NO3 Layered Double Hydroxides Research Articles

Ageing influences the toxicity of two innovative nanofertilizers to the soil invertebrates Enchytraeus crypticus and Folsomia candida

The increasing global food demand is threatening the sustainability of agrifood production systems. The intensification of agricultural practices, with inadequate use of pesticides and fertilizers, poses major challenges to the good functioning of agroecosystems and drastically degrades the soil quality. Nanotechnology is expected to optimize the current farming practices and mitigate some associated impacts. Layered double hydroxides (LDHs) are a class of nanomaterials with high potential for use in agricultural productions, mostly due to their sustained release of nutrients. Considering its novelty and lack of studies on the terrestrial ecosystem, it is essential to assess potential long-term harmful consequences to non-target organisms. Our study aimed to evaluate the effect of Zn–Al–NO3 LDH and Mg–Al–NO3 LDH ageing on the survival and reproduction of two soil invertebrate species Enchytraeus crypticus and Folsomia candida. We postulated that the toxicity of nanomaterials to soil invertebrates would change with time, such that the ageing of soil amendments would mediate their impacts on both species. Our results showed that the toxicity of LDHs was species-dependent, with Zn–Al–NO3 LDH being more toxic to E. crypticus, while Mg–Al–NO3 LDH affected more F. candida, especially in the last ageing period, where reproduction was the most sensitive biological parameter. The toxicity of both nanomaterials increased with ageing time, as shown by the decrease of the EC50 values over time. The influence of LDH dissolution and availability of Zn and Mg in the soil pore water was the main factor related to the toxicity, although we cannot rule out the influence of other structural constituents of LDHs (e.g., nitrates and aluminium). This study supports the importance of incorporating ageing in the ecotoxicity testing of nanomaterials, considering their slow release, as effects on soil organisms can change and lead to more severe impacts on the ecosystem functioning.

Stacking Ni–Al and Co–Al Layered Double Hydroxide for High-Energy and High-Power Composite Electrodes

The requirement for high-power performance of secondary batteries suffering from inherent sluggish charge transfer kinetics is urgent for the expanding energy storage and conversion applications such as electric vehicles. A successful combination of high-power supercapacitors with high-energy secondary batteries in one energy storage device will meet the needs of both high power and energy density. We study the electrochemical behaviors of alternately stacked super-capacitive [Co4Al(OH)10]NO3 and [Ni4Al(OH)10]NO3 layered double hydroxide (LDH) electrodes. By cyclic voltammetry studies, the sandwich of [Co4Al(OH)10]NO3 lDH between [Ni4Al(OH)10]NO3 LDH and the Pt current collector results in the current amplification of the oxidation or reduction peaks to 4∼35 times. By galvanostatic charging/discharging, the 3-stacked Ni–Al|Co–Al|Ni–Al LDH electrode behaves better than the Co–Al|Ni–Al|Co–Al LDH electrode, exhibiting a maximal capacity, 338.1 mAh·g−1 under a current density of 1000 mA·g−1 and maintaining 288.6 mAh·g−1 within 400 cycles. It also has a much lower liquid-solid interface capacitor resistance and lower self-discharge. These results suggest that stacking in a suitable sequence contributes to high electrode performances, providing a strategy for producing energy storage and conversion devices. A synergetic charge transfer for the combination of Ni–Al and Co–Al LDH suggests that Co–Al LDH outstands as a bridge, accelerating the transfer of electrons.

Theoretical study on the mechanism of removing harmful anions from environment via Mg2Al layered double hydroxide

Environmental pollution caused by harmful anions is becoming an increasingly prominent problem and should be addressed urgently. Layered double hydroxides (LDHs) have been used as excellent adsorbents and stabilizers. Here, three removal mechanisms (surface adsorption, anion exchange and ligand exchange) of Mg2Al–NO3 LDH for 13 harmful anions (F−, Cl−, Br−, I−, ClO3−, BrO3−, IO3−, CrO42−, SeO42−, MoO42−, AsO43−, VO43−, PO43−) are investigated by density functional theory (DFT). The adsorption energy of anions on 003 and 110 surface, the Gibbs free energy change of anion exchange and ligand exchange reactions are calculated thermodynamically. It is found that both divalent and trivalent harmful anions can be removed by the above three mechanisms. All anions except I− can undergo surface adsorption, with divalent and trivalent anions preferring to interact with 110 surface and monovalent more easily adsorbed on 003 surface. Kinetically, the energy barriers of the rate–determining steps for three mechanisms are further calculated. The results indicate that all harmful anions removed by LDHs favor the surface adsorption mechanism. Anion exchange mechanism cannot occur for anions with Mulliken electronegativity and ionic potential below 1.7 eV and 5 nm−1, respectively. Generally, the higher the charge of the oxyanion, the easier the ligand exchange mechanism.

