Cadmium Composition Research Articles

Cadmium and zinc isotope compositions indicate metal sources and retention mechanisms in different soil particle size fractions

Soil particle size may significantly affect metal distribution and stable isotopic behavior. Here, two soils were separated into four particle size fractions, namely fine sand, silt, fine silt, and colloidal particles and used to determine cadmium (Cd) and zinc (Zn) concentrations and isotope compositions. Concentrations of Cd and Zn were generally enriched in the finer particles and positively correlated with the iron (Fe) and manganese (Mn) oxide contents. However, Cd concentration in the fine sand was higher than in the silt fraction due to the higher soil organic matter contents in the former particle fraction. The maximum δ114/110Cd value was found in the colloidal particles (−0.02 and 0.01‰) of both soils while the minimum was in the silt particles (−0.12 and 0.06‰). Incorporation into the mineral lattice of Fe and Mn oxides is suggested to explain the slight enrichment of heavy Cd isotopes in the colloidal fraction. The similar δ66Zn values of the four particle fractions (0.20–0.29‰ with a mean of 0.25‰) indicate similar Zn sources in different particle sizes. Metal isotopic fingerprint of different soil particle size fractions provides further insight into the underlying metal retention mechanisms within soil micro-zones and helps in tracing metal sources and biogeochemical processes.

Potential of Hawleyite Cadmium Sulphide (CdS) Nanofilms for PV Cell Applications

The search for suitable materials as buffer layer in the development of photovoltaic cell necessitates the study. The objective is thus, to synthesize and characterize CdS nanofilm for photovoltaic cell application. Thin films of Cadmium Sulphide were deposited on degreased glass substrate, from a bath containing the precursors via Chemical Bath Deposition (CBD) technique. The Physical, Structural, and optical properties were investigated by X-Ray diffractometer, Scanning Electron microscopy (SEM), surface profilometer, Energy dispersive X-ray spectroscopy (EDX) and spectrophotometer. The 9 hours CdS sample showed peak intensities at 30.95o and 51.77o with hkl values of (1 1 1) and (2 2 0). The 12 hours sample showed peak intensities at 30.95o and 51.55o with hkl values of (1 1 1) and (2 2 0). The planes of cubic phase correspond to the mineral Hawleyites for both samples. The average Crystallite grain size for the 9 hours sample is 27.72nm and 38.99nm for the 12 hours samples. The Scanning Electron microscopy analyses illustrate the morphology and the level of uniformity of the CdS coating across the surface of the 9 hours sample and 12 hours samples. The micrographs although slightly similar, the 12 hours sample appeared to be more uniformly coated when compared to the 9 hours sample. Electron-Dispersive X-ray Spectroscopy (EDX) indicated the percentage composition of Cadmium and Sulphide present in the both 9 hours and 12 hours samples, with Cadmium having an average composition of 26.45% and sulphide 8.65% for the 9 hours sample, and 61.95% for Cadmium and 16.43% for Sulphide in the 12 hours CdS sample. The Spectrophotometer was used to investigate the behavior of both samples in the UV (≤ 400nm), Visible and part of the Infrared region. The bandgap energies of both 9 hours and 12 hours sample were 2.36eV and 2.257eV respectively. The average value for the optical conductivity for 9hours sample is 5.099 x 1013 and 7.75 x 1013 for 12 hours sample. The average values of the extinction coefficients, k for 9 hours sample is 1.07 x 109 and 2.02 x 109 for 12 hours sample. The average thickness value of CdS Sample deposited for 9 hours is 14.10 x10-9m while that of the CdS sample deposited for 12 hours is 14.5 x 10-9m. The results affirm the choice of CdS film as buffer layer of the photovoltaic cells.

Measurement of Mass‐Independent Perturbations of Cadmium in Nuclear Debris Samples

The isotopic composition of cadmium in nuclear debris was measured by multi‐collector inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS). Mass‐independent perturbations due to fission product decay on the isotopes of Cd were observed. Relative fission yields for masses 111, 112, 114 and 116 were determined in each sample of nuclear debris and compared with reported values found in irradiated plutonium and uranium fuels. Mass spectrometry measurements of the valley fission product endpoints are extremely challenging due to the low cumulative fission yields and small amounts of each isotope that are produced. To overcome these challenges, a new purification method for Cd was developed and validated by examination of a number of geological reference materials.

