Salt Matrix Research Articles

Enhancing the UV A1 screening ability of caffeic acid by encapsulation in layered basic zinc hydroxide matrix

An organic UV screening molecule, caffeic acid (CA), has been stabilised in a zinc basic salt (ZBS) matrix upon intercalative reaction into zinc hydroxide nitrate. According to the X-ray diffraction pattern, the basal spacing of the CA-ZBS nanohybrid is determined to be 10.4Å, which is in agreement with a result of cross-section TEM analysis. FT-IR analysis shows that carboxylate groups in organic anions interact coordinately with zinc atoms on inorganic hydroxide sheets. The resultant CA-ZBS nanohybrid exhibits a superior UV screening ability compared to pure CA molecule.

Simultaneous in vivo monitoring of multiple brain metals using an online microdialysis-in-loop solid phase extraction-inductively coupled plasma mass spectrometry system

Using a non-functionalized small-bore polytetrafluoroethylene (PTFE) sample loop as a preconcentrator, a novel hyphenated system—comprising microdialysis sampling, online automatic in-loop solid phase extraction (SPE), and inductively coupled plasma mass spectrometry (ICP-MS)—for monitoring the levels of trace metal ions in living rat brains was developed. Taking advantage of the selective polymer–ion interaction to online separate metal ions from highly saline operating in the in-loop PTFE SPE system, it could online remove the salt matrix selectively from the microdialysate of rat brain extracellular fluid after slightly adjusting the pH; the next analytical cycle could be performed without the need for a pre-conditioning procedure after the prior elution with HNO3. Owing to the simplicity and convenience of the developed operation sequence, this method combines extremely low blank level and detection limits (0.003–0.5 μg L−1) and acceptable spike recoveries (90–98%) with the ability to analyze multiple elements. To demonstrate analytical reliability and compatibility, the analysis of standard reference material NIST 1643e (trace elements in water) and 2670a (trace elements in human urine) as well as continuous long-term monitoring of the variations of multiple trace metal ions in rat brain were performed in this work. According to the analytical results, it showed that the developed hyphenation system had the ability to analyze the SRM samples accurately, and the basal values of Ni (0.36 ± 0.16 μg L−1), Zn (3.09 ± 0.31 μg L−1), and Mn (1.31 ± 0.06 μg L−1) in rat brain extracellular fluid could also be measured.

Determination of cadmium in high salt content matrices by flow injection cold vapor atomic absorption spectrometry

Flow injection cold vapor atomic absorption spectrometry (FI-CVAAS) was used for determination of cadmium in high salt matrices such as dialysis concentrates and textile leach solutions. The parameters such as acidity, concentration of reducing agent, reaction coil length, and carrier gas flow rate were investigated to obtain the best sensitivity. No significant background signal was observed even at high salt concentrations. Under the optimized conditions the limit of detection value (3s_b m^{-1}, where s_b is the standard deviation of the blank signals and m is the slope of the calibration graph) was found to be 0.05 ng mL^{-1} for an injection volume of 250 \mu L and the precision in terms of relative standard deviation was 3.2% using 11 consecutive measurements of 0.5 ng mL^{-1} standard. The standard addition method was used for quantitation. The accuracy of the method was tested using ETAAS as a comparison method and a certified reference material (Waste Water EU-L-1). In both cases, the results were in good agreement at 95% confidence level. The concentrations of cadmium in textile product leach solutions were found to be below the limit value assigned by Oeko-Tex standards.

Threshold silver concentration for facilitated olefin transport in polymer/silver salt membranes

The existence of a threshold concentration for silver ions has been observed in solid-state facilitated transport membranes comprising silver salt and a polymer matrix. The threshold silver concentration for facilitated olefin transport through the membranes was systematically investigated, with particular attention paid to the relative interactions of polymer/silver ions and of silver ions/counteranions. This behavior was assessed for membranes consisting of silver salt and polymer matrix with and without various ligands, specifically, phthalate, amide, ether, ketone, ester, or C = C bonds. The threshold concentration of silver salt for facilitated olefin transport was found to be strongly dependent on the polymeric ligand. With respect to the polymer, the determined order of highest threshold concentration capacity to lowest capacity is listed in the following order: phthalate > amide > ether >ketone ≈ C = C bond > ester > no ligand. This dependence of the threshold concentration on the polymeric ligand is correlated with both the interaction strength of silver ions with the different ligands and that with their counteranions. It has been concluded that when the former interaction is weak and, consequently, the latter interaction is strong, the threshold concentration for facilitated olefin transport is low, and vice versa. These interactions were characterized using X-ray photoelectron spectroscopy (XPS), FT-Raman spectroscopy, and theoretical ab initio calculation.

