Cesium Salts Research Articles

Liquid Phase Hydrogenation of MIBK over M/CsPW (M = Ag, Ru, Pt, and Pd)

Four different metal nanoparticles (metal = Ag, Ru, Pt, or Rh) were impregnated on the acidic cesium salt of tungstophosphoric acid Cs2.5H0.5PW12O40 (CsPW) with a loading amount of 2 wt%. The prepared catalysts were characterized by using X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), N2 sorption measurements, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Results confirmed the formation of highly distributed metallic nanoparticle centres over the acidic CsPW. The catalytic activity of the prepared catalysts were evaluated in the liquid phase hydrogenation of methyl isobutyl ketone (MIBK) to 2-methylpentane (2-MP) at 453 K. Pd-CsPW showed the highest activity compared to other catalysts, where 10% conversion was obtained with 91% selectivity after 4 h’s reaction time.

CO2 insertion into epoxides using cesium salts as catalysts at ambient pressure

Cesium salts (Cs2CO3, CsCl, and CsNO3) were used for the coupling of CO2 and epoxides.

Morphological regulation of all-inorganic perovskites for multilevel resistive switching

Enormous attention has been paid to all-inorganic cesium lead halide perovskites in various photoelectronic fields for their remarkable performances. However, comparing to their analogue organic-inorganic hybrid perovskites, the film morphology of such all-inorganic lead halide perovskites is difficult to control due to the low solubility of cesium salt. Here, we propose a new fabrication routine to control the film morphology of CsPbBr3. A series of CsPbBr3 thin films with big grains (≈800 nm) were successfully prepared. The memristors based on such CsPbBr3 thin films take on typical bipolar resistive switching behavior and remarkable characteristics such as high Ron/Roff ratio (≈105), very low working voltage (≈±1 V), and long data retention (≥104 s). Furthermore, through modulating the film morphology, memristors with multilevel resistive switching behavior can be easily prepared. These advantages demonstrate that the all-inorganic cesium lead halide memristors possess great potential for future application.

Investigation of catalytic properties of Cs salt of di-copper substituted phosphotungstate, Cs7[PW10Cu2(H2O)O38] in epoxidation of styrene

The present work describes a detailed investigation of the catalytic activity of Cesium salt of di-copper substituted phosphotungstate for the oxidation of styrene using tert-butyl hydroperoxide as the oxidant. Various parameters like time, catalyst amount, mole ratio of substrate to TBHP and temperature were optimized and good conversion (77.9%) was obtained along with high selectivity for the epoxide (51.6%). The catalyst was recycled and reused multiple times without significant loss of activity. A detailed kinetic study was carried out to gain a deeper understanding of the role of each component present in the reaction system. A plausible reaction mechanism was also proposed based on kinetic studies, ESR and Cyclic Voltammetry studies.

Effect of substituting molybdenum atoms with tungsten on photocatalyst activity of cesium salt of keggin type polyoxometalates decorated magnetic ceria

Herein the potential use of cesium salts of polyoxometalate incorporated ceria and magnetic ceria as a photocatalyst for the photodegradation of Congo red was studied. Polyoxometalates salts (cesium salts of tungestophosphoric acid (H3PW12O40), molybdophosphoric acid (H3PMo12O40), and 6-molybdo tungestophosphoric acid (H3PW6Mo6O40)), having Keggin structure with large cations like Cs+, are porous materials. The morphological and structural studies of synthesized nanocomposites were carried out using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Results indicated that the Fe3O4@CeO2/Cs-PMoyW12-yO40 and CeO2/Cs-PMoyW12-yO40 (y = 0, 6, 12) nanocomposites are successfully synthesized. UV–vis diffuse reflectance spectroscopy determined the absorption edge and band gap energies of the prepared nanocomposites as a direct semiconductor. All the obtained structures were applied as photocatalys for degradation of Congo red dye in aqueous solutions under visible light. The Fe3O4@CeO2/Cs-PMo6W6O40 photocatalyst exhibited the highest photocatalytic activity under visible light.

