Zn-Al Layered Double Hydroxides Research Articles

Chemical and physical modification of graphene oxide nano-sheets using casein, Zn-Al layered double hydroxide, alginate hydrogel, and magnetic nanoparticles for biomedical applications

In our study, we developed a novel nanobiocomposite using graphene oxide (GO), casein (Cas), ZnAl layered double hydroxide (LDH), sodium alginate (Alg), and Fe3O4 magnetic nanoparticles. To synthesize the GO, we used a modified Hummer's method and then covalently functionalized its surface with Cas protein. The functionalized GO was combined with as-synthesized ZnAl LDH, and the composite was conjugated with alginate hydrogel through the gelation process. Finally, we magnetized the nanobiocomposite using in-situ magnetization. The nanobiocomposite was comprehensively characterized using FT-IR, FE-SEM, EDX, and XRD. Its biological potential was assessed through cell viability, hemolysis, and anti-biofilm assays, as well as its application in hyperthermia. The MTT assay showed high cell viability percentages for Hu02 cells after 24, 48, and 72 h of incubation. The nanobiocomposite had a hemolytic effect lower than 3.84 %, and the measured bacterial growth inhibition percentages of E. coli and S. aureus bacteria in the presence of the nanobiocomposite were 52.18 % and 55.72 %, respectively. At a concentration of 1 mg.mL−1 and a frequency of 400 kHz, the nanocomposite exhibits a remarkable specific absorption rate (SAR) of 67.04 W.g−1, showcasing its promising prospects in hyperthermia applications.

Development of a novel fluorescence spectroscopy based method using layered double hydroxides to study degradation of E. coli in water

Layered double hydroxides (LDHs) belong to a class of 2D nanomaterials having metallic ions of varying valences and interlayer spacing as in brucite. Since their discovery, they are being used everywhere. However, their biomedical properties are the most explored as they exhibit advantages like biodegradability, biocompatibility, and ease of making composites. In this research, two types of LDHs i.e. MgAl and ZnAl LDHs are synthesized via hydrothermal route. Two types of doping; Gd and Yb, are done to create GdMgAl, GdZnAl, YbMgAl and YbZnAl. After synthesis, LDHs are characterized by X-ray Diffraction, Scanning Electron Microscopy, Dynamic Light Scattering, Energy dispersive X-ray Spectroscopy, and UV–vis spectroscopy. Average length for LDHs was found out to be in the range of 275–467 nm whereas thickness was in between 67 nm and 135 nm via SEM. Hydrodynamic size came out to be between 331 nm and 1720 nm for all samples. Absorption wavelength for all samples was between 251 and 261 nm. A novel antibacterial approach utilizing LDHs was introduced, employing antibacterial photodynamic treatment. The results were quantified using fluorescence spectroscopy, taking tryptophan peak as bacterial indicator at 270 nm excitation. Spectra recorded in 285–550 nm range showed considerable bacterial degradation, notably with YbZnAl LDHs. The efficacy was further tested with Colony Forming Units. Notably, all synthesized particles outperformed UV light alone, demonstrating their versatility as photocatalysts for bacterial inactivation. This pioneering method provides a unique and effective strategy for antibacterial treatment.

ZnAl LDH-based Derivative Materials as Photocatalysts: Synthesis, Characterization, and Catalytic Performance in Tetracycline Degradation

Layered Double Hydroxide (LDH)-derived materials exhibited different characteristics from LDH precursors. The conversion of ZnAl LDH into its derivative material has been carried out to find the best catalyst for TC degradation. ZnAl (LDH)-based catalysts in this study have been effectively synthesized using coprecipitation, calcination, and restacking procedures. ZnAl Layered Double Oxide (LDO) is derived from the calcination of ZnAl LDH at 500°C. ZnAl LDH was also modified by adding Garcinia mangostana pericarp extract (GME). XRD, FT-IR, UV-DRS, and SEM-EDX were used to investigate the synthesized catalyst. ZnAl LDH exhibited the typical LDH FT-IR spectra, whereas ZnAl LDO showed metal oxide-like spectra, and the ZnAl-GME composite displayed the combination spectra of precursor material. The ZnAl LDH XRD diffraction pattern exhibited the attributes of a layered material, whereas the other three catalysts did not. Calcination destroyed the layered structure of ZnAl LDH, whereas the addition of GME to LDH and LDO generated a single-layered composite. The modified ZnAl-GME composite showed a decrease in both particle size and bandgap energy. At an ideal pH of 5, the synthesized catalyst was used in a batch system photodegradation of 5 mg/L Tetracycline (TC), employing solar light irradiation. ZnAl LDO holds the most significant catalytic activity and structural stability through the fifth regeneration cycle, degraded TC up to 100% in 90 minutes.

