Intercalation Of Metal Ions Research Articles

V2O5 As the Cathode for Mg2+-Ion Batteries, Preparation and Characterization

Portable electronics and their commercial use are strongly dependent on the prize, performance and life cycle of the rechargeable batteries. This is even truer for the use in electric vehicles. Currently used Li+-ion batteries represent the state of art technology but there still is a strong demand for further improvement [1,2]. Low abundance and thus high costs for lithium have initiated intensive research for the possible replacement of lithium by other more abundant metals such as magnesium and sodium [3]. Ionic, electronic and chemical characteristics of Li+-, Na+- and Mg2+-ions are different and therefore host materials appropriate for Li+-ions intercalation are not necessarily suitable for Mg2+ and Na+ ions – as well known for the case of graphite anodes. The cathode material V2O5 is one candidate which already showed good performance not just for Li+ but also for Mg2+ and Na+ions [4,5]. Since the morphology and structure of the host materials strongly influence the intercalation process, in this study efforts have been done to synthesize V2O5 with different morphology by applying different synthetic routes and choosing the best material for the metal ion intercalation. V2O5 was prepared by means of sonochemical modification of commercial V2O5 powder, anodization of V metal, electrochemical deposition and hydrothermal synthesis. The obtained materials were characterized by means of scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The sonochemical treatment and electrochemical deposition yielded V2O5-nanofibers, the anodization method V2O5-nanotubes and the hydrothermal synthesis hollow nanospheres of V2O5. The performance of the obtained materials was tested by several electrochemical techniques such are cyclic voltammetry, potentiostatic intermittent titration technique (PITT) and galvanostatic charge/discharge cycles. Li, Na and Mg intercalation were studied. For Li, the rate capability of the sonochemically prepared material was clearly improved compared to commercial, microcrystalline V2O5, but the available voltage at a given discharge capacity was less. The electrodeposited material showed a rather poor performance, while the hollow nanospheres behaved very promising. Also for Na intercalation the latter material showed reasonable performance. First measurements for Mg insertion are shown as well. [1] Dunn B. et al., Electrical Energy Storage for the Grid: A Battery of Choices, Science 334 (2011) 928 [2] Gachot G. et al., Deciphering the multi-step degradation mechanisms of carbonate-based electrolyte in Li batteries, Journal of Power Sources 178 (2008) 409 [3] Besenhard J. et al., Advances in battery technology: rechargeable magnesium batteries and novel negative-electrode materials for lithium ion batteries, ChemPhysChem 3 (2002) 155 [4] Gershinsky G. et al., Electrochemical and Spectroscopic Analysis of Mg2+ Intercalation into Thin Films Electrodes of Layered Oxides: V2O5 and MoO3, Langmuir 29 (2013) 10964 [5] Su D. W. et al., Hierarchical orthorhombic V2O5hollow nanospheres as high performance cathode materials for sodium-ion batteries, J. Mater. Chem. 2 (2014) 11185

Sodium-Ion Intercalated Transparent Conductors with Printed Reduced Graphene Oxide Networks.

In this work, we report for the first time that Na-ion intercalation of reduced graphene oxide (RGO) can significantly improve its printed network's performance as a transparent conductor. Unlike pristine graphene that inhibits Na-ion intercalation, the larger layer-layer distance of RGO allows Na-ion intercalation, leading to simultaneously much higher DC conductivity and higher optical transmittance. The typical increase of transmittance from 36% to 79% and decrease of sheet resistance from 83k to 311 Ohms/sq in the printed network was observed after Na-ion intercalation. Compared with Li-intercalated graphene, Na-ion intercalated RGO shows much better environmental stability, which is likely due to the self-terminating oxidation of Na ions on the RGO edges. This study demonstrated the great potential of metal-ion intercalation to improve the performance of printed RGO network for transparent conductor applications.

Advanced Biomimetic Approach for Crystal Growth in Nonaqueous Media: Morphology and Orientation Control of Pentacosadiynoic Acid and Applications

In nature, biological macromolecules control the growth of inorganic crystals under mild conditions in aqueous media. Inspired by biomineralization, biomimetic approaches have been studied for growth control of inorganic crystals in aqueous media by using organic molecules and polymers. The approaches were not applied to nonaqueous systems for the development of functional organic materials. Here, we have applied biomimetic approaches to growth control of organic crystals in nonaqueous media. Morphology and orientation of 10,12-pentacosadiynoic acid (PCDA) crystals, a diacetylene derivative, were controlled in organic media with the additive organic polymers and surface-modified substrates. The oriented PCDA ribbons were obtained by an advanced biomimetic approach. After topochemical polymerization, the resultant polydiacetylenes (PDA) ribbons were applied to the thermochromic materials with intercalation of metal ions and the semiconductor layer of an organic field-effect transistor. The present work imp...

