Novel Intercalation Compounds of MoS2

Abstract

Intercalation of naphthalene and its substituted derivatives into MoS₂ has been achieved by exfoliation-reflocculation. Intercalation results in an expansion of the lattice in a direction perpendicular to the dichalcogenide layers and, in the case of naphthalene, modifies the electrical properties of the host.     

Iron-Chloranilate Intercalation Compounds: Synthesis,Crystal Structures,and Thermal Properties

Abstract

Hydrogen bond supported new iron-chloranilate assemblies, {(Hpy)[Fe(CA)₂(H₂O)₂](H₂O)}_n (py = pyridine, H₂CA = chloranilic acid, C₆H₂O₄Cl₂) (1), and [(phz)₂[Fe(CA)₂(H₂O)₂](H₂O)₂]_n (phz = phenazine, C₁₂H₈N₂) (2) have been synthesized and characterized. Compound 2 crystallizes in the monoclinic, space group C2/m (#12), with a= 29.135(6) Å, b= 16.886(6) Å, c = 15.017(5) Å, ß = 165.907(1)°, V= 1798(2) ų, Z = 2. In both the compounds two chloranilate dianions and two water molecules are coordinated to the iron ion making anionic monomers [Fe(CA)₂(H₂O)₂]^?, which are the building blocks of the compounds. The coordination environment around the iron ion in the building block is a distorted octahedron, where two water molecules sit on the trans position to each other. [Fe(CA)₂(H₂O)₂]^? anions form common layer structures, supported by hydrogen bonds. Hpy⁺ are intercalated in between the layers of 1 by electrostatic and hydrogen bonding interactions and phz are intercalated in that of 2 by electrostatic interactions. DSC traces of 1 show anomaly at 174 K, indicating phase transition in the compound.     

Impurity Scattering in 3d Transition Metal Intercalation Compounds M x TiS2

Abstract

From the resistivity measurements of 3d metal intercalates M _x TiS₂ (M = Mn, Fe, Co and Ni; x = 0.05) at 4.2 K in pulsed magnetic fields up to 31 T, we have found that the residual resistivity depends on the kind of guest species. Taking into account these results and available information, we have proposed a possible band model to understand the scattering mechanism by ionized impurities of the intercalated guest M²⁺ and host Ti³⁺ ions, in satisfactory agreement with the experiments.     

Preparation of New Fibrous Organic-Inorganic Layered Compounds Derived from Zinc Hydroxyde

Abstract

A new preparation method of the fibrous organic-inorganic nanohybrids was established by the reaction of Zn(OH)₂ with various organic carboxylic acids. Interlayer spacings of the reaction products of Zn(OH)₂ with benzoic acid and p-phenyl azobenzoic acid were 1.46 and 2.04 nm, and these reaction products have layered structure. In IR spectra, new peaks of RCOO-Zn band appeared at around 1400 cm^?1 and 1550 cm^?1 indicating that hydroxyl groups reacted with organic carboxylic acids. SEM images of these reaction products showed fibrous morphology. The TEM image showed that the layer structure was constructed along the fiber direction.     

Structural Analysis of the Layered Compounds Cu x TiS2

Abstract

A structural analysis of single crystals of the layered compounds Cu _x TiS₂ (x=0. 0.21 and 0.38), which were prepared by the iodine transport and the electrochemical methods, has been performed by X-ray diffraction. The displacement parameters of Ti and S atoms along the c axis are larger than those along the a axis. It is understood that the intra-layer bonding between Ti-Ti and S-S atoms is stronger than the inter-layer bonding between Ti-and S-layers. Both distances between Ti-and S-layers and between Cu-and S-layers are enlarged without changing the structure of the mother phase after intercalating Cu atoms.     

Structure and Electrochemical Properties of Carbon Nanotube Intercalation Compounds

Abstract

This article summarizes the current status of carbon nanotube intercalation compounds. It focuses on the structure and electrochemical properties of intercalated single-walled carbon nanotubes (SWNTs). Materials synthesis, purification and characterization methods are also discussed. This article draws mostly from works performed at UNC.     

Structural and Magnetic Properties of FexTiSe2 Intercalation Compounds

Abstract

Magnetic and neutron studies are done about iron-intercalated titanium diselenide, Fe^xTiSe² with 0<x≤0.5. A neutron diffraction measurement shows that Fe-atoms are located between neighboring selenium layers. Magnetic measurements show that FexTiSe² are spin glasses for 0. 15≤^x≤0.22 and antiferromagnets for 0.25≤^x≤0.5. T-x magnetic phase diagram is determined. This diagram is slightly different from that determined by Huntley et al. The difference may be caused by a formation of Fe-clusters in their samples. The x-dependence of the parameters of paramagnetic susceptibilities is determined.     