Preparation of CHA zeolite (chabazite) crystals and membranes without organic structural directing agents for CO2 separation

CHA zeolite (chabazite) crystals and membranes were prepared from organic structural directing agents-free (OSDA-free) gels. Chabazite membranes were grown on the tubular alumina supports. The effect of cesium and fluoride salts on the crystallization of chabazite crystals and membranes were investigated. Highly crystalline chabazite and uniform chabazite membranes were only obtained from the gel containing the cesium and fluoride salts. Single CO2, N2 and CH4 permeances and mixed gas separations in CO2/N2 and CO2/CH4 binary mixtures through chabazite membranes were measured. Temperature and pressure affected the permeances and separation selectivities in two mixtures. The best membrane showed CO2/N2 and CO2/CH4 separation selectivities as high as 16 and 46 together with CO2 permeances of ~ 1.0 × 10-7 mol/(m2 s Pa) at a high temperature of 473 K in equimolar dry CO2/N2 and CO2/CH4 binary mixtures, respectively. The CO2/N2 and CO2/CH4 selectivities lost only 11% and 15%, and CO2 permeances lost only 18% and 20% in equimolar wet CO2/N2 and CO2/CH4 mixtures (8% in mole of water vapor) at 473 K compared to these values in dry mixtures, respectively. The OSDA-free chabazite membranes were hydrothermally stable in the presence of vapor water for 4 d at 378 K.

Efficient N-acylation of sulfonamides using cesium salt of Wells–Dawson heteropolyacid as catalyst: Synthesis of new N-acyl sulfonamides and cyclic imides

N-acylation of substituted sulfonamides with different anhydrides in the presence of Cesium salt of Wells–Dawson heteropolyacid (Cs5HP2W18O62) as an efficient and reusable catalyst was investigated for the first time. Cs5HP2W18O62 was used with a catalytic amount in water as a green solvent. At room temperature, a series of N-acylsulfonamides were synthesized, while under refluxing conditions, new cyclic imides containing sulfonyl group were obtained. Atom-economy, high yields, easy work-up, as well as simple catalyst recovery and reusability are the key features of this procedure.

Surface behavior of low-temperature molten salt mixtures during the transition from liquid to solid

We report on surface investigations of cesium and tetraphenylphosphonium bis(trifluoromethylsulfonyl)imide (Cs[Tf2N], [PPh4][Tf2N]) molten salts and their mixtures. Depending on composition, these ionic compounds combine low melting points with exceptionally high thermal stability, and thus, exhibit considerably enlarged thermal operation windows compared to conventional ionic liquids. To elucidate their liquid-solid transition behavior in the near-surface region, temperature-dependent angle-resolved X-ray photoelectron spectroscopy (ARXPS) investigations were performed using our unique laboratory electron spectrometer DASSA (“Dual Analyzer System for Surface Analysis”), dedicated for investigations of macroscopic liquid samples. We followed temperature-induced changes in bulk and surface composition within the first nanometers of the neat salt melts and of Cs[Tf2N] : [PPh4][Tf2N] = 3 : 1 and 1 : 3 mixtures. In the mixtures, pronounced surface enrichment of Cs+ on expense of the bulky [PPh4]+ ions was found in the liquid state at temperatures close to the liquid-solid transition. In the solid state of Cs[Tf2N]-rich mixtures, [PPh4]+ completely vanishes from the near-surface region probed by XPS.

