Crystalline Zn Research Articles

Two crystalline Zn(II)-viologen compounds with photochromism, photomodulated luminescence and water-induced reversible crystal-to-amorphous transformation

In this work, two Zn(II)-viologen compounds, {[Zn(cpbpy)(L)](H2O)5}n (1) and [Zn(H2O)6](cpbpy)2(L)2(H2O)2 (2) (cpbpy = N-(3-carboxypyridin-5-yl)− 4,4′-bipyridinium, H2L = 1,4-benzenedicarboxylic acid) have been constructed via different synthetic routes. Structural analysis exhibits compound 1 features a two-dimension layered structure consisting of one-dimension [Zn(L)]n chains and bridging cpbpy ligands while compound 2 exists as a discrete monomeric structure. In a very short period of time, both compounds display electron-transfer photochromic behaviors. However, the photoproduct of compound 2 is more stable than compound 1 in air, which is attributed to better coplanarity of pyridyl rings of 4,4′-bipyridine moieties in compound 2. Also, both compounds show photomodulated luminescence properties. Strikingly, compound 2 also exhibits interesting water-induced reversible crystal-to-amorphous transformation accompanying with reversible luminescence switch behavior. To our knowledge, this is the first example of a crystalline viologen-based compound that displays water-induced reversible crystal-to-amorphous transformation.

Исследование сжимаемости цианамидов металлов и влияния давления на их электронные свойства

Based on the density functional theory, the effect of pressure on the structure and electronic properties of crystalline metal cyanamides Zn(CN2) and NaSc(CN2)2 has been studied. The negative linear compressibility of Zn(CN2) was revealed and its correlation with microscopic changes in the atomic structure under pressure was established. It is shown that NaSc(CN2)2 has a low compressibility (0.2 TPa-1) in a direction close to that of cyanamide anions. Based on the quantum topological analysis of the electron density, interatomic interactions were studied and it was found that the Zn-N and Sc-N bonds have a partially covalent character. The band gaps of Zn(CN2) and NaSc(CN2)2 at pressures up to 1 GPa have been determined and found to correspond to the UV range of 224-271 nm.

Design of Nanostructured Hybrid Electrodes Based on a Liquid Crystalline Zn(II) Coordination Complex-Carbon Nanotubes Composition for the Specific Electrochemical Sensing of Uric Acid

A metallomesogen based on an Zn(II) coordination complex was employed as precursor to obtain a complex matrix nanoplatform for the fabrication of a high-performance electrochemical hybrid sensor. Three representative paste electrodes, which differ by the weight ratio between Zn(II) metallomesogen and carbon nanotubes (CNT), i.e., PE_01, PE_02 and PE_03, were obtained by mixing the materials in different amounts. The composition with the largest amount of CNT with respect to Zn complex, i.e., PE_03, gives the best electrochemical signal for uric acid detection by cyclic voltammetry in an alkaline medium. The amphiphilic structure of the Zn(II) coordination complex likely induces a regular separation between the metal centers favoring the redox system through their reduction, followed by stripping, and is characterized by enhanced electrocatalytic activity towards uric acid oxidation. The comparative detection of uric acid between the PE_03 paste electrode and the commercial zinc electrode demonstrated the superiority of the former, and its great potential for the development of advanced electrochemical detection of uric acid. Advanced electrochemical techniques, such as differential-pulsed voltammetry (DPV) and square-wave voltammetry (SWV), allowed for the highly sensitive detection of uric acid in aqueous alkaline solutions. In addition, a good and fast amperometric signal for uric acid detection was achieved by multiple-pulsed amperometry, which was validated by urine analysis.

