ZnTe Nanocrystals Research Articles

In vitro cytotoxic activity of chemically synthesized ZnTe nanoparticles against human lung cancer cell line L-132 with supported molecular docking study

Among all the cancer cases, Lung cancer is the most common worldwide, which needs more potential therapy. But there are many limitations in the present therapy used for lung cancer treatment. Recently, many researchers are using different types of nanoparticles as an alternative for this purpose. Here, with such interest, ZnTe nanocrystals have been synthesized using a wet-chemical method, which is a cost-effective and easy method. After preparing the ZnTe nanocrystals, morphology has been analyzed through a scanning electron microscope (SEM) and the crystallinity of the prepared ZnTe nanocrystals has been investigated using X-ray diffraction analysis. After that, cytotoxicity of the prepared ZnTe nanoparticles has been examined at three different concentrations (100 ng/ml, 1 μg/ml, 100 μg/ml) on human lung cancer cell line L-132 using the MTT assay. From the experimental results, it is observed that a batter percentage of about 56 % of killing has been obtained at the concentration of 100 μg/ml after 24 h of treatment. It may happen that ZnTe nanoparticles enter through the cell membrane and induce cell apoptosis. For better understanding, molecular docking has been performed using ‘auto dock vina’ to find the binding confirmation of ZnTe nanoparticles with the lung cancer cell line L-132. Both the biological and computational methods confirm that nanocrystalline ZnTe is a therapeutic candidate for the treatment of lung cancer cells.

Colloidal synthesis of ZnTe nanocrystals by laser ablation and fabrication of hybrid light emitting device

Zinc telluride (ZnTe) nanocrystals (NCs) have generated the interest of researchers as an electrode material in hybrid light emitting devices (HLEDs) due to its potentially high capacity. However, due to the restricted fundamental charging capacity of the electrode materials, the available energy of existing nanomaterial light emitting devices remains enough for a wide range of applications. In this research, ZnTe nanocrystals were synthesized using Nd: YAG laser at energy 600 mJ by 150 pulse number to form a battery device out of ITO/ZnTe/TPD/Ni. The spectra of the ZnTe NCs were assessed using ultraviolet-visible (UV-VIS) and photoluminescence (PL). The results proved that the synthesized NCs were nanocrystalline structures. The energy gap (Eg) within ZnTe NCs regarded as (PL) spectrum has been identified to be about 3.6 eV. ZnTe NCs produced via laser ablation enhance the functionality of the HLEDs by increasing the carrier's charge mobility and, as a further benefit, by facilitating recombination processes inside ZnTe NCs with TPD organic polymer. In addition to lighting at 3V, current-voltage (I-V) specifications establish suitable environment as well as formation.

Confirmation of the presence of edge dislocations in the prepared FCC ZnTe nanocrystals from the study of structural analysis through the MWH method with added Fourier analysis (W-A method) of diffraction peaks

Nanocrystalline ZnTe with cubic mono-phase has been synthesized by a wet-chemical synthesis process for the study of the presence of dislocations through X-ray diffraction peak profile analysis. The average size of the ZnTe nanocrystals has been determined from the High-Resolution Transmission Electron Microscopic (HRTEM) analysis as 21.9 nm. In the XRD pattern, (111), (200), (220), (311), and (400) diffraction planes have been observed, which confirms the formation of cubic mono-phase of ZnTe. For the extraction of microstructural details, the Rietveld refinement has been performed using Fullprof software and from this refinement, the lattice constant has been obtained as 6.17 Å under the space group of f-43. Here, X-ray diffraction peak has been analyzed through the Williamson-Hall (W–H) analysis method and the Warren-Averbach (W-A) analysis method. Williamson-Hall approach is based on the full-width at half-maxima analysis, whereas the Warren-Averbach method is related to the analysis of the Fourier transform of the broadened X-ray diffraction peaks. For considering and analyzing the anisotropic broadening of the peak, modified Williamson-Hall and modified Warren-Averbach methods have been used for the calculation of size, strain, and dislocation density. The presence of prominent edge dislocation of about 71 % has been confirmed from the anisotropic peak broadening study. In addition, the HRTEM image directly verifies the presence of edge dislocations in both the lattice planes of (111) and (220).

