Replacement Of Zn Research Articles

Formation of Alloyed Cu2CoxZn1-xSn(S,Se)4 Absorption Layer and Its Application in Solar Cells.

Partial substitution of cations is crucial for suppressing harmful defects in Cu2ZnSn(S,Se)4 thin-film solar cells. In this study, based on the mixed n-butylammonium and butyrate solution system, the alloyed Cu2CoxZn1-xSn(S,Se)4 phase can be prepared by substituting Zn2+ with Co2+, which can suppress harmful defects and optimize the crystallinity of the Cu2ZnSn(S,Se)4 absorption layer, and improve the photoelectric conversion efficiency (PCE) of devices. By systematic investigation of the impact of Co content on the performance of devices, the optimal substitution amount of Zn2+ with Co2+ is 0.05. At this time, PCE, the open-circuit voltage (VOC), current density (JSC), and fill factor (FF) of the devices can reach 9.0%, 416 mV, 33.87 mA/cm2, and 64%, respectively. It is the first time that the replacement of Zn2+ with Co2+ is applied to optimize PCE of CZTSSe solar cells. The excellent results also demonstrate that the substitution of Zn2+ with Co2+ can become a new approach for further performance optimization of Cu2ZnSn(S,Se)4 solar cells.

Managing the micro-structure and properties of Sm-ZnO thin films by tuning the contents of Sm

The microstructural variations in zinc oxide (ZnO) nanostructures are probed caused by the incorporation of RE metal ion Sm3+ in replacement of Zn2+. Sm-doped ZnO nanostructures with Sm concentration of 6–10 wt % is synthesized via a simple sol gel-dip coating synthetic technique. The current research looks into the physical, surface morphology, dielectric, optical, and magnetic properties of Samarium doped ZnO nanostructures. Structural and morphological investigations are primarily carried out using XRD and SEM techniques. The data from XRD identified the synthesized Sm doped ZnO nanostructures crystallize in a wurtzite hexagonal structure. The Sm dopant is incorporated into the Zn matrix. After adding Sm in ZnO, a slight variation in crystallite size is noticed. The estimates of the optical energy band gap based on optical transmittance measurements show that the band gap is widened. The variation in dielectric properties of Sm-ZnO is assumed to be the result of the increase in Sm doping %. The various functional groups that appeared in the prepared nanostructures are identified using FTIR. These prepared nanostructures are highly recommended for sensing applications as well as for optoelectronic devices.

Toward Ideal Metal–Organic Framework Thin-Film Growth via Automated Layer-by-Layer Deposition: Examples Based on Perylene Diimide Linkers

Photoactive metal–organic framework (MOF) thin films offer an opportunity for translating the advantages of periodic, crystalline, and tailorable light-harvesting materials directly into devices such as those for photoelectrochemical solar energy conversion. In this study, we report the fabrication of light-absorbing perylene-diimide-containing pillared-paddlewheel MOF thin films using an automated layer-by-layer (LbL) deposition technique. Our focus here is on optimizing the growth of representative chromophoric MOFs as oriented films of uniform and predefined thickness. Growth was examined as a function of metal identity, pillaring ligand composition, and supporting-surface chemical functionality. Application of atomic force microscopy (AFM) and complementary techniques revealed that the surface-supported MOFs initially display island-type film growth (Volmer–Weber growth), resulting in comparatively rough films. Further growth is accompanied by the merging of islands, resulting in films that, depending on experimental details, can be remarkably smooth (i.e., roughness on the order of ±1 nm (one structural repeat unit in the pillaring direction)). These details include the use of 1,4-diazabicyclo[2.2.2]octane (DABCO) as a MOF pillar and ALD-grown zinc oxide as a film support (ALD = atomic layer deposition). Also helpful for mitigating island-type growth, at least in part, is the replacement of Zn2+ by Cu2+ as the metal component of the MOF. Notably, each of these adjustments entails replacing weaker chemical bonds with stronger ones.

