Cd Precursor Research Articles

Slow colloidal growth of PbSe nanocrystals for facile morphology and size control

We report colloidal growth of PbSe nanosheets and finely size-tuned PbSe nanocrystals (NCs) via simple control of reaction parameters. The approach involves slow injection of precursors with excess amounts of oleic acid. Retarded growth, due to both the slow supply of precursors and the surfeit of oleic acid, causes attachment of PbSe NCs through the (110) planes, which are more reactive than the (100) facet, into a two-dimensional geometry. In contrast, such attachment processes can be prevented by impurities, e.g., Cd chalcogenide (CdSe or CdS) NCs dispersed in chloroform. For instance, the slow injection of Pb and Se precursors into a reaction solution containing Cd chalcogenide NCs results in the growth of spherical PbSe NCs, as the Cd chalcogenide NCs hinder the PbSe nuclei from merging via (110) planes. Compared to conventional rapid-injection methods, PbSe NCs grow slowly, which enables fine control of NC size. Ab initio calculations suggest that Cd precursors strongly bound on the surface of PbSe NCs may impede nanosheet formation and may slow PbSe NC growth.

Effect of amine addition on the synthesis of CdSe nanocrystals in liquid paraffin via one-pot method

The effect of n-octylamine (OA) and octadecylamine (ODA) addition on the synthesis of CdSe nanocrystals in liquid paraffin via one-pot method is investigated via the measurements of their ultraviolet–visible absorption and fluorescence emission spectra. Our results showed that the in situ added amines can activate the formation reaction of Cd precursor and, as a result, substantially decrease the initial reaction temperature and accelerate the particle growth. By adding OA at high temperature of 200°C, remarkable improvement on particle quality is achieved, giving relatively narrow size distribution of 33.1nm and high photoluminescence quantum yield (PLQY) of 81.9% for the CdSe nanoparticles. OA addition at low temperature shows also good quality improvement for the nanoparticles. With regard to the primary amine of ODA, it may be inappropriate for quality improvement of the CdSe nanoparticles from liquid paraffin via one-pot method.

Selective epitaxial growth of zinc blende-derivative on wurtzite-derivative: the case of polytypic Cu2CdSn(S1−xSex)4 nanocrystals

Polytypic nanocrystals with zinc blende (ZB) cores and wurtzite (WZ) arms, such as tetrapod and octopod nanocrystals, have been widely reported. However, polytypic nanocrystals with WZ cores and ZB arms or ends have been rarely reported. Here, we report a facile, solution-based approach to the synthesis of polytypic Cu2CdSn(S1-xSex)4 (CCTSSe) nanocrystals with ZB-derivative selectively engineered on (000±2)WZ facets of WZ-derived cores. Accordingly, two typical morphologies, i.e., bullet-like nanocrystals with a WZ-derivative core and one ZB-derivative end, and rugby ball-like nanocrystals with a WZ-derivative core and two ZB-derivative ends, can be selectively prepared. The epitaxial growth mechanism is confirmed by the time-dependent experiments. The ratio of rugby ball-like and bullet-like polytypic CCTSSe nanocrystals can be tuned through changing the amount of Cd precursor to adjust the reactivity difference between (0002)WZ and (000-2)WZ facets. These unique polytypic CCTSSe nanocrystals may find applications in energetic semiconducting materials for energy conversion in the future.

Nanostructure of CdxZn1−xSe heterogeneous nanorods

Growth of nanorods with a large bandgap core (zinc selenite or ZnSe) and a small bandgap shell (cadmium selenite or CdSe) was attempted. The resulting nanopowders were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL) and UV–vis absorption. It was found that the ZnSe core was not uniformly covered by CdSe. Instead, the nanorods resulted from self-assembly of prolate nanospheres by aligned attachment. The PL from the pure ZnSe exhibited some small quantum confinement red shifting for short growth times, but the emission peak stabilized at 440nm after growth for longer than 2h at 280°C. When Cd precursors were added to grow CdSe, the PL emission peak red-shifted to wavelengths greater than 600nm, and up to 660nm. TEM data showed nonuniform diffraction along the nanorod and XRD showed formation of a ternary compound with an average stoichiometry of Cd0.2Zn0.8Se. These data are only consistent with inhomogeneous nanorods, and a schematic representation of inhomogeneities is presented.

