Ion-exchange Route Research Articles

Sonochemical synthesis of silver nanoparticles in Y-zeolite substrate

Silver ions can be reduced by 24 kHz ultrasonic waves in ion-exchanged Ag+–Y zeolite. In this research, silver ions were introduced into the nano-porous (1.2 nm) zeolite lattice by ion-exchange route. After the reduction process, silver nanoparticles were placed in the cavities, with a size of about 1 nm and also on the external surfaces of the zeolite, with sizes about less than 10 nm. Fast and simple lab-scale reduction of silver ions in the zeolite is important for researchers who work on catalytic properties of metallic silver–zeolite. Several reduction methods have been reported but reduction by ultrasonic waves is a new, simple, and size-controllable method with a high practical value which does not need any complicated facilities. In a sonochemical process, a huge density of energy is provided by the collapse of bubbles which formed by ultrasonic waves. The released energy causes the formation of reducing radicals that consequently reduce the silver ions. It is concluded that the higher silver content may result in the formation of larger silver crystals on the external surface of zeolite crystals. Also, the addition of 1-propanol and 2-propanol to the aqueous reaction medium does not cause better reduction. In addition, increasing the irradiation time and ultrasonic power does not affect the silver crystal growth significantly but the extent of silver ion reduction increases when the power of ultrasonic waves increases. All samples were irradiated under the same ultrasonic conditions. The samples were analyzed by XRD, EDS, SEM, and TEM.

Plasticised polymer inclusion membrane as tunable host for stable gold nanoparticles

Stable Au nanoparticles (nps) were synthesised in matrix of the self-supported plasticised polymer inclusion anion-exchange membrane using the ion-exchange route for loading AuCl4− anions in membrane and their subsequent reduction with BH4− anions. The compositions of membrane was varied by changing concentration of the anion exchanger, and also using different plasticiser. X-ray diffraction patterns of the membrane samples embedded with Au nps were taken to study the parameters involved in the formation of Au nps in the plasticised polymer matrix. The content of Au nps in the membrane was increased by: 1) repeating the sequential cycles of loading of AuCl4− ions followed by the reduction with BH4− in the membrane matrix; 2) increasing the concentration of anion exchanger in the membrane matrix. It was observed in TEM images of cross section of membrane that spherical Au nps of 10 nm sizes were dispersed throughout the matrix of membrane. The increase in Au0 content in the membrane did not alter the average size of Au nps significantly, but slightly increased the range of size distribution. The nanostructures like prism, rod, sphere, bipyramid and cuboid were also observed in the membrane matrix, but their number density was 5% of nanoparticles present in the membrane matrix. The analyses of isotopic-exchange rate profiles of iodide ions between the membrane sample and well-stirred equilibrating salt solution indicated that formation of Au nps lead to a significant increase in self-diffusion mobility of the anions in membrane. The surface plasmon band (SPB λmax = 535 nm) of Au nps did not change on equilibration of the membrane samples with the solutions containing Cl−, I−, ClO4−, and CH3COO− anions, but completely disappeared on equilibration with solution containing molecular iodine.

Synthesis of Al-substituted mesoporous silica coupled with CdS nanoparticles for photocatalytic generation of hydrogen

Aluminum-substituted mesoporous silica (Al-HMS) molecular sieve coupled with CdS nanoparticles (CdS/Al-HMS) were prepared by template assembly, ion-exchange and sulfuration routes. The XRD and TEM results indicated that the assembly of less than 2 wt% CdS nanoparticles in the porous channels of Al-HMS didn't significantly affect the wormhole-like mesoporous framework structure of Al-HMS, whereas the porous channels of Al-HMS were filled up by CdS nanoparticles after loading of 21 wt% CdS. The diffuse reflectance UV–visible spectra exhibited that the absorption edge was gradually blue-shifted with decrease in CdS content due to the quantum confinement effect. The CdS/Al-HMS sample loaded 0.99 wt% Ru showed the highest H 2 evolution at a rate of 13.23 mL h −1 with an apparent quantum yield of 5.92% at 420 nm by photocatalytic degradation of formic acid under visible light irradiation.