Pentacoordinated Liquid Crystalline Zn(II) Complex Organized in Smectic Mesophase: Synthesis, Structural and Electrochemical Properties

The synthesis and structural characterization of a new liquid crystalline coordination complex based on pentacoordinated Zn(II) metal centre with the coordination fulfilled by the tridentate chelating N^N^N 2,2′;6′,2″-terpyridine ligand and two monoanionic gallates decorated with several long alkyl chains is described. The mesomorphic properties were accurately investigated by small- and wide-angle X-ray scattering studies. Despite the bulky coordination around the metal centre, the complex self-organizes into a smectic phase and, based on the structural and geometrical parameters, a model for the supramolecular organization in the liquid crystalline phase is proposed. Electrochemical investigations showed the importance of the molecular structure of the coordination complex in enhancing its aqueous sensing capacities: the bulky organic ligands form an organic shell separating the metal centres and favouring the redox system through their reduction followed by stripping.

EFFECTS OF Co CONCENTRATION ON THE STRUCTURAL AND OPTICAL PROPERTIES OF Zn1−xCoxS FILMS

Amorphous and crystalline Zn[Formula: see text]CoxS ([Formula: see text], 0.3, 0.5) thin films were grown on sapphire (Al2O3) substrates by pulsed laser deposition at substrate temperature of 25∘C and 800∘C, respectively. The X-ray diffraction results show that the crystalline film has a cubic zinc blende structure and the crystalline quality decreased with increasing Co-doping concentration. The X-ray diffraction and X-ray photoelectron spectroscopy spectra reveal that the samples reached an overdoping state at Co-doping concentration of [Formula: see text]. The absorbance of films increases and the absorption edge shifts to longer wave length direction with increasing Co-doping concentration. The redshift of the band gap energy depends on the Co composition associating with the Urbach energy. Furthermore, the refractive index and dielectric constant increase with increasing Co-doping concentration. The dispersion parameters, such as dispersion energy ([Formula: see text]), oscillator energy ([Formula: see text]), static refractive index ([Formula: see text]), static dielectric constant ([Formula: see text]), interband transition strength moments ([Formula: see text] and [Formula: see text]), oscillator strength [Formula: see text] and oscillator wavelength [Formula: see text], have been analyzed by Wemple–DiDomenico single oscillator model. All these parameters were found to be dependent upon the Co-doping concentration in the Zn[Formula: see text]CoxS thin films.

Self-supported nanoporous Zn–Ni–Co/Cu selenides microball arrays for hybrid energy storage and electrocatalytic water/urea splitting

The phase-pure multiple ternary or quaternary metal selenides in energy boosting, have not been reported yet. Here, self-supported porous crystalline Zn–Ni–Co/Cu selenides microballs arrays were constructed by selenation of the designed tubular Cu(OH)2 arrays decorated with ultrathin Zn–Co–Ni tri-metallic hydroxide on carbon cloth substrate. For this rational engineering, a novel precursor sample was firstly prepared by conversion of deposited Cu layer to hollow tubular Cu(OH)2 arrays on carbon cloth, then, Zn-Co–Ni layered ternary hydroxides with a thin layer structure was deposited around this tubular arrays. The selenation with an exciting morphology change from amorphous tube to highly crystalline microballs lead to the advanced electrode materials that successfully combine the desired merits such as high conductivity, large specific surface areas, and multiple redox and electrocatalytic active sites for asymmetric supercapacitors, oxygen evolution reaction (OER), and urea oxidation reaction (UOR) applications. Interestingly, the Zn–Ni–Co/Cu microballs selenide does not demonstrate striking capacitive behaviors, when evaluated as a battery-type material for electrochemical energy storage (ESs) with the maximum capacity reaching as high as 884.6 C g−1 (or 2211.5 F g−1) at 1 A g−1 and excellent rate capability. But it exhibits competitive OER and UOR electrocatalytic performances with excellent stability, which requires a low potential of 0.312 V (vs. AgCl) to drive 100 mA cm−2 in UOR and remarkable catalytic current of 325 mA cm−2 at 1.6 V vs. RHE for OER in alkaline solutions, which superior than that of the reported metal selenides or oxides materials up to date.

Sequence-Dependent Peptide Surface Functionalization of Metal-Organic Frameworks.

