Solid Cd Research Articles

Equilibrium composition in II–VI telluride MOCVD systems

Thermodynamic calculations, or computer simulation of the equilibrium composition, offer an excellent possibility to reduce drastically the elaborate trial-and-error experimental efforts of finding the optimal preparation conditions for MOCVD processes (temperature T, pressure P, initial composition of the vapors X), to limit them only to the P– T– X field of existence of the solid to be prepared and an acceptable yield of the product. In this communication equilibrium composition was investigated for MOCVD processes of CdTe, ZnTe, HgTe and solid solutions Cd x Zn 1− x Te and Hg x Cd 1− x Te. A number of volatile organometallic compounds have been used as precursors for MOCVD growth. These are dimethylcadmium (CH 3) 2Cd, DMCd; diethylzinc (C 2H 5) 2Zn, DEZn; diisopropylzinc [CH(CH 3) 2] 2Zn, DiPZn; diethyltellurium (C 2H 5) 2Te, DETe; diisopropyltellurium [CH(CH 3) 2] 2Te, DiPTe; methylallyltellurium CH 3TeCH 2CHCH 2, MATe. A choice of the particular combination of the precursors largely depends on the desired composition of the film to be prepared, especially in cases of solid solutions Cd x Zn 1− x Te and Hg x Cd 1− x Te where the vapor pressure of the precursors is instrumental for the composition of the vapor in the reaction zone and, ultimately, for the composition x of the solid solution. Equilibrium composition for II–VI telluride MOCVD systems was investigated at temperatures up to 873 K in hydrogen and inert gas atmospheres at pressures up to 1 atm. P– T– X regions of existence were outlined for each of the five materials.

Kinetic study of the thermal decomposition on bis(dialkyldithiocarbamate) Cd(II) complexes by isothermal and non-isothermal thermogravimetry

The thermal decomposition kinetics of solid Cd(S 2CNR 2) 2 complexes, where R=C 2H 5, n-C 3H 7, n-C 4H 9 and iso-C 4H 9, has been studied using isothermal and non-isothermal thermogravimetry. Superimposed TG/DTG/DSC curves show that thermal decomposition reactions occur in the liquid phase. The kinetic model that best adjusted the experimental isothermal TG data was the one-dimensional phase-boundary reaction controlling process R 1. The thermal analysis data suggest the thermal stability sequence Cd(S 2CNBu n 2) 2>Cd(S 2CNPr n 2) 2>Cd(S 2CNBu i 2) 2>Cd(S 2CNEt 2) 2, according to the order of stability of apparent activation energy.

Magnitudes and orientations of NMR interaction tensors in isolated three-spin systems ABX

Possibilities and limitations for the complete determination of all orientational parameters from iterative fitting of various MAS NMR spectra of ABX three-spin systems are explored. The practical example chosen is the (31P)2 113Cd ABX spin system in solid Cd(NO3)2 · 2PMe2Ph1 where 113Cd is an X nucleus of low natural abundance. Conventional 31P and 113Cd MAS NMR spectra, plus 113Cd MAS NMR spectra obtained under conditions of either simultaneous high power 31P and 1H decoupling, or under conditions of 31P rotary resonance recoupling are considered. Considerable anisotropy of the heteronuclear J coupling 1J(113Cd, 31P) is observed.

Magnitudes and orientations of NMR interaction tensors in isolated three-spin systems ABX

Possibilities and limitations for the complete determination of all orientational parameters from iterative fitting of various MAS NMR spectra of ABX three-spin systems are explored. The practical example chosen is the (31P)2 113Cd ABX spin system in solid Cd(NO3)2 · 2PMe2Ph1 where 113Cd is an X nucleus of low natural abundance. Conventional 31P and 113Cd MAS NMR spectra, plus 113Cd MAS NMR spectra obtained under conditions of either simultaneous high power 31P and 1H decoupling, or under conditions of 31P rotary resonance recoupling are considered. Considerable anisotropy of the heteronuclear J coupling 1J(113Cd, 31P) is observed.

