Simple Inorganic Salts Research Articles

Coarse-Grained Molecular Dynamics Simulations of the Sphere to Rod Transition in Surfactant Micelles

Surfactant molecules self-assemble in aqueous solutions to form various micellar structures such as spheres, rods, or lamellae. Although phase transitions in surfactant solutions have been studied experimentally, their molecular mechanisms are still not well understood. In this work, we show that molecular dynamics (MD) simulations using the coarse-grained (CG) MARTINI force field and explicit CG solvent, validated against atomistic MD studies, can accurately represent micellar assemblies of cetyltrimethylammonium chloride (CTAC). The effect of salt on micellar structures is studied for aromatic anionic salts, e.g., sodium salicylate, and simple inorganic salts, e.g., sodium chloride. Above a threshold concentration, sodium salicylate induces a sphere to rod transition in the micelle. CG MD simulations are shown to capture the dynamics of this shape transition and support a mechanism based on the reduction in the micelle-water interfacial tension induced by the adsorption of the amphiphilic salicylate ions. At the threshold salt concentration, the interface is nearly saturated with adsorbed salicylate ions. Predictions of the effect of salt on the micelle structure in different CG solvent models, namely, single-site standard water and three-site polarizable water, show qualitative agreement. This suggests that phase transitions in aqueous micelle solutions could be investigated by using standard CG water models which allow for 3 orders of magnitude reduction in the computational time as compared to that required for atomistic MD simulations.

Synthesis of Single Crystal Metal Sulfide Nanowires and Nanowire Arrays by Chemical Precipitation in Templates

Single crystal metal sulfide nanowires and nanowire arrays were synthesized by chemical precipitation reaction in the channels of anodic aluminum oxide templates under ambient conditions with simple inorganic salts as precursors. Aligned metal sulfide arrays were achieved by dissolving the template. This template-directed synthesis yielded well-defined nanowires of varied lengths and diameters for almost all precursors. The crystal quality of metal sulfide nanowires was concentration-dependent, high single crystal nanowires were achieved at low concentrations.

Guggenheim’s Rule and the Enthalpy of Vaporization of Simple and Polar Fluids, Molten Salts, and Room Temperature Ionic Liquids

One of Guggenheim's many corresponding-states rules for simple fluids implies that the molar enthalpy of vaporization (determined at the temperature at which the pressure reaches 1/50th of its critical value, which approximately coincides with the normal boiling point) divided by the critical temperature has a value of roughly 5.2R, where R is the universal gas constant. For more complex fluids, such as strongly polar and ionic fluids, one must expect deviations from Guggenheim's rule. Such a deviation has far-reaching consequences for other empirical rules related to the vaporization of fluids, namely Guldberg's rule and Trouton's rule. We evaluate these characteristic quantities for simple fluids, polar fluids, hydrogen-bonding fluids, simple inorganic molten salts, and room temperature ionic liquids (RTILs). For the ionic fluids, the critical parameters are not accessible to direct experimental observation; therefore, suitable extrapolation schemes have to be applied. For the RTILs [1-n-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides, where the alkyl chain is ethyl, butyl, hexyl, or octyl], the critical temperature is estimated by extrapolating the surface tension to zero using Guggenheim's and Eotvos' rules; the critical density is obtained using the linear-diameter rule. It is shown that the RTILs adhere to Guggenheim's master curve for the reduced surface tension of simple and moderately polar fluids, but that they deviate significantly from his rule for the reduced enthalpy of vaporization of simple fluids. Consequences for evaluating the Trouton constant of RTILs, the value of which has been discussed controversially in the literature, are indicated.