Cs Salt of Undecatungstophospho(aqua) Cuprate(II): Microwave Synthesis, Characterization, Catalytic and Kinetic Study for Epoxidation of cis‐Cyclooctene with TBHP

AbstractThe present paper describes a facile microwave route for the synthesis of Cesium salt of mono‐copper substituted phosphotungstate, Cs5[PW11Cu(H2O)O39].4H2O, from H3PW12O40, CuCl2 and CsCl, its characterization and catalytic activity towards solvent‐free, selective epoxidation of cis‐cyclooctene using TBHP as the oxidant. In order to confirm the superiority of the microwave technique, the said complex was also synthesized by reflux method and the same studies were carried out. The present complex is found to be sustainable as well as recyclable without any change in % conversion as well as % selectivity towards epoxide. A detailed kinetic study showed an overall second order dependence of the reaction with respect to cyclooctene and TBHP.

Novel solutions for closed-loop reverse electrodialysis: Thermodynamic characterisation and perspective analysis

Closed-loop Reverse Electrodialysis is a novel technology to directly convert low-grade heat into electricity. It consists of a reverse electrodialysis (RED) unit where electricity is produced exploiting the salinity gradient between two salt-water solutions, coupled with a regeneration unit where waste-heat is used to treat the solutions exiting from the RED unit and restore their initial composition. One of the most important advantages of closed-loop systems compared to the open systems is the possibility to select ad-hoc salt solutions to achieve high efficiencies. Therefore, the properties of the salt solutions are essential to assess the performance of the energy generation and solution regeneration processes. The aim of this study is to analyse the influence of thermodynamic properties of non-conventional salt solutions (i.e. other than NaCl-aqueous solutions) and their influence on the operation of the closed-loop RED. New data for caesium and potassium acetate salts, i.e. osmotic and activity coefficients in aqueous solutions, at temperature between 20 and 90 °C are reported as a function of molality. The data are correlated using Pitzer's model, which is then used to assess the theoretical performance of the whole closed-loop RED system considering both single and multi-stage regeneration units. Results indicate that KAc, CsAc and LiCl are the most promising salts among those screened.

Thermochemical Measurements of Alkali Cation Association to Hexatantalate.

Ion association is an important process in aqueous dissolution, precipitation, and crystallization of ionic inorganic, organic, and biological materials. Polyoxometalates (POMs) are good model compounds for understanding the complex relationships between lattice energy, ion-pairing in solution, and salt solubility. Here we perform calorimetric measurements to elucidate trends in cluster stability, lattice energy, and ion-pairing behavior studies of simple hexatantalate salts in neat water, parent hydroxide solutions, and molybdate melts, extending previous studies on the isostructural hexaniobates. High temperature calorimetry of alkali salts of hexatantalate reveals that the enthalpies of formation from oxides of the K, Rb, and Cs salts are more similar to each other than they are for their niobate analogues and that the tantalate cluster is energetically less stable than hexaniobate. Aqueous dissolution calorimetry reveals that the cesium salt of hexatantalate has a similar concentration dependence on its dissolution enthalpy to that of hexaniobate. However, unlike rubidium hexaniobate, rubidium hexatantalate also exhibits increased concentration dependence, indicating that hextantalate can undergo increased ion-pairing with alkali salts other than cesium, despite the dilute environments studied. Dissolution enthalpies of POM salts in the parent alkali hydroxides shows that protonation of clusters stabilizes lattices even more than the strongly associating heavy alkali cations do. Additionally, neither weak nor strong lattice ion associations necessarily correlates with respectively high or low aqueous solubility. These studies illuminate the importance of considering ion-pairing among the interrelated processes in the aqueous dissolution of ionic salts that can be extended to serving as a model of cation association to metal oxide surfaces.

Acidic Dressing Based on Agarose/Cs2.5H0.5PW12O40 Nanocomposite for Infection Control in Wound Care.