Solid State Resources CD

The Solid State Resources CD-ROM for Mac OS and Windows compatible computers has been updated with a new HTML interface and video identical to that published in the General Chemistry Collection, 2nd Edition. This includes both new video and improved versions of some of the movies on the original Solid State Resources CD. All resources on the CD are now accessed through HTML pages using a WWW browser. This provides a single, identical version for Mac OS and Windows and eliminates problems some encountered when playing movies in the slide shows of the previous version.

Solid Solution Cd<sub>x</sub>Zn<sub>1-x</sub>S Thin Films Grown by Atomic Layer Epitaxy and Successive Ionic Layer Adsorption and Reaction Techniques

Solid solution Cd x Zn 1-x S thin films were grown by atomic layer epitaxy (ALE) and successive ionic layer adsorption and reaction (SILAR) technique. Various values for x in Cd x Zn 1-x S structure could be tailored. The thin films were polycrystalline and hexagonal (002) oriented according to XRD. The stoichiometry was studied by RBS and EDX.

Determination of the amount of Zn in electrochemically deposited Zn + Cd alloys by anodic linear sweep voltammetry

A detailed qualitative and quantitative analysis of the anodic linear sweep voltammograms of the dissolution of electrodeposited Zn + Cd alloys of different compositions has been performed in order to obtain the data about the solubility (miscibility) of solid Zn in solid Cd. It was shown that up to about 5 at.% of solid Zn dissolves in electrodeposited Zn + Cd alloys and that this amount of Zn dissolves in the peak corresponding to dissolution of pure Cd. The conclusion rests on the quantitative analysis of the charge under the peaks of Zn and Cd dissolution. A precise quantitative analysis can be performed only in sulphate electrolyte where dissolved Zn forms simple Zn 2+ cations, while in chloride electrolyte the presence of different complexes of Zn with Cl − anions influences the kinetics of the dissolution of pure Zn from the alloy.

Conformational stability and vibrational assignment of propanal

Variable temperature (−52 to −100°C) studies of the infrared spectra (3500–400 cm −1) of propanal, CH 3CH 2CHO, dissolved in liquid xenon have been recorded and bands due to both the cis and gauche conformers have been identified. From these data, the enthalpy difference has been determined to be 370±21 cm −1 (4.43±0.25 kJ mol −1) with the cis conformer (methyl group eclipsing the oxygen atom) the more stable form. Utilizing the new infrared data from the xenon solution, along with some additional Raman data, and ab initio predictions from MP2/6-31G* calculations, several reassignments of the fundamentals have been made for the cis conformer. Additionally, several bands which have been identified as arising from the gauche conformer have also been assigned. Infrared (3500–80 cm −1) and Raman (3500–30 cm −1) spectra of gaseous, liquid and/or solid CD 3CD 2CHO are also reported and the fundamentals assigned for the cis conformer. The spectroscopic and theoretical results are compared to the corresponding quantities for some similar molecules.

Novel oligodeoxyribonucleotides incorporating L-related isodeoxynucleosides: Solid phase synthesis, enzymology, and CD studies

The synthesis of self-complementary oligodeoxyribonucleotides incorporating the L-related isodeoxynucleosides, isodA, (1) and/or isodT (4) is described. These novel oligomers exhibit high resistance towards exonucleases. Temperature- and concentration-dependent CD spectra and thermodynamic data of the oligomers show that isodA-isodT base pairs participate in duplex stabilization.

Study of bimolecular processes in ternary cyclodextrin complexes in the solid state by diffuse reflectance laser flash photolysis

The photochemistry of binary inclusion complexes of nitroveratrole (NV) and p-dinitrobenzene (DNB) with β-cyclodextrin (β-CD) and of ternary inclusion complexes of NV or DNB and L-phenylethylamine (PhEA) with β-CD has been examined in the solid state by diffuse reflectance laser flash photolysis. The binary NV/β-CD complex shows a transient absorption signal assigned to the triplet excited state of NV. The binary DNB/β-CD complex shows a transient signal assigned to the protonated anion of DNB formed via hydrogen abstraction from the β-CD cavity. Laser excitation of the ternary complexes generates the corresponding radical ion pairs via photoinduced electron transfer from the amine to the nitroaromatic triplet state. Comparison with previously described conventional laser flash photolysis studies in solution shows that the investigation of solid ternary CD inclusion complexes by diffuse reflectance laser flash photolysis is valuable in the case of bimolecular photoreactions that are difficult to study in solution due to the existence of other competitive processes.