Zn-Al layered double hydroxide / polyurethane as a novel nanocomposite for cefixime antibiotic adsorption

Wastewater contaminated with antibiotics requires innovative solutions to remove such pollutants efficiently. In this work, Zn-Al layered double hydroxide (LDH) adsorbent supported on polyurethane (PU) (Zn-Al LDH/PU) was synthesized using a simple co-precipitation method. The synthesized material was characterized using XRD, FTIR, SEM, TEM, TGA, zeta potential, and hydrodynamic size. This adsorbent was investigated for the removal of cefixime (CFX), which is a model third-generation cephalosporin antibiotic. The LDH phase showed a typical hexagonal layered morphology with layer sizes larger than 200 nm in diameter. CFX adsorption on PU, Zn-Al LDH and Zn-Al LDH/PU showed a maximum adsorption capacity of 94.43, 57.17 mg/g and 115.69 mg/g, respectively. The Redlich-Peterson and Baudu isotherm models were found to be the best fit models for CFX adsorption of Zn-Al LDH and Zn-Al/PU, respectively. The equilibrium time was found to be 175 min and 250 min for CFX adsorption of Zn-Al LDH and Zn-Al/PU, respectively. CFX adsorption kinetics on Zn-Al LDH/PU best fitted the pseudo-second order model indicating chemisorption and diffusion limited adsorption process. Numerous types of bonding between functional groups of CFX and both Zn-Al LDH and PU could explain the adsorption mechanism. The selectivity study of CFX adsorption on Zn-Al LDH/PU using Sulfamethoxazole and Ciprofloxacin with different concentrations was investigated and discussed. . The recyclability of this Zn-Al LDH/PU was also studied. Also, the effect of temperature was investigated at (23, 35, 45, 55°C) and the thermodynamic parameters (∆H°, ∆S° and ∆G°) were calculated showing exothermic and spontaneous adsorption process.The MTT assay indicated that the biocompatibility of Zn-Al LDH nanostructures was enhanced following modification with PU, demonstrating regulated and minimal cytotoxic effects towards normal liver cell line (WRL-68).The Zn-Al LDH/PU can be considered as a promising low-cost adsorbent for CFX antibiotic from wastewater streams.

Visible light-driven novel chlorine modified g-C3N4/ZnAl LDHs heterojunction with improved photodegradation activity towards organic pollutants

In this regard, an NH4Cl-modified g-C3N4/ZnAl-layered double hydroxides (CCN/LDHs) was successfully prepared by combining the calcine and hydrothermal treatment. The heterojunction samples are a hierarchical nanosheet structure self-assembled from the stacked hybrid flakes. The CCN/LDHs heterojunctions exhibited a superior synergistic effect between CCN and LDHs for decomposing typical tetracycline (TC) antibiotics in modulated seawater. The photodegradation kinetics constant of TC in seawater of CCN/LDHs hybrids showed 2.12 and 2.61 times higher than that of CCN and LDHs under visible light irradiation, respectively. The reusability and stability of the materials was also proved via cycling experiments. Additionally, the possible photo-degradation mechanism was illustrated based on the trapping experiments, EPR results and electron-hole pairs migration pathway analysis. With all results, this study complies the CCN/LDHs composite heterojunction and exhibits a tremendous synergistic effect for accelerating the separation of photogenerated charge carriers, which is beneficial for enhanced visible light photodegradation capacity. The exploration of CCN/LDHs in natural water systems (Xiangjiang River and underground water, Changsha, China) and heavy metal ions (Cr(VI)) demonstrated a great potential for its practical application.

