Concentration Of KBr Research Articles

Controlling the size of silver nanowires through one-pot polyol method with trace halide and its effect on kinetic process

Silver nanowires (Ag NWs) of different aspect ratios have emerged as promising materials toward manufacturing optoelectronic devices for various applications. We report herein a facile, polyol-based one-pot strategy that has allowed us to synthesize Ag NWs ranging in length from 4–7 to 20–34 µm and diameter of 49 ± 10 nm, by simply controlling the concentration of MnCl2 and KBr. The kinetics of Ag+ converted to Ag0 have been thoroughly investigated, revealing that the introduction of MnCl2 and KBr plays a key role toward the growing of Ag NWs with a high aspect ratio. Cl− and Br− would significantly influence the reaction rate of Ag+ as well as the reaction activation energy, which controls the nucleation, seeding and growth process of Ag NWs. In addition, MnCl2 and KBr promote an efficient conversion of Ag+ and thus, productivity of Ag NWs up to 90% and 70%, respectively. Without further post-treatment, the conductive film made of this Ag NWs on glass had a sheet resistance of 24 Ω/sq and the specular transmittance of it were 92.4%, which proved it is highly potential for optoelectronic applications.

Conservative tracer bromide inhibits pesticide mineralisation in soil

Bromide is a conservative tracer that is often applied with non-conservative solutes such as pesticides to estimate their retardation in the soil. It has been applied in concentrations of up to 250 g Br L−1, levels at which the growth of single-celled organisms can be inhibited. Bromide applications may therefore affect the biodegradation of non-conservative solutes in soil.The present study investigated the effect of potassium bromide (KBr) on the mineralisation of three pesticides – glyphosate, MCPA and metribuzin – in four agricultural A-horizon soils. KBr was added to soil microcosms at concentrations of 0, 0.5, 2.5 and 5 g Br− L−1 in the soil solution. The study concluded that KBr had a negative effect on pesticide mineralisation. The inhibitory effect varied depending on the KBr concentration, the type of pesticide and the type of soil. Furthermore, 16 S amplicon sequencing revealed that the KBr treatment generally reduced the abundance of bacteroidetes and proteobacteria on both an RNA and DNA level.Therefore, in order to reduce the effect of KBr on the soil bacterial community and consequently also on xenobiotic degradation, it is recommended that KBr be applied in a concentration that does not exceed 0.5 g Br− L−1 in the soil water.

Parameterization of Lamellar Repeat Spacings for Lipid Bilayers in Binary Salt Mixtures

For lipids that form multilamellar vesicles, the interlamellar equilibrium spacing (D-spacing) depends on the chemical composition of the aqueous solution. For example, the D-spacing of phosphatidylcholine lipids increases with increasing KCl or KBr concentrations. However, the variation of D-spacing is specific to each salt. One can then consider binary solutions in which the fraction of ions is varied at constant total concentration. The question is whether the resulting D-spacing variation follows any general functional form when plotted versus fractional composition. We show that general variations of this kind can be parameterized with simple power functions that reflect the cooperativity or competition of ion types in binary mixtures.

Interaction of hexadecylpyridinium bromide with glycine in aqueous medium using the Krafft temperature from conductivity measurement

Conductivity measurements were employed to investigate Kraft temperature (TK) of aqueous solution of hexadecylpyridinium bromide (HPyBr) and HPyBr+glycine with added counter-ions. The pseudophase ion exchange model was adopted for HPyBr in pure water, glycine (Gly) and potassium bromide (KBr). The TK values for HPyBr increase with the increase in concentration of Gly and KBr. However, the experimental results show that the degree of counter-ion dissociation or ionization (α) remains nearly constant as the total surfactant concentration or counter-ion concentrations of salt are varied at the slower rate of micellar growth. Although the (α) is dependent on micellar shapes and changes as the micellar shape changes. The TK measurements for ionic micelles can be used to estimate counter-ion dissociation (α). The TK increase with increase in the counter-ion concentration because the solubility of surfactant is reduced at faster rate than critical micellar concentration (CMC). Kraft temperature measurements were employed to find the interaction between HPyBr and Glycine.