A silicon-based two-dimensional chalcogenide: growth of Si₂Te₃ nanoribbons and nanoplates.

We report the synthesis of high-quality single-crystal two-dimensional, layered nanostructures of silicon telluride, Si2Te3, in multiple morphologies controlled by substrate temperature and Te seeding. Morphologies include nanoribbons formed by VLS growth from Te droplets, vertical hexagonal nanoplates through vapor-solid crystallographically oriented growth on amorphous oxide substrates, and flat hexagonal nanoplates formed through large-area VLS growth in liquid Te pools. We show the potential for doping through the choice of substrate and growth conditions. Vertical nanoplates grown on sapphire substrates, for example, can incorporate a uniform density of Al atoms from the substrate. We also show that the material may be modified after synthesis, including both mechanical exfoliation (reducing the thickness to as few as five layers) and intercalation of metal ions including Li(+) and Mg(2+), which suggests applications in energy storage materials. The material exhibits an intense red color corresponding to its strong and broad interband absorption extending from the red into the infrared. Si2Te3 enjoys chemical and processing compatibility with other silicon-based material including amorphous SiO2 but is very chemically sensitive to its environment, which suggests applications in silicon-based devices ranging from fully integrated thermoelectrics to optoelectronics to chemical sensors.

Novel synthesis of hexagonal WO3 nanostructures

This paper discusses the synthesis and characterization of a new form of WO3 nanostructures based on the hexagonal WO3 (h-WO3) polymorph. This typically “metastable” phase was synthesized from a substoichiometric metal alkoxide precursor-tungsten (V) isopropoxide, by a novel colloidal synthesis method. Nanowires of h-WO3 were obtained upon heat-treating the sol–gel precursor at 400 °C. Further processing at elevated temperatures (515 °C) resulted in coarsening of the nanowires and the formation of nanowire bundles with polytypic character. Hexagonal WO3 differs from the other tungsten oxide polymorphs in that it possesses unique structural features such as long, hexagonal prism channels parallel to the c-axis and layered oxygen octahedra. This makes it a very attractive host matrix for metal ion intercalation for rechargeable batteries and for the selective gas sensing of amines.

Stable alkali metal ion intercalation compounds as optimized metal oxide nanowire cathodes for lithium batteries.

Intercalation of ions in electrode materials has been explored to improve the rate capability in lithium batteries and supercapacitors, due to the enhanced diffusion of Li(+) or electrolyte cations. Here, we describe a synergistic effect between crystal structure and intercalated ion by experimental characterization and ab initio calculations, based on more than 20 nanomaterials: five typical cathode materials together with their alkali metal ion intercalation compounds A-M-O (A = Li, Na, K, Rb; M = V, Mo, Co, Mn, Fe-P). Our focus on nanowires is motivated by general enhancements afforded by nanoscale structures that better sustain lattice distortions associated with charge/discharge cycles. We show that preintercalation of alkali metal ions in V-O and Mo-O yields substantial improvement in the Li ion charge/discharge cycling and rate, compared to A-Co-O, A-Mn-O, and A-Fe-P-O. Diffraction and modeling studies reveal that preintercalation with K and Rb ions yields a more stable interlayer expansion, which prevents destructive collapse of layers and allow Li ions to diffuse more freely. This study demonstrates that appropriate alkali metal ion intercalation in admissible structure can overcome the limitation of cyclability as well as rate capability of cathode materials, besides, the preintercalation strategy provides an effective method to enlarge diffusion channel at the technical level, and more generally, it suggests that the optimized design of stable intercalation compounds could lead to substantial improvements for applications in energy storage.

Plasmon-induced photoluminescence immunoassay for tuberculosis monitoring using gold-nanoparticle-decorated graphene.

