Mixed Zn Research Articles

Nanostructuring of Zn–Li-based alloys through severe plastic deformation: Microstructure, mechanical properties, and corrosion behaviors

To date, nanostructuring through plastic deformation has rarely been reported in biodegradable zinc (Zn) based alloys that have great potential in load-bearing conditions. Here, typical high-strength Zn–Li-based alloys were subjected to SPD processes, including equal channel angular pressing (ECAP) and high-pressure torsion (HPT), to achieve nanostructured microstructures. The effects of SPD on the microstructures, mechanical properties, and corrosion behaviors were generally investigated. The two SPD routes resulted in totally different microstructures. ECAPed samples processed at 150 ​°C exhibited a complicated multilevel structure (nm to μm) with mixed Zn equiaxed grains and lamellar-like eutectoid regions (Zn ​+ ​α-LiZn4), and HPTed ones (25 ​°C) possessed a fully dynamically recrystallized (DRXed) microstructure with an average grain size below 0.4 ​μm. The tensile strength of the SPD samples could reach 500 ​MPa. Meanwhile, HPTed samples exhibited extraordinary fracture elongations higher than 100 ​%, because of a different grain boundary sliding deformation mechanism. HPTed samples and ECAPed samples displayed different corrosion patterns, and the former exhibited a much higher corrosion rate in Hank's solution, possibly due to the accelerated corrosion at grain boundaries. In summary, SPD is an efficient way to refine the microstructure of biodegradable Zn-based alloys, possibly improving their performances and clinical applications.

Chemical CO2 fixation using a cyanido bridged heterometallic Zn(II)-Mn(II) 2D coordination polymer.

A new cyanido bridged Zn(II)-Mn(II) mixed-metal coordination polymer, {[Zn(μ-L)(μ-CN)2Mn0.5]·(CH3OH)}n (1), has been synthesized by the reaction of Zn(CN)2, Mn(II) salts and a hydrazone ligand (HL = (E)-N'-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide) in methanol. Compound 1 was characterized using various analytical methods (including elemental analysis, photoluminescence, FT-IR, XRD, SEM, and EDX analyses, and TGA), and its structure was determined by X-ray analysis. These analyses confirmed the formation of a mixed metal Zn(II)-Mn(II) coordination polymer containing both cyanide and hydrazone bridging ligands. This mixed metal coordination polymer exhibits interesting emission spectra by having several emissions via excitation at 230, 270, 375 and 385 nm. The catalytic activity of compound 1 in chemical CO2 fixation was investigated in the presence of epoxides, and the effects of various parameters on its catalytic performance were evaluated. The results of catalytic studies show that compound 1 can efficiently catalyze the chemical CO2 fixation reaction under mild conditions. The amount of co-catalyst, temperature of the reaction, nature of the solvent and also the substituent connected to the epoxide ring are some of the important parameters that have considerable effects on the catalytic activity of 1.

Ultrasmall Cu Nanoparticles Supported on Crystalline, Mesoporous ZnO for Selective CO2 Hydrogenation

AbstractConverting CO2 to value‐added chemicals, e. g., CH3OH, is highly desirable in terms of the carbon cycling while reducing CO2 emission from fossil fuel combustion. Cu‐based nanocatalysts are among the most efficient for selective CO2‐to‐CH3OH transformation; this conversion, however, suffers from low reactivity especially in the thermodynamically favored low temperature range. We herein report ultrasmall copper (Cu) nanocatalysts supported on crystalline, mesoporous zinc oxide nanoplate (Cu@mZnO) with notable activity and selectivity of CO2‐to‐CH3OH in the low temperature range of 200–250 °C. Cu@mZnO nanoplates are prepared based on the crystal‐crystal transition of mixed Cu and Zn basic carbonates to mesoporous metal oxides and subsequent hydrogen reduction. Under the nanoconfinement of mesopores in crystalline ZnO frameworks, ultrasmall Cu nanoparticles with an average diameter of 2.5 nm are produced. Cu@mZnO catalysts have a peak CH3OH formation rate of 1.13 mol h−1 per 1 kg under ambient pressure at 246 °C, about 25 °C lower as compared to that of the benchmark catalyst of Cu−Zn−Al oxides. Our new synthetic strategy sheds some valuable insights into the design of porous catalysts for the important conversion of CO2‐to‐CH3OH.

