Zinc Salt Precursors Research Articles

Differential Impact of Zinc Salt Precursors on Physiognomies, Anticancerous, and Antibacterial Activities of Zinc Oxide Nanoparticles.

Zinc oxide nanoparticles (ZnONPs) are enormously popular semi-conductor metal oxides with diverse applications in every field of science. Many physical and chemical methods applied for the synthesis of ZnONPs are being rejected due to their environmental hazards. Therefore, ZnONPs synthesized from plant extracts are steered as eco-friendly showing more biocompatibility and biodegradability. Additionally, various synthesis conditions such as the type of precursor salt also play a role in influencing the physicochemical and biological properties of ZnONPs. In this study, green synthesis of ZnONPs from Acacia nilotica was carried out using zinc acetate (ZA-AN-ZNPs), zinc nitrate (ZN-AN-ZNPs), and zinc sulfate (ZS-AN-ZNPs) precursor salts. Surprisingly, characterization of ZnONPs using UV-visible spectroscopy, TEM, XRD, and EDX revealed the important role precursor salts played in influencing the size and shape of ZnONPs, i.e., 20-23nm spherical (ZA-AN-ZNPs), 55-59nm triangular (ZN-AN-ZNPs), and 94-97nm nano-flowers (ZS-AN-ZNPs). FTIR analysis showed the involvement of alkaloids, alcohols, carboxylic acid, and phenolic compounds present in Acacia nilotica extract during the synthesis process. Since different precursor salts showed different morphology of ZnONPs, their biological activities were also variable. ZN-AN-ZNPs showed the highest cytotoxicity towards HepG2 cells with the lowest cell viability (28.92 ± 0.99%), highest ROS/RNS production (3425.3 ± 184.58 relative DHR123 fluorescence), and loss of mitochondrial membrane potential (1645.2 ± 32.12 relative fluorescence unit) as well as induced significant caspase-3 gene expression. In addition to this, studying the zone of inhibitions and minimum bactericidal and inhibitory concentrations of ZnONPs showed their exceptional potential as antibacterial agents. At MIC as low as 8µg/mL, ZA-AN-ZNPs and ZN-AN-ZNPs exhibited significant bactericidal activities against human pathogens Klebsiella pneumoniae and Listeria monocytogenes, respectively. Furthermore, alkaline phosphatase, DNA/RNA leakage, and phosphate ion leakage studies revealed that a damage to the bacterial cell membrane and cell wall is involved in mediating the antibacterial effects of ZnONPs.

ZIF-8 derived hierarchical ZnO@ZnFe2O4 hollow polyhedrons anchored with CdS for efficient photocatalytic CO2 reduction

Converting CO2 into chemical energy by efficient photocatalysts is a promising strategy to meet the increasing energy demand and decrease greenhouse gases. In this work, hierarchical ZnO@ZnFe2O4 hollow polyhedrons decorated with CdS quantum dots were designed and prepared to improve photocatalytic CO2 reduction performance. The facile strategy for the synthesis of hierarchical ZnO@ZnFe2O4 hollow polyhedrons involves the synthesis of ZnO hollow polyhedrons derived from the thermal decomposition of 2-Methylimidazole zinc salt (ZIF-8) precursor and in situ generating Zn-Fe layer double hydroxide nanosheets on the surface of ZnO hollow polyhedrons and subsequent thermal treatment. More importantly, the in situ formation of ZnFe2O4 nanosheets can form strong interaction between ZnO hollow polyhedrons and ZnFe2O4 nanosheets. The hierarchical hollow polyhedral structure of the ZnO@ZnFe2O4 sample possesses more preferable active sites to promote CO2 adsorption and reduction process. The prepared hierarchical ZnO@ZnFe2O4 hollow polyhedron sample shows a significantly enhanced performance for photocatalytic CO2 reduction compared with single-component catalysts (ZnO, ZnFe2O4, and CdS) with a CO evolution rate of 95.84 μmol g−1h−1. The decoration of CdS quantum dots makes the ternary heterostructure hybrid form multichannel charge transfer path, which further accelerate charge separation and enhance electrons utilization, resulting in a significant improvement of photocatalytic activity. Noticeably, the CO evolution rate reaches 197.66 μmol g−1h−1, 3 and 2 times higher than that of the bare ZnO and binary ZnO@ZnFe2O4 hollow polyhedrons, respectively. This work gives a promising direction to prepare high-active photocatalysts for solar fuel production.