Composite Layered Double Hydroxide Zn-Al/Magnetic Biochar Modified for Highly Effective Malachite Green Adsorption

One of the main needs of humans is water, one source of water pollutantion is from dyes. Adsorption is the most popular method in removing pollutants as it is proven to be efficient. One of the dyes harmful to living things is malachite green. In this study, malachite green dye was removed using a layered double hydroxide (LDH) Zn-Al/magnetic biochar composite. The XRD, FTIR, BET, and VSM analyses show that the LDH Zn-Al, magnetic biochar, and LDH Zn-Al/magnetic biochar composite were successfully produced. The surface area of the Zn-Al/magnetic biochar composite made up of LDH increased from 9.621 m2/g to 99.473 m2/g. The point of zero charge of LDH Zn-Al and magnetic biochar were at pH 6, whereas the composite of these two materials was at pH 7. For LDH Zn-Al, magnetic biochar, and composite LDH Zn-Al/magnetic biochar, pH 8 is the ideal value for adsorption of malachite green. PSO (pseudo-second order) kinetics is the best-fit model. LDH Zn-Al, magnetic biochar, and LDH Zn-Al/magnetic biochar composite had adsorption capacities of 14.472, 15.552, and 25.907 mg/g, respectively, at a temperature of 60°C. Regeneration showed the LDH Zn-Al/magnetic biochar composite had superior and more effective ability compared to LDH Zn-Al and magnetic biochar.

Directional Activation of Oxygen by the Au-Loaded ZnAl-LDH with Defect Structure for Highly Efficient Photocatalytic Oxidative Coupling of Methane.

Photocatalytic oxidative coupling of CH4 (OCM) is a promising CH4 conversion process that can achieve efficient methane conversion with the assistance of O2 . It remains to be highly challenging to improve the photocatalytic OCM activity from catalyst design and to deepen the understanding of the reactant activation in the OCM process. In this work, the Au-loaded ZnAl-layered double hydroxides (LDHs) with and without oxygen vacancy are constructed (denoted as Au/ZnAl and Au/ZnAl-v), respectively. When applied for photocatalytic OCM, the Au/ZnAl-v shows a CH4 conversion rate of 8.5 mmol g-1 h-1 with 92% selectivity of C2 H6 at 40°C, outperforming most reported photocatalytic OCM systems at low temperature reported in the literature. Furthermore, the catalytic performance of Au/ZnAl-v can be stable for 100h. In contrast, the An/ZnAl exhibits a CH4 conversion rate of 0.8 mmol g-1 h-1 with 46% selectivity of C2 H6 . Detailed characterizations and DFT calculation studies reveal that the introduced Ov sites on Au/ZnAl-v are able to activate O2 , and the resulting superoxide radical O2 ·- greatly promotes the activation of CH4 . The coupling of CH3 · groups with the assistance of Au cocatalyst leads to the formation of C2 H6 with high photocatalytic activity.

Polydopamine-modified Zn–Al-layered double hydroxide supported silver nanoparticles as recyclable heterogeneous nanocatalyst for reduction of 4-nitrophenol

This article introduces the design and synthesis of Ag NP garlanded polydopamine (PDA)-functionalized Zn–Al-layered double hydroxide (Zn-Al LDH@PDA) as a hybrid green nanocomposite material, hitherto unreported. The precursor Zn-Al LDH@PDA acted as a suitable shelter and stabilizing support for the in situ generated Ag NPs. The electron rich amino functions over the PDA facilitated the toxic reagent free green reduction of Ag ions in situ. A diverse range of advanced methods, including Fourier Transform Infrared Spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDX), elemental mapping, Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HR-TEM), Fast Fourier Transform (FFT), Inductively Coupled Plasma (ICP), N2 adsorption–desorption, and X-ray Diffraction (XRD) were employed to analyze the physicochemical features of the Zn-Al LDH@PDA/Ag nanomaterial. Catalytic performance of the Zn-Al LDH@PDA/Ag nanocomposite was subsequently appraised in the reduction of 4-nitrophenol (4-NP). The reactions were evaluated through time dependent UV–Vis spectroscopic study which proved the excellent potential of the catalyst. The Zn-Al LDH@PDA/Ag NPs nanocatalyst was isolated by centrifuge and stable enough to be reused for 8 consecutive times without considerable loss in activity.