Synthesis and physicochemical characterization of Zn–Al layered double hydroxides (LDHs) as a delivery system for amphotericin B: In vitro and in silico antileishmanial study

Leishmaniasis as a widespread neglected vector-borne protozoan disease is a major public health concern in endemic areas due to 12 million people affected worldwide and 60,000 deaths annually. Several problems and side effects in using current chemotherapies leads to progression of new drug delivery systems against leishmaniasis. For instance, layered double hydroxides (LDHs) so-called anionic clays due to their proper characteristics, have been considered recently. In the present study, LDH nanocarriers were prepared using co-precipitation method. Then, the intercalation reactions with amphotericin B were conducted via indirect ion exchange assay. Finally, after characterization of prepared LDHs, the anti-leishmanial effects of Amp-Zn/Al-LDH nanocomposites against Leishmania major were evaluated using an in vitro and in silico model. According to results, current study demonstrated that Zn/Al–NO3 LDH nanocarriers can be used as a new promising delivery system by intercalating amphotericin B into its interlayer space for leishmaniasis treatment by eliminating the L. major parasites by remarkable immunomodulatory, antioxidant and apoptotic effects.

Layered Double Hydroxide for Carbon dioxide mitigation from Bitumen and formation of Carbonic acid: A Step toward Achieving Greener Pavements

ABSTRACT Carbon dioxide (CO2) emission in light of global climate change has become a burgeoning issue across several disciplines. In the transportation sector, which is a leading cause of global emissions, greenhouse gases emitted from bitumen are a significant issue. This paper aims to add to the existing literature on the use of nanoparticles in reducing CO2 emissions from bitumen. The use of layered double hydroxides (LDHs) has been investigated in this paper to evaluate the degree of their impact in reducing carbon dioxide (CO2) emissions from bitumen. To reduce the emission of CO2 from bitumen (VG 20), Calcium Aluminum Nitrate layered double hydroxide (Ca−Al−NO3 LDH) nanocomposite was synthesized, and characterized by powder XRD, FTIR, SEM, and TEM. The synthesized LDH was then checked for its efficiency for the reduction of CO2 emission in the laboratory by a simple experiment. To minimize the CO2 emission from bitumen, the LDH was applied to VG 20 grade of bitumen. Remarkably, the synthesized LDH derivatives due to their lamellar structure showed high potential for CO2 reduction at 120–160°C from bitumen at the hour of adaptable asphalt development. This was accomplished by converting the emitted carbon dioxide (CO2) into carbonic acid (H2CO3) due to the proton transfer from hydroxyl (-OH) group of the LDH. From this study, it was observed that the best reduction of CO2 without altering the fundamental properties of the bitumen was achieved at a 6% dosage of the additive (LDH) in bitumen. This alluring property of Ca−Al−NO3 layered double hydroxide (LDH) for CO2 removal from bitumen (VG 20) at high temperatures (up to 160°C) during the manufacture of flexible pavement has been reported in this study. This article, therefore, presents a novel approach of utilizing the CO2 adsorption capacity of LDHs to reduce the CO2 emissions from bitumen and addresses the worldwide challenge, to decrease the emission of carbon dioxide from fossil fuels or their derivatives.

Synthesis of CaFeAl layered double hydroxides 2D nanosheets and the adsorption behaviour of chloride in simulated marine concrete