Electrochemical sensing platform based on tris(2,2′-bipyridyl)cobalt(III) and multiwall carbon nanotubes–Nafion composite for immunoassay of carcinoma antigen-125

A new strategy for constructing a sensitive mediator-type electrochemical immunosensor for the detection of carcinoma antigen-125 (CA125) was developed. In this strategy, mediator tris(2,2′-bipyridyl)cobalt(III) (Co(bpy) 3 3+) was incoporated into the multiwall carbon nanotubes–Nafion (MWNTs–Nafion) composite film via a simple ion-exchange route. Then, gold colloidal nanoparticles (nano-Au) were attached onto Co(bpy) 3 3+/MWNTs–Nafion film through electrostatic interaction between negatively charged nano-Au and positively charged Co(bpy) 3 3+. Finally, CA125 monoclonal antibody (anti-CA125), used as a model antibody, was assembled onto the surface of nano-Au to achieve an immunosensor for the determination of CA125 antigen. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to characterize the assembly process of the modified electrode. The resulting immunosensor showed a high sensitivity, wide dynamic range consisting of two linear parts from 1.0 to 30 U mL −1 and 30 to 150 U mL −1 with a low detection limit of 0.36 U mL −1 at 3 times the background noise. Moreover, it displayed good reproducibility and stability, and would be potentially attractive for clinical immunoassay of CA125. The integration of mediator Co(bpy) 3 3+ and MWNTs–Nafion composite would offer potential promise for the fabrication of biosensors and biocatalysts.

Synthesis and ammonia sensing property of Ag3CuS2 nanocages obtained from Cu7S4 18-facet hollow nanopolyhedra

Ag3CuS2 nanocages were successfully fabricated for the first time via a convenient ion-exchange route by Ag+ reacting with Cu7S4 18-facet hollow nanopolyhedra. The average size and shell thickness of Ag3CuS2 nanocages were around 400 and 30nm, respectively. Room-temperature response of Ag3CuS2 nanocages to ammonia was investigated by photoluminescence-type sensor. Sensing results suggested that these hollow-structured Ag3CuS2 exhibited better performances including higher sensitivity, shorter response and recovery time than their rod-shape counterparts. A possible hole trapping mechanism was proposed.

A simple route to incorporate redox mediator into carbon nanotubes/Nafion composite film and its application to determine NADH at low potential

Through a new and simple ion-exchange route, two-electron redox mediator thionine has been deliberately incorporated into the carbon nanotubes (CNTs)/Nafion composite film due to the fact that there is strong interaction between any of two among the three materials (ion-exchange process between thionine and Nafion, strong adsorption of thionine by CNTs, and wrapping and solubilizing of CNTs with Nafion). The good homogenization of electron conductor CNTs in the integrated films provides the possibility of three-dimensional electron conductive network. The resulting integrated films exhibited high and stable electrocatalytic activity toward NADH oxidation with the significant decrease of high overpotential, which responds more sensitively more than those modified by thioine or CNTs alone. Such high electrocatalytic activity facilitated the low potential determination of NADH (as low as −0.1 V), which eliminated the interferences from other easily oxidizable species. In a word, the immobilization approach is very simple, timesaving and effective, which could be extended to the immobilization of other cationic redox mediators into the CNTs/Nafion composite film. And these features may offer potential promise for the design of amperometric biosensors.

New Inorganic-Based Drug Delivery System of Indole-3-Acetic Acid-Layered Metal Hydroxide Nanohybrids with Controlled Release Rate

We have developed new inorganic-based drug delivery systems through the hybridization of indole-3-acetic acid (IAA) and layered metal hydroxide such as zinc basic hydroxide salt (ZBS) and zinc aluminum layered double hydroxide (ZALDH). A coprecipitation method as well as an ion-exchange route is found to be commonly effective in synthesizing both IAA-ZBS and IAA-ZALDH nanohybrids, in which the tilted bilayers of IAA are stabilized in the interlayer space of layered metal hydroxide lattice. According to the FT-IR spectroscopic analyses, IAA molecules interact more strongly with the ZBS lattice than the ZALDH one, which is due to the formation of coordination bonds between carboxyl groups of the guest species and coordinatively unsaturated Zn(OH)3 units of the host ZBS lattice. Such an interaction gives rise to a slower release of the IAA molecules from the ZBS-based nanohybrid than from the ZALDH-based one. The present results underscore that the layered hydroxydouble salt like ZBS makes it possible to des...