Bromide-Assisted Anisotropic Growth of Gold Nanoparticles as Substrates for Surface-Enhanced Raman Scattering

We report herein a one-step synthesis of gold nanoparticles (Au NPs) of various shapes such as triangles, hexagons, and semispheres, using 5-hydroxyindoleacetic acid (5-HIAA) as the reducing agent in the presence of potassium bromide (KBr). Anisotropic Au NPs have received ever-increasing attention in various areas of research due to their unique physical and chemical properties. Numerous synthetic methods involving either top-down or bottom-up approaches have been developed to synthesize Au NPs with deliberately varied shapes, sizes, and configurations; however, the production of templateless, seedless, and surfactant-free singular-shaped anisotropic Au NPs remains a significant challenge. The concentrations of hydrogen tetrachloroaurate (HAuCl4), 5-HIAA, and KBr, as well as the reaction temperature, were found to influence the resulting product morphology. A detailed characterization of the resulting Au NPs was performed using ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy. The as-prepared Au NPs exhibited excellent surface-enhanced Raman scattering (SERS) properties, which make them very attractive for the development of SERS-based chemical and biological sensors.

Sub 30 nm silver nanowire synthesized using KBr as co-nucleant through one-pot polyol method for optoelectronic applications

Ultrathin, high aspect ratio silver nanowires synthesized in solution has attracted significant attention for fabricating optoelectronic devices with good properties and relatively low cost, and has been the most promising material to replace ITO. In this paper, a novel method is proposed to synthesis ultrathin nanowires through facile one-pot polyol method using KBr as a co-nucleant to NaCl. The effect of three common nucleants NaCl, FeCl3 and KBr on nucleation rate and product size were well studied. KBr is found to be beneficial for decreasing product size but unable to generate nanowires effectively alone. By adjusting the exact concentration of KBr, silver nanowires with an average length of 21μm and average diameter of 26nm could be synthesized conveniently. Conductive film prepared using these nanowires had transmittance over 90% and sheet resistance about 10Ω/□, which is better than the average level of common ITO-glass and highly potential to be applied in optoelectronic applications.

Direct Synthesis of Palladium Nanocrystals in Aqueous Solution with Systematic Shape Evolution.

Palladium octahedra, truncated octahedra, cuboctahedra, truncated cubes, and nanocubes with sizes of tens of nanometers have been synthesized in an aqueous mixture of H2PdCl4 solution, cetyltrimethylammonium chloride (CTAC) surfactant, KBr solution, dilute KI solution, and ascorbic acid solution at 35 °C for 30 min. By tuning the amount of dilute KBr solution introduced, particle shape control can be achieved. Adjusting the volumes of the Pd precursor and KBr solutions added, smaller and larger Pd nanocrystals were obtained with excellent shape control. Extensive structural and optical characterization of these nanocrystals has been performed. Two absorption bands in the ultraviolet region can be discerned for these Pd nanocrystals. Concave Pd cubes can also be prepared. Pd cubes were found to grow at a faster rate than that for the formation of octahedra. The concentrations of KBr and KI in the solution are so low that spectral shifts were not detected upon their addition to the solution. The Pd nanocrystals can readily be used for various applications after simple removal of surfactant.

Ultrasound-Assisted Fabrication of AgBr/Ag3PO4/TiO2 Nanorod Heterostructure on Ti Mesh

TiO2 nanorod (TNR) deposited by AgBr/Ag3PO4 nanoparticles was fabricated on Ti mesh substrate through ultrasound-assisted successive ionic layer adsorption and reaction technology. It was revealed that the ultrasound-assisted process is helpful in ensuring uniform deposition of Ag3PO4 on the surface of TNR and in inhibiting the accumulation of Ag3PO4 nanoparticles. The concentration of KBr and the adsorption duration strongly influence the deposition of AgBr. The enhanced photocatalytic activity of Ag3PO4/TNR toward methyl orange compared to that of pure TNR is attributed to the enhanced adsorption ability of visible light and to the efficient charge carrier separation owing to the surface plasmon resonance (SPR) effect of Ag3PO4/Ag/TNR system. The further enhanced photocatalytic activity of the heterostructured AgBr/Ag3PO4/TNR is attributed to the SPR effect resulting from the evolution of AgBr/Ag/Ag3PO4/TNR heterostructures and the synergistic energy band structure of Ag3PO4, AgBr, and TNR.

