In Situ Growth and Interlayer Modulation of Layered Double Hydroxide Thin Films from a Transparent Conducting Oxide Precursor

Abstract

Layered double hydroxides (LDHs) are a class of cationic-layered solids that can be synthetically designed for a variety of advanced functions. Facile thin film growth of LDHs is an important requisite for a variety of applications including functional coatings, displays, and sensing. In this work we demonstrate, for the first time, an in situ and patternable thin film synthesis of interconnected Zn–Cr LDH particles from a transparent conducting oxide precursor, aluminum-doped zinc oxide, at room temperature within minutes. Synthetic parameters such as chromium­(III) nitrate concentration, solvent composition, and reaction time were found to significantly affect the thickness and morphology of the resulting LDH films. These LDH thin films can undergo interlayer anion exchange, which modulates the interlayer distance of the LDH sheets and surface energy of the thin film. Replacement of the interlayer anion with perfluorooctanoate increases the interlayer sheet distance from 0.9 to 2.8 nm and induces a super-hydrophobic thin film that is capable of adsolubilizing and retaining organic guest molecules. The synthetic method and structural analysis of the LDH thin films introduced in this work opens new avenues of application for LDH films.

A Comparison of Nitrate Release from Zn/Al-, Mg/Al-, and Mg–Zn/Al Layered Double Hydroxides and Composite Beads: Utilization as Slow-Release Fertilizers

“…Although all of the prepared LDH materials showed a crystalline nature, Mg/Al LDH and Mg–Zn/Al LDH presented peak broadening for reflections. According to Ellis et al, disordered anions in the interlayer region that exist at various angles relative to the hydroxide sheets will result in the broadening of XRD peaks while well-ordered anions perpendicular to the hydroxide sheets will make sharp, intense peaks. The peak broadening could also be attributed to a structural disorder like stacking faults or Scherrer’s broadening due to smaller crystallites leading to a decrease in crystallinity .…”

“…A similar d-spacing of 8.84 Å was reported for nitrate Zn−Al LDH by Mahjoubi et al, 44 where the synthesis was done by coprecipitation method using NaOH in the presence of excess nitrate anions. Shafigh et al 45 prepared Zn−Mg/Fe LDH with nitrate in the interlayer and observed a basal d-spacing of 8. , 47 disordered anions in the interlayer region that exist at various angles relative to the hydroxide sheets will result in the broadening of XRD peaks while well-ordered anions perpendicular to the hydroxide sheets will make sharp, intense peaks. The peak broadening could also be attributed to a structural disorder like stacking faults or Scherrer's broadening due to smaller crystallites leading to a decrease in crystallinity.…”

Efficient and Rapid Synthesis of a Solvent and Ion-Responsive Luminescent Copper 2-Aminoterephthalate Thin Film

“…Importantly, thin film growth was only observed on the AZO-coated portion of the substrate, minimizing waste. We have previously demonstrated that AZO, upon exposure to cations, can rapidly convert to HDS , and layered double hydroxide (LDH) structures, making it a well-suited substrate for templating the growth of coordination polymer films. AZO was also selected due to its conductivity and visible-range optical transparency, which has enabled its widespread use as a versatile sensing material. , Copper was selected as the coordination polymer metal center due to the demonstrated ability of Cu 2+ ions to rapidly form HDSs (and, by extension, Cu-containing coordination polymers) with zinc oxide , and AZO, , a process which is influenced by the low solubility product constant of Cu­(OH) 2 relative to other metal­(II) hydroxides. , 2-ATA is a common linker used in luminescent coordination polymers, − including those comprised of copper metal centers, , and therefore is a logical candidate linker for developing luminescent films.…”

“…Importantly, thin film growth was only observed on the AZOcoated portion of the substrate, minimizing waste. We have previously demonstrated that AZO, upon exposure to cations, can rapidly convert to HDS 7,16 and layered double hydroxide (LDH) 24 structures, making it a well-suited substrate for templating the growth of coordination polymer films. AZO was also selected due to its conductivity and visible-range optical transparency, which has enabled its widespread use as a versatile sensing material.…”

“…25,26 Copper was selected as the coordination polymer metal center due to the demonstrated ability of Cu 2+ ions to rapidly form HDSs (and, by extension, Cu-containing coordination polymers) with zinc oxide 27,28 and AZO, 7,16 a process which is influenced by the low solubility product constant of Cu(OH) 2 relative to other metal(II) hydroxides. 24,29 2-ATA is a common linker used in luminescent coordination polymers, 30−32 including those comprised of copper metal centers, 33,34 and therefore is a logical candidate linker for developing luminescent films.…”