Effect of salt composition on photovoltaic performance of the dye-sensitized solar cells prepared from nano anatase TiO2 powder using NaCl–Na2HPO4·2H2O salt matrices

Photovoltaic performances of dye-sensitized solar cells based on mesoporous TiO2 coating of nanocrystalline anatase prepared by solid salt synthesis were investigated in this study. Three different salt compositions pure NaCl, NaCl and DSP 50–50 wt% mixture, and pure DSP have been used as the reaction mediums. The best photovoltaic performances were obtained for the device made using the powder from DSP matrix. The dye-sensitized solar cells built from DSP and NaCl50 powders showed 13.8 and 6.5% improvements in the short-circuit current density, and 34 and 20% improvement in overall efficiency, respectively, than those of the cell made from Degussa P-25 powder. These results have been explained from the microstructural point of view of the powders. Electron microscopy, XRD, Raman, and nitrogen adsorption–desorption studies showed that the coatings made from the powders obtained via NaCl 50 and DSP salt medium treatments were of smaller sizes and contained higher densities of narrower mesoporous distribution than that obtained by the coating from NaCl and no-salt-synthesized materials.

Control of the composition and structure of Fe–O nanoparticles during Fe3O4 electron beam evaporation

The paper examines the structure of porous Fe3O4 + NaCl condensates and analyzes the phase and chemical composition and sizes of Fe3O4 nanoparticles produced by electron beam evaporation and vacuum condensation. It is shown that Fe3O4 nanoparticles in a porous salt matrix are highly adsorptive to air oxygen. The adsorptivity decreases when iron concentration in the condensate increases. Thermogravimetric analysis is used to study the kinetics of variation in the weight of porous NaCl and Fe3O4 + NaCl condensates during heating to 650°C and cooling in air. The results are considered in terms of physical and chemical adsorption. Stabilized colloidal systems of magnetite nanoparticles are obtained. Photon correlation spectroscopy is used to determine their quantitative size distribution in an aqueous solution of surface active agents. The physical method for obtaining nanoparticles in electron beam vacuum setups is highly efficient and competitive with previous methods for synthesis of nanoparticles.

Photovoltaic performance of dye sensitized solar cell based on rutile TiO 2 scaffold electrode prepared by a 2 step bi-layer process using molten salt matrices

Dye sensitized solar cells were made on TiO 2 scaffold anodes of rutile particles. These TiO 2 scaffold anodes were grown from rutile seeds by using a molten salt synthesis technique. Different thickness coatings of mixed amorphous titanium hydroxide and NaCl–KCl eutectic salt mixture on the rutile seeds were heat treated at different temperatures. The rutile whiskers of different aspect ratios were grown depending on the growth temperature. The best photovoltaic performances were obtained for the device made from the scaffold of 20–50 nm diameter and 0.5–1 μm length nanowhiskers obtained at 700 °C for 5 h of treatment.

α-Fe 2O 3 nano-platelets prepared by mechanochemical/thermal processing

A new method to prepare plate-shaped Fe 2O 3 nanoparticles was investigated and their magnetic properties were characterised. First, Fe 2O 3 nanoparticles of ~ 6 nm in diameter were synthesised by mechanochemical processing, involving the solid-state exchange reaction Fe 2(SO 4) 3 + 3 Na 2CO 3 → Fe 2(CO 3) 3 + 3 Na 2SO 4 → Fe 2O 3 + 3 Na 2SO 4 + 3 CO 2 (g) effected by high-energy ball milling and subsequent heat treatment at 400 °C. Next, nano-platelets were grown from the nanoparticles by further heat treatment in a salt matrix at 700 °C. Removal of the salt and by-product phases after heat treatment led to well-dispersed platy haematite particles of 20–200 nm in diameter with aspect ratio of 4–10. The hematite nano-platelets were weakly ferromagnetic with coercivity of ~ 160 Oe and remanent magnetisation of 0.2 emu/g.

Fe 50Co 50 nanoparticles via self-propagating high-temperature synthesis during milling

Self-propagating exothermic reactions during mechanical milling of FeCl 3/CoCl 2 mixture together with sodium seeds resulted in formation of Fe 50Co 50 nanoparticles. Highly exothermic reactions resulted in temperature raise and formation of Fe 50Co 50 phase within the first 5 min; however Fe 50Co 50 single-phase was obtained after 30 min of milling. The products were characterized by XRD, SEM, EDS, TEM and VSM. Obtained results showed that both milling time and NaCl salt matrix affected the size, morphology, microstructure and magnetic properties of the produced particles.