Neutron Magnetic Scattering of Intercalation Compounds Fex TiS2

Abstract

Neutron magnetic scattering of intercalation compounds Fe^xTiS² has been measured systematically as a function of Fe concentration x. In the x = 0.15 and 1/4 samples, so-called small-angle scattering was observed associated with a spin-glass transition. In the x = 1/2 sample, clear magnetic Bragg reflections were observed. The position of the magnetic peak with the smallest Q number was not commensurate with the nuclear lattice-unit. The magnetic structure of Fe^1/2TiS² was found not to be a simple ferromagnetic structure as was ever suggested but a long-period magnetic structure. In the x = 1/3 sample, broad magnetic diffuse peak whose Q number was also not commensurate with the nuclear lattice-unit was observed. The origin of the magnetism of Fe^1/3TiS², what is called a cluster-glass, seems the short-range ordered magnetic-clusters with a long-period magnetic structure.     

Application of Rietveld Method to the Structural Characteristics of Substituted Copper Ferrite Compounds

A series of ferrite samples of the chemical composition Cu_0.7 (Zn_0.3‐xMg_x)Al_0.3Fe_1.7O₄ [x=0.05, 0.1, 0.15 and 0.2], prepared by ceramic technique at 1000°C, were found to have cubic spinel structure. On applying the full pattern fitting of Rietveld method using FullProf program, the exact coordinates of atoms, the unit cell dimensions, the atom occupation factors, isotropic temperature factors, the profile shape parameters as well as the interatomic distances have been determined. It was found that the lattice parameter decreases with increasing the Mg content. Also the variation of the cation distribution has been discussed on the basis of site preference, size and valence of the substituting cations. The low isotropic microstrain values obtained during the refinement process may be attributed to the method of the preparation in which the samples after the last sintering were treated by annealing.     

Photoluminescence Spectra of GaS0.75Se0.25 Layered Single Crystals

Photoluminescence (PL) spectra of GaS_0.75Se_0.25 layered single crystals have been studied in the wavelength region of 500‐850 nm and in the temperature range of 10‐200 K. Two PL bands centered at 527 ( 2.353 eV, A‐band) and 658 nm (1.884 eV, B‐band) were observed at T = 10 K. Variations of both bands have been studied as a function of excitation laser intensity in the range from 8 × 10^‐3 to 10.7 W cm^‐2. These bands are attributed to recombination of charge carriers through donor‐acceptor pairs located in the band gap. Radiative transitions from shallow donor levels located 0.043 and 0.064 eV below the bottom of conduction band to acceptor levels located 0.088 and 0.536 eV above the top of the valence band are suggested to be responsible for the observed A‐ and B‐bands in the PL spectra, respectively.     

Thermally Stimulated Current Observation of Trapping Centers in Undoped GaSe Layered Single Crystals

Undoped p‐GaSe layered single crystals were grown using Bridgman technique. Thermally stimulated current measurements in the temperature range of 10‐300 K were performed at a heating rate of 0.18 K/s. The analysis of the data revealed three trap levels at 0.02 , 0.10 and 0.26 eV. The calculation for these traps yielded 8.8 × 10^‐27, 1.9 × 10^‐25, and 3.2 × 10^‐21 cm² for capture cross sections and 3.2 × 10¹⁴, 1.1 × 10¹⁶, and 1.2 × 10¹⁶ cm^‐3 for the concentrations, respectively.     

Structural Phase Transition of an Intercalation Compound Mn1/4NbS2

Abstract

A structural phase transition of an intercalation compound Mn_1/4NbS₂ has been investigated by X-ray diffraction at high temperatures. The lattice parameter c exhibited a discontinuous change at 640K. The superlattice reflections observed below 640K disappeared suddenly above 640K. The phase transition at 640K took an aspect of the first-order phase transition. The precise structure analyses were performed at various temperatures above and below the phase-transition temperature. It was revealed that Mn atoms were arranged in disorder in the high-temperature phase, while the Mn atoms were ordered forming the 2a ₀ × 2a ₀ × c ₀ superlattice in the low-temperature phase. The Nb and S atoms around the ordered Mn atoms slightly shifted from the high-symmetry position in the low-temperature phase. The order parameters were the degree of order of the Mn atoms and the degree of displacement of the Nb and S atoms.     

Modification of the Interlayer in HTiNbO5 and its Physicochemical Characterization

Abstract

A layered titanoniobate, in which the interlayer of the metal oxide based on octahedral framework is pillared with silica, has been prepared from HTiNbO₅ by employing alkylamines (C_nH_2n+1NH₂, n = 4, 6, 8, 10) and tetraethylorthosilicate as interlayer exchange guests and a pillar precursor, respectively. The incorporated amine had bilayer arrangements in the interlayer space and their ammonium head groups pointed to the host (TiNbO5₅ ^?) layers. While the basal spacing of the compounds increased with the chain length of alkylamine. the inclination angle also increased. The intercalated structure facilitated the incorporation of tetraethylorthosilicate into the interlayers, and silica-pillared layered titanoniobate was obtained after calcination. The physicochemical properties of the resultant pillared compounds were characterized on the interlayer microstructure, nitrogen adsorption and UV-VIS absorption spectra.     