The Polyelectrolyte Complex/Coacervate Continuum

Stoichiometric polyelectrolyte complexes (PECs) of the strong polyelectrolytes poly(styrenesulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA) were dissociated and dissolved in aqueous KBr. Water was added to dilute the salt, allowing polyelectrolytes to reassociate. After appropriate equilibration, these mixtures yielded compositions spanning complexes (solid) to coacervates (elastic liquid) to dissolved solutions with increasing [KBr]. These compositions were defined by a ternary polymer/water/salt phase diagram. For coacervates, transient microphase separation could be induced by a small departure from equilibration temperature. A boundary between complex and coacervate states was defined by the crossover point between loss and storage modulus. Salt ions within the complex/coacervate were identified as either ion paired with polyelectrolytes (“doping”) or unassociated. The fraction of ion pair cross-links between polyelectrolytes as a function of KBr concentration was used to account for viscosity using a model of “sticky” reptation.

Thermodynamic Studies of Aqueous Solutions of 2,2,2-Cryptand at 298.15 K: Enthalpy–Entropy Compensation, Partial Entropies, and Complexation with K+ Ions

The osmotic coefficient measurements for binary aqueous solutions of 2,2,2-cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8] hexacosane) in the concentration range of ~0.009 to ~0.24 mol·kg(-1) and in ternary aqueous solutions containing a fixed concentration of 2,2,2-cryptand of ~0.1 mol·kg(-1) with varying concentration of KBr (~0.06 to ~0.16 mol·kg(-1)) have been reported at 298.15 K. The diamine gets hydrolyzed in aqueous solutions and needs proper approach to obtain meaningful thermodynamic properties. The measured osmotic coefficient values are corrected for hydrolysis and are used to determine the solvent activity and mean ionic activity coefficients of solute as a function of concentration. Strong ion-pair formation is observed, and the ion-pair dissociation constant for the species [CrptH](+)[OH(-)] is reported. The excess and mixing thermodynamic properties (Gibbs free energy, enthalpy, and entropy changes) have been obtained using the activity data from this study and the heat data reported in the literature. Further, the data are utilized to compute the partial molal entropies of solvent and solute at finite as well as infinite dilution of 2,2,2-cryptand in water. The concentration dependent non-linear enthalpy-entropy compensation effect has been observed for the studied system, and the compensation temperature along with entropic parameter are reported. Using solute activity coefficient data in ternary solutions, the transfer Gibbs free energies for transfer of the cryptand from water to aqueous KBr as well as transfer of KBr from water to aqueous cryptand were obtained and utilized to obtain the salting constant (ks) and thermodynamic equilibrium constant (log K) values for the complex (2,2,2-cryptand:K(+)) at 298.15 K. The value of log K = 5.8 ± 0.1 obtained in this work is found to be in good agreement with that reported by Lehn and Sauvage. The standard molar entropy for complexation is also estimated for the 2,2,2-cryptand-KBr complex in aqueous medium.