UV Screening of Ferulic Acid–Zinc Basic Salt Nanohybrid with Controlled Release Rate

Ferulic acid (FA), an organic UV absorber and free radical scavenger, was intercalated into an inorganic zinc basic salt (ZBS) matrix to prepare a UV screening material. FA molecules were vertically oriented bilayer in the ZBS lattice with an expansion of approximately 22.7 angstroms along the c-axis. The FA-ZBS nanohybrid exhibited a superior UV-A approximately UV-B screening ability and an antioxidant activity that was comparable to that of a pure FA molecule. The in vitro release test showed the biphasic release of the FA molecules from the FA-ZBS nanohybrid that consisted of an initial burst, followed by a slow and sustained release.

Salt matrix voltammetry: Microphase redox processes at ammonium chloride | gold | gas triple phase boundaries

Electrochemical processes at the electrode | ammonium chloride salt crystal | gas triple phase boundary are detected under the condition that (i) microscopic contact points of salt crystals to a suitable working electrode are formed and (ii) the relative humidity level is adjusted to allow sufficient surface ion conduction in a thin water film within the salt matrix. In this preliminary report, redox systems such as Fe(CN)63−/4−, hydroquinone/benzoquinone, decamethylferrocene+/0, ferrocenedimethanol+/0, and Cu2+/+/0 are investigated embedded into an ammonium chloride salt matrix (by mechanical grinding) and then brought into contact with a macroscopic gold disc electrode. Voltammetric current responses are demonstrated consistent with the processes in the microphase formed at the salt | electrode | gas triple phase boundary. Copper metal electro-deposition is observed. Direct electrochemistry of dioxygen from the gas phase at the salt crystal | gold electrode contact is observed and gas sensing applications are proposed.

Tunable Chiral Reaction Media Based on Two-Component Liquid Crystals: Regio-, Diastereo-, and Enantiocontrolled Photodimerization of Anthracenecarboxylic Acids

Three kinds of enantiopure amphiphilic amino alcohols (1a-c) were newly synthesized, of which the stereochemistry of the stereogenic carbons adjacent to the amino (C2) and hydroxy (C1) groups was systematically varied. By using these amino alcohols and four photoreactive carboxylic acids, 12 kinds of salts were prepared. The structure and thermal behavior of the salts were thoroughly investigated by various techniques, which revealed that the stereochemistry of the amino alcohol unit has significant effects on the properties of the salts; the salts of 1a with (1R,2S)-configuration did not exhibit any liquid crystal (LC) phase but showed high crystallinity, whereas 1b and 1c with (1S,2S)- and (1S)-configurations, respectively, generally afforded stable LC salts with smectic structure(s). Within the matrix of these amphiphilic salts, the in situ photodimerizations of 2-anthracenecarboxylic acid (2c) and 1-anthracenecarboxylic acid (2d) were conducted by the irradiation with UV/vis light (500 W, a high-pressure mercury arc lamp, >380 nm). Concerning reactivity and regio-/diastereo-/enantioselectivities, the LC phases were found to be superior to isotropic and crystalline phases. For the two substrates 2c and 2d, every LC phase promoted the photodimerization with unprecedentedly high head-to-head selectivity. Particularly in the case of 2c, diastereoselecitivity (syn(HH) vs anti(HH)) could be rationally controlled by the choice of the amino alcohol unit and mesophase (syn(HH):anti(HH) = 61:37 to 26:72). Moreover, one of the LC phases exhibited by 1b·2c afforded the anti(HH)-dimer of 2c with excellent enantioselectivity (up to 86% ee). On the basis of the hypothesis that the present photochemical outcome arises from the preorientation of the substrates, a preliminary structural model of these LCs was proposed.

Photoinduced formation of reactive oxygen species in suspensions of titania mechanochemically synthesized from TiCl 4

Titanium dioxide nanopowders were synthesized mechanochemically using TiCl 4 and (NH 4) 2CO 3 (series TC) or TiCl 4/(NH 4) 2CO 3 and Na 2SO 4–Na 2SO 4·10H 2O (series TCSM), as precursors and post-annealing in the temperature range 150–850 °C. Crystal structure and crystallite size of the titania nanomaterials were characterized by X-ray diffraction, and the optical properties of aqueous suspensions at various TiO 2 loadings were measured using UV/visible spectroscopy. The photoinduced activity was measured in situ by EPR spectroscopy applying a variety of experimental techniques (spin trapping, spin probes, 4-hydroxy-2,2,6,6-tetramethylpiperidine oxidation). In the series TC the presence of an NH 4Cl salt matrix, which was removed by decomposition to gaseous byproducts in the post-annealing process, leads to the formation of anatase nanocrystals with optimal size for high photoactivity (23–50 nm) at temperatures of 550 and 650 °C, and these titania samples are the most active in the photoinduced production of reactive oxygen species. The results found for TCSM series confirmed that the presence of a sulfate salt matrix (Na 2SO 4) during mechanochemical and annealing processes significantly hindered TiO 2 nanocrystallite growth, increased agglomerate formation in aqueous media and lowered the values of photonic efficiencies determined via paramagnetic species formation or termination.

