Zinc Aluminum Layered Double Hydroxide Research Articles

Cross-linked ZnAl-LDH/PEDOT:PSS/MoS2 coating in-situ grown on aluminum alloy for excellent protection against both corrosion and wear

In this study, a new Al-LPM composite coating was in-situ deposited on the Al alloy via a facile one-pot hydrothermal method. Morphological and compositional characterizations revealed a tri-layered structure of the Al-LPM coating, namely, zinc aluminum-layered double hydroxide (ZnAl-LDH)/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)/MoS2. ZnAL-LDH was deposited closest to the surface of Al alloy, and the metallic ion-cross-linking of PEDOT:PSS makes the 3D coating more robust. The unique structure endows the coating with superior protective properties against both corrosion and wear. For anti-corrosion, the Al-LPM coating showed very high self-corrosion potential (-0.092 V) and small self-corrosion current density (46.0 μA cm−2) (vs. Al substrate with -1.157 V and 354.8 μA cm−2, respectively), long-lasting high corrosion resistance (>57,000 Ω cm2) during the immersion test, and the almost intact surface morphology and composition after 360 h corrosion. For anti-wear, the friction coefficient of the Al-LPM coating was determined to be < 0.2, which was much smaller than for the Al substrate (> 0.4). Also, there were no serious wear marks and grooves left after the dry-friction test.

Anti-metastatic Immunotherapy of Advanced Tumors Based on EDTA Intercalated Zinc-aluminum Layered Double Hydroxide

Anti-metastatic Immunotherapy of Advanced Tumors Based on EDTA Intercalated Zinc-aluminum Layered Double Hydroxide

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.

In Situ Synthesis of Graphene Oxide-Sealed LDHs Coatings: A Novel Approach to Enhancing Corrosion Resistance and Tribological Performance on Magnesium Alloys

This study introduces an innovative approach to enhancing the corrosion resistance and tribological performance of magnesium alloys by in situ growing zinc-aluminum layered double hydroxide (ZnAl-LDHs) with graphene oxide (GO) sealing. Traditional LDHs coatings exhibit limitations in corrosion protection due to their porous structure. This paper advances the LDHs coating technology by integrating GO, forming a composite LDHs/GO coating on magnesium alloys. The novel incorporation of GO provides a unique two-layered defense system against corrosion: the GO layer serves as a high-resistance barrier to corrosive agents, while the LDHs layer absorbs NO3− ions, offering a secondary protection. The coating’s properties were meticulously characterized using techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) Raman spectroscopy, electrochemical assays, and friction-wear tests. Experimental findings reveal that the synergistic action between LDHs and GO results in significant improvements in corrosion resistance and friction reduction. Specifically, GO’s adherence to the LDHs coating’s pores and its ability to transfer into the friction layer during wear significantly enhances the coating’s integrity and stability. The successful in situ synthesis of LDHs /GO coatings opens new horizons for composite coatings, with potential implications across various industrial applications.

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.

Enhancing the Corrosion Resistance of ZnAl-LDHs Films on AZ91D Magnesium Alloys by Designing Surface Roughness

Zinc–aluminum layered double hydroxides (ZnAl-LDHs) film is a typical effective corrosion resistant film currently being explored. In this study, ZnAl-LDHs film was prepared on magnesium alloys with different surface roughness by means of metallographic preparation combined with the hydrothermal method. When the surface roughness Sa was at a minimum of 0.094 μm, the ZnAl-LDH films grew the most intensely, reaching 3.8 μm in thickness with a static contact angle of 84.34° and a minimum corrosion current density (icorr) of 1.12 × 10−4 A/cm2. After the neutral salt spray test, the sample mass was only increased by 0.0424 g. The results show that the size of ZnAl-LDHs nanosheets can be tailored by roughness of Mg alloy surface. The low roughness of magnesium substrate can accelerate the growth rate of ZnAl-LDH films, increase the thickness of films, and improve their corrosion resistance, but it is disadvantageous to the excellent hydrophobic properties of the surface. Finally, the possible growth and corrosion prevention mechanisms of LDHs films were proposed. This also provides a theoretical basis for the optimal processing parameters of magnesium alloy surface.

Functional Regulation of ZnAl-LDHs and Mechanism of Photocatalytic Reduction of CO2: A DFT Study.

