Zn-Fe Layered Double Hydroxide Research Articles

Tailored thymoquinone intercalated Layered Double Hydroxide (LDH) nanocomposites to accelerate mineralization for enhanced osteogenesis

The tunable nature of two-dimensional nanostructured Layered Double Hydroxides [LDH] and their effective intercalation ability with biomolecules make them inevitable functional hybrid materials for versatile biomedical applications. In an attempt to meet the limitations in existing bone reconstruction practice, the present work reports the synthesis of zinc and iron-based LDH [Zn-Fe LDH] and its subsequent intercalation with thymoquinone [TQ-Zn-Fe LDH] to augment osteoblastic differentiation and proliferation for accelerated bone mineralization. Structural studies depicted the polycrystalline and amorphous nature of ZnFe LDH and TQ-Zn-Fe LDH respectively. The biocompatible nature of LDHs was proven by negative cytotoxicity, cell adhesion, and proliferation assays studied in MG-63 cell lines. Gene expression studies of the nanocomposites showed a fold change of 5–10 in osteoblastic differentiation and proliferation. However, TQ-Zn-Fe LDH treated cells showed significantly higher protein translation levels of osteogenesis markers and elevated alkaline phosphatase secretion and calcium deposition on day 21, confirming their osteogenic efficiency. Thus, acquired results speculate the osteogenic potential of thymoquinone intercalated TQ-Zn-Fe-LDH to meet the limitations in bone reconstruction practice.

Efficient Dye Degradation and Antimicrobial Behavior with Molecular Docking Performance of Silver and Polyvinylpyrrolidone-Doped Zn-Fe Layered Double Hydroxide.

Zn-Fe layered double hydroxide (LDH) was synthesized through the low-temperature-based coprecipitation method. Various concentrations of Ag (1, 3, and 5 wt %) with a fixed amount (5 wt %) of polyvinylpyrrolidone (PVP) were doped into LDH nanocomposites. This research aims to improve the bactericidal properties and catalytic activities of doping-dependent nanocomposites. Adding Ag and PVP to LDH enhanced oxygen vacancies, which increased the amount of hydroxide adsorption sites and the number of active sites. The doped LDH was employed to degrade rhodamine-B dye in the presence of a reducing agent (NaBH4), and the obtained results showed maximum dye degradation in a basic medium compared to acidic and neutral. The bactericidal efficacy of doped Zn-Fe (5 wt %) showed a considerably greater inhibition zone of 3.65 mm against Gram-negative (G-ve) or Escherichia coli (E. coli). Furthermore, molecular docking was used to decipher the mystery behind the microbicidal action of Ag-doped PVP/Zn-Fe LDH and to propose an inhibition mechanism of β-ketoacyl-acyl carrier protein synthase IIE.coli (FabH) and deoxyribonucleic acid gyrase E.coli behind in vitro results.

Intercalation vs Adsorption Strategies of Myo-Inositol Hexakisphosphate into Zn-Fe Layered Double Hydroxide: A Tiff between Anion Exchange and Coprecipitation.

Myo-inositol hexakisphosphates (IHPs) or phytates are the most abundant organic phosphates having the potential to serve as a phosphorus reserve in soil. Understanding the fate of IHP interaction with soil minerals tends to be crucial for its efficient storage and utilization as a slow-release organic phosphate fertilizer. We have systematically compared the effective intercalation strategy of a phytate onto Zn-Fe layered double hydroxide (LDH) acting as storage/carrier material through coprecipitation and anion exchange. Powder X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, thermogravimetric analysis, FTIR spectra, and molecular modeling demonstrated the formation of phytate-intercalated Zn-Fe LDH through coprecipitation with a maximum loading of 41.34% (w/w) in the pH range of ∼9-10 in a vertical alignment through monolayer formation. No intercalation product was obtained from the anion exchange method, which was concluded based on the absence of shifting in the XRD (003) peak. A change in the zeta potential values from positive to negative and subsequent increase in solution pH, with decreasing phytate concentration, are suggestive of adsorption of IHP onto the LDH surface. The batch adsorption data were best fitted with Langmuir isotherm equation and followed the pseudo-second-order kinetic model. The maximum adsorption capacity was found to be 45.87 mg g-1 at a temperature of 25 ± 0.5 °C and pH 5.63.