Cathodoluminescence and structural properties of ZnTe nanocrystals synthesized from Te/ZnO thin films

Highly mismatched alloys are of substantial interest for composition-dependent bandgap tunability for solar cell applications. Using low-energy ion implantation and subsequent thermal treatment, we have synthesized ZnTe nanocrystals from Te/ZnO bilayer thin films. However, only thermal treatment without ion implantation does not show any ZnTe nanocrystal characteristics that demonstrate the role of defects via ion implantation in nucleation growth. High-resolution transmission electron microscopy measurements confirmed the nanocrystalline growth of ZnTe and ZnTeO3 inside the mixed layer of ZnO and Te. From X-ray diffraction, it has been observed that a critical fluence of ions is required to produce a certain quantity of defects to assist in stoichiometric ZnTe formation. The absorption spectroscopy illustrates dual bandgap in the mixed alloys. Cathodoluminescence spectroscopy confirms two visible emission bands at 2.1 eV and 2.35 eV corresponding to the ZnTe and ZnO defect band along with the near band UV emission of ZnO at 3.26 eV. Such composition-dependent bandgap and light emission tunability from a mixed alloy are suitable for semiconductor device technology and energy harvesting.

Enhanced white light emitting device based on ZnTe nanocrystals and conductive organic polymer by surface excitons

The white organic lighting has been intended device appearing an emission cover lightemitting conductive polymer (Poly (p-phenylene vinylene) (PPV) and poly (p-phenylene sulfide) (PPS)) as a host material for zinc telluride (ZnTe) nanocrystals (NCs) or quantum dots (QDs) and tris-(8-hydroxyquinoline)-aluminum (Alq3) together of titanium oxide (TiO2) thin layer as white light emitters. The white light-emitting electroluminescence (EL) procedure be defined by of three covers deposited successively upon the ITO glasssubstrate surface ITO/PVV: PSS/ZnTe NCs/Alq3 with TiO2/Ni. Current-voltage (I-V) attributes show a strong output current relative to the few voltages (4 V) that are used to produce acceptable white light output performance. The Commission International de l’Eclairage coordinates of the device's emitting light was recognized (X= 0.31, Y= 0.34) which were only slightly changed over a range of applied voltage (4 Volts) and correlated color temperature (CCT) was realized nearly 6250 K. The production of ZnTe NCs lightemitting device with organic polymer hole injection (PVV: PSS) and organic molecules (Alq3 with TiO2) was successful in white-light production.

2.86 μm emission and fluorescence enhancement through controlled precipitation of ZnTe nanocrystals in DyF3 doped multicomponent tellurite oxyfluoride glass

Tellurite oxyfluoride glasses with composition of 71TeO2-10ZnO-10BaF2-4K2O-3Nb2O5-2TiO2 doped with different concentrations of DyF3 (0.3, 0.4, 0.5, 0.7, 1 wt%) were prepared by melt-quenching method under dry O2 atmosphere. Under 808 nm laser pumping, infrared (IR) fluorescence emission with central wavelength of 2.86 μm was detected. Basing on the Judd-Ofelt (J-O) theory, the intensity parameters (Ωλ, λ=2, 4 and 6) and radiative property were calculated and characterized through the transmission and fluorescence spectra. The tellurite oxyfluoride glass had high thermal stability and large emission cross-section at 2.86 μm (7.82 × 10−21 cm2). DyF3 doped tellurite oxyfluoride glass ceramic were prepared via in-situ crystallization of ZnTe nanocrystals through heat treatment to ameliorate the surrounding environment of rare earth (RE) ions. The tellurite oxyfluoride glass ceramic prepared by heat treatment at 390°C had great enhancement in 2.86 μm fluorescence intensity (about 7 times), longer fluorescence lifetime (126 μs), indicating that the in-situ crystallization method may be helpful for exploring tellurite based high gain laser glass.