Chloride-induced reinforcement corrosion in marine concrete structures adversely impacts its durability, which leads to the decrease of the actual service life of concrete. Three kinds of layered double hydroxides (LDHs), CaFe–NO3 LDHs (LDHs-CF), CaAl–NO3 LDHs (LDHs-CA) and CaFeAl–NO3 LDHs (LDHs-CFA), were synthesized to bind chloride. The results showed that all of the synthetized LDHs could effectively adsorb chloride from simulated concrete pore solutions (SCPSs) and artificial seawater (ASW) through the surface adsorption and ion exchange. The maximum chloride adsorption capacity of the LDHs-CFA was 3.18 mmol g−1. The adsorption process could be described by the Langmuir isotherm and pseudo-second-order kinetic models. For the chloride desorption experiments, the chloride desorption rate of the LDHs-CF (29.20%) and LDHs-CFA (39.31%) were lower than that of the LDHs-CA (47.45%), because the presence of Fe3+ in LDHs suppressed the concentration of dissolved metals, and a crystal transformation occurred to form 3CaO·Fe2O3·0.5CaSO4·0.5CaCl2·10H2O, exhibiting excellent stability for LDHs-CF and LDHs-CFA. In conclusion, LDHs show excellent chloride binding behaviour, which makes it promising to achieve the goal of high efficiency and stability of chloride binding for marine concrete by LDHs.

High-Power Ultrasonic Synthesis and Magnetic-Field-Assisted Arrangement of Nanosized Crystallites of Cobalt-Containing Layered Double Hydroxides

High-quality stoichiometric Co2Al–NO3 and Co2Al–CO3 layered double hydroxides (LDHs) have been obtained by precipitation followed by anion exchange, both high-power-sonication assisted. Application of high-power ultrasound has been demonstrated to result in a considerable acceleration of the crystallization process and the anion-exchange reaction. Two independent approaches were used to form bulk and 2-D samples of Co2Al–NO3 with the oriented crystallites, namely uniaxial pressing of deposits from sonicated LDH slurries and magnetic field-assisted arrangement of LDH crystallites precipitating on glass substrates. A convenient way of preparation of semi-transparent compacts with relatively big blocks of oriented crystallites have been demonstrated. Thin dense transparent films of highly-ordered crystallites of Co2Al–NO3 LDH have been produced and characterized.

Application of hydrotalcite in soil immobilization of iodate (IO3 -).

Radioactive iodine is quite mobile in soil and poses threats to human health and the ecosystem. Many materials, including layered double hydroxides (LDH), have been synthesized to successfully capture iodine from aqueous environments. However, limited information is available on the application of LDH in soil to immobilize iodine species. In the present study, the feasibility of using Mg–Al–NO3 LDH for retention of soil iodate (IO3−) in both batch and column systems was analyzed. The 2 : 1 Mg–Al–NO3 LDH exhibited the greatest removal efficiency of IO3− from aqueous solution, compared with 3 : 1 and 4 : 1 Mg–Al–NO3 LDH. The Mg2–Al–NO3 LDH demonstrated a strong affinity for IO3−, with a high sorption capacity of 149 528 mg kg−1 and a Freundlich affinity constant KF of 21 380 L kg−1. The addition of Mg2–Al–NO3 LDH in soil resulted in significant retention of IO3− in both the batch and column experiments. The affinity parameter KF of soil with the addition of 1.33% Mg2–Al–NO3 LDH was 136 L kg−1, which was 28.6 times higher than soil without LDH added. Moreover, the eluted iodate percentage was only 12.9% in the soil column with the 1.33% Mg2–Al–NO3 LDH addition, whereas almost 43.5% iodate was washed out in the soil column without LDH addition. The results suggested that Mg2–Al–NO3 LDH could effectively immobilize iodate in soil without obvious interference.

Synthesis of Ca-Al layered double hydroxide from concrete sludge and evaluation of its chromate removal ability

Concrete sludge is an industrial waste slurry containing hydrated cement, aggregates and water. The main components of concrete sludge are CaO, SiO2, Al2O3 and small amounts of metal oxides such as Fe2O3 and MgO. In this study, the calcium component of concrete sludge was used as a raw material for the synthesis of Ca-Al type layered double hydroxide (LDH). The chromate removal ability of the LDH was examined using a potassium chromate solution containing 180mg/L chromate. The LDH showed a high chromate removal ability with a concentration decrease of up to 0.4mg/L. The chromate is removed in the form of CrO42− by anion exchange with NO3− in the Ca-Al NO3 LDH.