Nucleation-promoting effect of mixed Zn and ZnO particles on tetra-n-butylammonium bromide hydrate

Tetra-n-butylammonium bromide (TBAB) hydrate is an ionic semi-clathrate hydrate, and it can be used as an energy-storage and gas-separation medium. Nucleation of TBAB hydrate is unlikely to occur and this characteristic causes problems in the refrigeration system due to the need for excessive cooling and delays in gas separation due to the slow formation. Therefore, a technique for rapid formation of TBAB hydrate is required. In a previous study, it was found that addition of mixed and ground Zn and ZnO particles (Zn–ZnO) to TBAB aqueous solution significantly promoted nucleation of TBAB hydrate. Since the nucleation of TBAB hydrates was effectively promoted by the very simple addition of Zn–ZnO, this technique can be easily applied to conventional systems. However, the nucleation-promoting mechanism have not been clarified. The clarification of the nucleation-promoting effect of Zn–ZnO on TBAB hydrates is important to elucidate the nucleation-promoting mechanism of clathrate hydrates by the addition of substances. Therefore, the objective of the present study was to investigate the nucleation-promoting mechanism of Zn–ZnO on TBAB hydrate. Experimental results showed that immersion of Zn–ZnO in TBAB aqueous solution reduced the nucleation-promoting effect, but a decrease in the nucleation-promoting effect was not observed when Zn–ZnO was immersed in water. Microscopy observation confirmed that immersion of Zn–ZnO in TBAB aqueous solution had little effect on its surface morphology, but X-ray diffraction and X-ray photoelectron spectroscopy indicated formation of solid TBAB on Zn–ZnO. Zn–ZnO did not show a significant nucleation-promoting effect on tetrahydrofuran hydrate, which is a non-ionic clathrate hydrate. This suggest that Zn–ZnO has properties that attract tetra-n-butylammonium and Br ions, and that the proximity of these ions may promote formation of TBAB hydrate. It was also suggested that the mechanism of nucleation promotion by the addition of substances is different for ionic clathrate hydrates and non-ionic clathrate hydrates.

Synthesis and investigation of mixed Zn–Ni spinel nanoparticles for microwave applications

Nickel ferrite solid solutions remain one of the main materials for a whole range of applications, including microwave equipment and components, the requirements for parameters and homogeneity of materials are constantly increasing. In this work, Ni1–xZnxFe2O4 nanoparticles with an average diameter of 12.5 nm were successfully synthesized by the microwave-assisted urea method. The temperature of a single-phase product formation was 400 °C, which is lower compared to more common precipitation from aqueous solution methods or solid-state route. Ni1–xZnxFe2O4 materials demonstrate high saturation magnetization and low coercive force. The magnetization changes with increasing Zn concentration and reaches the maximum at x = 0.5. Also, the increase in zinc content leads to an increase in the lattice parameters. The average size of ferrite nanoparticles synthesized by the microwave-assisted urea method is smaller compared to ferrites synthesized earlier by the co-precipitation method. Also, lower treatment temperatures provide higher stoichiometry, and homogeneity of materials while magnetization difference is negligible. These research results provide a general and effective route to synthesize other nanostructures for a variety of microwave components.

Spectral-luminescent properties of Zn(II) curcuminates

1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (curcumin, Cur) and mono- and mixed Zn(II) complexes based on it were synthesized using the improved method. It was established that curcumin forms metal chelates of the composition ZnCur22Н2О and Zn(Cur)2Phen with the zinc ion. Coordination of the curcumin ligand with the central atom is bidentate cyclic through the -diketone group, and the ortho-methoxyphenol fragment of Cur does not participate in chelation. The fluorescent properties of all synthesized compounds were studied. It was shown that the complex formation of zinc with curcumin causes an increase in the relative intensity of fluorescence and a shift of the emission band to the long-wave region. This indicates both the complexation process and the sensitizing effect of the zinc ion. When phenatroline is added to the zinc(II) complex, the fluorescence emission maximum undergoes a bathochromic shift compared to the ZnCur2 monoligand complex, and the relative fluorescence intensity decreases by 2.5 times. The shift of the radiation maximum to the region of low energies is due to the coordination of the phenathroline molecule to metal ions; and the decrease in emission is due to the shielding ability of the phenathroline donor molecule in relation to the weaker curcumin donor, which increases the number of non-radiative energy losses caused by its inefficient transfer due to the large energy gap between the triplet levels of the ligands.