Effect of addends in C60 derivatives on the electrochemical behavior of the compounds in salt matrices of artificial lipids

Effect of addends in fullerene compounds on the fullerenes’ redox behavior in the matrix of tetraoctylammonium bromide, an artificial cationic lipid, deposited on conducting glass is studied by example of di- and trisubstituted fullerenopyrrolidines and a methanofullerene derivative. It is shown by cyclic voltammetry that in all cases the hydrophobic interaction of fullerenes with alkyl radicals in the matrix, as well as electrostatic interaction of the fullerene reduction products (anions), shifts the fullerene reduction potentials toward positive values. This allows performing quasireversible redox-transformation in neutral aqueous media. It is shown that the rate of electron transfer to and from fullerene in the fullerenopyrrolidines is higher than in methanofullerene, which presumably can be explained by violation of the symmetry and conjugation partial lack due to the introducing of the methane fragment.

Thermodynamic Changes in Mechanochemically Synthesized Magnesium Hydride Nanoparticles

The thermodynamic properties of magnesium hydride nanoparticles have been investigated by hydrogen decomposition pressure measurements using the Sieverts technique. A mechanochemical method was used to synthesize MgH(2) nanoparticles (down to approximately 7 nm in size) embedded in a LiCl salt matrix. In comparison to bulk MgH(2), the mechanochemically produced MgH(2) with the smallest particle size showed a small but measurable decrease in the decomposition reaction enthalpy (DeltaH decrease of 2.84 kJ/mol H(2) from DeltaH(bulk) = 74.06 +/- 0.42 kJ/mol H(2) to DeltaH(nano) = 71.22 +/- 0.49 kJ/mol H(2)). The reduction in DeltaH matches theoretical predictions and was also coupled with a similar reduction in reaction entropy (DeltaS decrease of 3.8 J/mol H(2)/K from DeltaS(bulk) = 133.4 +/- 0.7 J/mol H(2)/K to DeltaS(nano) = 129.6 +/- 0.8 J/mol H(2)/K). The thermodynamic changes in the MgH(2) nanoparticle system correspond to a drop in the 1 bar hydrogen equilibrium temperature (T(1 bar)) by approximately 6 degrees C to 276.2 +/- 2.4 degrees C in contrast to the bulk MgH(2) system at 281.8 +/- 2.2 degrees C. The reduction in the desorption temperature is less than that expected from theoretical studies due to the decrease in DeltaS that acts to partially counteract the effect from the change in DeltaH.

Magnetic behavior of chemically synthesized FePt–FeRh nanostructures

We describe here the chemical synthesis and magnetization behavior of FeRh–FePt nanostructures fabricated using a two-step procedure. The first step involved chemical synthesis of FeRh nanoparticles using a polyol co-reduction process accompanied by the second stage of encapsulation of FeRh nanoparticles with FePt. The FeRh–FePt nanoparticles were subsequently annealed in a salt matrix at 600 °C for 3 h. Magnetic measurements were made on films of FeRh–FePt nanostructures cast onto silicon wafers before and after the salt matrix annealing. The coercivity of as-synthesized FeRh–FePt nanostructures was ∼70 Oe at room temperature, while the coercivity of salt-matrix annealed FeRh–FePt nanoparticles was ∼7065 Oe. The temperature dependent magnetization measurement of annealed FeRh–FePt nanostructures indicated antiferromagnetic–ferromagnetic transition that is supported by X-ray diffraction study. The observations point toward the potential realization of FeRh–FePt nanostructures for ultra-high density magnetic recording media.

Thermal inactivation and growth potential of Listeriainnocua in rehydrated salt-cured cod prepared for ready-to-eat products

The aim of this work was to study thermal inactivation at 55 and 60 °C and growth potential at 4 and 8 °C of Listeria innocua in rehydrated salt-cured cod prepared for ready-to-eat (RTE) products. The results demonstrated that both level of salt stress and matrix i.e. rehydrated or fresh cod muscle, did affect the thermal inactivation of L. innocua towards non-linearity with an upward concavity. During subsequent storage of the heat treated samples, the lag time of the strain was 9–10 days regardless of salt stress level or matrix. In the raw products (controls), however, the lag time varied. The results indicate that detailed knowledge about the sequences of salt stress before heat treatment is of limited importance for the growth potential of L. innocua in heat treated RTE products.