Regulation of wound pH from alkaline to acidic is a simple and powerful approach to reduce wound microbial colonization and infection. Here, we present a nanocomposite material possessing intrinsic acidic surface pH as an innovative antimicrobial wound dressing. This material comprises an agarose matrix nanocomposite containing nanoparticles (NPs) of the cesium salt of phosphotungstic heteropolyacid (Cs2.5H0.5PW12O40). Self-supporting films were prepared by a casting method incorporating 5-20 wt % Cs2.5H0.5PW12O40 NPs into the matrix. Films are flexible with tensile strengths between 28.55 and 32.15 MPa and exhibit broad biocidal activity against neutralophilic pathogens, including Gram-positive bacteria, Gram-negative bacteria, yeast, and filamentous fungi. The nano-antimicrobial Cs2.5H0.5PW12O40 functions as an efficient and self-controlled proton delivery agent that lowers the surface pH of the nanocomposites to the range 7.0 > pH ≥ 3.0. Nanocomposite films containing 20 wt % Cs2.5H0.5PW12O40 NPs presented a surface pH of 3.0 and highest antimicrobial activity. Using quantitative reverse transcription polymerase chain reaction, we demonstrated that the antimicrobial mechanism of the nanocomposites is acid-induced because of the transcriptional induction of glutamate-dependent acid resistance genes in Escherichia coli. Additionally, nanocomposite films do not damage skin according to an in vivo rabbit skin model with no derived edema or erythema. The wound care safety of this material is due to low release of heavy metal heteropolyanions ([PW12O40]3-), no nanoparticle leaching, and proton controlled release resulting in nonirritating acid levels for human skin models.

Porous Cubic Cesium Salts of Silicododecatungstate(molybdate)/Borododecatungstate Blends: Synthesis and Molecular Adsorption Properties.

In this work, the synthesis and molecular adsorption properties of cubic cesium salts of Keggin-type silicododecametalates (SiM; M = W or Mo) and borododecatungstate (BW) blends were reported. Pentavalent BW, which is normally packed in a monoclinic fashion, could be packed into the desired cubic fashion by being blended with tetravalent SiW or SiMo. By simply mixing aqueous solutions containing SiM and BW in different SiM:BW molar ratios [SiM:BW = N:(100 - N), where N is the percentage of SiM in the synthetic solution and equals 100, 80, 50, 30, 20, 10, or 5] with a cesium nitrate solution, we obtained a series of cubic cesium salts (CsSiMBW- N) with POM vacancy-like pores (i.e., kinetically formed interparticle pores). Notably, the yields, compositions, and BET surface areas of the obtained CsSiMBW- N were dependent on only the N values and independent of SiW or SiMo. In CsSiMBW- N, SiM and BW were well blended at the molecular (nanometer) level. The nitrogen, water, and ethanol adsorption properties of CsSiWBW- N systematically changed according to the SiW:BW molar ratios. In the case of SiW-rich salts, nitrogen, water, and ethanol were adsorbed in the pores; the amounts of nitrogen, water, and ethanol adsorbed were nearly identical for CsSiWBW-100. When the SiW:BW molar ratio was decreased, the salts selectively incorporated water and ethanol within the pores. In the case of CsSiWBW-5, barely any nitrogen was adsorbed. The plausible mechanisms for particle growth and interparticle POM vacancy-like pore formation are also discussed.

Surface strengthening of lithium disilicate glass-ceramic by ion-exchange using Rb, Cs nitrates

In order to further improve the flexural strength of lithium disilicate glass-ceramic, surface strengthening by ion exchange using Rb, Cs nitrates has been studied for the first time. The influences of ion exchange using rubidium and cesium salts on the flexural strength and corrosion resistance have been investigated. It was found that the mechanical properties of the lithium disilicate glass-ceramic could be increased greatly by the ion exchange in rubidium nitrate (RbNO3) salt. After ion exchange for 4 h in RbNO3 salt, the flexural strength and microhardness increased from 169 MPa and 587 kgf mm−2 (5.75 Gpa) of the original lithium disilicate glass-ceramic to 493 MPa and 654 kgf mm−2 (6.4 Gpa), respectively. Moreover, the corrosion resistance of the lithium disilicate glass-ceramic was further improved by ion exchange in rubidium and cesium nitrate salts. Furthermore, the maximum thickness of the ion exchange layer using RbNO3 and CsNO3 was only 4.3 µm and 0.45 µm respectively. Such a thin exchange layer, which will only require very low Rb+, Cs+ ions exchange amount, indicates that the molten salts of RbNO3 and CsNO3 can be reused for many times. So it is suggested that surface strengthening of lithium disilicate glass-ceramic by ion exchange using Rb, Cs nitrates is cost-efficient and very suitable for the actual production and applications.