Assessing the potential of green CdO2 nano-catalyst for the synthesis of biodiesel using non-edible seed oil of Malabar Ebony

Sustainable biodiesel synthesisfrom waste, toxic and non-edible oil seeds give a sustainable opportunity to combat energy crises and environmental depreciation.A new non-edible oil ofDiospyros malabarica(Malabar Ebony) was analyzed for the synthesis ofeco-friendly biodiesel using newly synthesized green nanoparticles (NPs) of Cadmium oxide (CdO2) prepared from leaf extract of Buxus papillosavia biological method followed by in situ wet impregnation approach. The highest fatty acid methyl ester (FAME) yield of 94 wt% was attained through the process of transesterification at ideal experimental conditions i.e., 1:9 M ratio of oil to methanol, catalyst loading 0.5 wt%, experiment duration 180 min and reaction temperature of 90 °C. Optimize biodiesel yield from Diospyros malabarica using response surface methodology was also applied. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetric analysis and X-ray diffraction (XRD) were utilized for the characterization of newly synthesized CdO2 NPs. The findings obtained from SEM revealed that CdO2 NPs were cubic in shape. The size of CdO2 NPs was 45 nm, which obtained from XRD analysis. EDX analysis showed 83.72 % cadmium composition. In thermogravimetric analysis, 5.2 % thermal degradation was observed which revealed that CdO2 NPs have strong thermal stability. The production of FAME was confirmed by using gas chromatography-mass spectroscopy (GC–MS), nuclear magnetic resonanceand Fourier transform infrared spectroscopy techniques. 9-Octadecenoic acid is the key fatty acid with the highest abundance in the GC–MS spectrum. This study revealed that inedible oil seed of Diospyros malabaricaand newly synthesized green NPs of CdO2 has the highest potential to be used as highly reliable cost-effective and sustainableentrants for synthesizing eco-friendly diesel which is ultimately open up the avenue for further research in the exploration and application of economical feedstock for biodiesel industry at a larger scale.

The cadmium and zinc isotope compositions of the silicate Earth – Implications for terrestrial volatile accretion

Zinc and Cd isotope compositions are presented for a comprehensive suite of terrestrial rocks to constrain the extent of Zn and Cd isotope fractionation during igneous processes and better define the δ66Zn and δ114Cd values of the silicate Earth (the δ values denote per mille deviations of 66Zn/64Zn from JMC Lyon Zn and of 114Cd/110Cd from NIST SRM 3108 Cd). Analyses of spinel lherzolites provide a bulk silicate Earth (BSE) δ114CdBSE value of –0.06 ± 0.03 ‰ (2SD). For Zn, the peridotite data of the current and previous studies define a mean δ66ZnBSE = 0.20 ± 0.05 ‰ (2SD). Komatiite analyses of this and published investigations yield similar mean values, which suggests that the Zn and Cd isotope compositions of the mantle remained fairly constant since the Archean. Data for loess provide upper continental crust compositions of δ114Cd = 0.03 ± 0.10 ‰ and δ66Zn = 0.23 ± 0.07 ‰. The Zn isotope and abundance data for peridotites and oceanic basalts are in accord with the previous observation of a mantle array, with basalts having higher Zn concentrations and δ66Zn values than the peridotites. To a first order, this reflects slightly incompatible behaviour of Zn during mantle melting and melt differentiation with associated enrichment of heavy Zn isotopes in the melt phase. Cadmium is marginally more incompatible than Zn during igneous processes and the oceanic basalts also display a minor enrichment of heavy Cd isotopes relative to peridotites. However, secondary processes produce significant Cd isotope variability in both mantle melts and peridotites, obscuring the primary igneous array. The δ66ZnBSE estimates of this and previous studies resemble the Zn isotope compositions of CV and CO carbonaceous and some enstatite chondrites. In contrast, the BSE has a lower δ114CdBSE value than enstatite and carbonaceous chondrites. This implies that the Cd isotope composition of the BSE was either fractionated during accretion or that Earth’s Cd inventory was not exclusively acquired from material related to carbonaceous and enstatite chondrites. Importantly, delivery of Zn and Cd to the BSE solely by CI and CM chondrites is not in accord with the meteorite and terrestrial stable isotope data of these elements.