Volumetric Studies of 2,2,2-Cryptand in Aqueous and Aqueous KBr Solutions at 298.15 K: An Example Involving Solvent-Induced Hydrophilic and Hydrophobic Interactions

Density measurements of good precision are reported for aqueous and aqueous salt (KBr) solutions containing 2,2,2-cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) (~0.009 to ~0.24 mol·kg−1) for the binary systems and for the ternary system with ~0.1 mol·kg−1 2,2,2-cryptand and varying KBr concentrations (~0.06 to ~ 0.16 mol·kg−1) at 298.15 K. The density data have been used to study the variation of apparent molar volume (\( \varphi_{V} \)) of 2,2,2-cryptand and of KBr as a function of concentration. 2,2,2-Cryptand is a diamine and hence it is hydrolyzed in aqueous solutions and needs an appropriate methodology to obtain meaningful thermodynamic properties. We have adopted a method of hydrolysis correction developed initially by Cabani et al. and later by Kaulgud et al. to analyze our volumetric data for the aqueous solutions. The method is described and we were successful in obtaining the limiting partial molar volume of the bare (free) cryptand in water at 298.15 K. Volumes of ionization as well as volumes of complexation (with KBr) are calculated. Estimations of the apparent molar volume of 2,2,2-cryptand in CCl4 are also reported. There is a loss in volume for the cryptand on transferring it from CCl4 to water. The volume changes due to ionization for the cryptand in water are calculated to be –20.5 and –0.6 cm3·mol−1 for the mono- and di-protonation equilibria respectively, while the volume of complexation for K+ is +24.5 cm3·mol−1. The results are discussed in terms of conformation, protonation equilibria and selective encapsulation of K+ ions in cryptand cavities. The solution volume properties seem to depend upon water–solute interaction as well on the solute–solute association because of hydrophobic interactions caused by lowering of the charge density on formation of cryptand-K+ species in solution.

Adsorption of Cr(III) and speciation of chromium in aqueous solution using Ambrosia beetle-generated acacia polycantha frass

Acacia polycantha frass (APF) generated by boring activity of Ambrosia beetles was investigated using a batch technique for its potential to adsorb Cr(III) ions from aqueous solution. Studies were carried out to determine the effect of pH, adsorbent dose, and KBr concentration on the sorption behavior Cr(III) on the adsorbent. The adsorption process was found to be highly dependent on solution pH with maximum removal occurring at pH 11. Thermodynamic studies indicated that the sorption process was exothermic and spontaneous. Adsorption recoveries of up to 75 and 95% for a 5 mgL-1 solution were obtained for untreated and acid-treated APF respectively at room temperature. In all experiments the acid-treated adsorbent showed an apparently higher metal uptake than the untreated one. Reduction of Cr(VI) to Cr(III) in synthetic solution using hydroxylamine prior to adsorption preconcentration showed potential for studying chromium speciation. Key words: Adsorption, entropy of activation, enthalpy of activation, chromium, speciation, acacia polycantha frass.

Optimization of Activated Carbon Sulfurization to Reach Adsorbent with the Highest Capacity for Mercury Adsorption

This work deals with the use of elemental sulfur immobilized on the activated carbon surface, as an active phase to enhance the sorbent's mercury adsorption capacity. The sulfurization procedure was optimized, and the influence of two factors (temperature and initial ratio of sulfur to carbon), on the final properties and mercury adsorption capacities of the adsorbents was investigated. The sulfurized adsorbents were characterized using CHNS/O elemental analysis, surface area and porosimetry, FT-IR spectroscopy, SEM-EDS, and pHpzc measurement. A series of batch studies were also conducted to delineate the effect of contact time, initial pH, solution temperature, and initial mercury concentration on the adsorption capacity of the adsorbents. Furthermore, attempts were made to desorb mercury from the metal loaded adsorbents using various concentrations of KCl, KBr and KI solutions.

Aqueous‐Phase Synthesis of Single‐Crystal Pd Seeds 3 nm in Diameter and Their Use for the Growth of Pd Nanocrystals with Different Shapes

This article describes an aqueous method for the synthesis of Pd seeds with a single-crystal structure and a uniform diameter of 3 nm and their use for the growth of Pd nanocrystals with a variety of shapes. We have also investigated the effects of a number of parameters, including the temperature, reducing power of the reductant, and capping agent on the reduction rate of a Pd precursor, and thus the final size, size distribution, and morphology of the Pd seeds. By taking advantage of the coordination effect of Br(-) ions with Pd(2+) ions and their selective adsorption on the Pd(100) surface, Pd nanocrystals with a number of distinct shapes could be conveniently produced by varying the concentration of KBr added into the growth solution. This work provides a general and facile method for the green synthesis of Pd nanocrystals with controlled shapes, especially for the preparation of Pd nanocrystals with sizes in the sub-10 nm regime.

