Layered zinc hydroxide salts: Delamination, preferred orientation of hydroxide lamellae, and formation of ZnO nanodiscs

Structure and release properties of pyrethroid/sulfobutyl ether β-cyclodextrin intercalated into layered double hydroxide and layered hydroxide salt

The aim of this study was to realize the intercalation of the pyrethroid pesticides beta-cypermethrin (BCT) and lambda-cyhalothrin (LCT) into ZnAl-layered double hydroxides (LDH) and NiZn-layered hydroxide salt (LHS). BCT (LCT)/SBECD-LDH and BCT (LCT)/SBECD-LHS hybrids were obtained with the aid of sulfobutyl ether β-cyclodextrin (SBECD) through one step method. The hybrids were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetry and differential thermal analysis (TGA/DTA). The hybrids based on LHS had larger basal spacing than those on LDH. The LDH-hybrids prepared in N-methylpyrrolidone (NMP) had larger basal spacing than those in ethanol. These results were discussed in terms of the matrix structure and solvent properties. The supramolecular structure of the hybrid was reasonably proposed. Furthermore, the release properties of BCT (LCT) from the hybrids were investigated and discussed in two media. The release rate in pH = 5.0 was slower than that in pH = 6.8. The accumulated release amount of pesticide in pH = 5.0 was lower than that in pH = 6.8. LHS-hybrids synthesized in ethanol exhibit a sustainable release property. These depend on the inclusion complexes’ arrangement and release medium. The release kinetic processes could be described by pseudo-second order and parabolic diffusion models. The release behavior can be controlled by adjusting the synthesis conditions and the releasing media. This provides the guidance for the application of SBECD and LDH (LHS) in pesticide formulation.

Multifunctional food supplements based on layered zinc hydroxide salts intercalated with vitamin anions and adsolubilized with vanillin

A layered hydroxide salt (LHS) was used as an inorganic matrix to obtain multifunctional food compounds. The aim is to obtain higher thermal stability for vitamin anions and a slow release of aroma. Thus, vitamin B3 (nicotinate), vitamin B5 (phantothenate) and vitamin L (2-aminobenzoate) anions were intercalated by co-precipitation method. The results show an increase in thermal stability of intercalated vitamin anion since decomposition of pure vitamin B3 starts at 120 °C and after intercalation, the HSL-B3 decomposition starts at 313 °C. The intercalation products were than reacted with vanillin (3-methoxy-4-hydroxybenzaldehyde). A kinetic study showed that the release of vanillin from its nanohybrid was found to occur in a controlled manner, evidencing that the synthesized compounds can be used in formulations for the sustained release of aromas. Results showed that the intercalated anions and adsolubilized vanillin were not only less volatile since it causes the aroma to remain in the LHS for a longer period of time resulting in slow release but also have higher thermal stability when they are confined between layers. In summary, the multifunctional food supplements obtained seems to have nutraceutical, olfactory and better thermal resistance properties being suitable for potential applications in the food industry.

Layered zinc hydroxide as an adsorbent for phosphate removal and recovery from wastewater

At present, phosphate removal and recovery from wastewater is gaining wide attention due to the dual issues of eutrophication, caused by the increased production of algae, and universal phosphorus scarcity. In this study, a layered zinc hydroxide (LZH) was synthesized by a simple precipitation method and characterized via various techniques. Experiments investigating the effect of contact time, pH, LZH dose, initial phosphate concentration, and co-existing ions on phosphate adsorption were conducted. LZH exhibited a high phosphate adsorption capacity (135.4 mg g⁻¹) at a neutral pH. More than 50% of phosphate was removed within the first 60 s of contact time at an initial phosphate concentration of 5 mg L⁻¹. Phosphate removal using the as-prepared LZH adsorbent was also tested in real treated sewage effluent reducing the residual phosphate amount to levels inhibiting to the growth of algae. Furthermore, phosphate desorption from LZH was investigated using acetic acid and sodium hydroxide regenerants which showed to be very effective for phosphate recovery.

This study demonstrates a novel LZH adsorbent synthesized, characterized and applied for high phosphate removal and recovery from wastewater.

Hydrothermal Synthesis of (001) Facet Highly Exposed ZnO Plates: A New Insight into the Effect of Citrate

In this work, two synthesis routes were applied to investigate the effect of citrates on the construction of the ZnO structure. Well-dispersed ZnO plates with (001) facet highly exposed were prepared via one-step hydrothermal route, while ZnO nanoparticles were obtained via two-step route. In one-step route, citrates were added before the formation of Zn(OH)2 precursor, while citrates were added after the formation of Zn(OH)2. For the first time, the interaction between citrates and the Zn(OH)2 precursor was investigated and citrates that participated in the formation of Zn(OH)2 were the main cause for (001) facet exposed structure construction. A growth mechanism about the formation of ZnO plates in the presence of citrates was proposed. The as-prepared ZnO plates showed enhanced photocatalytic activity for the degradation of methylene blue (MB).

Layered zinc hydroxide monolayers by hydrolysis of organozincs

Organometallic precursors provide a new and clean route to solutions of 2D materials relevant for applications including catalysis, electronics and sensing.