Structural features and dynamic behaviour of the interlayer space of layered double hydroxide coatings

Layered double hydroxide (LDH) offer great potentialities to design functional coatings with customizable properties by exploiting their anion exchange properties. We investigated the anion exchange properties and expansion capacity of the interlayer space relating to the starting film morphology. ZnAl LDH coatings of different thicknesses and morphologies were first obtained by an in situ method using Al-based substrates. When the anion to intercalate is relatively bigger than the starting nitrates, the intercalation may be constrained by the initial LDH particle size and density composing the film. After optimising the morphology, the intercalation of three functional anions with potential antimicrobial properties was successfully achieved with an expansion of the interlayer space up to 150 % while holding the coating integrity. The release of the guest anion was studied by immersion in physiological saline solution. Finally, the possibility to regenerate the coating was demonstrated supporting the potential of these hybrid coatings for applications.

Bi-doped ZnAl-layered double hydroxides with enhanced photocatalytic activity for ciprofloxacin degradation: the synergistic effect of Bi doping and oxygen vacancies

In this study, a series of Bi-ZnAl-LDHs (BZA-X) enriched with oxygen vacancies (OVs) were synthesized by doping ZnAl-LDHs with different ratios of bismuth ions.

Rapid and efficient removal of methylene blue dye from aqueous solutions using extract-modified Zn–Al LDH

Environmental pollution, particularly water pollution caused by organic substances like synthetic dyes, is a pressing global concern. This study focuses on enhancing the adsorption capacity of layered double hydroxides (LDHs) to remove methylene blue (MB) dye from water. The synthesized materials are characterized using techniques like FT-IR, XRD, SEM, TEM, TGA, EDS, BET, BJH, AFM, and UV–Vis DRS. Adsorption experiments show that Zn–Al LDH@ext exhibits a significant adsorption capacity for MB dye compared to pristine LDH. In addition, Zn–Al LDH@ext shows a significant increase in stability, which is attributed to the presence of phenolic compounds in the extract and the interactions between the functional groups of the extract and LDH. The pH and adsorbent dosage optimizations show that pH 7 and 0.7 g of Zn–Al LDH@ext are optimal conditions for efficient MB removal. The study assessed adsorption kinetics through the examination of Langmuir, Freundlich, and Temkin isotherms. Additionally, four kinetic models, namely pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich, were analyzed. The results indicated that the Temkin isotherm (R2 = 0.9927), and pseudo-second-order (R2 = 0.9999) kinetic provided the best fit to the experimental data. This study introduces a novel approach to enhance adsorption efficiency using modified LDHs, contributing to environmentally friendly and cost-effective water treatment methods.

Promotion effect of Ga3+ in ZnAlGa-x mixed oxides obtained from their layered double hydroxides on the enhancement in the transient photocurrent response, the inhibition in the recombination rate of photogenerated (e−, h+) charges and the photocatalytic activity in the photodegradation of 4-chlorophenol