Valorization of spent double substituted Co–Ni–Zn–Fe LDH wastewater nanoadsorbent as methanol electro-oxidation catalyst

Finding suitable non-expensive electrocatalyst materials for methanol oxidation is a significant challenge. Waste valorization of spent wastewater nanoadsorbents is a promising route toward achieving circular economy guidelines. In this study, the residual of layered double hydroxide (LDH) can be used as an electrocatalyst in direct methanol fuel cells as a novel approach. The Co–Ni–Zn–Fe LDH was prepared by the co-precipitation method followed by the adsorption of methyl orange (MO). Moreover, the spent adsorbent was calcined at different temperatures (200, 400, and 600 °C) to be converted to the corresponding mixed metal oxides (MMO). The prepared samples were characterized using XRD, FTIR, HRTEM, zeta potential, and hydrodynamic size measurements. The spent adsorbent was tested as an electro-catalyst for direct methanol electro-oxidation. The spent LDH/MO adsorbent showed a maximum current density of 6.66 mA/cm2 at a 50 mV/s scan rate and a 1 M methanol concentration. The spent MMO/MO adsorbent showed a maximum current density of 8.40 mA/cm2 at a 200 °C calcination temperature, 50 mV/s scan rate, and a 3 M methanol concentration. Both samples show reasonable stability over time, as indicated by the chronoamperometric response. Further nanoengineering of used nanoadsorbents could be a promising path to repurposing these wastes as electro-oxidation catalysts.

Generating High‐valent Iron‐oxo ≡FeIV=O Complexes in Neutral Microenvironments through Peroxymonosulfate Activation by Zn−Fe Layered Double Hydroxides

AbstractThe universal limit on the pH conditions is disturbing peroxymonosulfate (PMS)‐triggered high‐valent iron‐oxo systems in environmental applications. Here, we propose for the first time the construction of a neutral microenvironment on the surface of Zn−Fe layered double hydroxide (ZnFe‐LDH) by using the amphoteric properties of zinc hydroxide, which continuously generates ≡FeIV=O over a wide pH range of 3.0–11.0 in activating PMS. The ≡Zn(OH)2 moiety offers a neutral microenvironment at the phase interface, which mitigates the self‐decomposition of ≡FeIV=O by protons and the hydrolysis reaction of iron by hydroxyl groups, which is supported by the Mossbauer spectra, density functional theory calculations and designed experiments. Consequently, ZnFe‐LDH/PMS can satisfy the stability in long‐term experiments, selectivity under conditions with high salinity or natural organic matter and efficient treatment of actual wastewater.

Generating High‐valent Iron‐oxo ≡FeIV=O Complexes in Neutral Microenvironments through Peroxymonosulfate Activation by Zn−Fe Layered Double Hydroxides

The universal limit on the pH conditions is disturbing peroxymonosulfate (PMS)-triggered high-valent iron-oxo systems in environmental applications. Here, we propose for the first time the construction of a neutral microenvironment on the surface of Zn-Fe layered double hydroxide (ZnFe-LDH) by using the amphoteric properties of zinc hydroxide, which continuously generates ≡FeIV =O over a wide pH range of 3.0-11.0 in activating PMS. The ≡Zn(OH)2 moiety offers a neutral microenvironment at the phase interface, which mitigates the self-decomposition of ≡FeIV =O by protons and the hydrolysis reaction of iron by hydroxyl groups, which is supported by the Mossbauer spectra, density functional theory calculations and designed experiments. Consequently, ZnFe-LDH/PMS can satisfy the stability in long-term experiments, selectivity under conditions with high salinity or natural organic matter and efficient treatment of actual wastewater.

Co and Ni Double Substituted Zn-Fe Layered Double Hydroxide as 2D Nano-Adsorbent for Wastewater Treatment

Recently, several types of nanomaterials gained attention as promising nanoadsorbents to remove dyes from wastewater such as layered double hydroxides (LDHs). In this work, Fe-Zn-Co-Ni LDH was developed by the basic co-precipitation method. In order to emphasize and characterize the developing of this quaternary LDH, six techniques (x-ray diffraction (XRD), scan electron microscope (SEM), Fourier transforms infrared (FTIR), transmission electron microscope (TEM), zeta potential measurements) have been investigated. The LDH was studied for the uptake of anionic dye, methyl orange (MO), under numerous adsorption factors such as solution pH, contact time, dye initial concentration and adsorbent dosage, and. The XRD data states that the crystallite size of MO@LDH (93.1 nm) is increased compared with that of LDH (12.7 nm) owning to the adsorption of MO onto LDH surface. Two new peaks have appeared for the MO@LDH owning to the bending vibrations of the MO functional groups C-N and C-H. The highest adsorption capacity for the prepared MO@LDH was 418 mg/g and it reached the equilibrium state at 60 min. The adsorption kinetic was obeyed to the pseudo-first order model. Additionally, the LDH showed a positive antibacterial effect towards both Gram-negative and Gram-positive bacteria.