INNOVATIVE APPROACHES TO SYNTHESIS OF GT 267-004, A SEQUESTRANT FOR C. DIFFICILE TOXIN

GT 267-004 is a nonabsorbed, nonantibiotic, high molecular weight anionic polymer that is undergoing clinical evaluation as a Clostridium difficile toxin sequestrant. The active pharmaceutical ingredient (API) is a mixed salt form that consists of approximately 30 to 50% potassium and 70 to 50% sodium as the counterions on the polymer. The initial polymerization process results in an aqueous polymer solution with the polymer in the 100% sodium form. This article describes the use of two innovative approaches, electrodialysis (ED) and ion exchange using ion exchange resins (IXR), to convert the single-salt polymer to the mixed-salt form. Electrodialysis experiments were conducted using a stack of five cells, each of which contained two cation and one anion exchange membranes. The electrodialysis was run in batch mode with a sodium chloride solution as the concentrate stream and a potassium chloride solution as the diluate stream. The ED process was monitored on-line by measuring the conductivity of the streams. Yield loss of the API through the ED membranes was minimal. The ED process was found to be fast, efficient, and reproducible. The ion exchange experiments were conducted using a strong acid cation resin in the potassium form. By using a fixed bed column mode, an appropriate amount of ion exchange was carried out to produce the mixed-salt API in the effluent stream. The resin bed could be regenerated using KCl solution and reused for subsequent batches of polymer solution. The recovery of the API in the product solution was excellent. The ion exchange route was used to synthesize radio-labeled API for clinical trials.

Structural Evolution of Layered LixMnyO2: Combined Neutron, NMR, and Electrochemical Study

The conversion upon electrochemical cycling from a layered structure to a spinel in nonstoichiometric LixMnyO2 has been studied by neutron diffraction and NMR. This process occurs in all layered lithium manganate materials, irrespective of the ion-exchange route. The high temperature of the ion exchange under reflux in n-hexanol is sufficient to promote formation of some spinel within the as-synthesized material. Upon cycling, all the different layered LixMnyO2 compounds begin to transform to a spinel. In the first 50 or so cycles, the various layered LixMnyO2 compounds behave rather differently, with a higher spinel fraction being observed for materials ion-exchanged under more extreme conditions. However, the rate of this transformation is significantly slower than was observed in stoichiometric layered LiMnO2, with only 25% spinel observed after 100 cycles. Ultimately, upon extended cycling, the entire structure will form a well-ordered spinel phase.

NMR, PDF and RMC study of the positive electrode material Li(Ni0.5Mn0.5)O2 synthesized by ion-exchange methods

The local environment and short-range ordering of Li(Ni0.5Mn0.5)O2, a potential Li-ion battery positive electrode material obtained via an ion-exchange route from Na(Ni0.5Mn0.5)O2, were investigated by using a combination of 6Li Magic Angle Spinning (MAS) NMR spectroscopy and neutron Pair Distribution Function (PDF) analysis, associated with Reverse Monte Carlo (RMC) calculations. 6Li MAS NMR experiments on Li(Ni0.5Mn0.5)O2 showed that there are almost no Li ions in the transition metal layers. Neutron diffraction data for the precursor Na(Ni0.5Mn0.5)O2 indicated that there is no Na/Ni disorder and that the material is perfectly layered. Neutron PDF analysis of Li(Ni0.5Mn0.5)O2 and Na(Ni0.5Mn0.5)O2 revealed differences in the local transition metal arrangements between those present in the ion-exchanged material and its precursor, and those found in the cathode material synthesized directly from hydroxide starting materials. Large clusters of 3456 atoms were built to investigate cation ordering. Reverse Monte Carlo results, for both the Na and Li-containing compounds, showed a non-random distribution of Ni and Mn cations in the transition metal layers: in the first coordination shell, Ni atoms are on average close to more Mn ions than predicted based on a random distribution of these ions in the transition metal layers. Analysis of the number of Ni/Ni, Mn/Mn and Ni/Mn pairs in the second coordination shell revealed that the Ni and Mn cations show a clear preference for ordering in zigzags rather than in chains.