Structure and properties of a rhodium(III) pentanitrato complex embracing uni- and bidentate nitrato ligands

A novel rhodium [Rh(NO3)5]2− anionic complex with mixed denticity of nitrato ligands was isolated in a form of its poorly soluble caesium salt. The structure of the salt was studied by an X-ray single crystal method. DFT-based theoretical studies were carried out to gain insights into the electronic structure and the properties of the [Rh(NO3)5]2− complex. The calculated 15N NMR chemical shifts of nitrato groups in [Rh(NO3)5]2− complex was found to become sensitive to the nitrate ligand coordination bonding mode upon ion-pairing with caesium cations. In good agreement with experimental findings, the DFT calculated free energies for the addition of H2O or NO3− ligands to the [Rh(NO3)5]2− complex points to its low hydrolytic stability.

The Study of Anti-/Pro-Oxidant, Lipophilic, Microbial and Spectroscopic Properties of New Alkali Metal Salts of 5-O-Caffeoylquinic Acid.

Lithium, sodium, potassium, rubidium and caesium salts of 5-O-caffeoylquinic acid (chlorogenic acid, 5-CQA) were synthesized and described by FT-IR (infrared spectroscopy), FT-Raman (Raman spectroscopy), UV (UV absorption spectroscopy), 1H (400.15 MHz), 13C (100.63 MHz) NMR (nuclear magnetic resonance spectroscopy). The quantum–chemical calculations at the B3LYP/6-311++G** level were done in order to obtain the optimal structures, IR spectra, NBO (natural bond orbital) atomic charges, HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) orbitals and chemical reactivity parameters for 5-CQA and Li, Na and K 5-CQAs (chlorogenates). The DPPH (α, α-diphenyl-β-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) assays were used for the preliminary estimation of the antioxidant properties of alkali metal chlorogenates and chlorogenic acid. In the DPPH assay the EC50 parameter were equal to 7.39 μM for 5-CQA and was in the range of 4.50–5.89 μM for salts. The FRAP values for two different concentrations (5 and 2.5 μM) of the studied compounds were respectively 114.22 and 72.53 μM Fe2+ for 5-CQA, whereas for salts they were 106.92–141.13 and 78.93–132.00 μM Fe2+. The 5-CQA and its alkali metal salts possess higher antioxidant properties than commonly applied antioxidants (BHA, BHT, l-ascorbic acid). The pro-oxidant action of these compounds on trolox oxidation was studied in the range of their concentration 0.05–0.35 μM. The lipophilicity (logkw) of chlorogenates and chlorogenic acid was determined by RP-HPLC (reverse phase—high performance liquid chromatography) using five different columns (C8, PHE (phenyl), CN (cyano), C18, IAM (immobilized artificial membrane)). The compounds were screened for their in vitro antibacterial activity against E. coli, Bacillus sp., Staphylococcus sp., Streptococcus pyogenes and antifungal activity against Candida sp. The 5-CQA possessed lower antibacterial (minimal inhibitory concentration, MIC = 7.06 mM) and antifungal (MIC = 14.11 mM) properties than its alkali metal salts (MIC values: 6.46–2.63 mM and 12.91–5.27mM, respectively). The synthesized chlorogenates possessed better antioxidant, lipophilic, antimicrobial as well as lower pro-oxidant properties than the ligand alone. Moreover, a systematic change of the activity of alkali metal salts along the series Li→Cs suggests that there are correlations between the studied biological properties. The type of metal cation in the carboxylate group of chlorogenate is crucial for the activity of studied compounds.