Chloride absorption by nitrate, nitrite and aminobenzoate intercalated layered double hydroxides

The fabrication of Mg–Al layered double hydroxides (LDHs) intercalated with NO3 −, NO2 − and p-aminobenzoate and comparative investigation on their chloride absorption in aqueous solutions have been performed in this paper. The Mg–Al-LDHs intercalated with NO2 − and p-aminobenzoate were synthesized by anion exchange in the host materials, Mg–Al–NO3 LDH, which was prepared by a coprecipitation method. Also, the equilibrium isotherms of chloride adsorption on the as-obtained LDHs were measured. Besides, their morphologies and microstructures were observed using scanning electron microscopy, X-ray diffraction instrument, infrared spectroscopy and thermal analysis. It has been found that the as-obtained LDHs are well crystallized and have a very large distribution of size. The basal spacing of hexagonal plates is dependent on the types of intercalated anions. Langmuir isotherm is more suitable to fit the experimental data of chloride adsorption than Freundlich isotherm. Compared to Mg–Al–NO3 LDH, the maximum adsorption capacity of chloride is slightly reduced for Mg–Al–NO2 LDH, but remarkably decreased for the LDH intercalated with p-aminobenzoate anions.

Dynamic Characterization of Inter- and Intralamellar Domains of Cobalt-Based Layered Double Hydroxides upon Electrochemical Oxidation

This work investigated in situ changes in the structure of the layered double hydroxides (LDH) during electrochemical processes as well as followed the ion motion related to the charge balancing process. Electrogravimetric measurements, using an electrochemical quartz crystal microbalance (EQCM), allowed one to monitor simultaneously changes in current and in microbalance frequency when electroactive films of Co2Al–NO3 LDH were subjected to voltammetry potential cycling in alkaline solutions (0.1 M COH, C = Li+, Na+, and K+). EQCM results showed a strong dependence of the electrochemical process on the nature of electrolyte cations. Operando X-ray diffraction measurements, carried out during potential cycling of Co2Al–NO3 films in KOH electrolyte, showed the diffusion of OH– species gradually replacing NO3–. Total X-ray scattering experiments recorded ex situ on Co2Al–NO3 after successive oxidation and reduction revealed the presence of a high level of structural disorders even in the pristine material. A...

Excellent green emission of Tb3+ incorporated in MgAl–NO3 layered double hydroxides system

A series of Tb-doped MgAl–NO3 layered double hydroxides (LDHs) with Mg2+/(Al3++Tb3+) molar ratios ranging from 1.0 to 4.0 were synthesized through co-precipitation method at room temperature. X-ray diffraction (XRD) results indicated that the crystallinity of all the Tb-doped samples presented a single phase corresponding to LDHs. SEM measurement suggested that all the samples have similar morphologies. Fluorescence spectra show strong green emissions at 490 and 544nm, ascribed to the 5D4→7F6 and 5D4→7F5 transition of Tb3+, respectively. This result revealed that the MgAl–NO3 LDH system was favorable for the green emissions of Tb3+ ions.

Interlayer intercalation and arrangement of 2-mercaptobenzothiazolate and 1,2,3-benzotriazolate anions in layered double hydroxides: In situ X-ray diffraction study

2-mercaptobenzothiazole (MBT) and 1,2,3-benzotriazole (BTA) are very promising inhibitors for the corrosion protection of aluminum alloys. These inhibitors can be incorporated in protective coatings in the form of anions intercalated into interlayers of layered double hydroxides (LDHs). Capacity and performance of such LDH-nanocontainers depend on the arrangement of the anions in their interlayers. In this work, intercalation of MBT− and BTA− into Mg–Al–NO3 and Zn–Al–NO3 LDHs were studied in detail using X-ray diffraction (XRD) methods including in situ XRD. The nitrate-to-MBT(BTA) anion exchange is much faster than considered previously. Well-formed Mg–Al–MBT, Zn–Al–MBT, Mg–Al–BTA LDHs were obtained after a 20-min exchange reaction at pH 11.5 at room temperature. It was demonstrated that Zn–Al–BTA LDH cannot be obtained under the same conditions due to the reaction between BTA and the Zn–Al hydroxide layers. Substitution of nitrates by organic anions occurs with the participation of hydroxide anions. Although no intermediate LDH phase intercalated with the combination of NO3- and OH− appears, formation of the LDH–MBT and LDH–BTA phases results also in appearance of an LDH phase intercalated with OH− at the final stage of the anion exchange. In the LDH interlayer, MBT− and BTA− form a double layer in which these species have a tilted orientation against the layer plane (herringbone-like arrangement). Such an arrangement meets the LDH layer–interlayer electroneutrality and matches well with the observed values of the layer–interlayer distance.