Human pharmacology of hydrogen sulfide, putative gaseous mediator

Nitric oxide (NO), the first low molecular weight inorganic gas to be established as a biological mediator, had previously been regarded merely as a toxic pollutant. It was joined, similarly implausibly to the minds of a generation brought up with the hazards of coal gas as domestic heating, by carbon monoxide (CO) – potentially lethal as an exhaust gas, but also formed in mammalian tissues together with biliverdin by inducible and/ or constitutive forms of haem oxygenase, and implicated subsequently as a signalling molecule, not only in the central nervous system (especially olfactory pathways) and cardiovascular system but also in respiratory, gastrointestinal, endocrine and reproductive functions [1]. Hydrogen sulfide (H2S) was known to generations of schoolboys in one biological context – as the source of the odour of rotten eggs – but even so, the proposal in the early 2000s [2] that it too is a gaseous mediator was met with some scepticism.The toxicology of H2S had previously been studied [3], and actions on enzymes including monoamine oxidase and carbonic anhydrase identified, but more recent work has also shown a rich and diverse pharmacology consistent with functions as a signalling molecule under physiological conditions. It has also been implicated both as a harmful and also as a protective factor in the pathophysiology of a range of experimental models of disease [4], and its therapeutic potential has attracted comment [5]. There are striking similarities between these three gaseous mediators, as well as contrasts, that underlie complex and imperfectly understood functional interactions between them. All three are highly diffusible labile molecules that are rapidly eliminated from the body: NO as nitrite and nitrate in urine as well as NO in exhaled air; CO in exhaled air; H2S as thiosulfate, sulfite and sulfate in urine (Figure 1) as well as (it emerges, see below) in exhaled breath. All three react with haemoglobin, yielding methaemoglobin or nitrosylhaemoglobin (respectively inactive and active metabolites) from distinct reactions of haem and of globin with NO; carboxyhaemoglobin or sulfhaemoglobin from CO or H2S. All three affect cellular energetics via actions on cytochrome c oxidase. All three have vasodilator effects, and all have anti-inflammatory and cytoprotective effects at low concentrations in contrast to causing cellular injury at higher concentrations – consistent with Paracelsus’s aphorism that the distinction between drugs and poisons is determined exclusively by the dose.

Aerosol Synthesis of Porous Particles Using Simple Salts as a Pore Template

Ultrasonic spray pyrolysis has been used as a facile aerosol route to macroporous SiO(2) particles using simple inorganic salts as a pore template and colloidal SiO(2) as building blocks to the larger porous particles. As we found, the use of template salts with low melting points was vital to macroporous particle synthesis, as a dynamic droplet phase can be maintained throughout product formation. Otherwise, relatively compact particles are produced. Significantly, this approach avoids the need for post-isolation elimination of the template, instead permitting aqueous removal during product collection. Produced particles were characterized by SEM, TEM, and surface area and pore size measurements, while the influence of the selected salts on the reactivity between the building block SiO(2) colloids is discussed.

The Control of Solution Composition on Ligand-Promoted Dissolution: DTPA−Barite Interactions

The mechanism and kinetics of barite (BaSO4) dissolution in the presence of diethylenetriaminepentaacetic acid (DTPA) has been investigated as a function of solution composition. The dependence of the reaction rate on the background electrolyte present in solution (NaCl or KCl) and on the concentration of the chelating agent (DTPA) is explained by considering chemical speciation and conformational changes of DTPA in the aqueous phase. A mechanism for the promotion of the dissolution reaction by dissociated ionic species is proposed for an organic polyelectrolyte with a strong affinity to Ba2+ ions (DTPA) and for simple inorganic electrolytes. The mobilization of ions from the crystal structure is suggested to be induced mainly by water molecules and not by specific additive−surface interactions. Recognition of the correlation between solution composition, ion−water interactions (hydration phenomena), and the dissolution process enables an explanation of the faster dissolution kinetics of barite in the aqueous solution of a simple inorganic salt (NaCl) compared to in the solution of a strong chelating agent (DTPA). Our findings imply that because the mechanisms of complexation in solution and mobilization of ions from the solid surface are different, the sequestering capacity of the ligand toward dissolved ions cannot be used to predict the dissolution rate.

α-Fe2O3 Nanostructures: Inorganic Salt-Controlled Synthesis and Their Electrochemical Performance toward Lithium Storage

By applying the concept of an inorganic structure-directing agent, uniform α-Fe2O3 nanospheres of about 300 nm in diameter and well-defined nanorhombohedra of about 50−80 nm in size have been successfully synthesized using the simple inorganic sodium salt of NaAc and NaCl as the only structure-directing agent in the hydrothermal system, respectively. In comparison, only micrometer sphere-like aggregates composed of irregular nanoparticles of about 80−120 nm were obtained without the presence of any inorganic salt additives. All three nanostructures are investigated with XRD, SEM, TEM, and electrochemical tests toward lithium storage. It is found that the particle size and shape has a remarkable effect on the lithium insertion/extraction behavior. Among the three α-Fe2O3 nanostructures, nanospheres show a very high specific capacity of >600 mA h g−1 in the initial 10 cycles and >414 mA h g−1 after 60 cycles as well as good cycling performance, exhibiting great potential as anode materials in lithium-ion ba...