Antioxidant Activity and Photosynthesis Efficiency in Melissa officinalis Subjected to Heavy Metals Stress

The aim of this study was to assess influence of cadmium and zinc treatments on antioxidant activity combined with the photosynthesis efficiency in a popular herb lemon balm (Melissa officinalis L.). Plants were grown under greenhouse conditions by the pot method. The Mn, Cu, Cd, and Zn contents in soil and plants were measured by HR-CS FAAS. The activity of net photosynthesis, stomatal conductance, transpiration rate, intercellular CO2, and index of chlorophyll in leaves were determined for all investigated species. Reduction of the net photosynthesis was observed for cultivations subjected to either Zn or Cd treatments. Phenolic contents were determined by the chemical Folin-Ciocalteu method, while enhanced voltammetric analysis was applied to assess the antioxidant properties of plant extracts. Both of these approaches yielded similar results. Herbal extracts had exceptional antioxidant capacities and were good scavengers of free radicals and reactive oxygen species. Structural similarity of cadmium and zinc facilitated their mutual structural exchange and prompted substantial expansion of phenolics under the mixed Zn and Cd treatments.

Supersaturated solid solution enhanced biodegradable Zn-Mn alloys prepared by mechanical alloying and selective laser melting

Zn-Mn alloys have been recognized as promising biodegradable metals due to moderate degradation and good osteogenesis. However, the alloying content of Mn has been severely limited by the low solid solubility (0.8 wt%) in conventional preparation process to avoid the excessive formation of brittle intermetallics. In this work, supersaturated solid solution was achieved in Zn-Mn alloys via mechanical alloying (MA) and selective laser melting (SLM). During MA process, the mixed Zn and Mn powders experienced repeated welding and fracturing, which resulted in refined grains and abundant crystal defects that stored extra energy. This could reduce the energy barrier of interatomic diffusion and induce the rapid diffusion of Mn atoms, leading to supersaturated solid solution with ∼3.6 wt% Mn homogeneously dissolved in Zn lattices. Moreover, the rapid solidification process of SLM effectively maintained the metastable supersaturated structure. In addition, the Zn-15Mn alloys prepared by MA and SLM were composed of fine equiaxed grains (∼4.34 µm) and high content of high-angle grain boundaries (54.8%). Owing to solution strengthening and grain refinement, the Zn-15Mn alloy prepared by MA and SLM exhibited a compressive yield strength of 178 MPa which was 2.8 times and 1.6 times those of pure Zn and Zn-15Mn alloy without MA process, respectively, as well as a more ductile fracture. Meanwhile, the Zn-Mn alloys exhibited accelerated degradation and comparable cytocompatibility to pure Zn. These findings indicated that the combined process of MA and SLM may be an efficient strategy for the preparation of alloys characterized by supersaturated solid solution and refined grain structure.

Fabrication and characterization of ZnS and ZnSe absorber layers for UV-selective transparent photovoltaics

We have fabricated ZnS, ZnSe and mixed Zn(S,Se) thin film layers for application as solar cell absorbers in ultraviolet (UV)-selective solar cells. We fabricated the thin film layers using a two-step process involving evaporation of the Zn layer followed by an anneal in an H2S and/or H2Se containing atmosphere. A study of the annealing conditions was performed to minimize hole formation in the thin film layer. A mixed Sulfur and Selenium containing layer was also developed in order to reach a 3 eV band gap, such that the layer absorbs all the UV light and leaves the visible light passing through. Next, we tried to increase the conductivity of the layer by adding extrinsic doping elements. Cu was found to increase the conductivity by more than three orders of magnitude, while leaving the transparency of the layer mostly unchanged. Finally, solar cell devices were fabricated using transparent back and front contacts and a NiO buffer layer. We could measure a very small photocurrent of about 100 μA/cm2 and an open circuit voltage of about 500 mV under AM1.5 G illumination.