Effective Regulation of ZnO Surface Facets for Enhanced Photoluminescence Properties Assisted by Zinc Quaternary Ammonium Salts.

Novel ZnO twined-mushroom structures highly exposed in (001̅) planes were fabricated via a facile solvothermal synthesis with assistance of a zinc quaternary ammonium salt in the methanol–water solvent to show enhanced photoluminescence properties. A series of ZnO morphologies regulated with different surface facets were obtained in both MeOH–H2O and EtOH MeOH–H2O solvents respectively, tuning the proportion of alcohol. The self-aggregation mechanism was proposed based on the time-controlled experiment to evaluate the formation of twined-mushroom structures. The selective adsorptions of anions from zinc salt precursors determine the shape of subunits and direct the subunits, which act as building blocks to form the order aggregations.

Surface modified zinc ferrite as a carbon-alternative negative electrode for high-energy hybrid supercapacitor

The limited energy storage capacities of carbon-based negative electrodes, which rely on conventional double layer charge storage mechanisms, have limited the electrochemical performances of hybrid supercapacitors (HSCs). The development of nanostructured redox-active materials that serve as alternatives to carbon-based negative electrodes is crucial to overcome the limitations of current HSCs. In this work, a coordination chemistry approach is utilized to tune the nanostructure of zinc ferrite thin films on flexible stainless steel (SS) foil by using several zinc salt precursors, including ZnCl2·6H2O, Zn(NO3)2·6H2O, and ZnSO4·6H2O, while using the same iron precursor (FeCl2·4H2O). Materials prepared with the ZnCl2·6H2O metal salt form porous nanosheets with groundnut-like structures that exhibit maximum specific capacities of 544 mA h/g (454 F/g) at current density of 2.5 A/g. Redox-active solid-state HSCs are assembled by using zinc ferrite as a negative electrode, MnO2 nanoflakes as a positive electrode, and a polymer gel as the electrolyte. The developed solid-state HSC cells show excellent performance as exemplified by a maximum specific capacitance of 123.8 F/g and an energy density of 55.72 Wh/kg, both of which are superior to those of conventional carbon-based symmetric and HSCs.

Recent Advances in Zinc Oxide Nanostructures with Antimicrobial Activities.

This article reviews the recent developments in the synthesis, antibacterial activity, and visible-light photocatalytic bacterial inactivation of nano-zinc oxide. Polycrystalline wurtzite ZnO nanostructures with a hexagonal lattice having different shapes can be synthesized by means of vapor-, liquid-, and solid-phase processing techniques. Among these, ZnO hierarchical nanostructures prepared from the liquid phase route are commonly used for antimicrobial activity. In particular, plant extract-mediated biosynthesis is a single step process for preparing nano-ZnO without using surfactants and toxic chemicals. The phytochemical molecules of natural plant extracts are attractive agents for reducing and stabilizing zinc ions of zinc salt precursors to form green ZnO nanostructures. The peel extracts of certain citrus fruits like grapefruits, lemons and oranges, acting as excellent chelating agents for zinc ions. Furthermore, phytochemicals of the plant extracts capped on ZnO nanomaterials are very effective for killing various bacterial strains, leading to low minimum inhibitory concentration (MIC) values. Bioactive phytocompounds from green ZnO also inhibit hemolysis of Staphylococcus aureus infected red blood cells and inflammatory activity of mammalian immune system. In general, three mechanisms have been adopted to explain bactericidal activity of ZnO nanomaterials, including direct contact killing, reactive oxygen species (ROS) production, and released zinc ion inactivation. These toxic effects lead to the destruction of bacterial membrane, denaturation of enzyme, inhibition of cellular respiration and deoxyribonucleic acid replication, causing leakage of the cytoplasmic content and eventual cell death. Meanwhile, antimicrobial activity of doped and modified ZnO nanomaterials under visible light can be attributed to photogeneration of ROS on their surfaces. Thus particular attention is paid to the design and synthesis of visible light-activated ZnO photocatalysts with antibacterial properties

In-situ ionothermal precipitation of well-dispersed ZnO nanoparticles onto 2-dimension neat graphene sheets with excellent photocatalytic activity

