pH Sensitive Organic–Inorganic Layered Nanomaterials by Self-Assembly of Indigocarmine Between the Inorganic Layers

New pH sensitive organic–inorganic intercalation compounds having different interlayer spacing were prepared. Zn–Al layered double hydroxide (LDH)is an anion exchangeable inorganic layered compound whose interlayer spacing is 0.76 nm. In the reactions of indigocarmine (IDC) with the calcined Zn–Al LDH at pH = 7 (LDH-IDC7), interlayer spacing increased to 2.25 nm. The interlayer spacing of LDH-IDC7 decreased to 1.89 nm by the treatment in basic solution. In the reaction of IDC with the calcined Zn–Al LDH at pH = 10 (LDH-IDC10), interlayer spacing of the intercalation compounds was 1.89 nm. The interlayer spacing of these intercalation compounds was changed reversibly by the treatments in acidic or basic solution.