Effects of cadmium, copper, and zinc on growth and thiol content of aquatic hyphomycetes

The effects of cadmium, copper, and zinc on the growth of ten strains ofaquatic hyphomycetes were investigated. On a solid medium, Cd and Cu reducedradial growth of most strains by 50% at concentrations between150–400 µM; in a liquid medium, the strains were more sensitive.The inhibitory effects of zinc were much less severe. Two isolates(Articulospora tetracladia and Tetracladium marchalianum) from a copper-minestream were more resistant against copper than conspecific strains from anon-polluted stream. Heliscus lugdunensis and Varicosporium elodeaeresponded to Cd exposure, but not to Cu or Zn exposure, by increasedsynthesis of SH-containing compounds. Glutathione levels showed a unimodalresponse to increasing Cd and Zn exposure. With copper, glutathionedecreased at intermediate levels of contamination. In the presence of Cd, H. lugdunensis synthesized several unknown sulfur-rich substances that wereabsent or produced at reduced rates in control cultures.

Distribution of trace and major elements in sediment and pore waters of the Lena Delta and Laptev Sea

Sediment cores collected during the SPASIBA expedition in 1991 were analysed for their trace- and major element concentrations. Leachable (0.1 N HCl) as well as residual concentrations were determined. Fe and Mn were measured in the interstitial waters to characterize redox conditions. Lateral distribution patterns of solid phase Cu, Cd, Ni, Pb and Zn show a small increase in concentration from the Lena Delta in seaward direction. In general concentrations of these metals are very low and similar to natural background values. With some exceptions, solid phase profiles with depth of all investigated elements do not show strong variations. No enrichment of Pb and Zn in surface layers was found. Remobilization processes and transport of particles enriched in Mn are responsible for Mn accumulation in a particular area. Pore-water concentrations of dissolved Mn in the latter sediments are very high (> 700 μM) and suggest strong Mn reduction directly below the sediment-water interface. In contrast to Mn, the depth profiles of Cd show a surface layer with lower concentrations and an increase deeper down the sediment. The CN ratio in the sediment decreases from 13 in the Lena mouth to 9 in the more marine part of the Laptev Sea. Surface sediments in the Laptev Sea are very uniform and homogeneous and show only small concentration gradients.

Abstract for Special Issue Number 12: The Solid State Resources CD

The Solid State Resources CD-ROM for Macintosh computers is intended to help instructors to integrate materials science examples into introductory chemistry courses. The CD includes:•slide shows•overhead masters•QuickTime movies (animations and video)•the complete book, Teaching General Chemistry: A Materials Science Companion () (the Companion)•the Instruction Manual, ICE Solid State Model Kit ()•an Index to all materials on the CD•runtime software to allow access to all materials on the CDThose already using the Companion will find this CD a useful adjunct. The CD also is an excellent teaching resource for those who do not have the book. The material on the CD is intended for presentations and is not designed for use by individual students.

About This Issue: The Solid State Resources CD

About This Issue: The Solid State Resources CD

Free D atoms in pulse radiolysis of methane in cryogenic fluids

Spin-echo and free induction decay (FID) detected electron paramagnetic resonance were applied to detect free D atoms in the pulse radiolysis of CD{sub 1} in liquid argon, krypton, xenon, and nitrogen at 77-160 K. The D atoms were polarized through chemically induced dynamic electron polarization in random encounters. The decay of polarization was essentially independent of the fraction of methane (1-70 mol%) and the temperature of the liquid solution. Analysis of the polarization decay kinetics and the D atoms yield suggests that ion reactions dominate over energy transfer reactions in these mixtures (except for xenon solutions). In solid CD{sub 4}-Ar mixtures a satellite resonance line of unusually polarized D atoms was observed. This indicates microheterogeneous nature of these solid mixtures and explains anomalous chemistry observed in the media. 38 refs., 8 figs., 1 tab.