Neat graphene (NG) is rarely selected as a support to improve the photocatalytic performance of metal oxides due to its extremely poor processability in aqueous solutions. In this study, an in-situ ionothermal precipitation was developed to fabricate ZnO nanoparticle and few-layered NG sheet nanohybrids (ZnO/NG) in one-pot. Choline chloride/diethylene glycol-based deep eutectic solvent was used as reaction medium to dissolve the zinc salt precursor and disperse graphene. XRD, Raman, XPS and TEM analyses showed that ZnO particles with sizes of 15–25 nm were uniformly dispersed on the graphene sheets and a bond of ZnOC was formed between the interfaces. The UV–vis diffuse reflectance spectra measurement exhibited that the incorporation of graphene slightly narrowed the bandgap of ZnO nanoparticles, but significantly enhanced the light absorption of the nanohybrids in the visible range. Photocatalytic degradation of methylene blue dye evidenced that ZnO/NG offered excellent photocatalytic performance, regardless of UV or visible light irradiation. Under UV light, graphene as an electron transporter effectively promoted the separation of photogenerated carriers, while under visible light graphene was sensitized from the ground-state to the excited-state. The resulting electrons were injected into the conduction band of ZnO to transform wide bandgap ZnO into a photocatalyst driven by visible light. This work provided a green and simple method to prepare ZnO/NG nanohybrids with efficient and stable photocatalytic performance for water pollution remediation.

New carbon/ZnO/Li2O nanocomposites with enhanced photocatalytic activity

Our study was focused on the synthesis of photocatalytic materials for the degradation of organic dyes based on the valorization of biomass resources. The biochar resulted from pyrolysis process of cherry pits wastes was activated by CO2 flow. Activated and inactivated carbon was used to obtain carbon-based photocatalysts impregnated with different zinc salt precursors. The activation of carbon had no significant influence on the photodegradation process. The doping procedure used Li2CO3 and Zn(CH3COO)2 of different concentrations to impregnate the biochar. The carbon-ZnO-Li2O based nanomaterials were analysed by TEM and SEM, while the presence of hexagonal wurtzite ZnO was investigated by XRD. The solid samples were analysed by PL at 360 nm excitation fixed wavelength to correlate their morphology with the optical and photocatalytic properties. The presence of Li atoms led to photocatalytic activities of the doped ZnO similar to the undoped ZnO obtained at higher concentrations of zinc acetate precursor.

High performance gas sensors based on in-situ fabricated ZnO/polyaniline nanocomposite: The effect of morphology on the sensing properties

ZnO nanoparticles, nanorods and nanosheets were in-situ deposited on the interdigitated gold electrodes by hydrothermal treatment of electrospun nanofibers containing zinc salt precursors and seed-induced solution growth of ZnO. The nanostructured ZnO was further covered with polyaniline (PANI) via vapor phase polymerization of aniline or dip-coating with water-dispersible PANI to prepare ZnO/PANI nanocomposites. The morphology and structure of the nanocomposites were investigated by scanning electron microscopy, X-ray diffraction patterns and Fourier transform infrared spectroscopy. The electrical responses of the nanocomposites toward NH3 have been examined at room temperature, and the nanocomposite revealed much better gas sensing properties than ZnO or PANI alone. The morphology of the nanocomposites had a great effect on their sensing properties. Specifically, the composite of ZnO nanosheets covered with vapor phase polymerized aniline demonstrated optimal sensing performance, featuring high response magnitude (relevant resistance change of ∼2150% towards NH3 as low as 10 ppm), ultralow limit of detection (∼5 ppb), good repeatability and excellent selectivity. It is proposed that the morphology and the interactions between p-type PANI and n-type ZnO are responsible for the highly desirable sensing properties of the nanocomposites.