Defect engineering and heteroatom doping can significantly enhance the activity of zinc-aluminum layered double hydroxides (ZnAl-LDHs) in photocatalytic CO2 reduction to fuel. However, the in-depth understanding of the associated intrinsic mechanisms is limited. Herein, we systematically investigated Zn vacancies (VZn), oxygen vacancies (VO), and Cu doping on the geometry and electronic structure of ZnAl-LDH using density functional theory (DFT). We also revealed the related reaction mechanism. The results reveal the concerted roles of VO, VZn, and doped-Cu facilitate the formation of the unsaturated metal complexes (Znδ+-VO and Cuδ+-VO). They can localize the charge density distribution, function as new active centers, and form the intermediate band. Simultaneously, the intermediate band of functionalized ZnAl-LDHs narrows the band gap and lowers the band edge location. Therefore, it can broaden the absorption range of light and improve the selectivity of CO. Additionally, the unsaturated metal complex lowers the Gibbs free energy barrier for effective CO2 activation by bringing the d-band center level closer to the Fermi level. The work provided guidance for developing LDH photocatalysts with high activity and selectivity.

A facile, green and scalable approach to fabricate hierarchical ZnAl-LDH for efficient removal of hexavalent chromium

A feasible, green and scalable approach for the synthesis of hierarchical ZnAl-LDH with well adsorption capacity to Cr(vi).

Facile synthesis of Ag@AgCl/ZnAl-LDH sesame balls nanocomposites with enhanced photocatalytic performance for the degradation of neonicotinoid pesticides

In this study, the degradation of nitenpyram (NTP) using Ag@AgCl/ZnAl-LDH (AACMO) material photocatalytically activated peroxymonosulfate (PMS) system was analyzed. As photocatalysts, Ag@AgCl and calcined zinc-aluminum layered double hydroxide (MMO) had high efficiency to achieve the separation of charge. In addition, the electron injection from AACMO to PMS facilitated the production of active species. Through the AACMO/PMS/Vis system, 40 mg/L of nitenpyram (NTP, 50 mL) could be removed in 45 min with the use of 0.8 g/L of photocatalyst and 0.2 g/L of PMS on the basis of optimal reaction conditions and visible light (780 nm > λ > 420 nm). According to electron paramagnetic resonance technology and free radical quenching tests, the removal of contaminants was promoted by 1O2, h+, SO4-•, •O2–, and •OH. Moreover, the photodegradation of NTP occurring within the AACMO/PMS/Vis system was almost equally effective forthe water from four different water bodies. In general, the AACMO/PMS/Vis system had high efficiency and could be employed for the water pollution control in agricultural production.

Zinc aluminum-layered double hydroxide(LDH)-graphene oxide(GO) lubricating and corrosion-resistant composite coating on the surface of magnesium alloy

Zinc aluminum-layered double hydroxide (ZnAl-LDH) was grown in-situ on the low-pressure cold gas spraying (LPCGS) Al coating by hydrothermal method. Then the composite coating zinc aluminum-layered double hydroxide-Graphene oxide (LDH-G) was formed by electrostatic adsorption of graphene oxide (GO) and ZnAl-LDH. The structure, morphology, and composition of the coating were studied. A rotational ball-on-disk tribometer (WTM-2E, China) was used to test the tribological properties of the LDH-G coating. The polarization curve and EIS measured the electrochemical properties of the LDH-G coating in 3.5 wt% NaCl solution. Due to the good mechanical properties of graphene and the corrosion inhibition effect of ZnAl-LDH, LDH-G showed an excellent reduction in wear and corrosion resistance.

Construction of an epoxy coating with excellent protection performance on the AA 2024-T3 using ion-exchange materials loaded with eco-friendly corrosion inhibitors

Ion-exchange materials were used in this study to boost the active/passive anti-corrosive functionality for the epoxy coating applied on the AA2024-T3. For this purpose, a zinc-aluminum layered double hydroxide conversion coating (LDH) loaded with diethyldithiocarbamate molecules was synthesized as the surface pretreatment for the AA2024-T3. Also, sodium montmorillonite was filled with Ce3+ cations and then applied on the LDH layer after being mixed with the hybrid sol-gel silane solution. The surface-modified layer was finally coated with epoxy resin. The three-layer coating system's electrochemical behavior in the absence and presence of the ion-exchange materials and the corrosion inhibitors was examined using electrochemical impedance spectroscopy (EIS), electrochemical current noise, and salt spray testing. The synthesized layers' chemical composition and surface morphology were analyzed using SEM-EDS. Results indicated that the epoxy coating active/barrier anti-corrosive performance significantly improved in the presence of ion-exchange materials loaded with the corrosion inhibitors. Based on the findings, the loading of the corrosion inhibitors into the structure of the ion-exchange material coated on the AA2024-T3 substrate leads to an enhancement in the log|Z|10mHz of the three-layer coating from 6.3 to 8.27 Ω·cm2. Additionally, the incubation of active protection performance for the three-layer coating after being loaded with the corrosion inhibitors was illustrated through the electrochemical testing and surface analysis.