Effect of thioglycolic acid on the stability and photoluminescence properties of colloidal solutions of CdTe nanocrystals

We have studied the physicochemical properties of cadmium telluride nanostructures prepared by colloidal synthesis and analyzed the photoluminescence characteristics of CdTe nanocrystals stabilized with thioglycolic acid. The results demonstrate that the relationship between Cd and Te precursors and the synthesis time influence the nanocrystal size and the optical properties of the nanocrystal-based disperse system.

The Optical and Electrical Properties of CdSe Nanoparticles

The electrical properties of Cadmium Selenium (CdSe) nanoparticles were measured by using I-V characteristic under illumination of light (AM 1.5, 100mWcm-2) at room temperature. The cadmium chloride (CdCI) as the Cd precursor and selenium (Se) powder as the Se precursor. In this research, the surface profiler was used to know the thickness of CdSe nanoparticles on the glass substrate. The thickness was used to know the energy band gap by using Tauc plot. The optical properties was measured by using Photoluminescence (PL) at room temperature. The energy band gap for 20 min ,30 min ,40 min and 50 min were 4.25 eV, 4.22 eV, 4.09 eV, and 4.21 eV.

The Effect of Time Ageing of Spray-Deposited on the Growth of CdSe Nanoparticles

Cadmium Selenide (CdSe) was obtained by using spray-deposited method which is using the sodium selenosulfite as Se precursor and cadmium chloride (CdCI) as cadmium (Cd) precursor. Time for each spray-deposited was used as the main parameter to investigate the properties of CdSe nanoparticles. By using FESEM for surface morphology and X-ray Diffraction (XRD) studies reveal that the CdSe nanoparticles with cubic crystal structures. In this research, the effect of time of spray deposited was main parameter to know the CdSe properties. The set of time was set from 10 min until 50 min. From FESEM result the size of CdSe nanoparticles were in the range 60-70 nm and the crystalline was hexagonal from XRD result. By using Scherrer equation, the size of crystalline of CdSe nanoparticles was determined from XRD characterization, the size was 60-70 nm. The size of CdSe nanoparticles from FESEM images were 60-80nm.

Cd1 − xZnxS thin films with low Zn content obtained by an ammonia-free chemical bath deposition process

Cd1−xZnxS films with low Zn content were obtained on glass substrates by an ammonia-free chemical bath deposition process. Alkaline reaction solutions were prepared using cadmium chloride, zinc chloride, sodium citrate, thiourea and potassium hydroxide. As a result of varying the mixture ratio between Cd and Zn precursors, microstructural studies from X-ray diffraction reveal that the resulting films have hexagonal, wurzite type, crystalline structure with changes in the preferential growth orientation. Important changes on the surface morphology and thickness of the Cd1−xZnxS films were also observed as effects of adding Zn to the CdS lattice. Optical studies show that Cd1−xZnxS thin films with energy band gaps in the range from 2.48 to 2.65eV were obtained.

CdTe1‐xSex/Cd0.5Zn0.5S core/shell quantum dots: core composition and property

Alloy CdTe(1-x)Se(x) quantum dots (QDs) have been fabricated by an organic route using Cd, Te and Se precursors in a mixture of trioctylamine and octadecylphosphonic acid at 280 °C. The variation of photoluminescence (PL) peak wavelength of the CdTe(1-x)Se(x) QDs compared with CdTe QDs confirmed the formation of an alloy structure. The Se component drastically affected the stability of CdTe(1-x)Se(x) QDs. A Cd0.5Zn0.5S shell coating on CdTe(1-x)Se(x) cores was carried out using oleic acid as a capping agent. CdTe(1-x)Se(x)/Cd0.5Zn0.5S core/shell QDs revealed dark red PL while a yellow PL peak was observed for the CdTe(1-x)Se(x) cores. The PL efficiency of the core/shell QDs was drastically increased (less than 1% for the cores and up to 65% for the core/shell QDs). The stability of QDs in various buffer solutions was investigated. Core/shell QDs can be used for biological applications because of their high stability, tunable PL and high PL efficiency.