Dark Current and Gain Modeling of Mid-Wave and Short-Wave Infrared Compositionally Graded HgCdTe Avalanche Photodiodes

We present a detailed methodology for drift-diffusion (DD) modeling of gain and dark currents in mid-wave infrared (MWIR) and short-wave infrared (SWIR) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {Hg}}_{{1}-{x}}$ </tex-math></inline-formula> Cd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> Te <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-around-n</i> avalanche photodiodes (APDs) based on a comprehensive analysis of experimentally obtained data from three different sets of devices. These devices are fabricated on homogeneous and compositionally-graded films with cadmium composition ranging from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x}\,\,=0.37$ </tex-math></inline-formula> to 0.45, each with differing geometrical dimensions, and tested at operating temperatures ranging from 140 to 240 K. The temperature, composition, and electric-field dependent impact ionization (ImI) coefficients are calibrated first according to the given experimental gain data. The gain-normalized dark current (GNDC) curve, along with the presumption of electron-only multiplication, is then used to thoroughly understand and model the behavior of diffusion and generation currents. At high biases, the GNDC curve reveals contributions from tunneling, which are classified as either trap-assisted or band-to-band based on their temperature dependence. The tunneling mechanisms are modeled accordingly: trap-assisted tunneling (TAT) is scaled inversely with Shockley–Read–Hall (SRH) lifetime, while band-to-band tunneling (BTBT) is scaled with bandgap, effective mass, and an additional empirical temperature term. Finally, the comprehensive model is applied to all three experimental devices across the operating temperature range with good agreement.

In situ ellipsometric monitoring of composition and temperature of HgCdTe layers during their growth

An ellipsometric technique has been developed which makes it possible to observe changes in the composition and temperature of cadmium--mercury--tellurium layers during their growing by molecular beam epitaxy. The technique was tested for diagnostics the variations of the composition and the temperature during layer growth in the mode of constant power of the substrate heater and with its sharp change. It was found that the drop in power and a following decrease in the growth temperature were also accompanied by a monotonic decrease in the composition. In the case of a constant heater power, a slight increase in the sample temperature was observed with an almost unchanged composition of the growing layer. Keywords: ellipsometry, mercury--cadmium--telluride, in situ control, epitaxial growth, temperature.

Tailoring Cadmium Composition on Titanium Dioxide to Achieve Enhanced Photocatalytic Glucose Fuel Cell Anode Performance

Tailoring Cadmium Composition on Titanium Dioxide to Achieve Enhanced Photocatalytic Glucose Fuel Cell Anode Performance

Comparative analysis of Cd fractional composition in soils under anthropogenic and artificial pollution

The composition of cadmium (Cd) compounds in soils of both technogenic landscapes and a model experiment were studied using the sequential fractionation method. A model experiment was conducted with artificial soil contamination by easily soluble Cd compounds. Pollution doses simulated the level of pollutant content in the studied soils of the impact zones and corresponded to low, high, and very high pollution. Fractions revealed both general features and specific metal distribution characteristics in anthropogenically polluted soil and soil under artificial pollution. The largest amount of Cd in the soils was concentrated in the residual fraction (up to 60%). With increasing pollution level, the proportion of the residual fraction decreases and the proportion of mobile compounds (exchangeable fraction and carbonate fraction) of the metal increases (up to 22% and 18%, respectively). In contaminated soil, carbonates and Fe-Mn oxides play the main role in the Cd fractional distribution. Fractional distribution of Cd shows general regularities both under anthropogenic pollution and under artificial contamination; however, metal demonstrated high mobility at artificially contamination.