Synthesis and characterisation of layered double hydroxides with varying divalent metal cations: Mg2+, Zn2+, Ca2+

This study aims to investigate the physicochemical properties of layered double hydroxides (LDH) with different divalent metal (M2+) cations. A series of nitrate-based LDH materials was synthesised by using aluminium (Al3+) as a trivalent cation (M3+) with varying M2+ cations such as magnesium (Mg2+), zinc (Zn2+), and calcium (Ca2+) ions to prepare magnesium–aluminium-layered double hydroxide (MgAl-LDH), zinc–aluminium-layered double hydroxide (ZnAl-LDH), and calcium–aluminium-layered double hydroxide (CaAl-LDH), respectively. MgAl-LDH and ZnAl-LDH were synthesised by the co-precipitation method, whereas CaAl-LDH was prepared by the hydrothermal method. The samples were characterised by powder X-ray diffraction (PXRD), Fourier transform infrared spectra (FTIR), thermogravimetric and differential thermogravimetric analysis (TGA/DTG), field emission scanning electron microscope (FESEM), and accelerated surface area and porosity (ASAP) analysis. The PXRD patterns show that MgAl-LDH (9.8 Å) had the greatest interlayer spacing, followed by ZnAl-LDH (8.9 Å), and CaAl-LDH (8.7 Å). The FTIR spectra clearly confirms the presence of nitrate ions in the LDH structure. Two-step degradation behaviour of the samples was observed in the TGA curve. The LDHs exhibit Type IV isotherms and hexagonal structures were observed on the FESEM images.

Zn-Al layered double metal hydroxide anchored reduced graphene oxide for enhancing the fire performance of composite coatings

Layered double hydroxides acts as an effective inorganic nano-fire retardant, which is capable of releasing water, carbon dioxide and diluting the concentration of combustible gases when encountering flames, thus providing fire protection. Here, zinc-aluminum layered double hydroxides (Zn-Al/LDH) is uniformly anchored on the reduced graphene oxide (RGO) surface by a simple hydrothermal strategy in order to further enhance the barrier effect of the char layer. The obtained Zn-Al/LDH anchored reduced graphene oxide (Zn-Al/LDH@RGO) hybrids were added to waterborne epoxy resin and their fire resistance properties were measured by large plate combustion test, furnace storage test and thermal weight loss test. The results showed that the incorporation of nano-fillers effectively enhanced the fire resistance of the composite coatings. Among them, Zn-Al/LDH@RGO -based fireproof coatings presented better fire performance due to the active flame retardant mechanism of Zn-Al/LDH and the high barrier property of RGO nanosheets. In contrast, the composite coating with 1.5% of Zn-Al/LDH@RGO hybrids had the lowest backside temperature of 154.3 °C. Besides, the Zn-Al/LDH@RGO/EP (1.5%) coating also exhibited the highest expansion height (16.5 mm), expansion rate (12.13) and the highest char residue rate (32.2%), indicating its highest fire retardant performance.

ZnAl-LDH and B-impregnated polymeric semiconductor (g-C3N4) for solar light-driven photocatalysis to treat phenolic effluent

The structural transformation of graphitic carbon nitride (g-C3N4) has been done by means of Zinc Aluminium layered double hydroxide (ZnAl-LDH), and a non-metal, i.e. boron impregnation to enhance its visible light absorption. Optical and morphological study intimates that an altered band assembly formed due to the impregnation, resulting in a shorten bandgap in conjunction with the development of an irregular hexagonally interrelated morphology. In addition, the impregnated g-C3N4 (40% B-g-C3N4 and 30%ZnAl-LDH/g-C3N4) owns an expanded surface area of 14.3137, and 26.292 m2/g, which demonstrate 90.25, 86.31% degradation in phenol at 270 min illumination, with 700 mg/L of chemical oxidant concentration, and 5 L/h of flowrate, whereas under same conditions g-C3N4 impart 62.38% degradation. We hope this study will open a new dimensions for the sustainable use of solar energy for environmental applications.

Synthesis and Cytotoxicity Study of Magnetite Nanoparticles Coated with Polyethylene Glycol and Sorafenib-Zinc/Aluminium Layered Double Hydroxide.