Synthesis and characterization of porous chromia-pillared layered lanthanum niobic acid

The first chromia-pillared layered lanthanum niobic acid was prepared by an ion-exchange route, in which n-hexylamine-pre-expanded lanthanum niobate reacted with chromium(III) acetate [Cr(OAc) 3] aqueous solution under reflux condition, and the ion-exchanged product was calcined at 450 °C in air flow. The structure of the novel pillared material was examined by means of various analytical techniques, such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential analysis (TG/DTA), nitrogen adsorption–desorption, and transmission electron micrographs (TEM). The chromia-pillared layered lanthanum niobic acid exhibited a porous layered structure with a BET (Brunauer-Emmett-Teller) surface area of 89 m 2·g − 1 and an interlayer distance of 1.31 nm. The layered structure could be retained up to 550 °C.

Confined Synthesis of CdSe Quantum Dots and Characterization

Nanoclusters of II‐VI compound semiconductor CdSe were synthesized within the mesopores of MCM‐41 sodium aluminium silicate framework material following an ion exchange route after suitably protecting the outer walls of the pore. The integrity of the framework after formation of the nanocomposite was confirmed by XRD. XRD and elemental analysis revealed the formation of the clusters. The absorption and photoluminescence spectroscopy of the composite yields results consistent with the blue shift expected as a consequence of quantum confinement in these nanoclusters. The Raman spectrum of the CdSe‐MCM composite shows evidences of phonon confinement.

Designed formation of the stable adduct InP/CTAB/Clay

An ordered multilayered adduct InP/CTAB/Clay has been synthesized via simple ion-exchange route that utilizes the electrostatic self-assembly between the exfoliated sodium montmorillonite nanoplatelets and the substituted InP/CTAB cationic polyelectrolytes. The obtained samples exhibit a high degree of structural ordering, with the interlammellar spacing of ca. 36.8 Å, which is well manifested by low-angle X-ray powder diffraction (LXRD) patterns. Transmission electron microscopy (TEM) images indicate its structural hierarchy, while UV–Vis and PL spectrum demonstrates the existence of InP nanocrystals. It is found that the high CEC of Na-montmorillonite and the appropriate ratio of CTAB-to-InP, as well as the presence of the InP/CTAB polyelectrolytes would have the influence on the purity and the formation of the stable adducts InP/CTAB/Clay. This preparative method described here can be anticipated to offer a potential strategy for building the ordered stable adducts with sandwich-like structures due to its ease, reproducibility and versatility.

Silver-sensitized erbium-doped ion-exchanged sol–gel waveguides

Ag- and Er-doped glass films have been synthesized with a combined sol–gel and ion-exchange route. The introduction of silver as erbium sensitizer in the film was obtained by ion exchanging Er-doped SiO2–Al2O3–Na2O sol–gel films. The films were subsequently annealed under controlled atmosphere to induce the migration and aggregation of the metal ions. Films showed different Er3+ photoluminescence behaviors depending on silver concentration and aggregation state. The interaction between erbium ions and Ag centers has been investigated and enhancement of the excitation cross section due to the silver sensitizing effect has been demonstrated. The developed synthesis also allowed the realization of erbium-doped channel waveguides by a selective Na–Ag ion-exchange process .

Layered LixMn1−yLiyO2intercalation electrodes: synthesis, structure and electrochemistry

Layered LixMn1−yLiyO2 materials with the O3 (α-NaFeO2) structure have been synthesised by a low temperature ion exchange route from the corresponding sodium compounds. The effects on electrochemical performance (ability to store reversibly large quantities of lithium and hence charge) and crystal chemistry by partially substituting some of the Mn ions by Li have been investigated by structural and electrochemical techniques as well as chemical analysis. The materials deliver high discharge capacities; in excess of 200 mA h g−1 at 25 mA g−1 or C/8. On the first charge once all Mn is in the 4+ oxidation state further Li+ removal occurs by two unconventional mechanisms, one involving oxidation of O2− with subsequent O loss (effective removal of Li2O) and the other electrolyte oxidation generating H+ which exchanges for Li+ in the electrode. Although both mechanisms appear to occur at 30 and 55 °C, the former dominates at both temperatures. A mechanism for O loss involving O release at the surface with Mn migration into the bulk in order to fill up vacant octahedral sites in the transition metal layers is proposed, consistent with the neutron diffraction data. Evidence for tetrahedral Li and Li loss from the octahedral sites in the transition metal layers is also presented. The compounds in this study irreversibly transform to spinel-like materials on extended cycling. This is not, however, detrimental to their electrochemical performance and is analogous to the behaviour of other O3 layered lithium manganese oxides.