Cholesterol Reduction in Liquid Egg Yolk using β‐Cyclodextrin

ABSTRACTA process to reduce cholesterol in liquid egg yolk using β‐cyclodextrin (CD) was optimized by response surface methodology, based on cholesterol reduction and yield. The most important factors influencing cholesterol reduction were dilution of egg yolk to a defined water:solid ratio and CD concentration. In the final process, egg yolk was adjusted to pH 10.5, diluted to a water:solid ratio of 2.9, heated to 50°C, and CD added at a CD:cholesterol molar ratio of 4.0. The slurry was mixed for 6.5 min at 1800 rpm, cooled to 4°C and centrifuged. Cholesterol in the supernatant was reduced by 89.2%. The yield, cholesterol and CD in the final product were adjusted by varying centrifugal force and CD concentration.

Coherent propagation of subpicosecond pulses in the mid-infrared in condensed matter

Propagation of tunable pulses of 0.7 ps in the ir around 5 μm is investigated in the case of small intensity and a moderately short sample. Coherent pulse reshaping is observed and exploited to measure the dephasing time of the CD 3-stretching vibration ν 1 of liquid and solid CD 3I in the temperature range 296-180 K.

Crystal Structure and Optical Properties of Cd 32 S 14 (SC 6 H 5 ) 36 . DMF 4 , a Cluster with a 15 Angstrom CdS Core

Recrystallization of the solid Cd(10)S(4)(SC(6)H(5))(12) from a solution of pyridine and N, N-di-methylformamide (DMF) results in the formation of the cluster Cd(32)S(14)(SC(6)H(5))(36)-DMF(4) as pale yellow cubes. The structure consists of an 82-atom CdS core that is a roughly spherical piece of the cubic sphalerite lattice approximately 12 angstroms in diameter. The four corners of the lattice are capped by hexagonal wurtzite-like CdS units, which results in an overall tetrahedral cluster approximately 15 angstroms in diameter. This cluster dissolves intact in tetrahydrofuran where its absorption spectrum reveals a sharp peak at 358 nanometers at room temperature and its emission spectra show a strong broad band at 500 nanometers.

Optical properties of CdTe- Cd0.90Mn0.10Te multiple quantum well structures grown by pulsed laser evaporation and epitaxy

Low-temperature photoluminescence, photoluminescence excitation and Raman spectroscopy measurements of CdTeCd 0.90Mn 0.10Te multiple quantum well (MQW) structures grown by pulsed laser evaporation and epitaxy (PLEE) on (001) Cd 1- x Zn x Te substrates are carried out. The samples are grown from fluxes of Cd-Te and Cd-Mn-Te provided by ablation of solid CdTe and Cd 0.93Mn 0.07Te targets with Nd:YAG and excimer XeCl lasers, respectively. The excitonic lines corresponding to the quantum well E 1-HH 1 transition are investigated. Comparison between the observed PL excitonic emissions and calculated energy levels using a Kronig-Penney model with the well width as a fitting parameter allowed us to determine the “optical” well widths of the samples and to compare them with those determined from secondary ion mass spectroscopy in-depth profiles. Raman spectra for non-resonance excitation at 501.7 nm are dominated by the CdTe-like longitudinal optical (LO) modes at 166 cm -1 and MnTe-like LO modes at 194 cm -1 from the Cd 0.90Mn 0.10Te barriers. Under resonance conditions, with excitation at 476.5 nm the CdTe LO, 2LO and 3LO modes from the wells near 170,340 and 510 cm -1 dominate the spectra. The results clearly indicate that the PLEE-grown MQWs have the characteristics of the best currently available material.

A determination of librational splittings in solid cd 4-II from infrared spectra

The energy level scheme for oriented CD 4 molecules in phase II has been obtained from the infrared ν 3 spectrum. The observed librational splittings are consistent with theoretical predictions for a D 2d site symmetry. The strength of the molecular field has been derived, and the tunneling splittings A–T and T-E have been estimated.