We report a noncovalent surface functionalization technique for water-stable metal-organic frameworks using short peptide sequences identified via phage display. Specific frameworks-binding peptides were identified for crystalline Zn(MeIM)2 (MeIM: 2-methylimidazole, ZIF-8), semiamorphous Fe-BTC (BTC: 1,3,5-benzene-tricarboxylate), and Al(OH)(C4H2O4) (MIL-53(Al)-FA, FA: fumaric acid), and their thermodynamic binding affinities and specificities were measured. Electron microscopy, powder X-ray diffraction, and gas adsorption analysis confirmed that the peptide-functionalized frameworks retained similar characteristics compared to their as-synthesized counterparts. Confocal laser-scanning microscopy demonstrated that peptide was localized on the surface of the frameworks, whereas surface area measurements showed no evidence of pore blockage. Finally, we measured the pH-dependent release of fluorescein from peptide-functionalized frameworks and discovered that peptide binding can attenuate fluorescein release by improving framework stability under low pH conditions. Our results demonstrate that phage display can be used as a general method to identify specific peptide sequences with strong binding affinity to water-stable metal-organic frameworks and that these peptides can alter drug release kinetics by affecting framework stability in aqueous environments.

Heat capacity and thermodynamic functions of crystalline and amorphous forms of the metal organic framework zinc 2-ethylimidazolate, Zn(EtIm)2

Metal organic frameworks (MOFs) may be useful in a variety of applications, mostly related to their capacity to store gases and catalyze reactions. As several MOFs are mechanically milled, they transition through different structures, progressing toward denser and more energetically stable polymorphs. In this paper, we have measured the constant pressure heat capacities of four zeolitic imidazolate frameworks (ZIFs) based on the 2-ethylimadazolate (EtIm) linker exhibiting identical chemical compositions and different framework structures. Specifically, the crystalline Zn(EtIm)2 frameworks of zeolite rho (RHO), analcime (ANA), and β-quartz (qtz) topologies were compared to each other and to the amorphous form of the material prepared by milling. Molar heat capacities were measured from 1.8 K to 300 K using a Quantum Design Physical Property Measurement System (PPMS), and the data were fit to a sum of theoretical functions below 15 K, orthogonal polynomials from 10 K to 60 K, and a combination of Debye and Einstein functions above 50 K. These fits were then used to generate Cp,m°, Δ0TSm°, Δ0THm°, and Φm° values at smoothed temperatures from 0 K to 300 K. While these MOFs have somewhat different heat capacities reflecting their varying structures, they share an unusual feature in the heat capacity around 100 K that is likely due to some common vibrational behavior related to their common linker and metal node and/or their open frameworks. Though the enthalpies of transition scale with molar volume or density, the entropies of transition show more complex behavior and the Gibbs energies of the three energetically less stable polymorphs (RHO, am-RHO, and ANA) are very similar.

Structural Distortion and Bandgap Increment in Nanocrystalline Wurtzite Si Substituted ZnO.

Crystalline Zn(1−x) Si(x) O(0 ≤ x ≤ 0.156) nanoparticles reveal decreasing particle size with increasing Si content and a undistorted wurtzite form until x = 0.062 beyond which local deformation is observed maintaining the parent structure. There is a sharp increment in bandgap with nominal Si-doping and then almost saturates onwards. Moreover thermal annealing demonstrate the increase bandgap and decreasing lattice parameters. The details of samples synthesis and characterization is presented in the present manuscript.