ZnAlGa-x (x = 0, 0.5, 0.8, 1.0, 2.0 and 3.0 mol % of Ga3+) mixed oxides (MOs) obtained by calcination of their corresponding layered double hydroxides (LDHs) were characterized and evaluated in the photodegradation of 4-chlorophenol in aqueous media (4-CP) using UV light irradiation. Structural studies by X-ray diffraction (XRD) of ZnAlGa-x MOs indicated that the incorporation of a small molar concentration of Ga3+ (0.5–0.8 mol %) within the ZnAl LDH structure changed the micro-crystalline structure to an amorphous structure. A small molar content of Ga3+ in the ZnAlGa3+ MOx promotes the formation of a high amount of structural oxygen vacancies as evidenced by Raman and EPR spectroscopy studies. Transient photocurrent response (TPC) and fluorescence spectroscopy experiments reveal that the incorporation of a small molar concentration of Ga3+ in the structure of ZnAl MO promotes the enhancement in the transient photocurrent response, the separation of photogenerated charges and the inhibition of the recombination rate of (e−, h+) pairs. Furthermore, ZnAlGa-x MOs with a small molar concentration of Ga3+ reduced their band gap energies below of 3.0 eV. ZnAl MO photodegradated 69.0 % of 4-CP after 4 h of reaction. However, the photoconversion % of 4-CP increased to 80–90 % at 3 h of reaction using ZnAlGa-x MOs with a small molar concentration of Ga3+. ZnAlGa-x with small Ga3+ concentration mineralized approximately 70–75 % of total disolved organic carbon at 3 h of reaction. The photocatalytic degradation reaction of 4-CP fitted well to a pseudo-first order kinetics of Langmuir-Hinshelwood-type. The kinetic parameters of ZnAlGa-x MOs confirmed that ZnAlGa-0.8 MO was the best photocatalyst to photodegradate 4-CP in aqueous media. The highest photocatalytic activity and efficacy of ZnAlGa-0.8 MO to mineralize 4-CP in aqueous medium may be due to its higher amount of oxygen vacancies contained in its structure promoting a better separation of charges and the inhibition of the recombination rate of photogenerated (e−, h+) charges.

Layered-Double-Hydroxide (LDH) pyroelectric nanogenerators

Layered Double Hydroxides (LDHs) have outstanding properties, including straightforward fabrication and connection of high-density arrays of aligned nanostructures on almost every (e.g., large area and flexible) substrates, high surface-to-volume ratios, biocompatibility, flame retardancy and several degrees of freedom (divalent and trivalent cations, trivalent/divalent cations ratio, intercalated anions and geometries) for tuning their properties as well as their band diagrams. Nevertheless, LDH pyroelectric devices have never been reported. Here we suggest that LDHs can be ideal building blocks for pyroelectric nanogenerators because of high gradients of both composition and energy-levels, size effects and extraordinary simplicity of fabrication and tuning. For validation, we fabricated several LDH nanoplatelets pyroelectric nanogenerators and found that, without any poling, the equivalent pyroelectric coefficients can be positive, up to 150 µC/(K*m2), or negative, down to – 160 µC/(K*m2), for nanogenerators made of ZnAl LDH or MgAl LDH nanoplatelets, respectively. Beside demonstrating extremely simple and low cost pyroelectric nanogenerators, our results suggest that LDHs are outstanding candidates for high performance pyroelectric nanodevices as, first, the areas of the fabricated devices are orders of magnitude larger than the areas of the nanoplatelet-to-metal junctions and, second, the high number of degrees of freedom of LDHs leaves room for significant improvements.

Enhancing Metallocene Catalyst Activity: Utilizing Layered Double Hydroxide for Ethylene–Propylene Copolymerization

AbstractThis study reports the heterogenization of metallocene catalysts on sodium dodecyl sulfate (DDS)‐modified layered double hydroxides (LDHs) for efficient ethylene–propylene (EP) slurry‐phase copolymerization. The LDH support offers considerable compositional tunability. NiFe LDHs with different anions () and metallic compositions are applied as support for the metallocene catalysts; these significantly influence the catalytic properties of the heterogenized catalyst system. The supported‐catalyst intercalating DDS− anion in the galleries of NiFe and ZnAl LDHs demonstrates a high catalytic activity. They produce EP copolymers with high molecular weights (Mw) and wide polydispersity, compared with the homogeneous Zr catalyst. Further, the supported catalyst complex containing anion produces EP with a tenfold high Mw and demonstrate subdued catalytic activity. The higher basicity of the support is associated with the enhanced activity and the wider polydispersity of the EP pertaining to the different interactions of the catalyst molecule with the support. Overall, Ni‐containing LDH favors a higher activity, whereas Fe‐containing LDH favors a higher Mw. Therefore, NiFe‐based LDH results in both higher activity and molecular weight. 13C and 27Al magnetic angle spinning solid‐state nuclear magnetic resonance confirm the formation of the supported catalyst complex.