Chloride binding of synthetic Ca–Al–NO3 LDHs in hardened cement paste

The chloride binding of synthetic Ca–Al–NO3 layered double hydroxides (LDHs) for the removal of chloride ions from pore solution of cementitious materials is studied. The Ca–Al–NO3 LDHs is synthesized and characterized by XRD, SEM, FT-IR and XRF analysis. Results of direct anion exchange tests show that chloride substitutes nitrate in the interlayer of Ca–Al–NO3 LDHs in aqueous solution and the adsorption model fits the Langmuir adsorption isotherm. Furthermore, the structural change of Ca–Al–NO3 LDHs in simulated pore solution and its transformation after binding chloride are investigated. Cement pastes with Ca–Al–NO3 LDHs are prepared with chloride solution. Microstructural analysis shows that the Ca–Al–NO3 LDHs can immobilize the chlorides in the hardened cement pastes.

A new, low-cost adsorbent: Preparation, characterization, and adsorption behavior of Pb(II) and Cu(II)

This work aimed to develop waste (i.e., sulfonated lignin) application in simulated wastewater treatment. Sulfonated lignin (LS), a byproduct of the paper industry, was intercalated into a parent host of layered double hydroxides (LDH) by swelling–restacking method. X-ray diffraction patterns of the composite confirmed that long-chain LS anions exited in the interlayer of Mg2Al–LDH in two forms: (1) a “flat” form with d003=0.88nm; and (2) a “vertical” form with d003=9.08nm. Results showed that the obtained Mg2Al–LS–LDH composite was highly selective and efficient for the removal of Pb2+ and Cu2+, especially Pb2+, compared with the NO3–LDH precursor. The coexisting cations decreased the removal efficiency of Pb2+ or Cu2+ on Mg2Al–LS–LDH composite, which could be ascribed to outer-sphere sorption style, and the effect order of cations is Li+>Ca2+>K+>Na+. The pseudo-second-order model appropriately described the sorption kinetics of Mg2Al–LS–LDH composite for Pb2+ and Cu2+. Sorption isotherms for Pb2+ and Cu2+ by the Mg2Al–LS–LDH composite were found to be more satisfactorily fitted by the Langmuir model than by the Freundlich one. With increased Pb2+ or Cu2+ concentration from 2ppm to 200ppm, the maximum absorption capacity of the composite toward Pb2+ was ∼123mg/g and that toward Cu2+ was ∼64mg/g. Therefore, a new, low-cost adsorbent was synthesized by utilizing the byproduct LS, which may be a potential remedy for Pb2+ or Cu2+ in contaminated water.

One-step synthesis of layered double hydroxide-intercalated gluconate for removal of borate

The sorption of borate by ion exchange using a traditional layered double hydroxide (LDH) is affected by external conditions such as coexisting anions. Hydrotalcite intercalated with d-gluconate (G–LDH) was synthesized through a one-step microwave-assisted treatment and characterized by XRD, TEM, FTIR, TG/DTA and two-dimensional 11B NMR. Several factors that influence sorption of borate were investigated: gluconate content in the LDH, G–LDH dosage, coexisting anions, initial pH of borate solution and sorption temperature. The synthesized adsorbent exhibited a greater borate sorption rate than the traditional hydrotalcite (NO3–LDH) or a boron-specific resin. The maximum sorption capacity was 1.27mmol/g (obtained by fitting to the Langmuir model). The G–LDH sorption density increased with increasing initial borate concentration and adsorbent dosage. In the presence of 50mM sulfate, sorption of borate by NO3–LDH significantly decreased and no obvious sorption could be observed, whereas the sorption of borate by G–LDH was maintained at ∼0.57mmol/g. 11B NMR indicated that the sorption mechanism of borate by G–LDH is mainly through bischelate and monodentate types of complexation with borate. This mechanism is similar to that of CRB05, and fundamentally different from that of NO3–LDH.

In situ formation of LDH membranes of different microstructures with molecular sieve gas selectivity

Research on interlayer gallery-based gas and liquid separation has gained widespread attention. A series of layered materials like lamellar ZSM-5, graphene and its derivatives have been fabricated into membranes showing fascinating gas/liquid separation properties. Layered double hydroxides (LDHs) are prominent representatives of layered compounds composed of regularly arranged brucite-like 2D sheets. Here we successfully prepared well-intergrown NiAl–CO3 LDH membranes in one step. Particularly it was found that CO2 dissolved in the precursor solution exerted great influence on the microstructure of prepared membranes. Trace amounts of CO2 in the precursor solution led to the formation of ab-oriented 0.6 μm thick LDH membranes, while randomly oriented 5 μm thick LDH membranes formed from CO2-saturated precursor solutions. Both ab- & randomly oriented LDH membranes showed clear size-based selectivity and H2 was found to preferentially permeate through the interlayer galleries. However, randomly oriented LDH membranes showed a much higher H2 selectivity possibly due to the decreased density of mesoscopic defects. Furthermore, in addition to the NiAl–CO3 LDH membrane, a compact and randomly oriented ZnAl–NO3 LDH membrane with reasonable gas selectivity was successfully prepared here by proper optimization of the synthesis conditions.