Electrical responses and dielectric properties of (Zn2+ + F−) co–doped CaCu3Ti4O12 ceramics

The effects of Zn2+ and F− ions on the ceramic microstructure, electrical properties, and colossal dielectric response of CaCu3Ti4O12 were investigated. The dopants influenced the microstructure of the CaCu3Ti4O12. The replacement of Zn2+ and F− ions reduced the low–frequency loss tangent while retaining the high dielectric constant of CaCu3Ti4O12. In co–doped ceramics, the high dielectric permittivity of around 5.76 – 7.59 × 104 and low loss tangent of 0.082 – 0.085 can be attained. The decrease in the loss tangent of the co–doped ceramic samples is commensurate with the significant increase in the grain boundary (GB) resistance and breakdown electric field. The Cu+ and Ti3+ ions in CaCu3Ti4O12 were identified using X–ray photoelectron spectroscopy and were found to be decreased by co–doping with Zn2+ and F−. The presence of these ions may play a crucial role in the semiconducting grains. The substitution of Zn2+ and F− ions can increase the electrostatic potential barriers at the GBs, resulting in improved GB resistance.

Purifying cyanide-bearing wastewaters by electrochemical precipitate process using sacrificial Zn anode

With the rapid development of society, wastewaters, such as cyanide-containing wastewaters (CBWs) have caused environmental problems. In the present work, an electrochemical approach using sacrificial Zn anode was investigated for the removal of cyanides from CBWs. The effects of operational parameters, such as current density, pH, initial cyanide concentration, and ionic strength, on the cyanides removal from synthetic solution were discussed in turn. Under the optimal conditions obtained, the treatment of industrial CBWs was considered. Subsequently, more attentions were paid to elucidate the removal mechanisms of cyanide ions and the corresponding metal-cyanide (copper and iron) complexes by a combination of cyclic voltammetry (CV), pHPZC, X-Ray diffractometer (XRD), scanning electron microscope with energy disperse spectroscopy (SEM/EDS) and X-ray photoelectron spectrometer (XPS) characterizations. Experimental results demonstrated that the removal efficiency of total cyanide (CNT), Cu, and Fe from industrial CBWs are 98%, 91%, and 96%, respectively, with an anode consumption of 1.78 kg/m3 and energy consumption of 2.50 kW·h/m3, of which 72% of Cu was collected on the cathode and almost all of Fe was in the precipitate. Removal mechanisms suggested that free cyanide (CN–) mainly presented as Zn(CN)2 into the electrolytic precipitate. The replacement of Zn2+ and electroreduction promoted 72% of Cu(I) to be reduced, while 57% of the remaining portion of Cu(I) was oxidized to Cu(II) and 43% of Cu(I) could form CuSCN into the precipitate by XPS analysis. With respect to Fe, it was mainly ascribed to the formation of Zn2Fe(CN)6 precipitate to be removed. From above, this work provided a method for enriching cyanides from wastewaters into the precipitate, while valuable metal Cu was deposited on the cathode, facilitating the separation and recovery of valuable resources.

Structural, Magnetic and Dielectric Analysis of Higher Magnetic Mn Doped Zn-Cr Oxide Nanoparticles

Higher magnetic Mn doped Zn-Cr oxide nanoparticles with general compositional formula MxZn0.95-xCr0.05O have been synthesized by using sol-gel auto combustion technique. Room temperature X-ray diffraction (XRD) technique has been employed to study the structural and microstructural parameters of the as-prepared samples. XRD analysis confirms the phase purity and hexagonal wurtzite structure of all the samples. Replacement of Zn2+ ions by Mn2+ ions shifts peak positions slightly towards the lower angles which in turn expands the lattice lengths ‘a’ from 3.2487 to 3.2528 Å and ‘c’ from 5.2043 to 5.2118 Å. Crystallite size obtained from Scherrer equation was confirmed by Williamson – Hall (W-H) and size – strain plot methods (SSP). Both W-H and SSP methods reveals the tensile type strain for undoped sample and comprehensive type strain for Mn2+ doped samples. Magnetic properties were investigated by using vibrating sample magnetometer. Diluted ferromagnetic behaviour is observed for all the samples and saturation magnetization (MS) increases from 0.0514 to 0.1163 emu/gm. Two-probe technique was employed to understand the dielectric behaviour of the samples as a function of frequency. At lower frequency region, both dielectric constant () and dielectric loss tangent (tan ) shows higher values and decreases with the increasing applied frequency.

