Rapid direct growth of Li-Al layered double hydroxide (LDH) film on glass, silicon wafer and carbon cloth and characterization of LDH film on substrates

This work presents a novel method for directly growing highly oriented Li-Al LDH films on substrates such as glass, Si wafer and carbon cloth in an aqueous alkaline Al3+- and Li+-containing solution. The substrate samples were each hanged and then respectively immersed in the solutions at 5-35 degrees C for 20 min or less than 6 h to form the LDH films. The Li-Al LDH film comprised of extra-high-density Li-Al LDH platelets, each standing almost perpendicularly on the surface of the substrate. The LDH film that was fabricated at 5 degrees C (similar to 1.4 mu m thick) exhibits good UV shielding (with only 9.7% UV transparency) and a maximum of 56% transparency to visible light. A more rapid method (only 20 min needed) can be utilized to develop a Li-Al LDH film to cover both hydrophobic and hydrophilic carbon cloth surfaces. Despite the modification of these surfaces, the Li-Al LDH film on carbon cloths retained or enhanced their original surface properties (including hydrophobicity or hydrophilicity). The LDH film thickness increased with immersion time and/or solution temperature. The thickness reached a plateau during LDH formation. CO2 in the atmosphere dissolved in the alkaline Al3+- and Li+-containing solution, yielding CO32- ions for Li-Al LDH formation. The heterogeneous nucleation and growth of each LDH platelet on the substrate surface finally produced an LDH film.