Densities and Refractive Indices of Potassium Salt Solutions in Binary Mixture of Different Compositions

Densities and refractive indices of solutions of different concentrations of potassium salts, namely, KCl, KBr, and KI in 10%, 20%, 40%, and 60% (v/v) ethanol-water mixture were measured at 303.15 K. Specific refractions () and molar refractions () have been estimated from measured refractive indices and densities of solutions and interpreted in terms of interactions in salt solutions. Refractive indices increased with an increase in percentage of ethanol as well as with concentrations of potassium salts for given composition of binary solvent mixture.

A mesocosm study on biogeochemical role of rice paddy soils in controlling water chemistry and nitrate attenuation during infiltration

Rice paddies typically lie near surface water and play an important role in controlling surface water quality. To evaluate the role of rice paddy soils in determining the fate of nitrate, three different mesocosms were used in this study. Two mesocosms (M1 and M2) were covered with a rice paddy soil and the other mesocosm (M3) with a dry field soil. Rice was harvested in two mesocosms (M2 and M3) during the growing season. An amended groundwater containing high concentrations of NaNO3 and KBr was repeatedly applied to the mesocosms to infiltrate under saturated conditions. Under these experimental conditions, we monitored time-series variations of pH, Eh, DO, DOC, alkalinity and the concentrations of nitrate, bromide (as a conservative tracer) and dissolved Fe and Mn in the inflow water (flooding water just below the water/soil interface) and outflow water (drained water after infiltration through mesocosm materials) for about two months to examine the fate of nitrate. The Eh and DO data in all mesocosms showed that strong reducing conditions were rapidly and efficiently established in infiltrating waters. In the mesocosms (M1 and M2) with a rice paddy soil, dramatic decreases of nitrate concentrations were observed both in the inflow and outflow waters. Nitrate removal from the inflow waters occurs due to immobilization, while nitrate is removed during infiltration through mesocosm materials by denitrification coupled with organic carbon oxidation, as is indicated by the increases in alkalinity and dissolved Fe and Mn. Interestingly, there was no significant difference in the nitrate removal capacity between M1 (no cultivation) and M2 (rice cropping). In contrast to M1 and M2, there was no large decrease of nitrate concentrations in the inflow waters of M3 (rice cropping with a dry field soil). In addition, nitrate concentrations in the outflow waters of M3 rose steeply again after 30 days, in concert with increasing Eh and decreasing alkalinity. These observations in M3 are attributed to both the low organic carbon content and the generation of large pores by root growth, resulting in the rapid loss of denitrification capacity. This study implies that rice paddy fields play an important role in controlling (attenuate) agricultural nitrate in groundwater discharging to streams; thus, the extent of rice paddies should be carefully considered when evaluating the nitrate loads to streams via groundwater flow.

Controllable Synthesis and Acetylene Hydrogenation Performance of Supported Pd Nanowire and Cuboctahedron Catalysts

Supported Pd nanowire and cuboctahedron catalysts have been synthesized in an ethylene glycol–poly(vinylpyrrolidone)–KBr system using a precipitation–reduction method. KBr plays a critical role in controlling the morphology of Pd: with a variety of relatively low KBr concentrations, Pd nanowires with different lengths were obtained, but after adding sufficient KBr, shape evolution from nanowires to cuboctahedrons was observed. HRTEM images showed that the twisted Pd nanowires were actually composed of primary cuboctahedrons. Furthermore, lattice distortion was observed at interfacial regions, and the number of crystal boundaries increased with increasing length of the nanowires. The catalytic performance of the Pd materials was investigated in the selective hydrogenation of acetylene. The activities of the Pd nanowire catalysts were significantly higher than those of the cuboctahedron catalyst and gradually increased with the increasing number of crystal boundaries, indicating that the defect sites at crystal boundaries are more active owing to the exposure of larger numbers of Pd atoms. However, higher activity resulted in excessive hydrogenation and a decrease in ethylene selectivity. Therefore, the Pd cuboctahedron catalyst possessed higher selectivity. The relationship between crystal boundaries and catalytic performance was quantified, and the catalytic activity was found to increase linearly with an increasing number of crystal boundaries, whereas the trend in the selectivity was the reverse.

