CuI Crystals Research Articles

CuI Crystal Growth in Acetonitrile Solvent by the Cycle-Evaporation Method

Acetonitrile solvent was applied to grow CuI crystals by the cycle-evaporation method with Cu as the reductant. The growth temperature was 70 °C. The process was performed in a nitrogen atmosphere. Clear, millimeter-scaled CuI single crystals were obtained. Moreover, UV−visible spectra, IR spectra, and XRD were used to investigate the redox processes in the solution. The crystal was characterized by X-ray powder diffraction and differential thermal /thermogravimetry analysis.

Morphogenesis of CuI Nanocrystals by a TSA‐Assisted Photochemical Route: Synthesis, Optical Properties, and Growth Mechanism

AbstractSynthesis of nanosized CuI crystals has become more and more important due to their wide range of applications. However, it is usually difficult to control the morphology and size of CuI crystals because of the preferential growth of the (111) face. In this study, single‐crystalline γ‐CuI nanocrystals with diamond and platelet morphologies have been successfully synthesised by utilising UV‐irradiated 12‐tungstosilicate (TSA) as a reducing agent for the reduction of Cu2+ under ambient conditions. A possible growth mechanism has been proposed and this suggests that the formation of diamond‐shaped CuI nanocrystals is in accordance with homogeneous nucleation theory and the formation of CuI platelets is due to reaction‐controlled growth with (111) facets as the basal planes. Both diamond‐shaped and platelet‐shaped CuI nanocrystals have a strong emission band at 365 nm which is different from the previous reports and a high electrical conductivity, indicating their promising applications in optical and electronic nanodevices. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The structure of 1D CuI crystals inside SWNTs

Nanocomposites consisting of one-dimensional CuI crystals inside single-walled carbon nanotubes were obtained using the capillary technique. high-resolution transmission electron microscopy investigations of the atomic structure of the encapsulated 1D CuI crystals revealed two types of 1D CuI crystals with growth direction <001> and <110> relative to the bulk hexagonal CuI structure. Atomic structure models were proposed based on the high-resolution transmission electron microscopy images. According to the proposed models and image simulations, the main contrast in the 1D crystal images arises from the iodine atoms whereas copper atoms, with lower atomic number giving lower contrast, are thought to be statistically distributed.

A rapid sonochemical approach to semiconductor thin films: The case of metal iodides

Thin films of metal iodides (e.g., CuI, AgI and PbI 2) were rapidly synthesized by a sonochemical method. For example, perfect CuI crystals with uniform polyhedral structures could be formed directly on copper foils with the irradiation time as short as 10 s via interfacial reaction between copper foils and elemental iodine in ethanol at ambient temperature. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectra (PL). A probable mechanism was proposed to explain the rapid growth of CuI crystals. This facile approach could also be used to grow other metal iodides such as AgI and PbI 2 nanocrystals. It was found experimentally that the resultant metal iodide films could better resist spinning under the drastic ultrasound irradiations in a liquid media. Particularly, the resulting CuI films showed strong, room temperature PL emissions at the energy around their band gaps. This method is believed to be the fastest way for in-situ fabrication of semiconductor films on various metal substrates for subsequent applications related to the metal iodide semiconductor films.

Understanding the growth mechanism of CuI crystals during gel growth experiments

AbstractCuprous iodide crystals have been grown with decomplexation method in silica gel. Various crystal morphologies, such as polycrystalline aggregate, skeletal, dendrite, hopper crystals and regular tetrahedron crystals, were observed in different growth regions with an optical microscope. Their surfaces were photographed using a binocular metallographic microscope and the results were explained with the crystal growth mechanism which was determined by supersaturation. These observations support the general hypothesis that the concentration of reactant affects the relative growth rate by controlling the nucleation and diffusion. The mutual influence of the crystals grown in different regions was also discussed. Additionally, the suitable condition for getting regular tetrahedron crystals or large hopper crystals was obtained by changing the concentration of CuI·HI complex in the later period of crystal growth. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

A Facile Surface-Etching Route to Thin Films of Metal Iodides

A facile surface-etching approach was developed for the synthesis of CuI, PbI2, and AgI thin films. Tetrahedral-shaped CuI crystals were formed on a variety of copper substrates (e.g., grids, flat or porous foils, and macro- or nanowires) via an interfacial reaction between a copper substrate and iodine in water at room temperature. A possible mechanism was proposed to explain the growth of tetrahedral-shaped CuI single crystals. The resulting materials were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy-dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). This preparation approach can also be used to grow PbI2 and AgI nano- and microcrystals with different morphologies on corresponding substrates.