Metal-nanoparticle-functionalized graphene, in particular, graphene sheets containing Au nanoparticles (Au NPs), have generated considerable interest because of their unique optical and electrical characteristics. In this study, we successfully produced graphene sheets decorated with Au NPs (AuGrp) using phytochemicals as reducing agents. During this reaction, Au ions intercalated into the layered graphene flakes and were then reduced into NPs, exfoliating the graphene sheets. The physicochemical properties of the AuGrp nanocomposites were characterized, and the exfoliation process was investigated using a molecular dynamics simulation of Au NPs between graphene sheets. Our proposed technique is advantageous because the phytochemicals are mild reducing agents that preserve the graphene structure during exfoliation and NP decoration. The dispersity of the NPs on the graphene sheets was drastically improved due to the use of metal-ion intercalation. Moreover, the electrical conductivity was 6-30 times higher than that of bare graphene and reduced graphene oxide. Using antibody (Ab) modified AuGrp sheets and quantum dots, a plasmonic-induced photoluminescence immunoassay of tuberculosis (TB) antigen (aG) CFP-10 was demonstrated for a potential application of these materials. The enhancement of photoluminescence (PL) response was monitored depending on the various TB aG concentrations from 5.1 pg/mL to 51 μg/mL, and the detection limit for CFP-10 was 4.5 pg/mL. Furthermore, the selectivity was demonstrated with Ag85 as the other TB aG, and PL enhancement was not observed in this case. Therefore, AuGrp-based immunoassay showed the potential for biosensor application.

A study on the intercalation of heavy metal ions in a wastewater by synthetic layered inorganic adsorbents

This study examined the intercalation mechanism of Co2+, Ni2+, Zn2+, Mn2+ and Fe3+ ions into synthetic layered inorganic adsorbents—hydrotalcite and gyrolite under different conditions. It was observed that the process parameters above depend on the chemical nature of both solutions and adsorbents. An extremely high and selective uptake of Fe3+ ions was observed in both cases (~98–99%). The selectivity sequence of studied metal ions by gyrolite can be written as follows: Co2+ > Zn2+/Mn2+/Ni2+ > Fe3+, while with calcined hydrotalcite: Co2+/Ni2+/Mn2+ > Zn2+ > Fe3+. It was determined that, during simultaneous adsorption, the intercalation of heavy metal ions into the structure of gyrolite or calcined hydrotalcite proceeds differently, because the amount of adsorbed Mex+ ions is higher than the amount of leached Ca2+ and Mg2+ ions, resulting in the occurrence of two types of chemical reactions – substitution and addition. It should be noted that almost all heavy metal ions (~99.84%) are chemisorbed by both adsorbents. Moreover, after chemisorption, no other compounds were observed in X-ray powder diffraction patterns of both adsorbents. It was observed that hydrothermally treated and calcined hydrotalcite reconstructs its structure during the chemisorption process, while the structure of gyrolite remains stable.

V2O5-Based Composite As Mg-Ion Battery Electrode Material Studied By Electrochemical SPM at the Nanoscale

The science and technology of rechargeable Li-ion batteries have dominated the field of advanced power sources and replaced many other batteries in the market, particularly in the areas of communication, computers, electronics, and in very high power devices such as power tools and electric vehicles.1 The critical challenges for rechargeable Li-ion batteries are cost, safety, and energy density.2 Since an innovative Mg-ion battery was demonstrated successfully by the Aurbach et al.,3 it has received much attention as a potential rechargeable battery to replace the Li-ion battery because of safety, abundance and inexpensiveness of Mg. Moreover, Mg anodes, being divalent and elemental, theoretically provide a higher volumetric capacity of up to ~3800 mAh cm-3 compared to ~2050 mAh cm-3 of Li.2 Despite many promising aspects, there is few research work associated with Mg-ion batteries so far. Indeed, the development of rechargeable Mg-ion batteries has been impeded from various intrinsic limitations relating to the use of Mg metal anodes and Mg-ion intercalation cathodes.4 Passivation of Mg metal in the conventional non-aqueous electrolyte solution is a serious challenge, and Mg-ion intercalation is very slow or even impossible for most of the transition metal oxides serving as Li-ion insertion electrodes. In spite of these difficulties, it has been shown that Mg-ion may insert into transition metal oxides even in conventional non-aqueous Mg salt electrolyte solutions with a certain degree of reversibility.4 Specifically, nanostructured V2O5-based composites are known as high power and high energy density materials that might insert Mg ions reversibly, and they have already been studied intensively as anode and cathode materials for Li-ion batteries demonstrating a high reversible capacity, excellent cycling performance, and good rate capability.5 However, it is important to note that the research efforts dedicated to Mg-ion batteries are still in infancy. Recently, Gershinsky et al.6 explored that highly reversible Mg-ion insertion/extraction was possible with highly pure V2O5 thin-film electrodes using various electrochemical and spectroscopic analytical tools. A growing practical experience related to nanostructured materials suitable for Mg-ion battery applications requires a fundamental insight at nanoscale. In virtue of the Electrochemical Scanning Probe Microscopy (ECSPM) technique, especially Electrochemical Scanning Tunneling Microscopy (ECSTM), our approach to study magnesium intercalation is to use single-crystalline V2O5 to obtain an insight and accurate prediction of reaction mechanisms for the electrode of rechargeable Mg-ion batteries. In order to analyze the intercalation mechanisms of Mg2+, topographical changes of V2O5 will be analyzed under stepwise polarization to different potentials by ECSTM. The results will be described in terms of the combination among physicochemical phenomena, electrochemical metal-ion intercalation into single-crystalline host structures with different electrolyte systems, and electrochemical performance in rechargeable Mg-ion batteries. These studies will be complemented by three electrode electrochemical studies at nanostructured VOxcomposites, and compared to results obtained for Li-ion insertion.