Influence of mass ratio and calcination temperature on physical and photoelectrochemical properties of ZnFe-layered double oxide/cobalt oxide heterojunction semiconductor for dye degradation applications

A visible light-active photoelectrocatalyst, ZnFe-layered double oxide (LDO)/cobalt(II,III) oxide (Co3O4) composites were obtained by calcining the Co loaded ZnFe-layered double hydroxide (LDH) prepared by a hydrothermal and microwave hydrothermal method. The morphological studies revealed that the ZnFe-LDO/Co3O4 composites exhibited a flower-like structure comprising Co3O4 nanowires and ZnFe-LDO nanosheets. Further, when the mass ratio of Co(NO3)2·6H2O/LDH was 1:1.8 and the calcination temperature was 550 °C, the ZnFe-LDO/Co3O4 composite exhibited 93.3% degradation efficiency for methylene blue (MB) at the applied voltage of 1.0 V under visible light after 3 h. Furthermore, the Mott-Schottky model experiments showed that the formation of a p-n heterojunction between ZnFe-LDO and Co3O4 could effectively inhibit the recombination of electrons and holes in the photoelectrocatalytic process. Meanwhile, free radical scavenging experiments showed that the active radicals of ⋅OH played an important role in the degradation of MB. Therefore, the photoelectrocatalytic effect of ZnFe-LDO/Co3O4 provides a simple and effective strategy for the removal of organic pollutants.

Visible-Light-Active Zn–Fe Layered Double Hydroxide (LDH) for the Photocatalytic Conversion of Rice Husk Extract to Value-Added Products

One of the major causes of excess CO2 in the atmosphere is the direct burning of biomass waste, which can be obviated by the photocatalytic biomass conversion to useful/valuable chemicals/fuels, a sustainable and renewable approach. The present research work is focused on the development of a novel Zn–Fe LDH by a simple co-precipitation method and its utilization for the photocatalytic conversion of a rice husk extract (extracted from rice husk by means of pyrolysis) to value-added products. The synthesized, pure Zn–Fe LDH was characterized by various analytical techniques such as XRD, SEM, FTIR, and UV–Visible DRS spectroscopy. The rice husk extract was converted in a photocatalytic reactor under irradiation with 75 W white light, and the valued-added chemicals were analyzed by gas chromatography–mass spectrometry (GC–MS). It was found that the compounds in the rice husk extract before the photocatalytic reaction were mainly carboxylic acids, phenols, alcohols, alkanes (in a small amount), aldehydes, ketones, and amines. After the photocatalytic reaction, all the carboxylic acids and phenols were completely converted into alkanes by complex reactions. Hence, photocatalytic biomass conversion of a rice husk extract was successfully carried out in the present experimental work, opening new avenues for the development of related research domains, with a great potential for obtaining an alternate fuel and overcoming environmental pollution.

Facile fabrication of ZnO decorated ZnFe-layered double hydroxides @ biochar nanocomposites for synergistic photodegradation of tetracycline under visible light

To explore effective treatment of antibiotics-contaminated water using visible light-responsive photocatalyst, a series of ZnO decorated ZnFe-layered double hydroxide @ biochar (ZnO/ZnFe-LDH@BC) nanocomposites were obtained via a facile hydrothermal method. The fabricated nanocomposites exhibited uniform distribution of ZnO/ZnFe-LDH on BC matrix, allowing more active sites of ZnO/ZnFe-LDH to be utilized. The BC matrix brought widened visible-light absorbance, narrowed bandgap, and improved charge separation and transfer. During photocatalytic degradation of tetracycline (TC) under visible LED light, the nanocomposites showed significant enhancement of degradation efficiency, compared to ZnO/ZnFe-LDH or BC alone, indicating a strong synergy between ZnO/ZnFe-LDH and BC. The nanocomposite containing 23.0 wt% of BC (ZnO/ZnFe-LDH@BC0.2) showed optimal performance (achieving 87.7% of degradation within 4 h) in comparison to the reported LDHs@carbon photocatalysts. Alkaline condition and co-existing CO32– ions could enhance the stability and recyclability of the nanocomposites. Additionally, the possible degradation pathway of TC was analyzed via LC-MS and the reduction in toxicity resulting from photocatalytic degradation was confirmed by the culture of mung bean sprouts. This study provides a rational design strategy and performance assessment of LDH-based nanocomposites for the treatment of antibiotics-contaminated water.