Zinc, cadmium and sulphur isotopic compositions reveal biological activity during formation of a volcanic-hosted massive sulphide deposit

Zinc and Cd isotopes fractionate strongly within a range of hydrothermal systems; consequently, metal stable isotopes have been used to understand the formation of hydrothermal ore deposits. We investigated the Zn–Cd–S isotopic compositions of sulphides from the Carboniferous-Permian Xiaobaliang Cu–Au deposit, Inner Mongolia, China. This ancient seafloor hydrothermal system is the only known Cyprus-type volcanic-hosted massive sulphide (VHMS) deposit in the Central Asian Orogenic Belt. The S isotopic compositions of sulphide minerals are highly variable with δ34SCDT values ranging from −21.2‰ to 25.2‰. We infer that negative δ34SCDT values reflect mixing of volcanogenic S and S derived from bacterial sulphate reduction (BSR), and that positive δ34SCDT values reflect mixing of volcanogenic S with S derived from thermochemical sulphate reduction (TSR). Zinc isotopic compositions are relatively consistent at the deposit; δ66Zn values range from 0.10‰ to 0.70‰. These values are similar to those reported for modern seafloor sulphides. We infer that consistency of δ66Zn values relates to the Zn species ([ZnCl4]2−) present in the ore-forming fluids during sulphide precipitation. All of the sulphides are enriched in the light Cd isotopes; δ114/110Cd values range from −0.74‰ to −0.08‰. Zinc and Cd can be affected by biological activity, and we infer that biological activity caused the negative δ114/110Cd values at this deposit because: (1) biological processes (e.g., bacterial activity) enrich fluids in the light Cd isotopes, leading to the precipitation of sulphides with negative δ114/110Cd values; and (2) the Cd isotopic composition of ore-forming fluid is readily modified because the concentration of Cd is much lower than that of Zn in ore and basalt. Our results indicate that Cd isotopes might record ancient biological activity, and that organisms might play a more important role than previously thought in the formation of VHMS systems.

Cationic and anionic concentration dependent elastic properties of zinc blende specimens within CdxZn1-xSySe1-y quaternary system: Calculations with density functional theory

Elastic properties of zinc blende CdxZn1-xSySe1-y quaternary alloys have been calculated with density functional theory oriented FP-LAPW scheme. Elastic stiffness constants and hardness of specimens have been increased almost linearly with increasing sulphur composition at each fixed cadmium composition, while their decrease have been observed with increasing cadmium composition at each fixed sulphur composition in any binary-ternary/ternary-quaternary system. Mechanical and dynamical stability, elastic anisotropy, compressibility, ductility and fair plasticity have been calculated as the key features of each specimen. Mixture of covalent and ionic bonding with dominant role of covalent, central nature of interatomic forces and bending over stretching in chemical bonds have been observed in each compound. Calculated Debye temperature suggests ZnS as the stiffest and CdSe as the softest among all compounds. Calculated Gruneisen parameter has confirmed anharmonic nature of interaction between the atoms. Thermal conductivities and melting temperatures of all the specimens have also been computed.

Development of a reliable analytical method for the precise extractive spectrophotometric determination of cadmium(II) by using of chromogenic reagent: analysis of real samples