Structural and thermal study of ZnTe nanocrystals doped with Cr and Mn in phosphate glasses

In this study, structural and thermal features of phosphate glasses doped with diluted magnetic semiconductors are investigated. The samples were ZnTe nanocrystals doped with different concentrations of Cr and Mn. UV-visible absorption spectra showed the presence of Cr2+ and Cr3+ ions into the matrix. Depolymerization of the phosphate network is observed by Raman spectroscopy due to the addition of Cr ions breaking the phosphate chains. The thermal diffusivity (D), thermal conductivity (K), specific heat capacity (ρc) and optical path variation with temperature (dS/dT) of samples are measured by thermal lens and ρc techniques. The thermal conductivity values show that although the formation of crystalline structures of ZnTe inside the matrix glasses leads to a decrease, the incorporation of the Cr and Mn do not show a definite trend. A monotonic reduction in optical path variation with temperature is observed with nanocrystal formation and Cr addition.

Effects of Cu2+ ion incorporation into ZnTe nanocrystals dispersed within a glass matrix

This paper reports on the optical, morphological, structural and magnetic properties of Zn1-xCuxTe nanocrystals, doped with Cu (x varying from 0.000 to 0.100) and grown by thermal annealing at 500 °C in a P2O5–ZnO–Al2O3–BaO–PbO glass system that had been synthesized by fusion. At higher levels of Cu-doping, optical absorption (OA) showed that Cu2+ ions were incorporated within and dispersed throughout the lattice of the ZnTe semiconductor. The OA spectra also showed that the growth kinetics of these NCs were influenced by the Cu2+ magnetic ions. Transmission electron microscopy (TEM) images revealed that the lattice parameter of the nanocrystals was not affected by the incorporation of Cu2+ ions. Finally, electron paramagnetic resonance (EPR) spectra of the Cu2+ ions showed asymmetrical hyperfine lines as well as proved a substitutive incorporation of Cu2+ in ZnTe NCs.

Preparation, structure and optical properties of ZnTe and PbTe nanocrystals grown in fluorophosphate glass

ZnTe and PbTe nanocrystals with average radii of 2.42 and 4.25 nm, respectively, were grown in a fluorophosphate glass host. A strong quantum confinement effect was induced as a result of the blue shifted optical absorption due to the ZnTe and PbTe nanocrystals. Optical constants, like the refractive index (n), complex dielectric constant, dissipation factor (tan δ) and optical conductivity (σopt), were extracted from the experimental transmittance T(λ) and reflectance R(λ) data. Moreover, the presence of both the ZnTe and PbTe nanocrystals were confirmed by X-ray diffraction analysis, revealing cubic and hexagonal wurtzite structures, respectively. The results of the optical absorption spectra were confirmed by the similar nanocrystal radii identified using transmission electron microscopy and X-ray diffraction analyses. Raman analysis of the heat-treated glass sample confirmed that bands at 65 and 103 cm−1 are due to the longitudinal optical (LO) modes of PbTe NCs. Also, the band at 214 cm−1 is attributed to first harmonic or fundamental LO mode of ZnTe NCs.

Optical properties of Cr-doped Zn1−xMnxTe semimagnetic nanocrystals

The effect of Cr co-doping on the optical properties of Mn-doped ZnTe nanocrystals (NCs) embedded in a glass matrix is studied in this paper. The substitutional incorporation of Cr2+ ions into these semiconducting NCs was strongly evidenced by optical absorption and crystal field theory analyses, which showed the characteristic transitions of Cr2+ and Cr3+ ions. Transmission electron microscopy images revealed the NC size and invariance lattice parameter, with the incorporation of Mn2+ and Cr2+ ions. PL spectra showed that co-doping with Cr favors a competition between Mn2+ and Cr2+ ions, resulting in a decrease in the rate of Mn2+ substitution, zinc vacancy filling (VZn) in Zn1−x−yMnxCryTe NCs, and the formation of interstitial Cr3+ ions in the host glass system.

Effect of Co co-doping on the optical properties of ZnTe:Mn nanocrystals.