Reactivity of a (Benzene)Ruthenium(II) Cation on a Di‐lacunary γ‐Keggin‐Type Silicotungstate and Synthesis of a Mono‐(Benzene)Ruthenium(II)‐Attached γ‐Keggin‐Type Silicotungstate

Reaction of a (benzene)Ru2+ complex, [Ru(C6H6)Cl2]2, with a di‐lacunary γ‐Keggin‐type silicodecatungstate, K8[γ‐SiW10O36], at a (C6H6)Ru2+/[γ‐SiW10O36]8– ratio of 1 produces [γ‐SiW10O36Ru(C6H6)]6–. The cesium salt was characterized using experimental and theoretical methods; one (C6H6)Ru2+ moiety is attached through three bridging oxygen atoms of the non‐lacunary site, and the anion is stable in aqueous solution. 1H NMR spectroscopy and high‐resolution electrospray ionization mass spectrometry measurements of the reaction mixture with different (C6H6)Ru2+/[γ‐SiW10O36]8– ratios indicate that the (C6H6)Ru2+ complex first reacts with the three bridging oxygen atoms to form [γ‐SiW10O36Ru(C6H6)]6–, and then react on the terminal oxygen atoms of the lacunary site to form a [γ‐SiW10O36Ru(C6H6)]6– complex, which was reported by the Kortz and Nadjo group.

Cesium-substituted mesoporous phosphotungstic acid embedded chitosan hybrid polymer membrane for direct methanol fuel cells

Non-ionic polyethylene glycol dodecyl ether (Brij 76) template novel single-step process is successfully evolved for preparation of mesoporous cesium salt of phosphotungstic acid (PTA) with tunable porosity. Hybrid proton exchange membranes are prepared by embedding mesoporous cesium salt of PTA into chitosan (CS) polymer and are characterized by FTIR, TGA, and SEM mapping studies. To elucidate advantages of mesoporous structure, a series of CS hybrid membranes comprising non-porous cesium salt of phosphotungstic acid is also prepared and their functional properties are compared with mesoporous counterparts. Mesoporous nature helps to integrate membrane network creating maximum intermolecular interaction between organic and inorganic components. Both selective water sorption feature of CS and highly hydrophilic nature of mesoporous cesium salt of PTA together play a vital role in selective proton transport process through CS/m-PTA hybrid membranes. At optimal loading of m-PTA, maximum peak power density of 83 mW cm−2 was achievable with 2 M methanol as a fuel feed. On the basis of thermal stability, low methanol crossover, and appropriate proton conductivity, CS/m-PTA-5 wt% hybrid membrane could be proposed as novel polyelectrolytes for direct methanol fuel cell.

Sila-polyethers as innocent crystallization reagents for heavy alkali metal compounds

Sila-polyethers are used as innocent crystallization reagents for the formation of single crystals of different elusive rubidium and cesium salts.

Combating pathogens with Cs2.5H0.5PW12O40 nanoparticles: a new proton-regulated antimicrobial agent.

The transfer of pathogens from contaminated surfaces to patients is one of the main causes of health care-associated infections (HCAIs). Cases of HCAIs due to multidrug-resistant organisms have been growing worldwide, whereas inorganic nano-antimicrobials are valuable today for the prevention and control of HCAIs. Here, we present a cesium salt of phosphotungstic heteropolyacid (Cs2.5H0.5PW12O40) as a promising nanomaterial for use in antimicrobial product technologies. This water-insoluble Keggin salt exhibits a broad biocide spectrum against Gram-positive and Gram-negative bacteria, yeasts, and filamentous fungi even under dark conditions. The Cs2.5H0.5PW12O40 nanoparticles (NPs) act as a proton-regulated antimicrobial whose activity is mediated on the release of hydronium ions (H3O+), yielding an in situ acidic pH several units below those tolerable by most of the fungal and bacterial nosocomial pathogens.