Significant thermal conductivity enhancement in graphene oxide papers modified with alkaline earth metal ions

The thermal conductivities of graphene oxide paper (GOP) and the alkaline earth metal ions (Mg2+, Ca2+) modified analogues, prepared by a facile vacuum filtration method, were measured by a laser flash method. The thermal conductivities of GOP, Mg-modified GOP, and Ca-modified GOP are 3.91 W/(m × K), 32.05 W/(m × K), and 61.38 W/(m × K), respectively, which indicate the modification of GOP with metal ions has resulted in significant enhancement in thermal conduction properties compared with unmodified GOP. The crosslink between graphene oxide sheet and metal ions, the neat stacking of graphene oxide sheets in modified GOP, together with the intercalation of metal ions into the gallery spaces between the graphene oxide sheet basal planes, result in a decrease of thermal resistance of the boundary and an increase of contact surface, thus increases the thermal conductivity of modified graphene oxide paper.

Selective detection of metal ions based on nanocrystalline ionochromic polydiacetylene

Metal ion detection using commercially available ionochromic polydiacetylenes has not been selective. In this work, we report selective detection of metal ions in small organic compound (SOC)-stabilized poly(10,12-pentacosadiynoic acid) (PDA) nanocrystals suspended in an aqueous solution. These PDA nanocrystals were topochemically polymerized using a 254-nm UV light from the corresponding SOC-stabilized DA nanocrystals prepared by a solvent/nonsolvent micellization method. In this detection, the stabilizing SOC could selectively regulate the intercalation of specific metal ions into the galleries of PDA nanocrystals. Whenever the specific metal ions were intercalated, a fast (<1 min) ionochromic transition was observed. In addition, different metal ion selectivity could be achieved by utilization of different SOCs. For example, selective detections of Pb2+ and Ag+ with different detection sensitivities were achieved for a PDA/glycine (Gly) nanocrystal suspension and selective detection of Zn2+ was found for a PDA/boric acid nanocrystal suspension. X-ray diffraction and Fourier transform infrared studies revealed that Pb2+ and Ag+ intercalated into the galleries of PDA nanocrystals and deprotonated most –COOH groups in the side chains of PDA, forming a strong ionic interaction. This strong ionic interaction effectively reduced the conjugation length in the PDA main chain, and therefore selectively induced a blue-to-red ionochromic transition.

Superconductivity in YbxMyHfNCl (M=NH3and THF)

The intercalated layered nitride $\beta$-HfNCl has attracted much attention due to the high superconducting transition temperature up to 25.5 K. Electrons can be introduced into $\beta$-$M$NCl ($M$=Zr and Hf) through alkali-metals intercalation to realize the superconductivity. Here, we report the observation of superconductivity in rare-earth metals cointercalated compounds Yb$_x$($Me$)$_y$HfNCl with $Me$ = NH$_3$ and tetrahydrofuran (THF), which were synthesized by the liquid ammonia method at room temperature. The superconducting transition temperature is about 23 K and 24.6 K for Yb$_{0.2}$(NH$_3$)$_y$HfNCl and Yb$_{0.3}$(NH$_3$)$_y$HfNCl, respectively. Replacing the NH$_3$ with a larger molecule THF, superconducting transition temperature increases to 25.2 K in Yb$_{0.2}$(THF)$_y$HfNCl, which is almost the same as the highest $T_{\rm c}$ reported in the alkali-metals intercalated HfNCl superconductors. The $T_{\rm c}$ of Yb$_{0.2}$(THF)$_y$HfNCl is apparently suppressed by pressure up to 0.5 GPa, while the pressure effect on $T_{\rm c}$ becomes very small above 0.5 GPa. The liquid ammonia method is proved to be an effective synthetic method to intercalate metal ions into HfNCl. Our results suggest that the superconductivity in these layered intercalated superconductors nearly does not rely on the intercalated metal ions, even magnetic ion.