Electrical and Optical Properties of Conducting Polymer and Carbons in Nano-Scale Periodic Structure and their Intercalation Effects

Abstract

Nano-scale periodic structures of conducting polymer and carbons, which were prepared by infiltration of polymers and carbons in nano-scale interconnected periodic pores in synthetic opals made of regular array of SiO₂ spheres and then removing SiO₂ by etching, have been found to exhibit novel electrical and optical properties. Their electrical and optical properties in thus fabricated conducting polymer and carbon replicas change drastically upon pyrolysis due to progress of carbonization and graphitization. That is, due to the changes in periodicity, pore size, carbonization degree and crystal structure, electrical conductivity, magnetoconductance and their temperature dependences and optical reflection spectra have changed drastically. These replicas with porous nature can be infiltrated and also intercalated with various materials, resulting in also remarkable changes of properties. The synthetic opal infiltrated with conducting polymer can be electrochemically doped, with which remarkable change of optical properties have been observed due to the shift of the diffraction peak accompanying with the change in refractive index. Alkali metal intercalated carbon and graphite with nano-scale periodic structures have been also studied. The applications of these nano-scale periodic structures of conducting polymer and carbon are also discussed.     

Dynamics of Intercalated Water Molecules in Synthetic Layered Silicates

Abstract

Diffusional motions of water molecules in a synthetic fluorinated layered silicate have been studied by neutron scattering. Motions in a one-water-layer hydration state are slower than in those in a two-water-layer hydration state. Good fits to the data were obtained with the Kohlrausch-Williams-Watt lineshape that is often applied to disordered systems.     

Technology of Intercalation and New Effects in PbI2 Single Crystals Intercalated by Hydrazine

Abstract

The hydrazine intercalated lead iodide single crystal technology was developed. A new type of excitons named as interlayer excitons is described. The amplification of polariton emission (Sugakov's phenomenon) and the structure phase transition under intercalation are found and studied.     

Aggregation of a Cationic Cyanine Dye Intercalated in the Interlayer Space of a Layered Titanate Na2Ti3O7

Abstract

A cationic cyanine dye. 1,1′-diethyl-2,2′-cyanine (PIC), was successfully intercalated into Na₂Ti₃O₇ by a guest-exchange method using a propylamine/Ti₃O₇ intercalation compound as the intermediate. Based on the XRD and chemical analytical results, it was presumed that PIC was densely packed in the interlayer space with the short axis of its quinoline-ring almost perpendicular to the host layer. Spectroscopic results revealed that the PIC formed J-aggre-gates even in the restricted space between the titanate layers.     

二维层状金属碘化物的制备及光电磁器件的应用进展

二维金属碘化物,呈现范德瓦耳斯层状堆垛结构,平均原子序数大,具有合适的能带间隙、强的磁电耦合效应,是一种新型的光电探测材料,能被用于制备高能射线探测器,且一些磁性二维金属碘化物能被用于磁电器件。由于其在光电磁器件方面的潜在应用,近期成为了低维材料研究的热点。并且在材料制备方面,层状金属碘化物一般熔点较低,制备条件温和简单,可用于二维层状材料生长机理的研究。本文首先介绍了层状金属碘化物的结构、性质,然后着重阐述了二维层状金属碘化物的制备方法,最后讨论了层状金属碘化物在光电磁器件方面的应用。期望读者对二维层状金属碘化物有更深入的了解,更好地推动二维层状金属碘化物的应用。     

Intercalation of O2 and its Effect on the Properties of C60 and C70 Solids

Abstract

The intercalation of O₂ in C₆₀ and C₇₀ solids have been studied. In both gas effusion spectra of C₆₀ and C₇₀ powder exposed to O₂ at room temperature, two evolution peaks of O₂ are found near 80 and 150°C. In both C₆₀ and C₇₀ powder, the peak near 80°C does not depend on a heating ratio and the peak near 150°C shifts to higher temperature with the heating ratio. The activation energy on diffusion of O₂ in C₆₀ and C₇₀ solids are ～0.27eV and ～0.46eV, respectively. The number of O₂ intercalated in C₇₀ powder is larger than that in C₆₀ powder. Electron spin density of 02-intercalated C₆₀ film is larger than that of C₇₀ film. The effect on the properties of C₆₀ and C₇₀ solids by the intercalation of O₂ are discussed.