Corrosion behavior of Ni-based coating with Ni-coated TiC-reinforced particles by induction cladding in molten brass

In order to improve the wettability of TiC-reinforced particles with Ni-based alloy and decrease electrical resistivity of TiC-reinforced particles, Ni-coated TiC particles were fabricated by electroless plating method. Further, Ni-based coatings with Ni-coated TiC-reinforced particles on the surface of H13 steel were prepared by induction cladding. The microstructure and phase compositions of the coatings were analyzed by optical microscopy, scanning electron microscopy and X-ray diffraction. The microhardness of the coatings was measured by a microhardness tester. The corrosion behaviors of the H13 substrate and Ni-based coatings with and without Ni-coated TiC-reinforced particles in molten brass were investigated. The results showed that the addition of Ni-P layer of approximately 1.2 μm thickness on TiC particles by electroless plating significantly increased cladding temperature of Ni-based coating reinforced by TiC particles, and reduced coating thickness, defects, size of the precipitated phases and microstructure inhomogeneities. The surface microhardness of the Ni-based coating with Ni-coated TiC-reinforced particles is 168% higher than that of the substrate and 17% higher than that of the Ni-based coating. The zinc in the molten brass intruded into the H13 steel and formed mixed oxides of iron, chromium and zinc in the surface layer of the substrate with the intruded oxygen. Then the mixed oxides peeled off in the mixed oxide zoneⅡof Fe and Zn adjacent to corroded surface, while the corrosive mechanism of the Ni-based coatings involves the rapid dissolution of Ni and Si of the received coatings into the molten brass and the oxidation of Si and Zn at the corrosion interface which then peeled off in the mixed oxide zone Ⅰ of Zn and Si adjacent to the coating. The addition of Ni-coated TiC-reinforced particles refined the size of carbide and boride precipitates, preventing the formation of large corrosion pits formed in the matrix phase, and effectively slowed down uneven corrosion of the Ni-based coating.

On the high-temperature oxidation of ZnSb for thermoelectric applications

Thermoelectric ZnSb has a native surface oxide layer of Sb2O5 +ZnO, while HT oxidation in air resulted in selective oxidation to ZnO, with no detectable Sb by STEM-EDS. The ZnO consisted of an inner nano-granular and a more columnar outer layer. Thermogravimetry showed parabolic oxidation kinetics at 200–325 °C with an activation energy of 117 kJ/mol, comparing well with literature for oxidation of Zn. Two-stage 16O2 +18O2 oxidation followed by SIMS suggests growth by mixed Zn and O diffusion through a protective ZnO layer that still cannot prevent considerable high temperature oxidation in air, with formation of insulating electrical contacts, unless metallised.

N-doped graphitic carbon encapsulated cobalt oxide nanoparticles from ZIF-67 on ZIF-8 as an anode material for Li-ion batteries

Recently, cobalt (II, III) oxide (Co 3 O 4 ) is considered as an alternative anode material for high-performance LIBs because of its high safety and theoretical capacity (890 mAh g −1 ). However, Co 3 O 4 anode materials suffer from low conductivity and poor cycle life due to structural strain and huge volume change during lithiation/delithiation processes. In this work, porous N-doped graphitic carbon encapsulated Co 3 O 4 structure (Co 3 O 4 @PNGC) was synthesized by using mixed Zn and Co metal-organic frameworks templates (ZIF-67/ZIF-8) and coated with polydopamine as a nitrogen and carbon source. During the synthesis, Zn species was evaporated to form the structural pores, and the in-situ formation of Co(0) occurred that served as a catalyst in the graphitization of the carbon matrix. The Co 3 O 4 /PNGC exhibited an improved discharge capacity of 847.4 mAh g −1 after 500 cycles at 1 C when compared to the bare sample. • Co 3 O 4 @PNGC was prepared from cuboidal ZIF-67 @ZIF-8 particles wrapped by PDA via a facile method. • The unique PNGC structure can prevent undesirable Co 3 O 4 growth and enhance electrical conductivity of electrodes. • Co 3 O 4 @PNGC sample exhibits significantly improved electrochemical performances.