An Amorphous Phase of Zinc and Silicon at Composition Zn2Si5(:H, OH)

An amorphous phase at composition Zn2Si5(:H,OH) was prepared by oxidation of the precursor phase Li2ZnSi at 80 °C in the ionic liquid of n‐dodecyltrimethylammonium chloride (DTAC) and AlCl3 in 1:1 molar ratio, followed by removal of elemental zinc by dilute aqueous HCl. The product was structurally amorphous according to HRTEM, XRPD, and Raman spectroscopy. Zn2Si5(:H,OH) forms layers embedded in a matrix of a silica by‐product. On annealing at 150 °C, amorphous Zn2Si5(:H,OH) decomposed into crystalline Zn and α‐Si. The decomposition comes along with the release of H2 revealed by TG‐MS studies. IR and solid‐state NMR spectroscopy revealed that the Zn2Si5 bulk is terminated by Si‐OH and Si‐H groups. The absence of Knight shift in the 29Si NMR signal assigned to Zn2Si5(:H,OH) suggests semiconducting behavior.

Catalytic growth and characterization of single crystalline Zn doped p-type β-Ga2O3 nanowires

Single crystalline β-Ga2O3 nanowires with different Zn doping contents were grown via catalytic chemical vapor deposition method. The field-emission scanning electron microscopy showed that when the Zn content was 1.3%, the Zn doped β-Ga2O3 nanowires with uniform size and high density were synthesized. The diameter and length of nanowires were about 50 nm and dozens of micron, respectively. The X-ray diffraction measurements indicated that the position of (202) diffraction peak of samples shifted toward lower diffracting angle with increasing Zn content, which was explained by the substitution of Ga3+ by Zn2+ during Zn doping process. Furthermore, the Zn-doped β-Ga2O3 nanowires/n-type β-Ga2O3 thin film p-n homojunction was fabricated. The current-voltage (I-V) characteristic of the homojunction device showed a good rectifying behavior. This result is suggested that the Zn doped β-Ga2O3 nanowires showed p-type conductivity.

Mycorrhizal (Rhizophagus Intraradices) Symbiosis and Fe and Zn Availability in Calcareous Soil

ABSTRACTGreenhouse experiment was conducted to assess the iron (Fe) and zinc (Zn) fractionation patterns in soils of arbuscular mycorrhizal (AM) fungus-inoculated and uninoculated maize plants fertilized with varying levels of Fe and Zn. Soil samples were collected for Fe and Zn fractions and available Fe, Zn and phosphorus (P) contents besides organic and biomass carbon (BMC), soil enzymes and glomalin. Major portion of Fe and Zn fractionations was found to occur in the residual form. Mycorrhizal symbiosis increased the organically bound forms of Fe and Zn while reducing the crystalline oxide, residual Fe and Zn fractions, indicating the transformation of unavailable forms into available forms. Soil enzymes, viz. dehydrogenase and acid phosphatase activities in M+ soils, were significantly higher than M− soil consistently. Overall, the data suggest that mycorrhizal symbiosis enhanced the availability of Fe and Zn as a result of preferential fractionation and biochemical changes that may alleviate micronutrient deficiencies in calcareous soil.Abbreviations: AM: arbuscular mycorrhiza; Fe: Iron; Zn: Zinc; P: Phosphorous; Amox-Zn: amorphous oxide bound zinc; Cryox-Zn: crystalline oxide bound zinc; DAS: days after sowing; DTPA: diethylene Triamine Penta Acetic Acid; MnO2-Zn: manganese oxide bound zinc; OC-Zn: organically bound zinc; WSEX: water soluble plus exchangeable zinc; MnO2 Fe: manganese oxide bound iron; OC-Fe: Organically bound iron; WSEX Fe: water soluble plus exchangeable iron.

Voltammetric Study and Electrodeposition of Zinc from Room Temperature Ionic Liquid 1-Butyl-1-Methylpyrrolidinium Bis((trifluoromethyl)Sulfonyl)Imide

