Layered double hydroxides (LDH) represent a class of layered compounds, also known as anionic clays or hydrotalcite-like compounds. Interest in LDH compounds has recently increased significantly due to their multifunctional structure, relatively straightforward synthesis, low cytotoxicity, good biocompatibility, and wide range of potential applications. LDHs possess a substantial surface area and the capacity to incorporate a variety of anionic materials, both organic and inorganic, into the interlayer. These modifications make LDHs promising candidates for drug delivery systems, as they can incorporate drug molecules into the interlayer and control their release into the body [1-3].
Over the past decade, research on LDH materials as potential gene and drug carriers has increased substantially, demonstrating successful intercalation of biocatalysts, anti-inflammatory drugs, and anticancer drugs. Such drug delivery systems could potentially aid in the release of poorly soluble or unstable drugs, reduce side effects such as stomach irritation, and minimize the required drug dose [3,4]. However, to develop an efficient LDH-based drug delivery system, it is first necessary to determine the optimal conditions for LDH synthesis and interlayer anion replacement.
The key objective of this research is to investigate LDH compounds synthesized by co-precipitation, with a focus on identifying the optimal synthesis conditions. The formation of LDHs is significantly influenced by the pH value during fabrication, as an inadequate pH can lead to poor purity or even the absence of LDH formation [5]. The syntheses of Zn₂Al₁-CO₃, Mg₂Al₁-CO₃, Cu₂Al₁-CO₃, and Ni₂Fe₁-CO₃ LDHs were conducted via co-precipitation at different pH ranges (from 8 to 12 ± 0.2). The reactions were carried out using appropriate metal nitrate solutions and different bases, depending on the desired pH for synthesis. The resulting crystals were filtered, washed with water until reaching a neutral pH, and dried in an oven at 80 °C for 24 hours.
The crystal structure and morphological properties were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Based on the XRD data obtained, the optimal pH values for LDH synthesis were determined as follows: Zn₂Al₁-CO₃ – pH 10-12, Mg₂Al₁-CO₃ – pH 10-12, Cu₂Al₁-CO₃ – pH 8-9, and Ni₂Fe₁-CO₃ – pH 9-10.