Effect of Temperature and Concentration of KBr or KNO3 on the Volumetric and Transport Properties of Aqueous Solutions of Tripotassium Citrate

Volumetric and transport properties of ternary aqueous solutions of tripotassium citrate in (KBr or KNO3) + water have been determined in the different molality ranges of KBr and KNO3 [(0.2, 0.3, 0.4, 0.5, 0.6, and 0.7) mol·kg–1] at T = (293.15 to 313.15) K. The apparent molar volume and apparent molar isentropic compressibility have been calculated from the measured density and speed of sound data for ternary aqueous solutions of tripotassium citrate. The apparent molar volume and apparent molar isentropic compressibility of ternary aqueous solutions of tripotassium citrate + (KBr or KNO3) have been correlated with the Redlich–Mayer equation. Viscosity values of ternary aqueous solutions of tripotassium citrate + (KBr or KNO3) have been fitted with the Jones–Dole equation. The results obtained have been interpreted in elucidating the effect of KBr or KNO3 and temperature on the interaction of tripotassium citrate with water. Furthermore, density and viscosity values of ternary aqueous solutions of tripot...

Side‐chain polypseudorotaxanes by threading cucurbit[7]uril onto poly‐N‐n‐butyl‐N′‐(4‐vinylbenzyl)‐4,4′‐bipyridinium bromide chloride: Synthesis, characterization, and properties

AbstractA novel side‐chain polypseudorotaxanes P4VBVBu/CB[7] was synthesized from poly‐N‐n‐butyl‐N′‐(4‐vinylbenzyl)‐4,4′‐bipyridinium bromide chloride (P4VBVBu) and cucurbit [7]uril (CB[7]) in water by simple stirring at room temperature. CB[7] beads are localized on viologen units in side chains of polypseudorotaxanes as shown by 1H NMR, IR, XRD, and UV–vis studies, and it is considered that the hydrophobic and charge‐dipole interactions are the driving forces. TGA data show that thermal stability of the polypseudorotaxanes increases with the adding of CB[7] threaded. DLS data show that P4VBVBu and CB[7] could form polypseudorotaxanes, and the average hydrodynamic radius of the polypseudorotaxanes increases with increasing the concentration of CB[7]. The typical cyclic voltammograms indicate that the oxidation reduction characteristic of P4VBVBu is remarkably affected by the addition of CB[7] because of the formation of polypseudorotaxanes and the shielding effects of CB[7] threaded on the viologen units of polypseudorotaxanes. With the increase of the concentration of KBr or K2SO4, the formation of the polypseudorotaxanes was inhibited due to the shielding effects of both Br− or SO to viologen ion and K+ to CB[7] by UV–vis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2135–2142, 2010

Kinetic investigation of aquation of some Fe(II) Schiff base amino acid complexes

Kinetics of aquation of some Fe(II) Schiff base amino acid complexes was followed spectrophotometrically. The Schiff base ligands were derived from salicylaldehyde and isoleucine, leucine, serine, methionine, tryptophan, or histidine. The reaction was studied in aqueous media, aqua–propanol mixtures, and in the presence of different concentrations of KBr. Moreover, the activation parameters were calculated and discussed for structures and other physical properties observed. The reaction was acid catalyzed and the general rate equation was suggested as follows: rate = kobs [complex], where kobs = k2 [H+]. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 372–379, 2010