Voltammetric behavior of Zn(II) introduced into the room temperature ionic liquid 1-butyl-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide (RTIL BMP-TFSI) via the addition of ZnCl2 or Zn(TFSI)2 salt was studied. It is surprised that ZnCl2 is highly soluble in this IL because many transition metal chlorides are insoluble in the TFSI-based ILs, leading to the retardation of applying the RTIL BMP-TFSI to electrodeposition. Two redox couples both associated to the redox reaction Zn(II) + 2e− ↔ Zn were observed in the ZnCl2 solution, which resulted from the nonchloride-coordinated and chloride-coordinated Zn(II) species, respectively. However, a single redox couple corresponding to Zn(II) + 2e− ↔ Zn was observed in the Zn(TFSI)2 solution (Figure 1). According to the experiments of voltammetric titration, it was supposed that TFSI anions exhibit much stronger coordinating ability towards Zn2+ ions than to other common transition metal ions, resulting in the high solubility of ZnCl2 in BMP-TFSI. A sufficient amount of chloride anion must be introduced in order to observe the chloride-coordinated Zn(II) species in the Zn(TFSI)2 solution. Afterwards, TFSI anions coordinated to Zn2+ ions were gradually replaced by chloride ions continuously introduced into the Zn(TFSI)2 solution. Finally, no zinc redox couple could be observed once Zn2+ions were completely coordinated with chloride ions. Electrodeposition of Zn was achieved by potentiostatic electrolysis using copper substrates as the electrodes from the IL containing ZnCl2 and Zn(TFSI)2, respectively. Crystalline Zn could be obtained from the two different solutions. The crystallinity and surface morphology of the Zn electrodeposits depended on the applied potentials, and nanostructured Zn could be obtained at some particular electrodepositing potentials. An interesting current-vibration behavior was observed during the potentiostatic electrodeposition of Zn from ZnCl2 solution, and this vibration behavior obviously depended on the applied potentials. It was supposed that the current-vibration behavior was due to a chloride-releasing & chloride-combination mechanism accompanied with the diffusion-drove supplementary of electroactive Zn(II) species because the vibration phenomenon was only observed while the applied potentials were set at where the chloride-coordinated Zn(II) species was reduced in the ZnCl2 solution. Figure 1

Highly crystalline Zn2SnO4 nanoparticles as efficient electron-transporting layers toward stable inverted and flexible conventional perovskite solar cells

Highly crystalline Zn2SnO4 NPs were applied as an efficient electron-transporting layer that can enable both efficient inverted p–i–n PVSC with enhanced ambient stability and efficient conventional n–i–p PVSC on a flexible substrate.

Exciton emission of crystalline Zn(S)Se thin films arranged in microcavities based on amorphous insulating coatings

A technology for the production of fully hybrid microcavities on the basis of Zn(S)Se films and amorphous insulating SiO2/Ta2O5 coatings is proposed. The influence of all stages of the manufacturing cycle on the structure of exciton states in the Zn(S)Se films is demonstrated. This influence is reduced to four main effects: the appearance of a fine structure of emission lines related to free excitons; a decrease in the relative contribution of excitons bound at neutral acceptors to the exciton-emission spectrum; a shift of the emission lines related to exciton–impurity complexes and free excitons to lower frequencies; and a decrease in the splitting between emission lines related to heavy and light excitons. Samples of fully hybrid microcavities, in which the high structural and optical quality of Zn(S)Se films is retained, are fabricated.

Construction of a series of zero-dimensional/one-dimensional crystalline Zn–S clusters – effect of the character of bridging organic ligands on structural diversity

A series of Zn–S clusters have been synthesised and a very rare 1D helical structure was illustrated by first-principles calculations.

Prediction of subgap states in Zn- and Sn-based oxides using various exchange-correlation functionals

We present a density-functional-theory analysis of crystalline and amorphous Zn- and Sn-based oxide systems which focuses on the electronic defect states within the band gap. A comparison of these electronic levels reveals that the hybrid functionals PBE0, HSE06, or B3LYP agree with a self-interaction corrected (SIC) local-density-approximation functional on occupied defect levels when similar treatments of the self-interaction are considered. However, for unoccupied levels, the hybrid functionals and the SIC approach lead to very different predictions. We show that a prerequisite for the determination of the energetic position of subgap states in these oxides is that a functional needs to predict correctly the electronic band structure over a wide energy range and not just close to the band gap. We conclude that for accurate defect levels, an adequate treatment of the self-interaction problem is required especially in the presence of nearby metal-metal interactions.