Synthesis of nanostructured SnO2 dispersed on amorphous alumina by hydrothermal method

Nanostructured SnO2 dispersed on amorphous alumina was synthesised by a simple hydrothermal method using urea as hydrolytic agent and simple inorganic salts [SnCl2.2H2O and Al(NO3)3.9H2O] as precursors. The synthesis was carried out in an autoclave at 180°C with an in situ pressure of 12 atmospheres and the powders were calcined at 600, 1000 and 1200°C. Single aluminium oxide and mixed oxides in the molar ratios 1:2 and 2:1 were also prepared under identical conditions. The oxides were characterised by X-ray diffraction (XRD), magic angle spinning nuclear magnetic resonance spectroscopy (27Al MAS NMR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), BET surface area, infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Quite interestingly, as prepared mixed oxide was formed of nanoSnO2 starting from stannous chloride precursor and of spherical particles in the range of 20–50 nm while Al species was formed as amorphous nanoAlOOH. On calcination, AlOOH was transformed to alumina but in all the calcined mixed oxides, alumina was in amorphous phase. Heat treatment reduced the surface area and increased the crystallite size with temperature. It was shown that the nitrate ion present in the hydrothermal solution acts as the internal oxidising agent, thus oxidising SnO to SnO2 and the presence of excess Al precursor favours the formation of stannic oxide only; on the other hand, excess Sn produces both SnO and SnO2 and the yield of SnO2 was directly proportional to ratio of Al precursor.

Synthesis and characterization of nanocrystalline NiSb and NiSb 2 at low temperature

Nanocrystalline NiSb and NiSb 2 have been prepared through a solvothermal co-reduction route at low temperatures (120–180 °C). The features of this method include: (1) the reactants are simple inorganic salts (NiCl 2·6H 2O and SbCl 3); (2) two types of nickel antimonides (NiSb and NiSb 2) can be obtained respectively by changing the reducing agents and temperatures. The as-prepared samples were characterized by XRD and TEM. A possible formation mechanism has been presented. The thermoelectric properties of as-prepared NiSb, and the magnetic properties of NiSb 2 were investigated.

Inside Front Cover: Green Synthesis and Property Characterization of Single‐Crystalline Perovskite Fluoride Nanorods (Adv. Funct. Mater. 1/2008)

AbstractThe synthesis of single‐crystalline, cubic perovskite KMnF3 and NH4MnF3 nanorods, and their rare‐earth‐ion‐doped analogues with reproducible shapes and sizes, has been realized using a modified template‐directed approach, report Stanislaus Wong and co‐workers on p. 103. The properties of the nanorods and their as‐doped counterparts suggest their practical incorporation into functional nanometer‐scale devices with applications in a number of fields. The cover shows the crystal structure of perovskite fluorides overlaid on a SEM image of as‐prepared KMnF3 nanorods with diameters measuring around 50 nm.The generalized green synthesis of single‐crystalline KMnF3 and NH4MnF3 nanorods as well as of their rare‐earth ion doped analogues, possessing reproducible shape and controllable size, has been achieved using a modified template‐directed approach under ambient room‐temperature conditions, with simple inorganic salts as functional precursors. Extensive characterization of the resulting nanorods has been performed using diffraction, electron microscopy, optical spectroscopy, as well as magnetic techniques. We have studied the antiferromagnetism of as‐prepared ternary metal fluoride nanorods as well as the luminescence of their as‐doped counterparts. Our collective data suggest the possibility of the incorporation of these high‐quality, chemically pure materials into functional nanoscale devices with various potential applications that exploit the interesting optomagnetic properties of these systems.

Green Synthesis and Property Characterization of Single‐Crystalline Perovskite Fluoride Nanorods

AbstractThe generalized green synthesis of single‐crystalline KMnF3 and NH4MnF3 nanorods as well as of their rare‐earth ion doped analogues, possessing reproducible shape and controllable size, has been achieved using a modified template‐directed approach under ambient room‐temperature conditions, with simple inorganic salts as functional precursors. Extensive characterization of the resulting nanorods has been performed using diffraction, electron microscopy, optical spectroscopy, as well as magnetic techniques. We have studied the antiferromagnetism of as‐prepared ternary metal fluoride nanorods as well as the luminescence of their as‐doped counterparts. Our collective data suggest the possibility of the incorporation of these high‐quality, chemically pure materials into functional nanoscale devices with various potential applications that exploit the interesting optomagnetic properties of these systems.