Novel cadmium substituted barium zinc niobate perovskites: Phase formation, structural and impedance studies

Herein we report the structural and impedance properties of the novel Cd-substituted perovskites, Ba(Zn1/3-xCdx)Nb2/3O3 (BZCN), 0 ≤ x ≤ 0.333, prepared by solid-state reaction at 1000 °C for 17 h. The doping mechanism of this complete substitutional solid solution was proposed to be a one-to-one replacement of Zn2+ by Cd2+ as to maintain the overall electroneutrality of the system. BZCN perovskites crystallised in a cubic symmetry, space group Pm3m, Z = 1 and their refined lattice constants, a = b = c were found to be in the range 4.0917(3)-4.1693(13) Å. A moderate unit cell expansion was discernible with increasing CdO concentration, thus portraying a linear correlation between lattice constant and composition that obeyed the Vegard's law. The surface microstructures of these BZCN perovskites were composed of irregular polyhedral grains and their determined crystallite sizes by both Scherrer and Williamson-Hall methods were found to be in the range 21.0–44.8 nm. Both TGA and DTA analyses also confirmed that these materials were thermally stable as neither phase transition nor weight loss was discernible within the studied temperature range 30–1000 °C. BZCN perovskites were highly insulating with high activation energies in the range ~ 2.51–3.19 eV. At 1 MHz and 30 °C, the recorded dielectric constants and losses were found to be ~ 24–29 and ~ 0.24–0.38, respectively.

Porous Zn1-xCdxS nanosheets/ZnO nanorod heterojunction photoanode via self-templated and cadmium ions exchanged conversion of ZnS(HDA)0.5 nanosheets/ZnO nanorod

Herein, we synthesized porous Zn1-xCdxS nanosheets (PNS)/ZnO nanorod (NR) heterojunction photoanode via self-templated conversion using successively hydrothermal and Cd2+ ion exchange methods. Moreover, after conversion of ZnO to inorganic–organic hybrid ZnS-1,6-hexanediamine (HDA)0.5nanosheets/ZnO NR material, Cd2+ ion exchange was conducted. It was confirmed from X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM) analyses that the inorganic–organic hybrid ZnS(HDA)0.5 NS was transformed into Zn1-xCdxS PNS/ZnO NR heterojunction photoanode via the replacement of Zn2+ by Cd2+ ion. Zn1-xCdxS PNS/ZnO NR-160C3H heterojunction photoanode synthesized at 160 °C for 3 h showed the highest photocurrent density of 4.10 mA cm−2 (vs. RHE) under 1.5 G illumination, which was 7.9 times higher than that of bare ZnO NR photoanode. The porous nanostructured morphology and larger surface area of Zn1-xCdxS PNS/ZnO NR heterojunction photoanode fabricated by Cd2+ ion exchange result in efficient light absorption and effective charge transfer pathway. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) results show the shorter lifetime (37 ns) and reduced recombination in Zn1-xCdxS PNS/ZnO NR-160C3H heterojunction photoanode. During PEC analysis, the possible charge transfer mechanism in Zn1-xCdxS PNS/ZnO NR heterojunction photoanode was proposed. Surface passivated Zn1-xCdxS PNS/ZnO NR-160C3H photoanode shows improved photostability and exhibited 3.8 times higher H2 evolution (161 μmol) than the Zn1-xCdxS PNS/ZnO NR-160C3H (42 μmol) photoelectrode at 0.9 V vs. RHE.