ABSTRACT A new analytical reagent N’’,N’’’-bis[(E)-(4-fluorophenyl)methylidene] thiocarbonohydrazide: bis-(4-fluoroPM)TCH was used for simple, fast and synergistic extractive spectrophotometric determination of cadmium(II). Cadmium(II) forms stable faint yellow coloured ternary complex at room temperature with reagent and pyridine as synergent having composition 1:2:2 (M:L:Py) at pH 4.0. The absorbance of coloured organic layer in iso amyl acetate is measured spectrophotometrically at 390 nm against reagent blank. In the extraction of cadmium(II), various affecting factors including the solution pH, reagent concentration, synergent concentration, equilibrium time, colour stability and effect of foreign ions are optimised. Beer’s law is obeyed in the concentration range 10–40 μg mL−1 of cadmium(II) and optimum range of 15–35 μg mL−1 of the metal as evaluated from Ringbom’s plot. Molar absorptivity and Sandell’s sensitivity value of complex in amyl acetate were 18,660 lit/mol cm and 6.0 × 10−3 μg/cm2, respectively. The composition of cadmium(II)–bis-(4-fluoroPM)TCH–pyridine adduct was established by slope ratio, mole ratio and Job’s method. Effects of foreign ions were also studied and use of suitable masking agent enhances the selectivity of method. Method has been successfully applied for determination of cadmium(II) in binary and synthetic mixtures, thin films, pharmaceuticals, coatings of ships, alloys, weeds in water and spiked water samples. The results obtained of proposed method were judged by using AAS for testing the validity of method. All the obtained results indicate a reliable, precise and fast analytical method for the extraction and quantification of trace levels of cadmium(II) from various synthetic and real samples without the use of sophisticated instrumentation and procedure.

Comparative studies of CdS thin films by chemical bath deposition techniques as a buffer layer for solar cell applications

Cadmium sulfide (CdS) buffer layer that decouples the absorber layer and window layer in thin-film solar cells was synthesized by two different chemical bath deposition (CBD) techniques with varying deposition parameters. X-ray diffraction (XRD) revealed that the CdS thin film crystallizes in a stable hexagonal wurtzite structure having a preferential orientation along (002) reflection plane with a crystallite size varying from 20 to 40 nm. First longitudinal optical phonon mode was identified at Raman shift of 305 cm−1. Uniform, granular, continuous, and smooth surface with an average grain sizes (< 100 nm) as well as small roughness (< 9 nm) was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The symmetric composition of cadmium and sulfur along with larger grains (20 nm) was observed at higher deposition temperatures and times. The optical band gap of CdS samples obtained from process one was in the range of 2.3–2.35 eV, while the band gap by the second CBD process lay in between 2.49 and 2.65 eV, showing the most stable compound of CdS. The presence of a green emission band in photoluminescence spectra (PL) demonstrated that the CdS material has better crystallinity with minimum defect density. Hall effect studies revealed the n-type conductivity of CdS thin films with a carrier concentration values in the order of 1016 cm−3. Furthermore, CdS thin films fabricated by CBD process exposed better quality that might be more suitable material as a buffer layer for thin-film solar cells.

Highly efficient and stable InP/ZnSe/ZnS quantum dot light-emitting diodes.

Quantum dot (QD) light-emitting diodes (LEDs) are ideal for large-panel displays because of their excellent efficiency, colour purity, reliability and cost-effective fabrication1-4. Intensive efforts have produced red-, green- and blue-emitting QD-LEDs with efficiencies of 20.5 per cent4, 21.0 per cent5 and 19.8 per cent6, respectively, but it is still desirable to improve the operating stability of the devices and to replace their toxic cadmium composition with a more environmentally benign alternative. The performance of indium phosphide (InP)-based materials and devices has remained far behind those of their Cd-containing counterparts. Here we present a synthetic method of preparing a uniform InP core and a highly symmetrical core/shell QD with a quantum yield of approximately 100 per cent. In particular, we add hydrofluoric acid to etch out the oxidative InP core surface during the growth of the initial ZnSe shell and then we enable high-temperature ZnSe growth at 340 degrees Celsius. The engineered shell thickness suppresses energy transfer and Auger recombination in order to maintain high luminescence efficiency, and the initial surface ligand is replaced with a shorter one for better charge injection. The optimized InP/ZnSe/ZnS QD-LEDs showed a theoretical maximum external quantum efficiency of 21.4 per cent, a maximum brightness of 100,000 candelas per square metre and an extremely long lifetime of a million hours at 100 candelas per square metre, representing a performance comparable to that of state-of-the-art Cd-containing QD-LEDs. These as-prepared InP-based QD-LEDs could soon be usable in commercial displays.