We study the effect of Co co-doping on the optical properties of Mn-doped ZnTe nanocrystals (NCs) embedded in a glass matrix. Optical absorption (OA) and crystal field theory strongly indicated the substitutional incorporation of Co2+ ions into these semiconducting NCs as well as the characteristic transitions of these ions in the visible and near infrared spectral region. Transmission electron microscopy (TEM) images revealed an invariant NC lattice parameter with the incorporation of Mn2+ and Co2+ ions. The same was confirmed by X-ray diffraction (XRD). The photoluminescence (PL) spectra showed that the characteristic emission bands of Co2+ ions (E1Co2+ and E2Co2+) are intense and evident at low temperatures. Indeed, Raman spectra showed that the dependence of luminescence intensity on temperature is due to the electron-phonon interaction that arises from multiphonon relaxation processes. The redshifts in the PL spectra from green to orange with the incorporation of Mn2+ ions into ZnTe NCs, and in the near infrared with increasing Co-concentration, result from sp-d exchange interactions associated with the increase in Mn2+ and Co2+ ions in tetrahedral sites of ZnTe NCs, which may be very interesting for applications in luminescent devices. These observations provide strong evidence that higher Co-concentrations inhibit the incorporation of Mn2+ into ZnTe NCs, suggesting that there may be competition between Co2+ and Mn2+ ions substituting Zn2+ ions and, furthermore, that these ions replace zinc vacancies (VZn) in these NCs.

Quantum efficiency of Yb3+–ZnTe co-doped phosphate glass system

The present paper deals with optical properties of a highly transparent phosphate glass co-doped with Yb3+ and ZnTe nanocrystals. The presence of ZnTe nanocrystals is due to a sequential melting–nucleation procedure evidenced by optical absorption and Atomic Force Microscopy. From the perspective of compositional variation of the dopants, photoluminescence and lifetime measurements were performed. As a result, it was demonstrated that the ZnTe nanocrystals increase the Yb3+ emission by a factor up to five, when the pumping wavelength is resonant with the ZnTe absorption. It was also verified that the ZnTe nanocrystals inhibit the self-trapping of the rare earth luminescence. As a consequence, the quantum efficiency of the 5F7/2→5F5/2 transitions of the Yb3+ is considerably increased. Finally, we have found that the glass thermal diffusivity is not sensitive to temperature variations comprising the interval from room temperature to cryogenic temperatures. This can be an important property when considering this material to future applications in high-power photonic devices.

Evidence of competition in the incorporation of Co2+and Mn2+ions into the structure of ZnTe nanocrystals

Glass-embedded Zn1−x−yMnxCoyTe nanocrystals (withx= 0.01 andyvarying from 0.000 to 0.800) were successfully synthesized using a protocol based on the melting–nucleation synthesis route and herein investigated by several experimental techniques.

Thermal analyzes of phosphate glasses doped with Yb3+ and ZnTe nanocrystals

This work studies the thermal properties of a glass matrix called PZABP doped with ZnTe and co-doped with Yb3+ with nominal composition 60P2O5, 15ZnO, 5Al2O3, 10BaO, and 10 PbO (mol%). The presence of ZnTe results in the formation of nanocrystals which are evidenced by optical absorption, X-Ray Diffraction (XRD) and Raman scattering. Thermal lens and Volumetric Heat Capacity techniques were used to investigate thermal diffusivity (D), thermal conductivity (K) and optical path variation with temperature (ds/dT). The outcomes indicate high values for the thermal diffusivity and a relatively small thermal conductivity, i.e., around 2.6×10−3cm2/s and 3.4×10−3Wcm−1K−1, respectively. On the other hand, a low ds/dT value, 1.0×10−6K−1, was obtained as required for an active laser medium. Moreover, it has been observed that the matrix allows high concentration of dopants without compromising its thermal properties. As a result, PZABP glasses may be pointed out as a promising material to applications in high power photonics devices.

Efficient implementation of effective core potential integrals and gradients on graphical processing units.

Effective core potential integral and gradient evaluations are accelerated via implementation on graphical processing units (GPUs). Two simple formulas are proposed to estimate the upper bounds of the integrals, and these are used for screening. A sorting strategy is designed to balance the workload between GPU threads properly. Significant improvements in performance and reduced scaling with system size are observed when combining the screening and sorting methods, and the calculations are highly efficient for systems containing up to 10 000 basis functions. The GPU implementation preserves the precision of the calculation; the ground state Hartree-Fock energy achieves good accuracy for CdSe and ZnTe nanocrystals, and energy is well conserved in ab initio molecular dynamics simulations.