Synthesis and Structural Manipulation of a Polyanionic Zincoborate [Zn(H2O)6](NO3)2·[Zn{B3O3(OH)4}2(H2O)4]·2H2O by the Molten Salt Method and its Potential Application as a Flame Retardant

A polyanionic borate [Zn(H2O)6](NO3)2·[Zn{B3O3(OH)4}2(H2O)4]·2H2O (1) have been synthesized by a molten salt method in this work. Its crystal structure consists of [B3O3(OH)4]− cluster and NO3− anions. Zn2+ cations are covalently bonded to the polyanionic clusters and water molecules leading to a [Zn(H2O)6] octahedron and a [Zn{B3O3(OH)4}2(H2O)4] cluster, which are connected by hydrogen bonds (H-Bs) to form a fictitious 3D structure, in which the NO3− anion are filled in the void. Crystal data for 1 is as following: Monoclinic, P21/c, a = 11.2817(12)A, b = 6.5374(7)A, c = 17.668(2)A, α = 90.00°, β = 100.981(5)°, γ = 90.00°, Z = 2. Two isostructural compounds, [Co(H2O)6](NO3)2·[Co{B3O3(OH)4}2(H2O)4]·2H2O (2) and [Ni(H2O)6](NO3)2·[Ni{B3O3(OH)4}2(H2O)4]·2H2O (3) have been obtained by similar molten salt method, indicating the structure of 1 can be manipulated by replacement of Zn2+ with Co2+ or Ni2+. Structures of the borates have been further confirmed by element analysis, FTIR, PXRD, TG, and UV–vis diffusion reflectance spectra. The bandgap of the borates showed a tunable performance with a change of metallic ions. Furthermore, we studied that flame retardant property of 1 by mixing it with Acrylonitrile Butadiene Styrene (ABS). The cone calorimetry tests confirmed that ABS/1 composites with 15 wt% loading of 1 exhibited superior performance.

Two-step gas adsorption induced by the transmetallation in a two-dimensional metal-organic framework.

Transmetallation or replacement of Zn2+ ions with Cu2+ ions in a two-dimensional metal-organic framework, Zn3(TCPB)2(H2O)2 (H3TCPB = 1,3,5-tri(4-carboxyphenoxy)benzene), gives rise to additional gas adsorption, where the additional adsorption amount linearly depends on the degree of the transmetallation.

Preparation of cobalt substituted zinc ferrite nanopowders via auto-combustion route: an investigation to their structural and magnetic properties

CoxZn1−xFe2O4 (x = 0, 0.1, 0.2, 0.3, 0.4) nanopowders were fabricated via auto-combustion synthesis followed by calcined treatment. The structural, morphological, compositional and magnetic properties of the as-synthesized samples were decided by X-ray diffraction (XRD), field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, specific surface area and Physical Property Measurement System analyses, respectively. The XRD patterns revealed all annealed cobalt substituted zinc nanoferrites display a single phase cubic spinel structure, the decrease in lattice constant with increasing Co2+ ions concentration is related to the lattice shrinkage originated from the replacement of Zn2+ ions (ionic radii of 0.82 A) by Co2+ ions (ionic radii of 0.78 A); the increase of crystallite size with increasing Co2+ ions content can be attributed to the less exothermic for the formation of cobalt ferrite than that for zinc ferrite. The M–H curves revealed that there are unsaturated magnetization and negligible hysteresis loops for all samples with lower cobalt concentration (x = 0, 0.1, 0.2, and 0.3), implying a superparamagnetic behavior; while the Co0.4Zn0.6Fe2O4 nanoparticles (x = 0.4) show ferromagnetism at room temperature. The M–T relations inferred the substitution of cobalt ions can remarkably enhance Curie temperature of the as-prepared Co–Zn ferrite nanoparticles. At room temperature lower cobalt-substituted zinc nanoferrites tend to show superparamagnetism while higher cobalt-substituted zinc nanoferrites prefer to present ferromagnetism.