Vanadium (V)-doped ZnFe layered double hydroxide for enhanced sonocatalytic degradation of pymetrozine

In ultrasonic (US) processes, the development of environmentally friendly, effective, low-cost, and durable catalysts is needed to degrade pollutants. Here, ZnFe layered double hydroxide (LDH) was doped with vanadium (V) for the sonocatalytic degradation of a pesticide pymetrozine. The resulting catalyst had an average thickness of 25 nm, a specific surface area of 125.38 m2/g, and a bandgap value of 2.20 eV. In 90 min ultrasonic treatment, V-doped ZnFe LDH had 73% pymetrozine removal efficiency, which was 32% more than that of undoped ZnFe LDH. The US/V-doped ZnFe LDH process had a strong synergistic effect (synergy factor 7.17), which resulted in 57% and 68% greater efficiencies than the US alone and V-doped ZnFe LDH alone, respectively. The role of radical oxygen species was confirmed by carrying out radical trapping experiments using different scavengers and electron paramagnetic resonance analyses. Due to its high stability, the catalyst had good reuse potential with only an 8% performance reduction after 5 reuse cycles. Besides, the leaching of heavy metals was insignificant owing to the high integrity of the catalyst as confirmed by SEM and X-ray diffraction analysis. According to the GC–MS analysis, pymetrozine was first transformed into cyclic compounds then into aliphatic compounds such as animated products and carboxylic acids.

Preparation of phosphate ion-doped Zn–Fe-layered double hydroxide with corrosion resistance and inducing Ca–P deposition on AZ31 Mg alloy

Preparation of phosphate ion-doped Zn–Fe-layered double hydroxide with corrosion resistance and inducing Ca–P deposition on AZ31 Mg alloy

Evaluation of deltamethrin-loaded Zn-Fe, Zn-Al-GA layered double hydroxide, and Fe-O nanoparticles against resistant Rhipicephalus annulatus ticks.

The over use of deltamethrin has resulted in the development of resistance. Thus, the search for a new method to improve its acaricidal effect is the target of the present study. Layered double hydroxide (LDH) compounds are now used as drug delivery systems. Deltamethrin (Butox®) was loaded on Zn-Fe LDH, Zn-Al-GA layered double hydroxide (LDH), and Fe-oxide nanoparticles NPs. Then its acaricidal efficacy was evaluated. The nanocomposites (NCs) were prepared by the co-precipitation method and characterized before and after deltamethrin loading. The deltamethrin-loaded NCs were applied against the phenotypically resistant Rhipicephalus annulatus tick (adult and larvae). The adult ticks treated by Butox® alone or Butox® loaded nanocomposites at different concentrations showed no mortality. A significant (P≤0.05) reduction in egg production index was observed at the recommended dose (X) (1 μl/ml distilled water) and its bi-folds (2X, 3X, and 4X) in ticks treated with deltamethrin/Zn-Fe LDH nanocomposites compared to deltamethrin alone. Moreover, no significant difference (P>0.05) was recorded in larval mortality between the treatments with deltamethrin alone and its loaded nanocomposites. Also, the nanomaterials alone without conjugation with deltamethrin revealed a low mortality rate. Deltamethrin-loaded nanocomposites even improve effect against adult tick but cannot overcome tick resistance to deltamethrin that needs more search. The acaricidal activity of deltamethrin was not improved after loading it with these nanocomposites.