Intercalation of a molybdenum(0)-tetracarbonyl–bipyridine complex in a layered double hydroxide

A Zn,Al layered double hydroxide (LDH) intercalated by cis-[Mo(CO)4(bpdc)]2− anions (bpdc = 2,2′-bipyridine-5,5′-dicarboxylate) has been prepared by ion exchange of a Zn,Al–NO3 LDH precursor, and characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), FT-IR, FT-Raman and UV–Vis spectroscopies. The ion exchange method gives rise to a highly organized intercalate with up to six (00l) basal reflections in the powder XRD pattern. The interlayer spacing of 18.0 Å indicates that the material contains a monolayer of guest anions positioned in such a way that the bpdc ligands are arranged with their longest dimension roughly perpendicular to the hydroxide layers of the host. Spectroscopic studies confirm the presence of structurally intact cis-[Mo(CO)4(bpdc)]2− anions in the freshly prepared material, while also showing that the guest anions undergo slow decarbonylation over a period of several days, which is accelerated upon exposure of the material to light and air. The oxidative decarbonylation can be performed rapidly by reaction of the LDH containing intercalated tetracarbonyl complexes with tert-butylhydroperoxide, leading to intercalated molybdenum oxide/bipyridine species, which may be polymeric species of the type [MoO3(bpdc)]2−. Catalytic tests for the epoxidation of olefins and the oxidative dehydrogenation of alcohols were carried out for this material.

Swelling and Gel/Sol Formation of Perchlorate-Type Layered Double Hydroxides in Concentrated Aqueous Solutions of Amino Acid-Related Zwitterionic Compounds

ClO(4)(-)MgAl-LDH3, a MgAl (Mg/Al = 3) layered double hydroxide (LDH) containing perchlorate, swells and forms colloidal suspensions (sols) via the gel state in concentrated aqueous solutions of zwitterionic compounds related to amino acids. In total, 36 zwitterionic compounds with different molecular structures and additional functional groups were examined at various concentrations, and the sol-formation ability was judged by the transmittance (at λ = 589 nm) of the resulting suspensions. At low concentration, the obtained suspensions were turbid, with transmittances of ~0%. However, above the threshold concentration (0.3-1.0 M), osmotic swelling occurred and the transmittances of the suspensions increased sharply with increases in concentration to reach maximum values of 70-95%. The threshold concentration and maximum transmittance value depended on the structure and the location of the functional groups. The enhancement of the permittivity of water by the zwitterions and the formation of H-bond networks were assumed to be the reasons for the swelling phenomenon. Similar gel/sol formation was observed for ClO(4)(-)LDHs with Mg/Al = 2, Ni/Al = 2, 3, and Co/Al = 2 and some NO(3)(-)LDHs. Large ClO(4)(-)LDH films could be prepared by filtration of the colloidal suspensions followed by washing and drying processes.

Synthesis and characterisation of nanocrystalline Ca–Al layered double hydroxide {[Ca2Al(OH)6]NO3.nH2O}: in vitro study

In this study, Ca–Al–NO3 layered double hydroxide (LDH) nanoparticles of varying sizes were synthesised by a process involving co-precipitation under hydrothermal condition. This method produces stable homogeneous LDH suspensions under variable hydrothermal treatment conditions with particle size in the range of 7·5–2·5 μm. Layered double hydroxides were characterised by X-ray diffraction, Fourier transform infrared spectroscopy, thermal gravimetric/differential thermal analysis, scanning electron microscopy and transmission electron microscopy (TEM) and nanosizer analyses. By increasing the hydrothermal treatment time, the crystallinity and the particle size of obtained LDH increased. Scanning electron microscopy and TEM observations showed uniform hexagonal flake-like particles with high aspect ratio. Finally, Ca–Al–NO3 LDH did not show any acute cytotoxic effect up to 100 μg mL−1 as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.