Physicochemical Characterization, and Relaxometry Studies of Micro-Graphite Oxide, Graphene Nanoplatelets, and Nanoribbons

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn2+ ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents.

Glucose‐Assisted Growth of MoS2 Nanosheets on CNT Backbone for Improved Lithium Storage Properties

As a typical layered inorganic material, molybdenum disulfide (MoS2) has a similar structure to graphite. In the crystal structure of MoS2, each Mo(IV) sits in the center of a triangular prism, and is bound to six S atoms. Each S atom is connected to three Mo centers. In this way, the triangular prisms are interconnected to give a layered structure, wherein the Mo atoms are sandwiched between two layers of S atoms. Because of the weak van der Waals interactions between the sheets, MoS2 has a low friction coefficient; this gives rise to its superior lubricating properties. It has also been found attractive in many other application, including catalysts and transistors. Additionally, the layered structure of MoS2 enables easy intercalation of metal ions, such as Li or Mg . Many different MoS2 nanostructures, such as nanoflakes, nanotubes and nanoflowers, have been reported so far as anode materials for lithium ion batteries (LIBs). Although some of them show relatively high capacities of up to 1000 mAhg , the unsatisfactory cycling stability hinders their practical application as anode materials of LIBs. Some methods have been proposed to improve the cycling performance of MoS2, for example, construction of composite materials of MoS2 and conductive carbonaceous materials, like amorphous carbon, carbon nanotubes (CNTs), or graphene. For example, Li et al. reported a hybrid material of CNTs coated with several layers of MoS2. [15] When tested for lithium storage capabilities, the CNT@MoS2 hybrid structure shows a relatively good cyclic capacity retention with a reversible capacity of only up to 400 mAhg , probably due to the low mass fraction of MoS2 in the composite. Thus, obtaining a high content of MoS2 in the CNT@MoS2 is important for a better lithium storage capability. Many CNT-based hybrid structures have been prepared for different applications. 17] Herein, we report a simple glucose-assisted hydrothermal method to directly grow MoS2 nanosheets (NSs) on the CNT backbone (CNT@MoS2 NSs). The content of MoS2 in the hybrid structure is greatly increased because the shell is composed of sheet-like subunits. At the same time, the large surface area provided by this unique hierarchical structure can perhaps help to store more lithium, and the void space between these sheet-like subunits can buffer the volume change during the charge/ discharge processes, and lead to improved cyclic capacity retention. Furthermore, the carbon derived from glucose could ensure an excellent contact between the CNT backbone and the shell of MoS2 NSs, and give rise to a good conducting network. As expected, in comparison with pure MoS2 flakes, these CNT@MoS2 NS nanocomposites show enhanced lithium storage properties with better cyclic capacity retention and a higher reversible capacity. Figure 1 shows the morphology of the as-prepared CNT@MoS2 NSs. From the scanning electron microscopy

Synthesis of Cation-Intercalated Titanate Nanobelts

Monovalent, bivalent and trivalent cations of Li+, Sn2+, Al3+, Fe3+ with different values of electronegativity were designed as doped-ions to prepare cations-intercalated titanate nanobelts through ex-situ ion-exchange reaction. XRD results revealed that the d200 values of layered TNBs decreased as the following sequence: Li-intercalated TNBs > Al-intercalated TNBs > Fe-intercalated TNBs > Sn-intercalated TNBs. The electronegativity differences between respective doped-cations and oxygen can well explain the trend of the reduction of d200 values for the synthesized layered nanobelts with different cations. The width change of nanobelts depending on intercalated cations showed similar tendency as that of d200 excluding Sn-intercalated case. That is mostly due to the crystallization of SnO2 nanoparticles on the nanobelts. Sn2+ is easily crystallized to form SnO2 nanoparticles on the surface of TNBs and being considered as unfavorable metal dopant for the present intercalation purpose. The reduction of d200 values of the doped TNBs from that of the undoped TNBs confirms the intercalation of the doped cations into layered structure. Such simple electronegativity-difference depending mechanism may be convenient for the designing of metal ion intercalation into octahedral TiO6 layered-oxide materials.