2D inorganic materials and their exfoliated counterparts are both of fundamental interest and relevant for applications including catalysis, electronics and sensing. Here, a new bottom-up synthesis route is used to prepare functionalised nanoplatelets, in apolar organic solvents, via the hydrolysis of organometallic reagents; the products can be prepared in high yield, at room temperature. In particular, a series of layered zinc hydroxides, coordinated by aliphatic carboxylate ligands, were produced by the hydrolysis of diethyl zinc and zinc carboxylate mixtures, optimally at a molar ratio of [COOR]/[Zn] = 0.6. Layered zinc hydroxides coordinated by oleate ligands form high concentration solutions of isolated monolayers (3 nm thick x ∼ 26 nm) in apolar organic solvents (up to 23 mg mL^–1 in toluene), as confirmed by both atomic force and transmission electron microscopies of deposited species. The high solubility of the product allows the synthetic pathway to be monitored directly in situ through ¹H NMR spectroscopy. The high solubility also provides a route to solution deposition of active functional materials, as illustrated by the formation of nanoporous films of optically transparent porous zinc oxide (1 μm thickness) after annealing at 500 °C. This new organometallic route to 2D materials obviates common complications of top-down exfoliation syntheses, including sonochemical-degradation and low yields of aggregated polydispersed layers, and may potentially be extended to a wide range of systems.

Inorganic–Organic Nanohybrid Materials of Layered Zinc Hydroxide Nitrate with Intercalated Salicylate: Preparation, Characterization and UV-Blocking Properties

Intercalation of salicylate (Sal) into layered zinc hydroxide nitrate (ZHN) nanohybrid materials was successfully synthesized by the coprecipitation method. The effect of pH, crystallization method, temperature and time of hydrothermal treatment on preparation was investigated in detail and compared. The products were confirmed by X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential thermal analysis (TG-DTA), and scanning electron microscope (SEM). The results revealed that ZHN–Sal with pure phase and good crystallinity was obtained at pH = 6.0–6.5, 60[Formula: see text]C and 3[Formula: see text]h of temperature and time of hydrothermal treatment. The TG-DTA data indicated that the intercalated Sal had a high stability compared to the isolated. And the phases and compositions of the sample calcined at increasing temperatures were also identified by XRPD and FTIR techniques. Furthermore, ZHN–Sal exhibited an improved UV-blocking ability, showing it can be used as a potential alternative matrix for the UV blocker.

Preparation and release behavior of chlorpyrifos adsolubilized into layered zinc hydroxide nitrate intercalated with dodecylbenzenesulfonate

A novel method was developed to make the charge-neutral and poorly water-soluble pesticide chlorpyrifos (CPF) adsolubilize into layered zinc hydroxide nitrate intercalated with dodecylbenzenesulfonate (ZHN-DBS). It included two steps: first, CPF was solubilized into the micelles formed by anionic surfactant sodium dodecylbenzenesulfonate (DBS), nonionic surfactant polyoxyethylene (10) nonyl phenyl ether (TX-10) or zwitterionic surfactant dodecyl betaine (DB), and then ZHN-DBS was poured into CPF micelles to synthesize ZHN-DBS-CPF, ZHN-TX-10-CPF, and ZHN-DB-CPF intercalated compounds. These intercalated compounds were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis and differential thermal analysis (TGA/DTA). The results showed that ZHN-DBS-CPF, ZHN-TX-10-CPF, and ZHN-DB-CPF had the basal spacings of 3.29-3.59, 2.57-2.87, and 1.97 nm, respectively, which was discussed from the intercalated mechanism. The intercalated CPF had the higher thermal stability. Release behaviors of CPF from intercalated compounds were investigated and analyzed in buffer solutions (pH 5.0 and 6.8). The results exhibited that the release rates and equilibrium release amounts of CPF were closely dependent on micelles types and release mediums. The release behaviors of ZHN-DBS-CPF and ZHN-TX-10-CPF were well described with pseudo second-order and parabolic diffusion models. The present study suggested that ZHN-DBS-CPF and ZHN-TX-10-CPF could be applied as a potential pesticide delivery system.

High photocatalytic activity of transparent films composed of ZnO nanosheets

Nanometric thin films were prepared by dip-coating and inkjet printing ZnO nanosheets on glass plates. The side-by-side alignment of the ZnO nanosheets on the substrate resulted in thin, transparent, oriented ZnO surfaces with the high-energy {001} facets exposed. The method of nanosheet deposition affected the film morphology; the dip-coated films were very smooth and nonporous, while the inkjet-printed films were rough and porous with the estimated void volume approximately 60-70% of the total film volume. The first-order rate constants for the photocatalytic degradation of 4-chlorophenol on the nanosheet-based films were approximately 2 times larger than those on nanocolumnar ZnO films or ZnO films prepared by the sol-gel technique. We attribute the high photocatalytic activity of the ZnO nanosheets to the fact that their {001} facets were predominantly exposed to the oxidized substrate. This surface arrangement and the simplicity of fabricating the ZnO nanosheet-based films make them promising for the construction of optical devices and dye-sensitized solar cells.

New metal phthalocyanines/metal simple hydroxide multilayers: experimental evidence of dipolar field-driven magnetic behavior

A series of new hybrid multilayers has been synthesized by insertion-grafting of transition metal (Cu(II), Co(II), Ni(II), and Zn(II)) tetrasulfonato phthalocyanines between layers of Cu(II) and Co(II) simple hydroxides. The structural and spectroscopic investigations confirm the formation of new layered hybrid materials in which the phthalocyanines act as pillars between the inorganic layers. The magnetic investigations show that all copper hydroxide-based compounds behave similarly, presenting an overall antiferromagnetic behavior with no ordering down to 1.8 K. On the contrary, the cobalt hydroxide-based compounds present a ferrimagnetic ordering around 6 K, regardless of the nature of the metal phthalocyanine between the inorganic layers. The latter observation points to strictly dipolar interactions between the inorganic layers. The amplitude of the dipolar field has been evaluated from X-band and Q-band EPR spectroscopy investigation (Bdipolar ≈ 30 mT).