The Optical Properties of CdSe Quantum Dots by Using Spray-Atomization Method

Cadmium Selenide (CdSe) quantum dots (QDs) is inorganic material by using spray-atomization method which is the novelty to find out the optical properties for the CdSe QDs. The Selenium (Se) precursor and Cadmium (Cd) precursor were prepared first. Se precursor by using sodium sulfite aqueous was mixed with selenium (Se) powder. For Cd precursor was used cadmium chloride (CdCI) as the Cd precursor. From previous research, CdSe QDs was obtained by using capping agent such as tri-n-octylphosphine oxide (TOPO) and trioctylphosphine (TOP). These capping agent are hazardous to environment and human. By using spray-atomization method it is more safe and economically. The photoluminescence (PL) was used to investigate the optical properties and to investigate the energy band gap from PL result. The field emission scanning electron microscopy (FESEM) was used to know the surface morphology of CdSe QDs. By PL result, the energy band gap was calculate and the comparison was investigate between the size of particle and the energy band gap. This important in this paper is to investigate the optical properties of CdSe QDs by using sprays-atomization method and to relate with the particle size.

Controlling the Crystallinity of Electrochemically Deposited CdS Nanowires

This report describes two distinct growth regimes occurring during the templated electrochemical deposition of CdS nanowires. The abundance of Cd2+ ions at the growth front dictates crystal nucleation and growth processes. At high Cd2+ concentration, randomly oriented polycrystalline material is formed, whereas local depletion of Cd2+ results in highly oriented crystals with the [002] crystalline direction aligned with the nanowire axis. Single nanowires exhibiting both regions were produced for direct imaging of the microstructure associated with these regimes. The current dependence of the time needed to locally deplete Cd2+ allowed for the extraction of a diffusion coefficient for Cd2+ of 1.23 × 10–6 cm2/s, which reflects reduced diffusion in nanoscale channels. Knowledge of these growth regimes and the parameters governing them allows for the growth of materials with targeted structural properties. Specifically, single-crystal materials can be preferentially formed by depositing at relatively high growth currents or by reducing the initial concentration of the Cd precursor in solution.

Structure and Band Edge Energy of Highly Luminescent CdSe1–xTex Alloyed Quantum Dots

CdSe1–xTex quantum dot (QD) alloys are characterized by high luminescence quantum yields and a strong band gap bowing as a function of the Se:Te ratio, featuring longer emission wavelengths than CdTe or CdSe dots of identical size. In this contribution, these properties are rationalized by examining the structure and band edge energy of CdSe1–xTex as functions of x. The QDs were synthesized employing the “hot-injection” method, in the presence of either trioctylphosphine oxide (TOPO) or octadecene (ODE) as the Cd precursor solvent. Elementary analysis of the QDs indicated that TOPO plays a crucial role in tuning the content of Se in the alloys, as only traces of this element were found when using ODE. Detailed studies based on X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) revealed a high degree of complexity in the structure of the alloyed dots. The analysis concluded that the structure of the QDs was essentially wurtzite, a...

Study of Time Effect to the Optical Properties of CdSe Nanocrystal

The synthesis of Cadmium Selenide (CdSe) by using wet chemical synthesis replace organometallic method. The oleic acid using as the capping agent for CdSe nanocrystals. Paraffin liquid using as solvent for Se and Cd precursor. In this paper, the optical properties at different time was investigated. For optical properties, photoluminescence spectroscopy (PL) was used and for surface morphology field emission scanning electron microscope (FESEM). This paper describe the effect of CdSe properties at different certain time.

Biparametric analyses of charge trapping in Cd0.9Zn0.1Te based virtual Frisch grid detectors

Detector grade Cd0.9Zn0.1Te (CZT) single crystals were grown from zone refined Cd, Zn, and Te (∼7 N) precursor materials, using a tellurium solvent method. Detectors with virtual Frisch grid configuration were fabricated using these crystals. I-V measurements revealed low leakage currents at room-temperature, ∼11 nA for one such detector D1 and ∼8 nA for another detector D2 at 1100 V. The spectroscopic performances of the two CZT virtual Frisch grid detectors have been evaluated and compared for high energy gamma ray detection. Detector D1 showed a well-resolved pulse-height spectrum with an energy resolution of ∼1.6% for the 662 keV gamma rays. Detector D2 also showed a distinct 662 keV peak but with a broader pulse-height distribution. A digital biparametric correlation study of the depth of interaction and energy deposited by the 662 keV gamma rays was carried out. A different kind of correlation pattern from that observed normally for hole trapping was noticed in the case of detector D2. Correlation of results from thermally stimulated current measurement studies suggested that the anomalous biparametric correlation pattern was due to the trapping of holes but modified by the virtual Frisch grid effect. The results also suggested that the effect of electron trapping could not be ruled out either. Finally, a digital correction scheme was applied to recover the 137Cs spectrum from the effect of charge loss.