Ionic conductivity and nano-crystallization of CuI–Cu 2MoO 4 glasses

The correlation between the ionic conductivity and the nano-crystallization processes of (CuI) x –(Cu 2MoO 4) 1− x superionic conducting glasses has been systematically investigated by X-ray diffraction and high-resolution transmission electron microscopy (HREM). In x = 0.52, CuI crystal precipitates as a primary phase. On the other hand, in x = 0.40, crystallization from homogeneous glass into CuI crystal and other phase has been observed. Nano-crystallization processes depend on CuI content. The difference of the nano-crystallization processes influences the electrical conductivity.

The influence of CuI·HI complex distribution on CuI crystal growth with decomplexation method in silica gel

CuI single crystals were grown in silica gel with decomplexation method modified by concentration programming. The influence of the concentration and its gradient of CuI·HI complex in silica gel on the crystal growth was studied by measuring concentration of copper ions with spectrophotometer. The results show that it is necessary to maintain low and stable values for both concentration of the complex and its gradient, if it is expected to grow CuI single crystals with regular shape and large size. For the case of decreasing the concentration of feed solution gradually, the concentration of the complex and its gradient in the region of crystal growth were controlled in the range of 0.01–0.03 mol/l and at about 0.012 mol/(l cm), respectively, so that the supersaturation of CuI·HI complex could keep a value which could make the CuI crystals growing gradually. In order to control the variation of the concentration of CuI·HI complex in silica gel, the diffusion rule of the complex was studied by increasing the concentration of feed solution gradually. The average diffusion coefficient was measured to be 1.521×10 −5 cm 2/s. The results could provide a useful clue to further optimize the experimental scheme.

Preparation and characterization of CuI nanorods using Cu(dmg) 2 as precursor via water-in-oil (w/o) microemulsions

CuI nanorods have been firstly prepared by water-in-oil microemulsions using Cu(dmg) 2 as precursor at low temperature as low as 70 °C. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements show that the CuI nanorods are pure γ-phase crystals with diameters ranging from 50 to 80 nm and lengths up to 500 nm. UV–vis spectrum reveals that the nanorods exhibit a blue shift and possess of wider band gap energy. Electrochemical impedance spectroscopy (EIS) reveals the nanorods own larger grain boundary resistance. Results of comparative experiments indicate that the rod-like structure of Cu(dmg) 2 crystals leads the CuI crystals growing in one direction especially and the reverse microemulsion system plays a crucial role in making products symmetrical and uniform.

Optical and structural studies of CuI clusters in zeolites LTA and FAU

CuI clusters were incorporated into α-cages and supercages of zeolites LTA and FAU, respectively, with various loading densities. From the powder XRD measurement of CuI clusters in FAU, it can be concluded that CuI clusters with homogeneous size were distributed in the cages. In case of using FAU as a host, when the loading density became close to the maximum, photo absorption intensity gradually decreased. A polariton effect, i.e. photo excited energy transfers among the clusters, may play an important role on this phenomenon. Cu and I atoms of bulk CuI crystal have tetrahedral chemical bondings. Supercages of FAU have an arrangement of a diamond structure. Coincidence on the symmetry of the chemical bondings in the CuI clusters and the arrangement of the clusters in the supercages may be the origin of a highly ordered state of CuI clusters and will enhance the polariton effect.

Electronic structure of intrinsic defects and mechanism of donor-acceptor pair luminescence in CuI crystal

The electronic structures of γ phase copper iodide crystal and the intrinsic point defects associated with iodine and copper have been studied with relativistic density functional theory and embedded cluster method. The simulations for point defects show that the tetrahedron interstitial copper atoms and copper vacancies may lead to the shallow donor and acceptor levels in the energy gap, which is related with the origins of the broad donor-acceptor pair recombination luminescence band 420—430 nm of CuI crystal.

Growth and shape evolution of octahedral CuI crystal by a SC-assisted hydrothermal method

Uniform γ-CuI octahedral crystals with average size of about 15 μm were prepared by a hydrothermal growth method with sodium citrate (SC). SEM observation shows that the shape evolutions of CuI particles from truncated octahedron to octahedron have been arrested. The additive, sodium citrate, plays an important role in the formation of the uniform γ-CuI octahedral crystals.