Influence of Sodium Chloride and Dibasic Sodium Phosphate Salt Matrices on the Anatase–Rutile Phase Transformation and Particle Size of Titanium Dioxide Powder

The influence of sodium chloride (NaCl) and dibasic sodium phosphate (Na2HPO4·2H2O, DSP) on the phase transformation and particle size of titanium dioxide powder had been investigated. The salt matrix was shown to suppress both the amorphous to anatase transition and the anatase to rutile transition. DSP was particularly effective. Irrespective of the additives, transformation versus time curves of the anatase to rutile conversion were observed to be sigmoidal, and were interpreted in terms of a first order, nucleation‐growth controlled phenomenon. Analysis of these curves using appropriate rate laws yielded activation energies for nucleation of ∼4.3 eV for NaCl salt matrix and ∼8.6 eV for DSP salt matrix, compared with ∼3.2 eV for a sample with no salt. Activation energies for the growth or propagation stage were ∼5 and ∼8.9 eV for NaCl and DSP powders, respectively, compared with ∼3.8 eV for no salt. In the solid state, salt matrices suppressed the particle growth as well. These behaviors, in general are thought to be governed by the presence of salt impurities, especially anions chemisorbed at the surface.

Mechanochemical-molten salt synthesis of Na 2Ti 6O 13 nanobelts

A novel route for the preparation of Na 2Ti 6O 13 nanobelts by mechanochemical treatment of the TiCl 4–Na 2SO 4·10H 2O–Na 2CO 3 mixture for 5 min followed by molten salt synthesis is described. The mixture of the amorphous TiO 2 and NaCl–Na 2SO 4· xH 2O–Na 2CO 3 salt matrix was generated during milling. The molten salt synthesis of the Na 2Ti 6O 13 nanobelts with lengths up to 0.5–2 μm and with a width in the range of 20–250 nm was carried out in the temperature range of 700–800 °C for 1 h. The partial formation of titanate nanotubes was observed after annealing at 600 °C and washing procedure. X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential thermal analysis (DTA) were used to characterize the formation and structure of Na 2Ti 6O 13 nanobelts.

Characterization of halophiles in natural MgSO 4 salts and laboratory enrichment samples: Astrobiological implications for Mars

The presence of sulfate salts and limited subsurface water (ice) on Mars suggests that any liquid water on Mars today will occur as (magnesium) sulfate-rich brines in regions containing sources of magnesium and sulfur. The Basque Lakes of British Columbia, Canada, represent a hypersaline terrestrial analogue site, which possesses chemical and physical properties similar to those observed on Mars. The Basque Lakes also contain diverse halophilic organisms representing all three Kingdoms of life, growing in surface and near-subsurface environments. Of interest from an astrobiological perspective, crushed magnesium sulfate samples that were analyzed using a modified Lowry protein assay contained biomass in every crystal inspected, with biomass values from 0.078 to 4.21 mg biomass/g salt; average=0.74±0.7 mg biomass/g salt. Bacteria and Archaea cells were easily observed even in low-biomass samples using light microscopy, and bacteria trapped within magnesium sulfate crystals were observed using confocal microscopy. Regions within the salt also contained bacterial pigments, e.g., carotenoids, which were separate from the cells, indicating that cell lysis might have occurred during entrapment within the salt matrix. These biosignatures, cells, and any ‘soluble’ organic constituents were primarily found trapped within fluid inclusions or fluid-filled void spaces between intergrown crystals. Diffuse reflectance infrared Fourier transform spectroscopy (reflectance IR) analysis of enrichment cultures, containing cyanobacteria, Archaea, or dissimilatory sulfate-reducing bacteria, highlighted molecular biosignature features between 550–1650 and 2400–3000 cm −1. Spectra from natural salts demonstrated that we can detect biomass within salt crystals using the most sensitive biosignatures, which are the 1530–1570 cm −1, C–N, N–H, –COOH absorptions and the 1030–1050 cm −1 C–OH, C–N, PO 4 3− bond features. The lowest detection limit for a biosignature absorption feature using reflectance IR was with a natural sample that possessed 0.78 mg biomass/g salt. In a model cell, i.e., a 0.5 by 1 μm bacillus, this biomass value corresponds to approximately 7.8×10 8 cells/g salt. Based on its ability to detect biomass entrapped within natural sulfate salts, reflectance IR may make an effective remote-sensing tool for finding enrichments of organic carbon within outcrops and surficial sedimentary deposits on Mars.