Fabrication of PSf nanocomposite membranes incorporated with ZnFe layered double hydroxide for separation and antifouling aspects

Herein, we report the effect of blending of various concentrations of ZnFe layered double hydroxide (LDH) on the filtration, antifouling, and antibacterial performances of Polysulfone (PSf) nanocomposite membranes for BSA and dye separation. ZnFe LDH with a molar ratio of M2+:M3+=3:1 was synthesized by the co-precipitation method. The PSf-ZnFe LDH nanocomposite membranes exhibited higher hydrophilicity (the lowest contact angle value of 64.42°), porosity (up to 58.7), and mean pore radius compared to the pristine PSf membrane. The water flux of the PSf-ZnFe LDH nanocomposite membrane (LDH content of 2.0 wt% of PSf) was 105 L/m2h, which is 2.3 times higher than the flux of pristine PSf membrane of 45 L/m2h. The rejection ratios for the fabricated membranes were 93%, 83%, and 16% for BSA, reactive red 198, and methylene blue, respectively. Additionally, 2.0 wt% ZnFe LDH incorporated membrane demonstrated better antifouling performance with a flux recovery ratio (FRR) of 95% compared to the pristine PSf membrane with 42% of FRR. Consequently, a bacterial viability inhibition test was utilized to determine the antibacterial properties, and the ZnFe LDH exhibited a high inhibition capacity. The fabricated PSf-ZnFe LDH nanocomposite membranes exhibited a higher filtration, antifouling, and antimicrobial performance as compared to pristine PSf.

LDH Nanocubes Synthesized with Zeolite Templates and Their High Performance as Adsorbents.

In this work, the efficiency of the adsorptive removal of the organic cationic dye methylene blue (MB) from polluted water was examined using three materials: natural clay (zeolite), Zn-Fe layered double hydroxide (LDH), and zeolite/LDH composite. These materials were characterized via X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) diffraction (XRF), low-temperature N2 adsorption, pore volume and average pore size distribution and field emission scanning electron microscopy (FE-SEM). The properties of the applied nanomaterials regarding the adsorption of MB were investigated by determining various experimental parameters, such as the contact time, initial dye concentration, and solution pH. In addition, the adsorption isotherm model was estimated using the Langmuir, Freundlich, and Langmuir–Freundlich isotherm models. The Langmuir model was the best-fitting for all applied nanomaterials. In addition, the kinetics were analyzed by using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models, and the pseudo-second-order model was an apparent fit for all three applied nanomaterials. The maximum Adsorption capacity toward MB obtained from the materials was in the order zeolite/LDH composite > zeolites > Zn-Fe LDH. Thus, the zeolite/LDH composite is an excellent adsorbent for the removal of MB from polluted water.

Understanding the physicochemical properties of Zn\u2013Fe LDH nanostructure as sorbent material for removing of anionic and cationic dyes mixture

In our work, the removal of cationic and anionic dyes from water was estimated both experimentally and computationally. We check the selectivity of the adsorbent, Zn–Fe layered double hydroxide (LDH) toward three dyes. The physical and chemical properties of the synthesis adsorbent before and after the adsorption process were investigated using X-ray photoelectron spectroscopy, energy dispersive X-ray, X-ray diffraction, FT-IR, HRTEM, and FESEM analysis, particle size, zeta potential, optical and electric properties were estimated. The effect of pH on the adsorption process was estimated. The chemical stability was investigated at pH 4. Monte Carlo simulations were achieved to understand the mechanism of the adsorption process and calculate the adsorption energies. Single dye adsorption tests revealed that Zn–Fe LDH effectively takes up anionic methyl orange (MO) more than the cationic dyes methylene blue (MB) and malachite green (MG). From MO/MB/MG mixture experiments, LDH selectively adsorbed in the following order: MO > MB > MG. The adsorption capacity of a single dye solution was 230.68, 133.29, and 57.34 mg/g for MO, MB, and MG, respectively; for the ternary solution, the adsorption capacity was 217.97, 93.122, and 49.57 mg/g for MO, MB, and MG, respectively. Zn–Fe LDH was also used as a photocatalyst, giving 92.2% and 84.7% degradation at concentrations of 10 and 20 mg/L, respectively. For visible radiation, the Zn–Fe LDH showed no activity.

In Situ Growth of Ni–Zn–Fe Layered Double Hydroxide on Graphene Aerogel: An Advanced Two‐in‐One Material for Both the Anode and Cathode of Supercapacitors