In the last two decades, the development of novel approaches for cancer treatment has attracted intense attention due to the growing number of patients and the inefficiency of the available current conventional treatments. In this study, superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized by the co-precipitation method in an alkaline medium. Then the nanoparticles were chemically modified by coating them with polyethylene glycol (PEG) and sorafenib (SO)–zinc/aluminum layered double hydroxide (ZLDH) to improve their biocompatibility. The SPIONs and their coated and drug-loaded nanoparticles, M-PEG–SO–ZLDH are of the crystalline phase with the presence of C, O, Al, Fe, Cl, Zn in the latter, indicating the presence of the coating layers on the surface of the SPIONs. The superparamagnetic properties of the bare SPIONs were found to be reduced but retained in its coated drug delivery nanoparticles, M-PEG–SO–ZLDH. The latter has an average particle size of 16 nm and the release of the drug from it was found to be governed by the pseudo-second-order kinetic. The cytotoxicity and biocompatibility evaluation of the drug-loaded magnetic nanoparticles using 3T3 and HepG2 cells using the diphenyltetrazolium bromide (MTT) assays shows that the synthesized nanoparticles were less toxic than the pure drug. This preliminary study indicates that the prepared nanoparticles are suitable to be used for the drug delivery system.

Nitrogen and sulfur doped ZnAl layered double hydroxide/reduced graphene oxide as an efficient nanoelectrocatalyst for oxygen reduction reactions

In this work, to synthesize an efficient and low-cost electrocatalysts for Oxygen Reduction Reaction (ORR), the combination of N,S-rGO and ZnAl-LDH with several concentrations is studied for the first time. For this purpose, six electrocatalysts including Graphene Oxide (GO), functionalized reduced graphene oxide with nitrogen and sulfur atoms (N,S–rGO), Zinc–Aluminum layered double hydroxides (ZnAl-LDH), and ZnAl-LDH/N,S–rGO hybrids in three weight ratios of 1:1, 1:3, and 1:5 (the weight ratio of N,S-rGO is 1) are synthesized by the hydrothermal method. The physical properties, morphology, and structure of the synthesized electrocatalysts are determined by using X-Ray Diffraction (XRD) analysis, Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray Analysis (EDX), the Fourier Transform Infrared Spectroscopy (FTIR) and Raman analysis. Electrochemical measurements are implemented by using Cyclic Voltammetry (CV), Linear Scanning Voltammetry (LSV), and chronoamperometric. Also, the electron transfer number is calculated by K-L plot. The obtained results for all samples are compared with the %20 Pt/C commercial catalyst. Based on the results of the physical tests, in addition to the uniform distribution and the correct deposition of the synthesized electrocatalysts, the particle size also reached the nanometer range. According to the electrochemical results, among the synthesized electrocatalysts, the ZnAl-LDH/N,S–rGO with 1:1 wt ratio has the best electrochemical activity. This result indicates a well synergistic and interaction effect between N,S–rGO and ZnAl-LDH for the ORR. The onset potential is obtained to be −0.01 V vs Ag/AgCl. The average of electron transfer number by this electrocatalyst is 3.60, which indicates that it is close to the 4e pathway for the ORR. The electrocatalytic stability was favorable in the alkaline medium. It can be concluded that the Layered Double Hydroxides (LDHs) improve the electrical conductivity, the electrocatalytic activity, the active surface area, and the stability for the oxygen reduction reaction after the combination with carbon bases. To be clear, the combination of N,S-rGO and ZnAl-LDH with several concentrations has been investigated for the first time on the ORR applications. The sensitivity analysis is implemented to determine the optimal concentration. This study proposes a new approach for using N, S-rGO composite to improve the low electron conductivity of LDHs.

Use of Zinc-Aluminum Layered Double Hydroxides as Nanofillers of Thermoplastic Vulcanizates

The synthesis of layered double hydroxides based on zinc and aluminum salts containing nitrate anion in the interplanar space is described. The samples prepared were investigated by X-ray structural analysis. It was found that the interplanar distance of brucite layers is 8.6 nm. The prepared samples were modified with stearate anions. X-ray diffraction spectra of the modified samples show that there was a complete substitution of the nitrate anion for the stearate anion, and the interplanar distance increased to 46.8 nm. Nanocomposites of dynamically crosslinked thermoplastic elastomer based on ethylene–propylene rubber and polypropylene in a ratio of 70 : 30 were produced using 3, 5, 7 wt. parts of modified double hydroxide. A significant increase in the physical and mechanical properties, as well as an increase in heat resistance and fire resistance of the sinthesized nanocomposites, has been established.

Exploitation of new approach to control of environmental pathogenic bacteria causing bovine clinical mastitis using novel anti-biofilm nanocomposite.