Electrochromism of rutile nanowires, vertically aligned along the [001] direction, due to alkali metal ion intercalation

Rutile nanowires were grown along the [001] direction and perpendicular to the fluorine doped tin oxide coated glass substrate (R⊥) by a solvothermal process using titanium isopropoxide as the precursor in acidic solution. The edge length of the nanowires obtained in isopropyl alcohol is ten times less than that of the nanowires obtained in water. Due to the high ionic diffusion rate along the rutile [001] direction and good optical transmittance, R⊥ was used as an electrochromism electrode. When −2 V was applied, the color of the electrode became blue with a 60% change in the transmittance for 30 s due to the cathodic polarization potential in LiClO4/PC electrolyte (where PC is propylene carbonate). The lithium ion intercalated/extracted densities of R⊥, P25-coated and rutile nanowires-coated electrodes are 138.6/129.1 mC cm−2, 93.6/83.2 mC cm−2 and 31.7/15.9 mC cm−2 respectively. After 50 cycles, the R⊥electrode still performs very well. Furthermore, a large amount of sodium cation intercalation into TiO2 was observed for the first time at −1.0 V. According to these results, the R⊥electrode is a promising candidate to be a multi-function device.

Interaction of sodium and potassium ions with sandwiched cytosine‐, guanine‐, thymine‐, and uracil‐base tetrads

Nucleic acid tetraplexes and lipophilic self-assembling G-quadruplexes contain stacked base tetrads with intercalated metal ions as basic building blocks. Thus far, quantum-chemical studies have been used to explore the geometric and energetic properties of base tetrads with and without metal ions. Recently, for the first time, work on a sandwiched G-tetrad complex has been studied. We report here results of a systematic B3LYP density functional study on sandwiched G-, C-, U-, and T-tetrads with Na+ and K+ at different symmetries that substantially extend the recent work. The results include detailed information on total energies as well as on metal ion tetrad and base-base interaction energies. The geometrical parameters of the sandwiched metal ion complexes are compared to both experimental structures and to calculated geometries of complexes of single tetrads with metal ions. A microsolvation model explains the ion selectivity preference of K+ over Na+ in a qualitative sense.

Intercalation Compounds Based on Vanadium(V) Oxide Xerogel

AbstractFor Abstract see ChemInform Abstract in Full Text.

Tetrasodium tetrahydroxytetrathiacalix[4]arenetetrasulfonate tetradecahydrate

The title compound, 4Na+·C24H12O16S84−·14H2O (Na4TCAS·14H2O), was found to crystallize in the triclinic space group P\overline 1. The X-ray structure revealed that the centrosymmetric TCAS4− anion adopts the 1,2-alternate conformation. The sodium cations are surrounded by five or six O atoms in the crystal structure. All sodium ions form centrosymmetric aqua-bridged dimers, Na(μ-H2O)2Na, which are also coordinated by sulfonate O atoms and contribute to the formation of a three-dimensional network. The compound exists in the solid state as layers of anionic thia­calixarenes, alternating with inorganic layers that contain sodium cations and water mol­ecules. Intercalation of metal ions into the solid-state layered structure was observed.

Enhancing the Diffusion Rate of Cytochrome c into Fatty Acid Films by Preordering the Lipid Film

We have previously studied the electrostatic entrapment of the heme proteins cytochrome c (Cyt c) and hemoglobin in thermally evaporated fatty lipid films (Gole et al. Langmuir 2001, 17, 5646−5656). It was observed that the diffusion of Cyt c from solution into thermally evaporated arachidic acid films was extremely slow requiring ca. 40 h for protein equilibration in 500 Å thick films thus marking this out as a disadvantage of the protocol. Preliminary attempts to enhance the diffusion rate of Cyt c in arachidic acid films organized in a lamellar structure by Pb2+ ion intercalation were promising. In this paper, we examine the use of stearic acid films organized in a lamellar c axis oriented structure in greater detail and demonstrate that such films grown either by the Langmuir−Blodgett technique or by thermal evaporation followed by metal ion intercalation enhances the diffusion rate of Cyt c by over an order of magnitude. The entrapment of the protein molecules in the lamellar hydrophilic regions of the lipid matrix is also expected to play an important role in enhancing the accessibility of entrapped enzymes to substrates (mass transport effect) where biocatalytic application of enzyme−lipid bioconjugates is envisaged. The process of Pb2+ ion/Cyt c entrapment in thermally evaporated stearic acid films was followed by quartz crystal microgravimetry while the lamellar ordering of the films and formation of salts of stearic acid were inferred from X-ray diffraction and Fourier transform infrared spectroscopy measurements.