Synthesis, spectral characterization, and biological studies of Schiff bases and their mixed ligand Zn(II) complexes with heterocyclic bases

In the present study, six mononuclear Zinc(II) complexes, [Zn(L1)(6-Methyl-2,2′-bpy)] (1), [Zn(L1)(1,10-Phen)] (2), [Zn(L1)(5-Amino-1,10-Phen)] (3), [Zn(L2)(6-Methyl-2,2′-bpy)] (4), [Zn(L2)(4,4′-Di-tert-butyl-2,2′-bpy)] (5), and [Zn(L2)(1,10-Phen)] (6) formed from Schiff bases, 2-methyl-1-phenyl-1-(pyridin-2-ylmethylimino)propan-2-ol (L1) and 4-chloro-5-methyl-2-(1-(pyridin-2-ylmethylimino)ethyl)phenol (L2) were synthesized. The synthesized Schiff base ligands and metal complexes were characterized by different spectroscopic techniques such as FTIR, UV–Visible, 1H & 13C NMR spectroscopy, in addition to Powder X-ray diffraction and cyclic voltammetry. Further, the synthesized metal complexes (1–6) and their parental Schiff bases (L1, L2) were evaluated for antibacterial, antifungal, and antioxidant activities. Of those, Complex 1 was shown to have significant antibacterial activity against all of the evaluated microorganisms. Schiff base ligands, L1 and L2, complexes 1, 4, and 5 were shown to have superior antifungal activity against Aspergillus niger than the standard drug, fluconazole. In addition, the synthesized compounds achieved good antioxidant activities when compared to the standard Ascorbic acid.

Correction to “Water or Anion? Uncovering the Zn2+ Solvation Environment in Mixed Zn(TFSI)2 and LiTFSI Water-in-Salt Electrolytes”

Correction to “Water or Anion? Uncovering the Zn²⁺ Solvation Environment in Mixed Zn(TFSI)₂ and LiTFSI Water-in-Salt Electrolytes”

Comprehensive Assessment of Biomolecular Interactions of Morpholine-Based Mixed Ligand Cu(II) and Zn(II) Complexes of 2,2'-Bipyridine as Potential Anticancer and SARS-CoV-2 Agents: A Synergistic Experimental and Structure-Based Virtual Screening.

A new class of pharmacologically active mixed-ligand complexes (1a-2a) [MII(L)2 (bpy)], where L = 2-(4-morpholinobenzylideneamino)phenol), bpy = 2,2'-bipyridine, MII = Cu (1a), and Zn (2a), were assigned an octahedral geometry by analytical and spectral measurements. Gel electrophoresis showed that complex (1a) demonstrated the complete DNA cleavage mediated by H2O2. The overall DNA-binding constants observed from UV-vis, fluorometric, hydrodynamic, and electrochemical titrations were in the following sequence: (1a) > (2a) > (HL), which suggests that the complexes might intercalate DNA, a possibility that is further supported by the biothermodynamic characteristics. The binding constant results of BSA by electronic absorption and fluorometric titration demonstrate that complex (1a) exhibits the highest binding effectiveness among others, which means that all compounds could interact with BSA through a static approach, additionally supported by FRET measurements. Density FunctionalTheory (DFT) and molecular docking calculations were relied on to unveil the electronic structure, reactivity, and interacting capability of all substances with DNA, BSA, and SARS-CoV-2 main protease (Mpro). These observed binding energies fell within the following ranges: -7.7 to -8.6, -7.2 to -10.2, and -6.7 to -8.2 kcal/mol, respectively. The higher reactivity of the complexes compared to free ligand is supported by the Frontier MolecularOrbital (FMO) theory. The in vitro antibacterial, cytotoxic, and radical scavenging characteristics revealed that complex (1a) has the best biological efficacy compared to others. This is encouraged because all experimental findings are closely correlated with the theoretical measurements.

Water or Anion? Uncovering the Zn2+ Solvation Environment in Mixed Zn(TFSI)2 and LiTFSI Water-in-Salt Electrolytes

Water or Anion? Uncovering the Zn²⁺ Solvation Environment in Mixed Zn(TFSI)₂ and LiTFSI Water-in-Salt Electrolytes

A combined XPS/ToF-SIMS approach for the 3D compositional characterization of Zr-based conversion of galvanized steel