Shape Control of CdTe Nanocrystals: Influence of the Solvent Composition and Ligand Effects

CdTe nanocrystals were synthesized by the hot-injection method with a mixture of oleylamine and octadecene as a solvent. The influence of the composition of the solvent and of the injection solution on the shape of CdTe nanoparticles was investigated. Various shapes of CdTe nanocrystals, such as nanodots, nanorods, multipods, and nanowires, could be obtained by changing the reaction conditions. Tuning the reactivity of both the cadmium and the tellurium precursors at the same time was found to be the main reason for the shape control of CdTe nanocrystals in this reaction system. The reactivity of the Cd precursor was controlled by the composition of the solvent, while the activity of the Te precursor could be influenced by using trioctylphosphine and tributylphosphine in the injection solution.

Formation of highly luminescent Zn1−xCdxSe nanocrystals using CdSe and ZnSe seeds

High-quality colloidal Zn1−xCdxSe nanocrystals (NCs) with tunable photoluminescence (PL) from blue to orange were synthesized using oleic acid as a capping agent. The Zn1−xCdxSe NCs were prepared through two approaches: using CdSe or ZnSe seeds. In the case of CdSe NCs as seeds, Zn1−xCdxSe NCs were fabricated by the reaction of Zn, Cd, and Se precursors in the coordinating solvent system at high temperature. The Zn1−xCdxSe NCs revealed orange emitting. A significant blue-shift of absorption and PL spectra were observed with time, indicating the formation of ternary NCs. In contrast, Zn1−xCdxSe NCs revealed blue to green PL for ZnSe NCs as seeds. This is ascribed to an embryonic nuclei-induced alloying process. With increasing time, the Zn1−xCdxSe NCs exhibited a red-shift both in their absorption and PL spectra. This is attributed to the engineering in band gap energy via the control of NC composition. The PL properties of as-prepared alloyed NCs are comparable or even better than those for the parent binary systems. The PL peak wavelength of the Zn1−xCdxSe NCs depended strongly on reaction time and the molar ratio of Cd/Zn. The Zn1−xCdxSe NCs revealed a spherical morphology and exhibited a wurtzite structure according to transmission electron microscopy observation and an X-ray diffraction analysis.

Facile Fabrication of Novel Magnetic and Fluorescent Fe<sub>3</sub>O<sub>4</sub>-CdSe Nanocomposites

Novel Fe3O4-CdSe nanocomposites were prepared by depositing semiconductor on monodisperse magnetic nanoparticles. First, monodisperse Fe3O4 nanoparticles were fabricated by a solvothermal process in which iron acetylacetonate (Fe(acac) 3 ) was used as precursor, phenyl ether as reaction medium, oleic acid as surfactant and oleylamine (OAm) as both surfactant and reducing agent. Novel Fe3O4 -CdSe heterostructures were prepared using 1-octadecene as high boiling solvent, cadmium oxide as Cd precursor, trioctyl phosphate (TOP)-Se as Se precursor, n-hexadecylamine (HDA) as surfactant, and stearic acid (SA) as growth promoter and nucleating agent. The structure and properties of the Fe3O4 -CdSe nanocomposite were fully characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrometry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), UV-Vis spectrum, and photoluminescence (PL). CdSe nanoparticles were successfully attached to the surface of Fe3O4 and grew along the c-axis to form novel jujube pit-liked and nail-liked heterostructures with a width of 3.6 nm and length of 14.5 and 32.5 nm,respectively. The novel nanocomposites were a combination of magnetite Fe3O4 and hexagonal CdSe rods, and exhibited strong fluorescent emission without obvious quenching and excellent superparamagnetic properties. Fluorescent absorption shifts to longer wavelength as the length of the CdSe rods increases. The saturation magnetization of Fe3O4 nanoparticles, jujube pit liked and nail liked Fe3O4-CdSe nanocomposites were 57.80, 40.76, and 31.10 emu·g -1 , respectively.

