed in situ with monovalent metal salts and ethylene glycol (EG). The macroscale superlubricity and antiwear properties of the ILs were studied between ceramic materials. Superlow coefficients of friction of less than 0.01 could be obtained for all ILs at silicon nitride (Si3N4) interfaces induced by tribochemical reactions. Notably, the IL ([Li(EG)]PF6) formed with LiPF6 and EG exhibited the greatest superlubricity and antiwear properties. The results of film thickness calculations and surface analysis showed that the lubrication regime during the superlubricity period was the mixed lubrication, and a composite tribochemical layer (composed of phosphates, fluorides, silica (SiO2), and ammonia-containing compounds), hydration layer, and fluid film contributed to superlubricity and wear protection. It was found that the small size of metal cations was beneficial for alleviating wear, and PF6- anions exhibited the smallest friction and best antiwear performance at Si3N4 interfaces. This work studied the lubricity and antiwear properties of ILs with different cations and anions, enriching the range of alternative ILs for macroscale superlubricity and low wear, and is of importance to engineering applications.

Structural diversity of the complexes of monovalent metal d10 ions with macrocyclic aggregates of iso-tellurazole N-oxides

Iso-tellurazole N-oxides yield a remarkable variety of structures with coinage-metal monocations.

Silicon nitride nanopore created by dielectric breakdown with a divalent cation: deceleration of translocation speed and identification of single nucleotides.

Nanopore DNA sequencing with a solid-state nanopore requires deceleration of the ultrafast translocation speed of single-stranded DNA (ssDNA). We report an unexpected phenomenon: controlled dielectric breakdown (CBD) with a divalent metal cation, especially Ca2+, provides a silicon nitride nanopore with the ability to decelerate ssDNA speed to 100 μs per base even after solution replacement. This speed is two orders of magnitude slower than that for CBD with a conventional monovalent metal cation. Temperature dependence experiments revealed that the enthalpic barrier for a nanopore created via CBD with Ca2+ is 25-30kBT, comparable to that of a biological nanopore. The slowing effect originates from the strong interaction between ssDNA and divalent cations, which were coated on the sidewall of the nanopore during the CBD process. In addition, we found that the nanopore created via CBD with Ca2+ can decelerate the speed of even single-nucleotide monomers, dNMPs, to 0.1-10 ms per base. The four single nucleotides could be statistically identified according to their blockade currents. Our approach is simple and practical because it simultaneously allows nanopore fabrication, ssDNA deceleration and the identification of nucleotide monomers.

Global Folding of a Na+ -Specific DNAzyme Studied by FRET.

Recently, a few RNA-cleaving DNAzymes have been isolated with excellent specificity for Na+ , and some of them contain a Na+ -binding aptamer. This metal recognition mechanism is different from that of most previously reported DNAzymes. When using 2-aminopurine (2AP) as a probe, interesting local folding induced by Na+ was recently observed. In this work, FRET was used to probe the global folding of the Ce13d DNAzyme; one of the Na+ -specific DNAzymes. FRET pairs were at different locations, which yielded a total of five constructs to probe the three-way junction structure with a large loop. With endlabeled DNAzymes, the global structure appears to be quite rigid with little folding upon adding up to 200 mm monovalent metal ions, although some minor differences were observed between Li+ , Na+ , and K+ . This lack of significant conformational change is also consistent with circular dichroism spectroscopy data. The loop was then labeled with an internal tetramethylrhodamine fluorophore at the G14 position, and its cleavage activity was partially retained. A clear Na+ -dependent folding was observed with spectral crossover. From a biosensing standpoint, global folding based sensors are unlikely to work due to the overall rigid structure of the DNAzyme. Therefore, the best way to use this DNAzyme to discriminate Na+ from K+ is based on cleavage activity, followed by probing local folding, whereas global folding is the least effective for metal discrimination.

Non-molecular monovalent metal organophosphonates and diphosphonates

The solid state chemistry of non-molecular monovalent metal organophosphonates and diphosphonates is relatively new and evolving research arena. The syntheses and structural characterization of about fifty such compounds are reported in the literature. They are a variety of mono- and di-phosphonates of inorganic monovalent cations, namely, alkali metal, thallium, cuprous, silver and mercurous ions and also ammonium ions. They have x:2 (x = 1–4) ratios of metal to phosphonate moieties and possess mostly layered and pillared-layered structures. Some of them function as solid Brönsted acids and exhibit proton conductivity.

Landau diamagnetic response in metals as a Fermi surface effect

It is demonstrated that the Landau diamagnetism of the free electron gas and a monovalent metal can be considered as a Fermi surface effect. Only relatively small number of electron states close to the Fermi surface are diamagnetically active whereas the majority of the electron states inside the Fermi surface are diamagnetically inert. This partitioning of the occupied electron states is driven by the structure of Landau levels, around which one can introduce magnetic tubes in the reciprocal space. Completely filled magnetic tubes do not change their energy in an applied magnetic field, and only partially occupied magnetic tubes in the neighborhood of the Fermi surface exhibit a diamagnetic response. Using this partitioning of the occupied electron states we derive a general expression for the steady diamagnetic susceptibility, for calculation of which one needs to know the shape of the Fermi surface and the energy gradient on it. The method is applied to alkali metals, whose Fermi surfaces and energy gradients have been obtained from ab initio band structure calculations. It has been found that the Landau diamagnetic susceptibility is anisotropic depending on the direction of the applied magnetic field in respect to the Fermi surface. This effect is more pronounced for Li and Cs, whose Fermi surfaces show a noticeable deformation from the spherical shape. The method opens a new route for ab initio calculations of the Landau diamagnetism of metals or intermetallic compounds. In the case of free electron gas it is shown that this approach also fully describes the oscillatory de Haas - van Alphen part of the diamagnetic susceptibility. Small oscillations of the Fermi energy found in the model are caused by redistribution (inflow or outflow) of electrons from the equatorial region of the Fermi surface.