The influence of thermal maturity on the stable isotope compositions and concentrations of molybdenum, zinc and cadmium in organic-rich marine mudrocks

The concentrations and isotopic compositions of molybdenum (Mo), zinc (Zn) and cadmium (Cd) in organic-rich marine mudrocks may be used to characterize ocean chemistry in the geological past. These approaches rely on the rarely tested assumption that the geochemical signatures of these metals are not affected by the thermal maturation of the organic matter with which they are associated. We have conducted a series of artificial maturation experiments on two well-known immature organic-rich mudrocks, the Kimmeridge Blackstone Band (Late Jurassic age), and the Posidonia Shale (Early Jurassic age). These pyrolysis experiments allow us to trace changes in the composition of organic matter through varying stages of maturation, and the concentration and isotopic compositions of metals in rock residues and evolved organic fluids. Our results indicate that the thermal maturation of organic matter does not result in significant alteration of the isotopic compositions of Mo, Zn and Cd in the rock residues, which thus retain primary palaeodepositional information. Systematic increases in the concentrations of Mo, Zn and Cd in rock residues with progressively higher thermal maturity are attributed to the loss of substrate mass in the form of fluids released during pyrolysis-induced cracking of kerogen, and to the relatively low concentrations of Mo, Zn and Cd in these fluids. The Mo-isotope compositions of fluids produced during pyrolysis are isotopically similar to the bulk rock; in contrast the isotopic composition of Zn in organic fluids is ∼0.4–0.6‰ lighter than the bulk rock. The progressive loss of organic matter from rock residues during maturation coupled with the increases in metal concentrations leads to an increase of metal/TOC ratios, which may be up to double their original (syn-depositional) value in thermally mature rocks. This observation must be taken into account when using metal/TOC ratios as proxies for oceanic metal inventories throughout geological time. Finally, calculations using the mass of asphaltenes recovered during the pyrolysis experiments suggest that organically bound Mo, Zn and Cd account for several percent of the total rock metal inventory.

A new anion exchange purification method for Cu stable isotopes in blood samples.

The isotopic composition of iron, zinc, copper, and cadmium (δ56Fe, δ66Zn, δ65Cu, and δ114Cd) are novel and promising tools to study the metabolism and homeostasis of trace metals in the human body. Serum δ65Cu has been proposed as a potential tool for diagnosis of cancer in liquid biopsy, and other metals may have similar utility. However, accurate analysis of trace metal isotopes is challenging because of the difficulties in purifying the metals from biological samples. Here we developed a simple and rapid method for sequential purification of Cu, Fe, Zn, and Cd from a single blood plasma sample. By using a combination of 11M acetic acid and 4M HCl in the first steps of column chemistry on AG-MP1 resin, we dramatically improve the separation of Cu from matrix elements compared to previous methods which use concentrated HCl alone. Our new method achieves full recovery of Cu, Fe, Zn, and Cd to prevent column-induced isotope fractionation effects, and effectively separates analytes from the matrix in order to reduce polyatomic interferences during isotope analysis. Our methods were verified by the analysis of isotope standards, a whole blood reference material, and a preliminary sample set including five plasma samples from healthy individuals and five plasma samples from cancer patients. This new method simplifies preparation of blood samples for metal isotope analysis, accelerating multi-isotope approaches to medical studies and contributing to our understanding of the cycling of Fe, Zn, Cu, and Cd in the human body. Graphical abstract ᅟ.

Theoretical and experimental investigations of the structural and optoelectronic properties of Zn1−xCdxO alloys