The present study investigates the surface and in-depth characteristics, and deposition mechanism of zirconium-based conversion coatings on hot dip galvanized (HDG) steel substrates for automotive applications, based on zinc galvanizing baths with small additions of aluminium. This contribution provides scientific proof of the chemical heterogeneity both at the surface and along the depth of the Zr-based conversion coatings on galvanized steel. To this purpose, the definition of two derivative model systems – pure zinc and pure aluminium – was indispensable due to Al-enrichment phenomena observed at the galvanized steel surface. A 3D evaluation of the sample chemistry before and after formation of the Zr-based conversion coatings was conducted by a combined approach based on X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) with 1-keV Cs+ sputtering. The experimental results provide direct evidence of the fact that Zr-based conversion coatings on the HDG steel are constituted by a mixed Zn, Al and Zr oxyhydroxide in combination with Zr oxy-/hydroxyfluoride on top of a complex fluoride (hydr)oxide Zn/Al layer, rather than a pure ZrO2 film on top of the galvanized layer mainly made of zinc (and aluminium) as previously reported in the literature.

CONFIGURATION AND COMPETITIVE REACTIVITY OF LIGANDS IN MIXED LIGAND COMPLEXES OF DIALKYLDITIOPHOSPHATES AND AMINOBENBENZIMIDAZOLE (Part 2. Zn, Fe, Ni)

With the aim of determination of electronic and geometrical structures of mixed-ligand complexes, theoretical modeling of the structures of coordination compounds of transition metals with dialkyldithiophosphate chelating ligands with aminobenzimidazoles carried out using quantum chemical methods. Using BIOVIA Materials Accelrys Studio 2017 software packages, the geometry, electron density distribution, and frontier orbitals calculated for the mixed ligand complexes Zn(II), Cu(II), Ni(II), Fe(III), which is necessary for understanding the electronic structure of coordination compounds with chelating ligands.

Basal-Plane Orientation of Zn Electrodeposits Induced by Loss of Free Water in Concentrated Aqueous Solutions

Concentrated aqueous solutions attract considerable attention because water electrolysis can be suppressed due to a decrease in the amount of free water. The present study focuses on electrodeposition behaviors of metallic zinc (Zn) using concentrated aqueous solutions containing bis(trifluoromethylsulfonyl)amide (Tf2N–) anions. An increase in Tf2N– concentration significantly enhances water-anion interactions, giving characteristic infrared spectra for the breakdown of the hydrogen-bonding networks of water clusters, i.e. loss of free water. For the Tf2N– system Zn electrodeposits with the preferred orientation of hcp basal plane was observed, while, for the SO4 2– system with the presence of the hydrogen-bonding networks, preferred orientation of basal plane was not observed. The preferred orientation of basal plane is not attributed to the adsorption of Tf2N– anions on the electrode, proved by the use of mixed Zn(Tf2N)2-ZnSO4 concentrated solutions. The loss of free water in the concentrated Zn(Tf2N)2 solutions will suppress hydrogen adsorption at the cathode to promote surface diffusion of intermediate Zn+ adions and growth of Zn crystals. Consequently, the promotions and the easier growth of Zn basal planes with the lowest interfacial free energy will enhance the horizontal growth of Zn basal planes.

Synthesis, structural and photophysical properties of mixed Zn:SnO2 nanowires

The present work demonstrates the structural and photophysical properties of mixed zinc tin oxide (Zn:SnO2) nanowires (NWs) synthesized via vapor transport technique with Zn content of 10, 25 and 50 wt%. The XRD spectra reveals the tetragonal phase of SnO2 for 10 wt% Zn content, whereas a combination of tetragonal SnO2 and hexagonal ZnO phases were observed for higher Zn ratios. The SEM images reveals the formation of smooth NWs for low Zn content, whereas a combination of NWs along with spherical nanoparticles have been observed for 50 wt% Zn:SnO2 sample. The optical band gap was decreased from 3.21 eV (10% Zn:SnO2) to 2.84 eV (50% Zn:SnO2), whereas the corresponding Urbach energy increased from 971 meV to 1132 meV. The refractive index values increased from 2.28 to 2.64 when Zn content increased from 10 to 50 wt%. The absorption spectra showed a red shift and the appearance of new band with increasing Zn wt.%, signaling the formation of new electronic states below the conduction band. The fabricated films displayed a broad steady state emission with peak around 462 nm, which intensity decreased with the increasing of Zn ratio. The effective life time of charge carrier was decreased from 198 ps for 10 wt% Zn:SnO2 to 172 ps for 50 wt% Zn:SnO2.