A rare porous zinc phosphonocarboxylate framework with high thermal stability and interesting structural transformation

A rare porous zinc-organic framework with ultrahigh thermal stability over 500°C was obtained, which exhibits a CaF2-type topology formed by 8-connected tetranuclear Zn4 clusters and 4-connected phosphonocarboxylate ligands. Interestingly, the similar reactions to the zinc-organic framework but in the absence of H2O or by the replacement of Zn2+ with Co2+ can yield three different 3D cluster-based frameworks but with the same CaF2-type topology.

Cu2ZnSnS4 thin films by simple replacement reaction route for solar photovoltaic application

A process for deposition of Cu2ZnSnS4 (CZTS) films using replacement of Zn2+ in ZnS is demonstrated. X-ray diffraction pattern and Raman spectroscopy confirm the formation of pure CZTS. Atomic force microscopy shows the films to be homogeneous and compact with root mean squared roughness of 6nm. The direct band gap of CZTS films as elucidated by UV–Vis-NIR spectroscopy is 1.45eV. The CZTS films exhibit p-type conduction with electrical conductivity of 4.6S/cm. The hole concentration and hole mobility is determined to be 3.6×1017cm−3 and 1.4cm2V−1s−1 respectively. Solar cells with structure: graphite/CZTS/CdS/ZnO/SnO2:In/Soda lime glass are also fabricated, gave photo-conversion efficiency of 6.17% with open circuit voltage and short circuit current density of 521mV and 19.13mA/cm2, respectively and a high fill factor of 0.62. The external quantum efficiency of the solar cell lies above 60% in the visible region.

Stability of ZnMgO oxide in a weak alkaline solution

Zinc oxide (ZnO) is a chemical compound of great interest used, for example, as photocatalyst in the purification of wastewater or polluted air. However, neither dissolution, nor photo-dissolution of ZnO is negligible: indeed, both processes reduce significantly the efficiency of photocatalysis and then lead to a secondary pollution by free Zn2+. In the present study, the stability of ZnMgO thin films in weak alkaline solution is investigated. We demonstrate that the replacement of Zn2+ ion with Mg2+ ion results in the production of a Zn0.84Mg0.16O solid solution, whose stability is higher than that of the ZnO sample. This alloy, thus, constitutes an alternative to the use of ZnO in photocatalysis applications. To gain more insights into the higher resistance of such alloys to the dissolution process, X-Ray photoelectron spectroscopy measurements were performed. They highlighted the role of OH group adsorption in the experimentally observed enhancement of ZnMgO stability.

Effects of Mn concentration on the ac magnetically induced heating characteristics of superparamagnetic MnxZn1−xFe2O4 nanoparticles for hyperthermia

The effects of Mn2+ cation concentration on the ac magnetically induced heating characteristics and the magnetic properties of superparamagnetic MnxZn1−xFe2O4 nanoparticles (SPNPs) were investigated to explore the biotechnical feasibility as a hyperthermia agent. Among the MnxZn1−xFe2O4 SPNPs, the Mn0.5Zn0.5Fe2O4 SPNP showed the highest ac magnetically induced heating temperature (ΔTac,mag), the highest specific absorption rate (SAR), and the highest biocompatibility. The higher out of phase susceptibility (χm″) value and the higher chemical stability systematically controlled by the replacement of Zn2+ cations by the Mn2+ cations on the A-site (tetrahedral site) are the primary physical reason for the promising biotechnical properties of Mn0.5Zn0.5Fe2O4 SPNP.