Growing CuI crystals with decomplexation method modified by concentration programming

AbstractAn attempt to grow CuI single crystal with decomplexation method modified by concentration programming in silica gel was performed. The results show that decreasing the concentration of feeding solution gradually can yield pure regular single crystals with larger size compared with those of increasing concentration. Replenishing feeding solution every 24 h produces crystals with higher quality than those of every 48 h. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Fabrication of an Efficient Solid-State Dye-Sensitized Solar Cell

A highly efficient solid-state solar cell (TiO2/dye/CuI) with improved stability was fabricated by controlling the pore filling of the porous dyed TiO2 layer with molten salt capped CuI crystals and improving the TiO2 by necking with ZnO. The molten salt controls the CuI crystal growth and acts as a protective coating for CuI nanocrystals, and necking with the more conductive ZnO improves electrical contact between TiO2 particles, both contributing to improved cell performance. Cells achieved efficiency as high as 3.8% with improved stability under continuous illumination for about 2 weeks.

Fabrication of Dye-Sensitized Solar Cells Using Triethylamine Hydrothiocyanate as a CuI Crystal Growth Inhibitor

Fabrication of Dye-Sensitized Solar Cells Using Triethylamine Hydrothiocyanate as a CuI Crystal Growth Inhibitor

63Cu magic angle spinning (MAS) nuclear magnetic resonance (NMR) study of CuX crystals (X=Cl, Br, and I) and CuX-based glasses (X=Cl, Br, and I)

63Cu MAS NMR spectra of CuX crystals (X=Cl, Br, and I) and CuX-based glasses (X=Cl, Br, and I) have been measured. The CuCl and CuI crystals gave the isotropic chemical shift values around 0 ppm, and the CuBr crystal, around −55 ppm. The peak positions of the chlorocuprate(I), bromocuprate(I), and iodocuprate(I) glasses were very close to those of the CuX crystals, respectively. This result indicates that these glasses mainly consist of CuX 4 tetrahedra (X=Cl, Br, and I). The halogen coordination environments around Cu + in bromochlorocuprate(I) glasses were dependent on the kind of modifying cation and the Br −/(Cl −+Br −) ratio. The bromochlorocuprate(I) glasses were mainly composed of CuCl m Br 4− m or CuCl n Br 4− n tetrahedra ( m=0, 1, 2, and 4; n=0, 1, and 4).

Analysis of compression for cuprous, silver and thallous halides

An analysis of compression, i.e., pressure-volume relationship is presented for CuCl, CuBr, CuI, AgCl, AgBr, AgI, TlCl, TlBr and TlI crystals. An interionic potential model using Harrison's repulsive interaction has been developed for calculating the pressures corresponding to different compression values. The results obtained are found to present close agreement with available experimental data on the equation of state for the crystals under investigation. It is concluded that thallous halides are more compressible as compared to cuprous and silver halides.

Picosecond Kinetics of Luminescence in Highly Excited Direct‐Gap Semiconductors

AbstractExperimental and theoretical investigations of luminescence spectra kinetics are carried out in CuI, CdS, and CdSe crystals at concentrations below the Mott threshold. The observed radiation is shown to be due to exciton‐phonon‐plasmon interaction caused by the coexistence of excitons and an electron‐hole plasma (EHP) during the time interval shorter than the time, necessary for the EHP to undergo the transition into the gas of excitons. It is found that the inhomogeneous distribution of excitons and EHP is developing in a crystal despite the initially homogeneous excitation. Theoretical lineshape analysis of exciton‐phonon‐plasmon luminescence is shown to be able to provide information of its spatial distribution.

Generation of photoritons—parametrically coupled photons and polaritons

An analysis is made of the tuning of the polariton spectrum of a solid, particularly a semiconductor, exposed to the parametric action of high-power optical radiation. The tuning spectrum corresponds to an elementary excitation described as a photoriton, which is a coupled pair consisting of a photon and a polariton of differing frequencies. Photoritons have two branches of nonlinear dispersion that differ substantially in an optical parametric amplifier and a frequency converter. Specific calculations of the dispersion curves for both these cases are given for CuI and CuCl crystals.

First‐Principles Calculation of Deformation Potentials of Copper Halides

AbstractSelf‐consistent, relativistic LMTO band structure calculations, using the local‐density approximation, are performed for strained CuCl and CuI crystals in the zinc‐blende structure. Equilibrium volumes and bulk moduli are derived. Calculations for uniaxially strained crystals are used to deduce deformation potentials for splitting of the Γ15‐state (top of the valence band) with and without spin—orbit coupling (SO). In case of trigonal strain, these quantities are calculated as a function of the internal‐strain parameter ζ. It is shown that the deformation potentials can be evaluated by moving the potentials obtained by one self‐consistent calculation for the unstrained crystal to the lattice positions of the strained crystal. The inclusion of SO is important in the calculation of the trigonal‐shear deformation potentials but affects only slightly those for tetragonal strain.