Characterization of Cd0.9Zn0.1Te based virtual Frisch grid detectors for high energy gamma ray detection

Detector grade CZT single crystals have been grown from zone refined Cd, Zn, and Te (∼7N) precursor materials using a tellurium solvent method. Infrared transmission imaging has shown an average tellurium inclusion size of ∼8μm in the as-grown crystal. Radiation detectors were fabricated in planar and virtual Frisch grid geometry and characterized for their spectroscopic performance. Charge transport properties revealed a high drift mobility of∼1200cm2/Vs and a mobility–lifetime product of ∼2.8×10−3cm2/V. A detector with planar configuration (dimensions 6.9×6.9×4.8mm3) showed an energy resolution of 4.7% for 59.5keV gamma rays. The detector in a Frisch grid configuration (dimensions 4.2×6.2×6.5mm3) exhibited an energy resolution of 1.4% for 662keV gamma rays. Digital spectroscopic measurements were carried out using a high-resolution digitizer card. A biparametric correlation scheme was employed to study the effect of charge loss on energy resolution of the planar detector. Based on this correlation scheme, a digital correction method was applied and improved pulse-height spectrum was obtained for 662keV gamma rays using the planar detector with spectral features comparable to those of the virtual Frisch grid detector.

Fabrication and Characterization of ${\rm Cd}_{0.9}{\rm Zn}_{0.1}{\rm Te}$ Schottky Diodes for High Resolution Nuclear Radiation Detectors

Cadmium zinc telluride (CZT) Schottky diodes with very low reverse leakage current have been fabricated and characterized for high resolution gamma ray detectors. The diodes were made using <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm Cd}_{0.9}{\rm Zn}_{0.1}{\rm Te}$</tex></formula> detector grade crystals grown from zone refined Cd, Zn, and Te (7N) precursor materials using low temperature tellurium solvent method. Various crystallographic defects including Te-inclusions/precipitates were identified and characterized using electron beam induced current (EBIC) measurement and thermally stimulated current (TSC) spectroscopy. The EBIC images were correlated with transmission infrared (TIR) images of CZT crystals and the EBIC contrast was attributed to the nonuniformities in spatial distribution of Te inclusions. Characterization by TSC revealed shallow and deep level centers with activation energies 0.25–0.4 eV and 0.65–0.8 eV respectively, which were attributed to intrinsic defects associated with Te inclusions. Pulse height measurements were carried out using <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{137}{\rm Cs}$</tex></formula> (662 keV) radiation source and energy resolution of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\sim 1.51}\%$</tex></formula> full width at half maximum (FWHM) was obtained from the as-grown boule.

Mechanochemically Synthesised Zn&lt;sub&gt;x&lt;/sub&gt;Cd&lt;sub&gt;1-x&lt;/sub&gt;S Nanoparticles for Solar Energy Applications

The mechanochemical solid-state synthesis of ZnxCd1-xS nanoparticles from zinc acetate, cadmium acetate and sodium sulphide in a planetary laboratory mill is described. Through changing the molar ratio of the Zn and Cd precursors, ZnxCd1-xS nanoparticles of different composition were prepared. Structural, surface and morphological properties were investigated by XRD, XPS, SEM and UV-VIS. Diffusion structural diagnostics was characterised by the emanation thermal analysis (ETA) results measured on heating of the samples. The cubic phase was found to be stable under mechanochemical treatment, as determined by XRD. The mixed phases were found to have ideal solution behaviours. In addition, microstructural characterisation indicated that mechanochemical treatment resulted in a structural refinement with a surface weighted crystallite size about 2 nm. The additional information of microstructure development and transport properties of the samples on heating was obtained by ETA. The calculated lattice parameters of mixed crystals linearly depend on the composition of ZnxCd1-xS nanoparticles. The S(2p), Zn(2p) and Cd(3d) core levels of the ZnxCd1-xS nanocrystallites reveal two different types of sulphur, zinc and cadmium unlike bulk CdS and ZnS. The calculated results indicate that the quantum-size effect in the nanoparticles is not negligible. The differences in the absorption edge and the emission peak position of the nanoparticles depend not only composition. Applied high-energy milling is a facile, efficient, and scalable process that does not require a solvent and can be performed under ambient conditions. Therefore, it is a promising candidate for the production of nanocrystalline materials.