Template ion exchange route to nanocrystalline MIn2S4 (M=Mn, Zn)

A template ion exchange method has been established to synthesize ternary sulfides MIn2S4 (M=Mn, Zn) by the reaction of metal chlorides and NaInS2 in absolute ethanol at 140 °C for 12 h. The effects of reactant NaInS2, temperature and reaction time on the template ion exchange reaction were investigated.

Template Synthesis of Ag2S Nanorods via an Ion-exchange Route

Abstract By using CdS nanorods as template, Ag2S nanorods were synthesized via a solution-phase ion-exchange route at room temperature. It is important to control a slow reaction speed by adding thiourea into the solution to form complex with Ag+ ion during the synthetic process.

Template ion exchange route to nanocrystalline MIn 2S 4 (M=Mn, Zn)

A template ion exchange method has been established to synthesize ternary sulfides MIn 2S 4 (M=Mn, Zn) by the reaction of metal chlorides and NaInS 2 in absolute ethanol at 140 °C for 12 h. The effects of reactant NaInS 2, temperature and reaction time on the template ion exchange reaction were investigated.

Dianionic silicate derivatives of transition metals: synthesis by a facile ion exchange route, characterization and thermolysis studies

A new series of transition metal complexes [M = Cr(III) ( 1), Mn(II) ( 2), Co(III) ( 3), Ni(II) ( 4a–d), and Cu(II) ( 5a–b)] with the dianionic hypervalent, tris(catecholato)silicate, [Si(C 6H 4O 2) 3] 2−, have been synthesized by an ion exchange method under both aqueous and non-aqueous conditions using bis(triethylammonium) tris(catecholato)silicate and a cationic transition metal complex, [ML n ]X [L = ethylenediamine (en), diethylenetriamine (dien), ammonia or water and X = Cl −, SO 4 2− ]. Different ammonium tris(catecholato)silicates [viz. morpholinium, diisopropylammonium and diethylammonium] also serve as appropriate for the ion exchange reaction. Ligands like H 2O and NH 3 afford less stable complexes compared to the ligands en and dien. The powdered form of Ni(II) complexes, [NiL 6][Si(C 6H 4O 2) 3] (L = H 2O, NH 3), readily convert to [Ni(en) 3][Si(C 6H 4O 2) 3] quantitatively when treated with en. The new derivatives have been characterized on the basis of analytical, spectroscopic (IR, UV–Vis, solid state NMR, EPR and MS) and magnetic data. The results of TG and EG analysis of the complexes 1– 5 reveal (i) different decomposition behaviour compared to ammonium catecholatosilicates and (ii) the influence of the bulky tris(catecholato)silicate anion on the thermal stability of these complexes. The bulk pyrolysis study of the above complexes provides a stoichiometric mixture of the corresponding metal oxide and silica except in case of Co(III) which gave the orthosilicate, Co 2SiO 4. Variable temperature magnetic susceptibility measurements indicate a weak antiferromagnetic interaction in case of [Ni(en) 3][Si(C 6H 4O 2) 3] and [Cu(en) 2][Si(C 6H 4O 2) 3].

Effect of silica sol of different routes on the properties of low cement castables

Silica sols synthesized through different routes viz. inorganic, organic and ion-exchange routes, have been incorporated in the low cement alumina castable composition in various proportions and cast samples in the form of 2 inch cube briquettes were prepared. The cast briquettes after curing were subjected to heat treatment at various temperatures. The effect of different sources of such sols on the important physico-mechanical properties of the castables such as bulk density, apparent porosity, compressive strength, volume shrinkage and residual strength after spalling have been studied. Some of the selected samples were also subjected to microstructural evaluation. It is observed that silica sol synthesized through cation exchange routes has significant beneficial role on the properties of castable with 3% addition.