Effects of zinc precursor, basicity and temperature on the aqueous synthesis of ZnO nanocrystals

The effects of the zinc salt precursors, the reaction temperature and the alkaline ratio b (b = [OH-]/[Zn 2+ ]) on the aqueous synthesis of ZnO nanocrystals were investigated. Depending on the type of the zinc precursor, Zn 5 (OH) 8 Cl 2 ·H 2 O or Zn 5 (OH) 8 (NO 3 ) 2 .2H 2 O lamellar phases were obtained at room temperature (20°C) when the alkaline ratio is lower (0.5 ≤ b ≤ 1, 6 ≤ pH ≤ 6.4). When the reaction temperature increased to 95 °C, zinc hydroxide chloride monohydrate was obtained in one case whereas zinc oxide was formed in the other, and no lamellar phase of Zn 5 (OH) 8 (NO 3 ) 2 .2H 2 O was obtained. Thermal decomposition of the two lamellar phases was carried out and mainly showed that Zn 5 (OH) 8 (NO 3 ) 2 .2H 2 O was completely decomposed to ZnO when the annealed temperature reached ~250 °C while Zn 5 (OH) 8 Cl 2 ·H 2 O was totally transformed to ZnO at about 400 °C, a higher comparative temperature that confirms the better thermal stability of the zinc hydroxide chloride monohydrate. Keywords: Oxides, ZnO, chemical synthesis, X-ray diffraction, crystal structure, luminescence

Comprehensive studies of the hydrothermal growth of ZnO nanocrystals on the surface of bamboo

To determine the hydrothermal growth conditions for ZnO nanocrystals on the surface of bamboo and to further develop new ZnO/bamboo hybrid materials, ZnO nanostructured materials with six morphologies, namely, spheroidal nanoparticles, nanoparticles, nanoneedles, nanograsses, nanowall networks, and nanoorchids, were successfully grown on the surface of bamboo via a low-temperature hydrothermal method based on sol–gel-prepared ZnO seed layers. The effects of temperature, time, molar ratio (zinc acetate/sodium hydroxide), and zinc salt precursor (zinc nitrate, zinc sulfate, zinc chloride, and zinc acetylacetonate) on the ZnO morphologies were comprehensively studied. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and energy dispersive spectrometry (EDS) were employed to characterize the morphology, chemical structure, and crystalline structure of the ZnO nanomaterials deposited on the bamboo surface. The ZnO nanostructure morphology was most sensitive to temperature and could be controlled by the reaction temperature. All of the as-prepared ZnO nanostructured materials were wurtzite. ZnO nanomaterials were bonded through the interaction between the hydroxyl moiety of the bamboo surface and the corresponding ZnO. A possible hydrothermal fabrication mechanism was also proposed. Further research is required to assess the improvements in the properties of bamboo from the hydrothermal deposition of nanomaterials at the bamboo surface.

Simple hydrothermal synthesis method for tailoring the physicochemical properties of ZnO: morphology, surface area and polarity

A simple urea-assisted hydrothermal synthesis method was used to tailor the physicochemical properties of ZnO materials. The role of Pluronic P123 block copolymer in the crystal growth, morphology and specific surface area of the as-prepared ZnO was studied. When Pluronic P123 is used, well-dispersed hierarchical microspheres, with a flower-like morphology, are obtained, but in its absence large spherical agglomerated clusters are formed. The polarity of the ZnO, measured as the ratio between plane (002) and plane (100), is also significantly higher for the Pluronic P123 sample. The influence of zinc salt precursors was also analysed. The use of zinc nitrate led to the formation of urchin-like ZnO structures, instead of the microflowers that result from zinc acetate salt. Despite having similar surface areas, the polarity of the zinc nitrate sample was much smaller. The decomposition of methylene blue corroborated the higher photocatalytic activity of the ZnO materials with a higher proportion of polar planes (higher polarity). The formation mechanism of the crystals is also suggested based on the observed gradual growth and assembly of the hydrozincite during the initial steps of the synthesis for the samples with and without Pluronic P123.

Water-based synthesis and cleaning methods for high purity ZnO nanoparticles – comparing acetate, chloride, sulphate and nitrate zinc salt precursors

The effect of using different zinc salts on size, morphology and photoluminescence of ZnO nanoparticles in high-yield aqueous precipitation synthesis.

ZnO micro-windbreak for enhanced gas diffusion

In this paper, a simple way is developed for the synthesis of the ZnO micro-windbreak film (ZMW) based on layered basic zinc salt precursor. The ZnO products maintain the original morphologies of precursors without deformation. Scanning electron microscopy, transmission electron microscopy, infrared spectrum and X-ray diffraction are used to characterize the detailed structures of the as-prepared products. Because of better gas diffusion in single layer ordered flower arrays (highly exposed surfaces) and thin belt-like branches (high diffusion coefficient) than other hierarchical structures, ZMW exhibits the highest responses to benzene gas. High responses allow ZMW to be used for the detection of benzene at ppb-level. By simply sputtering the platinum on both faces of ZMW to enhance the surface reaction, the optimal operating temperature for benzene detection could be reduced to 350°C and the responses are significantly improved.