Tungstophosphate Intercalated ZnAl Layered Double Hydroxide for Adsorptive and Visible Light Driven Photocatalytic Decolourisation of Organic Dyes

Tungstophosphate (PW<sub>12</sub>O<sub>40</sub><sup>3-</sup>) intercalated ZnAl-Layered double hydroxide (ZnAl-PW<sub>12</sub>) was successfully synthesized through the rehydration of calcined LDH. Chemical analyses and characterizations by powder XRD, FT-IR, and Diffuse reflectance UV-Vis spectra confirmed the intercalation of PW<sub>12</sub>O<sub>40</sub><sup>3-</sup> ions equivalent to ~80% of the residual positive charge in the brucite layer. The efficiency of ZnAl-PW<sub>12</sub> for decolourisation of four structurally different cationic/anionic dyes through simultaneous adsorption and photocatalysis under visible light irradiation was assessed. Under identical conditions, the photocatalytic efficiency of the ZnAl-PW<sub>12</sub> catalyst was found to be much higher than that of calcined ZnAl-LDH, indicating the promoting effect of PW<sub>12</sub>O<sub>40</sub><sup>3-</sup> ion. Moreover, the loss of costly polyoxometallate (POM) could be avoided by intercalating the POM ion in the interlayer of LDH, which can facilitate the use of synthesized catalysts for repeated cycles.

Highly atom-economic synthesis and scale-up production of zinc-aluminum layered double hydroxides

ZnAl layered double hydroxides (LDHs) has been widely applied as functional additives in polymers. The common coprecipitation method used to synthesize ZnAl LDHs has an atomic utilization of only 44.35 %, and is accompanied with the formation of sodium salt by-product, ZnO impurities and lots of waste water. In this work, we proposed a green and cost-effective synthesis route with 100 % atom economy to prepare ZnAl LDHs from mixed metal oxides and hydroxides. Pure ZnAl LDHs was synthesized at 120 °C. A dissolution-nucleation-diffusion reaction mechanism was proposed through structural and morphological studies and reaction kinetics calculations. The prepared ZnAl LDHs exhibited excellent smoke suppression properties, with a reduction in the smoke density of PVC from 705 to 340. This proposed method was successfully scaled-up and applied on a 1000 t/a industrial production line, providing a valuable opportunity for the reaction design and large-scale preparation of LDHs and other inorganic compounds.

Development of Novel Decarboxylation-Urea Method toward Interlayer-Anion-Controlled Layered Double Hydroxides.

Layered double hydroxides (LDHs) are representative of a 2D anionic clay. Simple and homogeneous synthesis of interlayer-anion-controlled LDH is essential for studies and industrial production. In this study, we report the one-pot synthesis of an LDH that is selective for interlayer anions, which was labeled as "decarboxylation-urea method". We obtained LDHs intercalated with NO3-, Cl-, and SO42- by removing CO2 in this method. The ionic conductivities of the prepared LDHs were investigated for their applicability to electrolytes, and it was found that Zn-Al LDH intercalated with NO3- showed the highest ionic conductivity (18 mS cm-1). Therefore, the LDH intercalated with NO3- synthesized using the decarboxylation-urea method is promising as an alkaline solid electrolyte.

Fabrication of Anion-Exchanged Electrodeposited Zn-Al Layered Double Hydroxides (LDHs) Coating on ZX21 Mg Alloy