Hydrothermal synthesis of stable mesoporous ZrO 2–Y 2O 3 and CeO 2–ZrO 2–Y 2O 3 from simple inorganic salts and CTAB template in aqueous medium

Mesoporous zirconia–yttria (ZYO) and ceria–zirconia–yttria (CZYO) have been synthesized for the first time from simple inorganic salts rather than expensive alkoxides in aqueous medium using CTAB as template. The approach is simple and economical. The fabricated ZYO and CZYO materials show typical mesoporous characteristics. The surface areas are 200 and 139 m 2 g −1 and the average pore diameters are ca. 5.7 and 6.8 nm, respectively. The framework of the meso-materials show high crystallinity, and the mesopores are narrow in pore size distribution and show interconnected feature. The high thermal stability and the large surface area at temperature as high as 550 °C suggests that the materials are suitable for high-temperature catalytic applications.

Simplified synthesis of isomorphously nickel substituted ZSM-5

Isomorphously nickel-substituted nano-crystalline ZSM-5 is synthesized in the absence of acidic aqueous fluoride medium incorporating simple and low-cost metal inorganic salt precursor NiCl2.6H2O instead of large organic cationic salt like bis (tetraethyl ammonium) tetrachloronickelate (II) with less water quantity to minimize the synthesis waste. PXRD, FT-IR, TG/DTG, XPS, UV–Vis DRS, SEM, TEM, ICP and N2 adsorption-desorption techniques were used to confirm the presence of nano-crystalline material having a MFI structure and heteroatom substitution. The unit cell dimensions increase with increasing levels of nickel substitution. The crystallite size of as synthesized samples was in the range of 60–75 nm, which increased to 60–160 nm after calcination at 550°C. Percentage crystallinity and crystallite size increases with increasing nickel substitution level up to 0.17 mol and beyond that the material becomes amorphous.

A simple method to synthesize single-crystalline β-wollastonite nanowires

The single-crystalline β-wollastonite ( β-CaSiO 3) nanowires were prepared via a simple hydrothermal method, in the absence of any template or surfactant using cheap and simple inorganic salts as raw materials. Xonotlite [Ca 6(Si 6O 17)(OH) 2] nanowires were first obtained after hydrothermal treatment at a lower temperature of 200 °C for 24 h, and after being calcinated at 800 °C for 2 h, xonotlite nanowires completely transformed into β-wollastonite nanowires and the wire-like structure was preserved. The synthesized β-wollastonite nanowires had a diameter of 10–30 nm, and a length up to tens of micrometers, and the single-crystalline monoclinic parawollastonite structured β-wollastonite was identified by XRD with the space group of P2 1/a and cell constants of a=15.42 Å, b=7.325 Å, c=7.069 Å and β=95.38°. A possible growth mechanism of β-wollastonite nanowires was also proposed. The advantages of this method for the nanowire synthesis lie in the high yield, low temperature and mild reaction conditions, which will allow large-scale production at low cost.

Analysis of electrochemical degradation products of sulphonated azo dyes using high‐performance liquid chromatography/tandem mass spectrometry

Electrochemical treatment of wastewaters containing azo dyes in the textile industry is a promising approach for their degradation. The monitoring of the course of the decomposition of azo dyes in wastewaters is essential due to the environmental impact of their degradation products. In this work, aqueous solutions of a simple azo dye with a low molecular weight (C.I. Acid Yellow 9) and more complex commercial dye (C.I. Reactive Black 5) were electrochemically treated in a laboratory-scale electrolytic cell in sodium chloride or ammonium acetate as supporting electrolytes. Ion-pairing reversed-phase high-performance liquid chromatography coupled with negative-ion electrospray ionization mass spectrometry is applied for the identification of electrochemical degradation products. In addition to simple inorganic salts, the formation of aromatic degradation products obtained due to the cleavage of azo bonds and further degradation reactions is shown, as well as chlorination where sodium chloride is the supporting electrolyte. Degradation mechanisms are suggested for the treatment with sodium chloride as the supporting electrolyte.

Synthesis and properties of mesoporous silica–alumina with narrow pore size distribution obtained without use of pore-regulating agents

The synthesis of a mesoporous silica–alumina (MSA) containing 50 wt.% alumina from simple inorganic salts (sodium metasilicate and aluminum nitrate) without the use of pore-regulating agents is described. The BET surface area of MSA was 491 m 2/g and its pore structure almost exclusively formed by 3–5 nm mesopores. From X-ray diffraction, electron microscopy and 27Al MAS NMR it follows that the MSA is amorphous with the disordered pore arrangement, with the majority of the aluminum atoms in the octahedral coordination. Its pore size distribution is much narrower in comparison to the distributions of commercial silica–aluminas. The MSA showed a good hydrothermal stability and its textural properties were influenced only slightly by treatment in boiling water and calcination at temperatures up to 800 °C.