Facile synthesis of Cu2ZnSnS4 nanocrystals and its use for dye-sensitized solar cells applications

Cu2ZnSnS4 (CZTS) nanocrystals were synthesized with a simple solution method. The effects of the amount of oleylamine, the quantity of zinc salt precursor and reaction time on the structure, composition, morphology and optical properties of the nanocrystals were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX) measurements. The zinc content in the nanocrystals increases with the increasing of the amount of oleylamine and the quantity of ZnCl2 precursor. But the particle sizes were influenced mainly by the reaction time. For dye-sensitized solar cells (DSSCs) using CZTS nanocrystals as the dye layer, the JSC was greatly decreased with the increasing of the sizes of the nanocrystals. Synthesis of small and uniformly dispersed CZTS nanocrystals was beneficial to enhance the power conversion efficiency of the DSSCs.

Synthesis and Characterization of ZnO Nanorods Based on a New Gel Pyrolysis Method

ZnO nanorods were fabricated by a template-free gel pyrrolysis method based on polyvinyl alcohol (PVA) polymeric network. In the present method, zinc salt precursor is trapped in the homogenized gel network to control the mechanism and kinetics of zinc salt calcinations process. By controlling the gel structure and gel pyrrolysis rate, zinc salt precursor can be calcinated to zinc oxide nanorods. The morphology and particle size of the synthesized sample depend on some parameters including amount of zinc salt and PVA in the initial solution, type and composition of the solvent, type and amount of the additives, solution pH, pyrrolysis temperature, and the time of pyrrolysis, which were optimized by the “one at a time” method. The prepared zinc oxide nanorods were carefully characterized using SEM, TEM, XRD, BET, and UV-visible spectrophotometer. The obtained result showed that the present method can be used to synthesize pure and uniform zinc oxide nanorods with energy band gap 3.31 eV, effective surface area of 19 m2·g−1, average diameters of 60 nm, and length of 1000 nm.

Facile Solution Synthesis and Characterization of ZnO Mesocrystals and Ultralong Nanowires from Layered Basic Zinc Salt Precursor

Novel hierarchical ZnO mesocrystals and ultralong ZnO nanowires have been prepared from a precursor of synthetic layered basic zinc acetate nanobelts by a facile solution route in the presence of poly(vinyl pyrrolidone) (PVP). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the products. Refluxing an aqueous dispersion of the nanobelts precursor in the presence of PVP at 100 °C for 6 h leads to the formation of well-defined hierarchical ZnO bundled mesocrystals. With an increase in the basicity of the reaction solution, ultralong ZnO nanowires were prepared. On the basis of the experimental results, a mechanism involving the self-organization of smaller inorganic building blocks during the crystallization of ZnO crystals was proposed. It has been demonstrated that PVP plays a key role in the formation of such novel hierarchical mesocrystals. Photoluminescence results ...

Porous Spherical Particles of ZnS Nanocrystallites

Abstract ZnS particles consisting of nanocrystallites have potential applications as light emitters for displays. The possibility of encapsulating chemicals into porous particles and the temperature-controlled release of them could also be of interest in chemical engineering. The objective of this study is to determine the size distribution, shape and morphology of ZnS particles synthesized under different conditions, since they strongly influence the optical and electric properties. The ZnS powders were prepared by precipitation from homogeneous aqueous solutions, following a procedure described elsewhere1-3 The initial solution consists of a zincsalt precursor dissolved in ultrapure water under acidic pH conditions. Adding Thioacetamide (TAA: CH3C(S)NH2) to this acidic solution at elevated temperature leads to the precipitation of ZnS nanocrystals. Four different types of zincsalt precursors were used to study their influence on the precipitation process and the final powder morphology: acetate (CH3COO), chloride (Cl-), trifluoromethanesulfonate (tFMS: CF3SO3 -) and dimethyldithiocarbamate (dMdTC: S4N2C6H12 -). The dried powder were subjected to 350°C and 700°C heat treatments, respectively.