Effect of ZnS shell on tight-binding simulation of zinc-blende ZnTe/ZnS core/shell nanocrystals

Results of theoretical investigations on the electronic structures and optical properties of spherical ZnTe nanocrystals and the consecutive coating with a ZnS shell to achieve the ZnTe/ZnS core/shell nanocrystals of experimentally relevant sizes are presented using the atomistic tight-binding theory with the aim to analyze the importance of the ZnS growth shell. Using this theoretical model, the calculations consisting of the electronic energy states, ground electron–hole coulomb energies, single-particle gaps, excitonic gaps, atomistic characters, radiative lifetimes and oscillation strengths under different shell thicknesses are mainly comprehended. The detailed analysis elucidates and quantifies the significance of shell thickness in determining the electronic structures and optical properties of ZnTe/ZnS core/shell nanocrystals. The simulation emphasizes that the calculations are primarily responsive with the ZnS shell. Besides, the results computed by tight-binding theory effectively demonstrate a good agreement with experimental data. In accordance with the comprehensive data, these computations mainly provide an obvious demonstration in the significant advantages of a shell thickness and an alternative way in choosing the cadmium-free nanostructures as non-intrinsic toxicity.

Annealing time on carrier dynamics of ZnTe nanoparticles embedded in a near ultraviolet-transparent glass

ZnTe nanocrystals were successfully grown by heat-treating a host glass matrix that had been synthesized by fusion. Room temperature optical absorption and photoluminescence excitation spectra and atomic force microscopy images showed the formation of three well-defined, different sized groups of nanocrystals: quantum dots and bulk-like nanocrystals. Photoluminescence spectra showed emissions belonging to both of these groups as well as deep defects in the electronic structure of the ZnTe nanocrystals. Strong agreement between the fit of the model based in rate equation and the experimental integrated photoluminescence intensity data showed that this described the temperature dependent carrier dynamics of ZnTe nanocrystals.

Optical properties of oxide glasses with semiconductor nanoparticles co-doped with rare earth ions

This letter investigates PZABP glasses with nominal composition, 60P2O5. 15ZnO. 5Al2O3. 10BaO. 10PbO, doped with tellurium and co-doped with different concentrations of rare earth ions, ytterbium and europium. AFM, optical absorption, photoluminescence (PL) and time-resolved photoluminescence (TRPL) techniques characterized the vitreous systems. The formation of semiconductor nanoclusters ZnTe bulk-like and ZnTe quantum dots were identified. PL and TRPL show the energy transfer from the ZnTe nanocrystals and Eu3+ ions to Yb3+ ions. The optical properties presented qualify the system as potentially useful for light emission devices in the infrared region from 920 to 1060nm.

Raman Scattering from ZnTe Nanocrystals Depending on Different Excitation Wavelengths

ZnTe nanocrystals were synthesized in NaOH solution by hydrothermal method and they were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and micro-Raman spectroscopy. The results indicate that the ZnTe nanocrystals were crystallized in cubic zincblende structure and their morphologies and sizes are polyhedron and diversified, respectively. The Raman results show that different scattering occurred from the ZnTe nanocrystals depending different excitation wavelengths. According to theories related to band-gap and Raman scattering, the excitation wavelength-dependent Raman scattering from the ZnTe nanocrystals was analyzed.

Intense white luminescence in ZnTe embedded porous silicon

Porous silicon layers were embedded with ZnTe using the isothermal close space sublimation technique. The presence of ZnTe was demonstrated using cross-sectional energy dispersive spectroscopy maps. ZnTe embedded samples present intense room temperature photoluminescence along the whole visible range. We ascribe this PL to ZnTe nanocrystals of different sizes grown on the internal pore surface. Such crystals, with different orientations and sizes, were observed in transmission electron microscopy images, while transmission electron diffraction images of the same regions reveal ZnTe characteristic patterns.