The effect of substitution of zinc with aluminium in the brucite-like layers on the physicochemical properties of zinc-aluminium-layered double hydroxide-pamoate nanocomposite

Abstract

Layered organic–inorganic hybrid materials of Zn-Al-layered double hydroxide (LDH)-pamoate nanocomposite (ZAPR) were prepared using various initial Zn/Al molar ratios (R_i) from 8:1 to 2:1 which gave initial values of A³⁺/(Zn²⁺ + Al³⁺) mole fractions, (x_i) from 0.11 to 0.33. The Al³⁺ mole fractions in the resulting nanocomposite material (x_f) were greater than x_i and the difference between x_i and x_f was found to be a constant value of 0.03. The increase in the x_f values will increase the Al³⁺ content in the interlayer spaces of layered double hydroxide and therefore increases the charge density of the inorganic brucite-like layers and give stronger electrostatic attraction between the excess positive charge of Al³⁺ and the negative charge of the interlayer pamoate anion and hence decreases the d value of the material. However, the BET surface area of the resulting materials will decreases when the x_f is increased. This shows that the mole fraction of Zn²⁺ replaced by Al³⁺ in the inorganic brucite-like layer plays an important role in controlling the physicochemical properties of the resulting material, which is particularly useful in determining tailor-made property required in the designed material.