A Bio-inspired approach to controlled crystallization at the nanoscale

Nature produces a wide variety of exquisite mineralized tissues fulfilling diverse functions, often from simple inorganic salts. Organisms exercise a level of molecular control over the physico-chemical properties of inorganic crystals that is unparalleled in today's technology. This reflects directly or indirectly the controlling activity of biological organic surfaces that are involved in the formation of these materials. Biological materials are intrinsically nanoscale. Biomineralization occurs within specific nanoenvironments, which implies stimulation of crystal formation at certain interfacial sites and relative inhibition of the process at all other sites. Our approach to artificial crystallization is based on the combination of the two latter concepts — i.e., the use of organized organic surfaces patterned with specific initiation domains on a nanoscale to study and orchestrate the crystallization process. This bio-inspired engineering effort made it possible to achieve a remarkable level of control over various aspects of the crystal nucleation and growth, including the precise localization of particles, nucleation density, crystal sizes, morphology, crystallographic orientation, arbitrary shapes, nanostructure, stability, and architecture. The ability to construct large, defect-free, patterned single crystals with controlled nanoporosity; periodic arrays of uniform, oriented nanocrystals; or films presenting patterns of nanocrystals offers a new, bio-inspired nanotechnology route to materials engineering.

Solubility of sodium soaps in aqueous salt solutions

The solubility of sodium soaps in dilute aqueous salt solutions has been systematically investigated by direct visual phase behavior observations. The added electrolytes, including simple inorganic salts and bulky organic salts, influence the solubility of sodium soaps in water, as represented by the varied soap Krafft point. Two inorganic salts, sodium chloride and sodium perchlorate, demonstrate a “salting-out” property. On the other hand, tetraalkylammonium bromides show an excellent ability to depress the soap Krafft point and enhance the soap solubility in water. With increasing the tetraalkylammonium ionic size, the degree of “salting-in” of soaps in water increases. However, solubility of pure tetraalkylammonium bromide in water decreases as the length of the alkyl chains increases. Furthermore, in the ternary water-tetrapentylammonium bromide (TPeAB)-sodium myristate (NaMy) system, we observed an upper cloud point phenomenon, which greatly shrinks the 1-phase micellar solution region in the phase diagram. This miscibility gap, together with the organic salt solubility limitation, restricts the use of tetraalkylammonium bromides with alkyl chains longer than 4 carbon atoms as effective soap solubility enhancement electrolytes. We also found that for sodium soap with a longer hydrocarbon chain, more tetrabutylammonium salt is required to reduce the soap Krafft point to room temperature.

Investigations on the Solubility Behavior of Cyanophycin. Solubility of Cyanophycin in Solutions of Simple Inorganic Salts

On the basis of a previous report on the occurrence of water-soluble cyanophycin (CGP, cyanophycin granule polypeptide) in a recombinant strain of Escherichia coli expressing the cyanophycin synthetase (CphA) of Desulfitobacterium hafniense published by others, the conditions of its production were investigated in this study. Although the incubation temperature, aeration level, and NaCl concentration during cultivation had effects on the in vivo production of water-soluble CGP, it could be isolated as a major variant irrespective of the cultivation conditions. The occurrence of the soluble variant was also not dependent on the E. coli host or on the origin of cphA. Furthermore, it was shown that water-insoluble CGP can be in vitro solubilized to extents of up to about 80% (w/w) in solutions of different inorganic salts such as LiCl, NaCl, KCl, RbCl, KBr, MgCl(2), or CaCl(2). Evidence was obtained that the salt ions bind tightly to CGP. If the ions were not removed from the salt solution by dialysis or dilution, the CGP remained stable in solution. This method to solubilize water-insoluble CGP could also be applied to high concentrations of the polymer. CGP that remained insoluble after the first treatment could only marginally be solubilized in following treatments. The polydisperse CGP molecules were solubilized to the same extent over the whole molecular weight range with no preference of a particular molecular weight.

Low-melting sugar–urea–salt mixtures as solvents for Diels–Alder reactions

Sweet solutions are obtained upon heating mixtures of simple carbohydrates, urea and inorganic salts to moderate temperatures, to give new chiral media for organic reactions.