Co doped ZnO(0001)-Zn by diffusion method and its magnetic properties

The diffusion behaviors of Co clusters on clean ZnO(0001)-Zn single crystal surface and their magnetic properties are studied. Co clusters are deposited on the clean ZnO(0001)-Zn surface at room temperature and then undergone ultrahigh vacuum annealing until fully reconstructed. The replacement of Zn2+ by Co2+ is confirmed by scanning tunneling microscopy and x-ray photoelectron spectroscopy. The Co doped ZnO shows a weak ferromagnetism at room temperature with a saturation magnetic moment of 1.08 μB/Co. Our observations indicate that surface Zn vacancies facilitate Co diffusion, and the interplay of Co ion with internal O vacancies leads to the ferromagnetism.

Influence of Iron Dopant on Structure, Surface Morphology and Optical Properties of ZnO Nanoparticles

Pure and two different concentration of Iron (Fe) doped Zinc Oxide (ZnO) nanoparticles (Zn(1-x)FexO) with x = 0.03 and 0.05 were synthesized by chemical co-precipitation method. The structural characterizations of the samples were done by X-ray powder Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD data indicate that the replacement of Zn2+ ion by Fe3+ ion does not influence the wurtzite structure of ZnO samples. With increase in annealing temperature the intensity of the Zn(1-x)FexO (0 0 2) diffraction peak increases, indicating that the crystallinity quality of the particle improves. Using Scherrer equation the average particle sizes of Zn(1-x)FexO are calculated. The strain-induced broadening at Full Width Half Maximum (FWHM) of the XRD profile of Zn(1-x)FexO were estimated from Williamson Hall (W-H) plot. The results of SEM apparently show that the sample comprises of highly agglomerated particles with no definite shape. Optical absorption Ultraviolet-visible (UV-vis) and Photo Luminescence (PL) properties have been characterized and the effect of Fe addition on optical properties of ZnO has been discussed.

Thermodynamics of Copper(II), Zinc(II), Cobalt(II), Mercury(II), and Nickel(II) Complexation with ,α-Dipyrrolylmethene in DMF

Thermodynamics of complexation reactions between Zn(II), Ni(II), Hg(II), Co(II), and Cu(II) acetates and 3,3′5,5′-tetramethyl-4,4′-dibutyldipyrrolylmethene in DMF at 298.15 K is studied by calorimetric and spectrophotometric methods. The replacement of Zn2+, Ni2+, and Hg2+ ions by Co2+ and Cu2+ ions was found to increase the equilibrium constants of reactions of complex formation with dipyrrolylmethene by more than two orders of magnitude. The role of solvation interactions in coordination of dipyrrolylmethene by d-metal ions is established.

Growth and optical properties of Zn:KLN single crystal

KLN and Zn:KLN crystal were grown by the Czochralski method along the [100] orientation. All crystals were transparent from 380 to 760nm by the ultraviolet-visible transmittance spectra of KLN and Zn:KLN crystals. Compared with KLN crystals, the transmittance of Zn:KLN increased and its absorption edge shifted to the ultraviolet band. The infrared transmittance spectra of KLN and Zn:KLN crystals were measured. The replacement of Zn2+ in the KLN crystals was analyzed. Laser lights of 420 and 405nm were obtained through noncritical phase-matching second harmonic generation for KLN and Zn:KLN crystal, respectively. A shorter wavelength output was obtained for Zn:KLN crystal. The frequency efficiency for all crystals reached 6–7%.

Chemistry and kinetics of ZnO growth from alkaline hydrothermal solutions

Special features (polar growth and nonstoichiometry) of ZnO single crystals grown on seed plates of various crystallographic orientations in the ZnO–KOH–H2O and ZnO–KOH–LiOH–H2O hydrothermal systems are analyzed. The growth proceeds via the interaction of ZnO2- 2 anions with crystal surfaces, and its rate depends on the atomic structure and electric charge of the surface. The mechanism underlying the influence of Li+ ions on polar ZnO growth is considered. Partial replacement of Zn2+ by Li+ decreases the positive charge on the (0001) face and hinders the attachment of ZnO2- 2 anions. The incorporation of Li ions into the (0001¯) face decreases its negative charge and accelerates growth in the [0001¯] direction.