New approaches are required for prevention and control of biofilm-producing bacteria and consequently mitigating the health problems of bovine clinical mastitis. This work designed to determine prevalence rates of biofilm-producing bacteria that causing bovine clinical mastitis and evaluate the anti-biofilm effectiveness of novel nanocomposite of zinc-aluminum layered double hydroxide intercalated with gallic acid (GA) as chelating agent (Zn-Al LDH/GA) on the prevention and control of environmental pathogenic bacteria; Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), Staphylococcus aureus (S. aureus), and Coagulase-negative staphylococci (CNS), besides Listeria monocytogenes (L. monocytogenes) and assess the ability to use as an antimicrobial agent, and/or sanitizer for milking equipment. All samples (n = 230) involved clinical mastitis cow's milk (n = 50) beside environmental samples (n = 180) were collected then examined for isolation and identification of bacterial pathogens. Zn-Al LDH/GA nanocomposite was synthesized using co-precipitation method, then characterized by Fourier-transform infrared spectroscopy (FT-IR); X-ray diffraction (XRD); field emission scanning electron microscopy (FESEM); high-resolution transmission electron microscopy (HRTEM); thermogravimetric analysis (TGA); differential thermal analysis (DTA); zeta potential; DLS analysis; and Brunauer, Emmett, and Teller (BET) surface area. The anti-biofilm activity of nanocomposite against mastitis-causing bacteria was detected using the broth micro-dilution and disc-diffusion assay. Results, the minimum concentration of Zn-Al LDH/GA that inhibited the growth of gram-positive and negative bacteria, were 312-625 and 5000μg/mL, respectively. The LD50 of Zn-Al LDH/GA was determined in mice at 1983.3mg/kg b.wt. As a conclusion, Zn-Al LDH/GA nanocomposite proved its efficiency as an antimicrobial agent and/or sanitizer used for cleaning of milking equipment, due to it could inhibit the growth and multiplication of potentially pathogenic bacteria that causing clinical mastitis and its formation of biofilm on the milking equipment. Zn-Al LDH/GA was found to use under varying pH conditions compared with other commercial sanitizer used besides the formation of nanocomposite increases the material stability.

Investigation of the photoanode based on graphene/zinc aluminum mixed metal oxide for dye-sensitized solar cell

In this study, zinc aluminum layered double hydroxide (ZnAl-LDH) with a Zn/Al molar ratio 8/1 was synthesized via a facile urea method, and the mixed metal oxide (MMO) was prepared using the corresponding LDH as a precursor. In order to improve the performance of electron transport layer, we introduced graphene into ZnAl-MMO to prepare new nanocomposites, ZnAl-MMO/graphene, as promising photoanodes for dye-sensitized solar cell (DSSC). The bare ZnAl-MMO and formed ZnAl-MMO/graphene nanocomposites were characterized by X-ray diffraction (XRD), Raman spectra, scanning electron microscope (SEM) and UV–vis absorption spectrum, confirming the presence of graphene and the wurtzite type phase of ZnO. A series of DSSC were fabricated by the corresponding nanocomposites and a D205 as dye. The photovoltaic behavior of these cells based on different graphene concentration was further investigated by electrochemical method. It turned out that the introduced graphene facilitated the dye adsorption and light-scattering, which heightened the performance of DSSC. The DSSC based on ZnAl-MMO/0.2 wt.% graphene reached the best power conversion efficiency (PCE) of 0.51%, showing a rise of 25% approximately when compared with plain ZnAl-MMO.

Efficient Photocatalytic Nitrogen Fixation over Cuδ+‐Modified Defective ZnAl‐Layered Double Hydroxide Nanosheets

AbstractThe photocatalytic reduction of nitrogen (N2) with water (H2O) as the reducing agent holds great promise as a sustainable future technology for the synthesis of ammonia (NH3). Herein, the effect of oxygen vacancies and electron‐rich Cuδ+ on the performance of zinc‐aluminium layered double hydroxide (ZnAl‐LDH) nanosheet photocatalysts for N2 reduction to NH3 under UV–vis excitation is systematically explored. Results show that a 0.5%‐ZnAl‐LDH nanosheet photocatalyst (containing 0.5 mol% Cu by metal basis) affords a remarkable NH3 production rate of 110 µmol g−1 h−1 and excellent stability in pure water. The X‐ray absorption spectroscopy, electron paramagnetic resonance, and density functional theory calculations reveal that Cu addition imparts oxygen vacancies and coordinatively unsaturated Cuδ+ (δ &lt; 2) with electron‐rich property in the ZnAl‐LDH nanosheets, both of which readily contribute to efficient separation and transfer of photogenerated electrons and holes and promote N2 adsorption, thereby both activating N2 and facilitating its multielectrons reduction to NH3.