Modification of the antibacterial activity of Zn/TiO2 nano-materials through different anions doped

Antibacterial activity of zinc-doped titania (Zn/TiO2) nano-materials through different anions (ZnCl2/TiO2, Zn(Ac)2/TiO2, Zn(NO3)2/TiO2 and ZnSO4/TiO2) doped calcinated at 500 °C under visible light irradiation and in the dark was investigated. A simple sol–gel method was used to synthesize TiO2 nano-materials. Samples ZnCl2/TiO2, Zn(Ac)2/TiO2, Zn(NO3)2/TiO2 and ZnSO4/TiO2 exhibit anatase phase TiO2 as the predominant crystalline phase and Zn ions exist in the form of ZnTiO3, Zn2Ti3O8, ZnO or ZnSO4 crystallites. The study on antibacterial effect of Zn/TiO2 nano-materials on fungal Candida albicans (ATCC10231), Gram-negative Escherichia coli (ATCC25922) and Gram-positive Staphylococcus aureus (ATCC6538) shows that the antibacterial action is more significant on C. albicans than on E. coli and S. aureus. Under visible light irradiation, the antibacterial activity is superior to that in the dark.

Density-functional theory study of stability and subgap states of crystalline and amorphous Zn–Sn–O

We present a density-functional theory analysis of stoichiometric and nonstoichiometric crystalline and amorphous Zn–Sn–O systems (c-ZTO, a-ZTO) which connects structural features with electronic properties in order to contribute to the understanding of the recently discovered subgap states in a-ZTO and other amorphous oxide films. In particular we show that defect levels originating from oxygen vacancies are too high in energy to be responsible for levels above the valence band edge. We offer an explanation for the experimentally seen decrease of subgap states with increasing oxygen content. From our analysis of the energetic stability of c- and a-ZTO compounds with different Zn/Sn ratios the decomposition of ZnSnO3 into Zn2SnO4 and SnO2 at sufficiently high temperatures is conceivable. Moreover, our results indicate that a lowering of the mass density of an a-ZTO sample leads to a rising of the conduction band edge.

Formation of Crystalline Zn–Al Layered Double Hydroxide Precipitates on γ-Alumina: The Role of Mineral Dissolution

To better understand the sequestration of toxic metals such as nickel (Ni), zinc (Zn), and cobalt (Co) as layered double hydroxide (LDH) phases in soils, we systematically examined the presence of Al and the role of mineral dissolution during Zn sorption/precipitation on γ-Al(2)O(3) (γ-alumina) at pH 7.5 using extended X-ray absorption fine structure spectroscopy (EXAFS), high-resolution transmission electron microscopy (HR-TEM), synchrotron-radiation powder X-ray diffraction (SR-XRD), and (27)Al solid-state NMR. The EXAFS analysis indicates the formation of Zn-Al LDH precipitates at Zn concentration ≥0.4 mM, and both HR-TEM and SR-XRD reveal that these precipitates are crystalline. These precipitates yield a small shoulder at δ(Al-27) = +12.5 ppm in the (27)Al solid-state NMR spectra, consistent with the mixed octahedral Al/Zn chemical environment in typical Zn-Al LDHs. The NMR analysis provides direct evidence for the existence of Al in the precipitates and the migration from the dissolution of γ-alumina substrate. To further address this issue, we compared the Zn sorption mechanism on a series of Al (hydr)oxides with similar chemical composition but differing dissolubility using EXAFS and TEM. These results suggest that, under the same experimental conditions, Zn-Al LDH precipitates formed on γ-alumina and corundum but not on less soluble minerals such as bayerite, boehmite, and gibbsite, which point outs that substrate mineral surface dissolution plays an important role in the formation of Zn-Al LDH precipitates.