Enhancement of the quinoline separation from pyridine: Study on competitive adsorption kinetics in foam fractionation with salt

Large amount of N-heterocycles are produced by various industries and most of them are extremely harmful toxicants. In the current work, the selective removal of quinoline and pyridine from their binary diluted aqueous solution by using a novel technology of foam fractionation with salt was investigated. In continuous foam fractionation, quinoline and pyridine could exert competitive adsorption when sodium dodecyl sulfate (SDS) was used as the collector. The influence mechanism of the salts on the competitive adsorption of quinoline and pyridine were elaborated through adding monovalent metal salts (NaCl and KCl) and bivalent metal salts (CaCl2 and MgCl2). In the stripping mode of foam fractionation with or without KCl, the competitive adsorption between quinoline and pyridine were determined by using Thomas adsorption kinetics models. Finally, a novel two-stage foam fractionation technology was developed to successively remove of quinoline and pyridine from their binary aqueous solution. The removal percentage and purity of quinoline in the first stage were 90.50% and 89.57%, respectively. After a second stage foam fractionation, the removal percentage of pyridine and the total removal percentage of quinoline could reach as high as 94.72% and 97.38%, respectively.

Application of atomic force microscopy-based single molecule force spectroscopy in G-quadruplex studies

Telomere plays a crucial role in the physiological and pathological processes of cells. At the end of the telomere, the single-stranded DNA repeat sequence rich in guanine (G) folds in the presence of monovalent metal ions such as Na+ or K+ to form a G-quadruplex structure. This structure can not be extended by telomerase and inhibits the activity of telomerase, thus becoming a potential anticancer target. Stabilizing the formation of DNA G-quadruplex structures by small molecule ligands has become a new strategy for designing many anticancer drugs, and studying the interaction strength of these small molecule ligands with G-quadruplex is thus of particular importance for screening highly effective anticancer drugs. Single molecule force spectroscopy enables direct measurement of the interaction between small molecule ligands and G-quadruplexes. This review highlights the advances of single-molecule force spectroscopy based on atomic force microscopy in the study of the G quadruplex structure and its interaction with small molecule ligands, and summarizes the application and development trend of single molecule force spectrum technology in G quadruplex.

Synthesis of pyrenocrown ethers as fluorescent sensors and their recognition ability of metal ions

Novel pyrenocrown ethers having different ring sizes were synthesized, and change of fluorescence spectra was investigated upon addition of metal ions. By the addition of Li+ and Na+ ions to 10–2 M CH3CN solutions of pyreno-15-crown-5 ether (3), excimer/monomer ratio decreased with 3–4 nm longer wavelength shift. Upon addition of Mg2+ and Ba2+ ions to the solution of 3, excimer emission increased with 11–25 nm longer wavelength shift. On the other hand, when these metal ions were added to pyreno-18-crown-6 ether (4), the excimer/monomer ratio monotonically decreased. Addition of Pb2+ ion to solutions of 3 and 4 caused dramatic decrease of both monomer and excimer fluorescence intensity. Inspection of these results indicates that 3 forms 1:1 and 2:1 complexes with respective monovalent and divalent metal ions, whereas 4 forms 1:1 complexes with both monovalent and divalent metal ions. The 1:1 complexes of 3 with monovalent and divalent metal ions emit respective excimer and monomer fluorescence, whereas the 2:1 complexes of 3 emit excimer fluorescence. Monotonical decrease of fluorescence intensity by the addition Pb2+ is attributed to heavy atom effect.

Polyacrylates in the presence of an extraordinary monovalent cation-Solution behavior and metal nanoparticle formation.

Sodium polyacrylate (NaPA) in dilute aqueous solution at an ionic strength of [NaNO3] = 0.01M establishes a rich phase behavior in the presence of low amounts of silver cations, which were introduced at a few millimoles or less by replacing the corresponding amount of Na+ cations. Beyond an extremely low level of Ag+ cations, anionic PA chains aggregate. By increasing the concentration of Ag+, the aggregates become denser and keep on growing without limit. Once a certain range of [Ag+] is reached, the instantaneously formed dense aggregates remain stable. Irradiation of the PA aggregate solutions with UV-light induces formation of silver nanoparticles (Ag-Nps). Based on a combination of UV-vis spectroscopy, light scattering, transmission electron microscopy, and small angle neutron scattering, the mechanism of this NaPA assisted formation of Ag-Nps is studied. One focus of the study is lying on the effect of the two different solution states of dense aggregates, corresponding to the unstable growing AgPA aggregates and to the stable AgPA aggregates and another focus is aiming at the characterisation of the morphology of the generated hybrid particles composed of Ag-Nps and hosting PA chains.

Refined Alkali Metal Ion Parameters for the OPC Water Model

Using all‐atom molecular dynamics simulations with Joung–Cheatham ion parameters and the OPC water model, the osmotic pressure values of monovalent alkali metal chloride solutions (KCl and NaCl) were calculated and compared to experimental values. The simulated osmotic pressure data were overestimated at high concentrations. To close the gap between simulation and experiment, we attempted to modify the Lennard–Jones interaction parameters of the cation–water oxygen pairs explicitly using the unequal Lorentz–Berthelot combination rule, such that experimental osmotic pressure values for a range of concentrations were well reproduced. These novel ion parameters could be potentially beneficial to simulation studies of G‐quadruplex DNA molecules, where ions play a key role in their folding process.