In this work, we report theoretical and experimental studies on the structural, electronic and optical properties of wurtzite Zn1−xCdxO alloys. The theoretical investigations were conducted using the density functional theory (DFT) as implemented in the Wien2k package which is based on the full potential linearized augmented plane wave (FPLAPW). The modified exchange potential proposed by Becke-Johson (mBJ) with local gradient generalized approximation (GGA) was used in this study. The lattice parameters, electronic structure and optical properties were studied in details for the composition x of cadmium 0, 0.16, 0.25, and 0.33. Experimentally, Zn1−xCdxO alloys were grown by the sol–gel spin coating method with different cadmium concentrations specifically x = 0, 0.10, 0.20, and 0.30. The obtained experimental results were systematically analyzed and compared with the DFT calculations. From the theoretical findings, it is noticed that the structural and electronic properties of Zn1−xCdxO are strongly affected by the Cd doping amount. The lattice parameters increase and the band gaps decrease with the x fraction of cadmium showing a quantitative agreement with the experimental results. Moreover, the investigation of the total and partial density of the Zn1−xCdxO alloy for the different bands reveals that the optical transition between O-2p states in the top of valence band and Zn-4s states in the bottom of the conduction band is shifted to lower energy range as the Cd concentration increases. In addition, the dielectric function, the absorption coefficient, and the refractive index and discussed for the different cadmium composition. Combining both theoretical calculations on Zn1−xCdxO alloys with the obtained experimental results provides better understanding of the physical properties dependence on the composition and would help to engineer such alloys for high performance optoelectronic and nonlinear optical devices.

Imaging and Targeting of the α(2-6) and α(2-3) Linked Sialic Acid Quantum Dots in Zebrafish and Mouse Models.

Sialic acid-conjugated nanocarriers have emerged as attractive biomarkers with promising biomedical applications. The translation of these nanocarriers into clinical applications requires in-depth assessment in animal models. However, due to the complexity, ethical concerns, and cost of the high-order animal system, there is an immediate need of information-rich simple animal models to decipher the biological significance. Herein, we performed in vivo head-to-head comparison of Neu5Acα(2-6) and α(2-3)Gal conjugated quantum dots (QDs) toxicity, biodistribution, and sequestration in wild-type zebrafish ( Danio rerio) and mouse model (C57BL). The fluorescent properties and cadmium composition of quantum dots were used to map the blood clearance, biodistribution, and sequestration of the sialylated QDs in major organs of both models. We observed that α(2-6) sialylated QDs preferentially have prolonged circulating half-life and broader biodistribution in both models. On the contrary, α(2-3) sialic acid and galactose-conjugated QDs have shortened blood circulation time and are sequestered in the liver, and cleared after several hours in both models. These results demonstrate the applicability of the zebrafish and sialylated QDs to target specific organs, as well as drug delivery and biomedical diagnostics.

Biexciton Dynamics in Alloy Quantum Dots

The biexciton Auger dynamics of alloyed Zn1–xCdxSe/ZnS and Zn1–xCdxSe/CdS core/shell nanoparticles are examined. A series of particles with increasing cadmium mole fractions are prepared by synthesizing ZnSe nanocrystals followed by cation exchange with cadmium oleate. This is followed by the low-temperature deposition of a CdS or ZnS shell to passivate surface traps. The percent composition of cadmium in the core particles is determined from the absorption spectrum upon cation exchange, and the excited-state dynamics are measured using power-dependent transient absorption spectroscopy. The biexciton lifetimes are controlled by Auger processes, and the results show that Auger recombination is faster for alloys than for either pure ZnSe or pure CdSe. The lifetimes go through a minimum at a composition that is approximately 10–40% cadmium. This behavior is assigned to partial hole localization at clusters of cadmium atoms in the alloy, which increases Auger rates through the same mechanism that is responsib...

Estimation of Thickness and Cadmium Composition Distributions in HgCdTe Focal Plane Arrays

Mercury cadmium telluride (HgCdTe) is one of the most commonly used material systems for infrared detection. The performance of infrared focal-plane arrays (IRFPAs) based on this material is limited by several noise sources. In this paper, we focus on the fixed pattern noise, which is related to disparities between the spectral responses of pixels. In our previous work, we showed that spectral nonuniformities in a HgCdTe IRFPA were caused by inhomogeneities of thickness and cadmium composition in the HgCdTe layer, using an optical description of the pixel structure. We propose to use this bidimensional dependence combined with experimental spectral responses to estimate disparities of thickness and cadmium composition in a specific HgCdTe-based IRFPA. The estimation methods and the resulting maps are presented, highlighting the accuracy of this nondestructive method.