The push toward high‐performance supercapacitors calls for the development of efficient pseudocapacitive negative electrode materials that can better match the high capacitance of the typical positive electrodes. Herein, a facile and one‐pot hydrothermal approach for the in situ growth of the nickel–zinc–iron layered double hydroxide (LDH) onto the graphene aerogel (GA) substrate is introduced. Proper selection of the metal precursors with prominent pseudocapacitive behavior over a wide potential range coupled with the excellent double‐layer capacitive and charge transport properties of the GA network results in an LDH–GA nanocomposite that displays outstanding supercapacitive performances as both negative (387 F g−1, 101 mA h g−1, at 1.0 A g−1) and positive (1235 F g−1, 103 mA h g−1) electrodes. An aqueous LDH–GA//LDH–GA device with a wide voltage window (1.55 V) that demonstrates a significantly enhanced specific capacitance (304 F g−1 at 1.0 A g−1), outstanding specific energy (95 W h kg−1), appreciable specific power (81 kW kg−1), along with 88% retention of the initial capacitance after 10 000 cycles, is also fabricated. The superior supercapacitive performance of the Ni–Zn–Fe LDH–GA nanocomposite over both negative and positive voltage ranges opens a promising pathway toward manufacturing high‐energy supercapacitors for state‐of‐the‐art applications.

The formation of Fe colloids and layered double hydroxides as sequestration agents in the natural remediation of mine drainage

The increasing need to treat wastewater from mine effluents has drawn attention to passive treatment systems. Colloids are common in mine waters and are highly reactive, so their formation, characteristics, behavior, and the critical factors that affect them need to be understood for designing efficient treatment systems. An investigation was conducted at the abandoned Ainai mine drainage, Japan, where aeration is utilized to remove Fe, As, and Zn from circumneutral wastewater drainage, during rainy and dry seasons of 2016 and 2018 respectively, based on observations of physiochemical characteristics, elemental concentrations in dissolved and colloidal fractions, transmission electron microscopy, and synthetic experiments. In this circumneutral Fe-rich mine drainage, Fe2+ is oxidized to Fe3+, resulting in the formation of Fe colloids that incorporate As during their formation. Colloid formation increases turbidity, and, in the rainy season, increased colloidal interaction enhances their aggregation and higher flow rates lead to greater mobilization of the colloids. Zn-bearing colloids are rare in Ainai mine drainage because the Zn concentrations are low. However, Zn-Fe layered double hydroxide (LDH) was identified and confirmed by geochemical modelling and experiments. The Zn-Fe LDH was formed by isomorphous substitution of Zn into an Fe2+–Fe3+–CO32–LDH, at pH greater than 7.5, thereby achieving efficient natural remediation of Zn and As in the drainage.

Toxicity of Zn-Fe Layered Double Hydroxide to Different Organisms in the Aquatic Environment.

The application of layered double hydroxide (LDH) nanomaterials as catalysts has attracted great interest due to their unique structural features. It also triggered the need to study their fate and behavior in the aquatic environment. In the present study, Zn-Fe nanolayered double hydroxides (Zn-Fe LDHs) were synthesized using a co-precipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption analyses. The toxicity of the home-made Zn-Fe LDHs catalyst was examined by employing a variety of aquatic organisms from different trophic levels, namely the marine photobacterium Vibrio fischeri, the freshwater microalga Pseudokirchneriella subcapitata, the freshwater crustacean Daphnia magna, and the duckweed Spirodela polyrhiza. From the experimental results, it was evident that the acute toxicity of the catalyst depended on the exposure time and type of selected test organism. Zn-Fe LDHs toxicity was also affected by its physical state in suspension, chemical composition, as well as interaction with the bioassay test medium.

Structural Characterization and Photoluminescent Behavior of CO3 Intercalated Zn-Fe Layered Double Hydroxide (LDH) and its Colloids

Carbonate intercalated Zn-Fe layered double hydroxide (LDH) with Zn2+/Fe3+ molar ratios 2, 3 and 4 were synthesized by coprecipitation in order to study the photoluminescent (PL) properties of their colloids with various wt.% of LDH in formamide. These synthesized LDHs were characterized by various techniques including x-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron mMicroscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), and photoluminescence spectroscopy (PL). The rhombohedral phase and crystallite size of Zn-Fe LDH were confirmed by XRD. Crystallite size plays an important role in the PL mechanism. HR-TEM showed hexagonal nanosheets with 5–6 nm average particle size. To investigate the PL mechanism of pristine LDH and their colloids, these prepared Zn-Fe LDHs were exfoliated in formamide by varying their Zn2+/Fe3+ molar ratios (2,3, 4) and LDH concentration (0.2 wt.%, 0.4 wt.%, 0.6 wt.%, 0.8 wt.% of LDH). Results revealed that surface charge density and surface defects are the main reasons for PL generation in LDH colloids.