Because of their low density and high specific strength, Mg alloys are considered promising lightweight alloys for various applications. However, due to the high electrochemical activity and poor corrosion resistance, surface modifications of Mg alloys are needed to increase the service life. Hence, an active layered double hydroxides (LDHs) coating was investigated in this study. Owing to the brucite-like layered structure, the weakly bonded interlayer anions can be easily exchanged with other anions in the environment. With the unique anion-exchange mechanism, LDHs coating provides dual protection to the Mg alloy substrate. It can not only act as a physical barrier but also absorb aggressive anions such as Cl- and release corrosion inhibitors to the environment.Compared to the commonly used hydrothermal method to fabricate LDHs coating, which requires high temperature and long process time, electrochemical deposition has the advantages of high deposition rates, simple experimental setup, and highly controllable process parameters. Therefore, in this study, a three-electrode electrochemical setup was used to fabricate Zn-Al LDHs coatings on a ZX21 Mg alloy. Moreover, different anions are intercalated into the interlayer galleries of the prepared Zn-Al LDHs coating through post anion-exchange processes.Through electrochemical analysis in a 3.5 wt% NaCl solution, the prepared anion-exchanged electrodeposited Zn-Al LDHs coating improved the corrosion resistance of ZX21 Mg alloy. Electrochemical impedance spectroscopy (EIS) showed that corrosion impedance increases, while potentiodynamic polarization curves revealed that the corrosion current density (i corr) of the coated sample was an order of magnitude lower than the ZX21 Mg alloy substrate. Besides the improvement of corrosion resistance, the formation mechanism of Zn-Al LDHs coating by electrodeposition was also investigated by electrochemical analysis and in situ optical microscopic (OM) observations. The corrosion behavior and microstructure of Zn-Al LDHs coating and the roles played by different intercalated anions will be discussed based on electrochemical analysis and microstructure characterizations. Figure 1

In Situ Growth of High-Performance ZnAl-Layered Double Hydroxides/Al2O3 Composite Coatings on Aluminum Alloy

In this research, high-performance ZnAl-layered double hydroxides (ZnAl-LDHs) with different Zn2+ concentrations were prepared on the surface of an anodized 1060 aluminum alloy using the in situ growth method, and the influence of Zn2+ concentration on corrosion resistance and tribological behavior was further explored. The surface morphology, element distribution, phase composition, and mechanical performance of ZnAl-LDHs/anodic aluminum oxide (AAO) composite coatings were tested and analyzed. Subsequently, the investigation of the anti-corrosion properties and tribological behavior of as-prepared composite coatings and AAO were conducted experimentally. The results show that with the increase in Zn2+ concentration, the thickness and bonding strength of the coatings gradually increase, and the hardness progressively decreases. The ZnAl-LDHs/AAO composite coating with a Zn2+ concentration of 0.3 mol/L exhibits the best anti-corrosion ability, which has the minimum corrosion current density of 2.435 × 10−9 A/cm2. This can be attributed to the uniform and compact ZnAl-LDH films where the porous structure of the AAO is well sealed. Moreover, the excellent friction-reduction and anti-wear properties of ZnAl-LDHs/AAO composite coatings with larger Zn2+ concentrations are verified using a ball-on-disc rotating wear tester under dry wear. A reasonable mechanism for improving tribological properties of resulting ZnAl-LDHs/AAO composite coatings is proposed.

Functionalization of ZnAl-Layered Double Hydroxide with Ensulizole and Its Application as a UV-Protective Agent in a Transparent Polymer Coating.

In this study, we propose a promising photoprotective additive that combines the advantages of both organic UV absorbers and inorganic particles without compromising the properties of the paint material. This additive involves the intercalation of a well-known organic UV absorber, 2-phenylbenzimidazole-5-sulfonic acid (PBISA), into zinc-aluminum layered double hydroxide (ZnAl-LDH). Three ZnAl-LDH intercalates with PBISA were prepared using various methods based on either anion exchange or direct synthesis. The intercalates were characterized using powder X-ray diffraction, thermogravimetry, elemental analysis, and IR and UV-Vis spectroscopies. The composition and basal spacings of all three intercalates are very similar. An effective UV protection film was prepared when the ZnAl-PBISA-1 intercalate was incorporated into polyurethane-acrylate lacquer. The resultant UV protective film exhibited stability and uniform distribution of the intercalated fillers. Some minimal particle sedimentation and aggregation were observed on the cured film's underside, but did not compromise the films' UV protective properties. The prepared lacquers with intercalated fillers offer a viable solution for the surface modification of plastic products.