Abstract

This study demonstrates the effect of (co)intercalated anion compositions on nanostructure evolution to understand the formation mechanisms of layered double hydroxide (LDH) nanoparticles following coprecipitation and hydrothermal treatments (HT). Initially, the room temperature coprecipitation resulted in amorphous primary nanoparticles that agglomerated at the edges due to low surface charge densities. The reversibility of such agglomeration was determined by the crystalline quality upon HT and consequent surface charge density, which in turn were strongly influenced by the composition of the intercalated anions. Upon crystallization, the agglomerated Zn<inf>2</inf>Al(OH)<inf>6</inf>(NO<inf>3</inf>)<inf>0.3</inf>(CO<inf>3</inf>)<inf>0.35</inf>{dot operator}xH<inf>2</inf>O primary nanoparticles re-dispersed, but the Zn<inf>2</inf>Al(OH)<inf>6</inf>(NO<inf>3</inf>){dot operator}xH<inf>2</inf>O nanoparticles with much lower stability and higher disorder (especially at the edges) exhibited irreversible agglomeration, and transformed into secondary nanoparticles via aggregational growth. Additionally, the stability studies on Zn<inf>2</inf>Al(OH)<inf>6</inf>(NO<inf>3</inf>)<inf>y</inf>(CO<inf>3</inf>)<inf>0.5(1-</inf><inf>y</inf><inf>)</inf>{dot operator}xH<inf>2</inf>O nanoparticles (y=0-1) showed that the size difference between the cointercalated anions caused phase separation when 0.9≥y≥0.6, leading to bimodal size distributions. Moreover, the coarsening rates were controlled through the cointercalated anion compositions. By gradually varying the ratio of cointercalated NO<inf>3</inf><sup>-</sup> to CO<inf>3</inf><sup>2-</sup>, monodispersed Zn<inf>2</inf>Al(OH)<inf>6</inf>(NO<inf>3</inf>)<inf>y</inf>(CO<inf>3</inf>)<inf>0.5(1-</inf><inf>y</inf><inf>)</inf>{dot operator}xH<inf>2</inf>O (0.5≥y≥0) nanoparticles with systematic variation in the particle size of ~200-400nm were obtained after HT at 85°C for 12h.

Original languageEnglish (US)
Pages (from-to)160-168
Number of pages9
JournalJournal of Colloid and Interface Science
Volume458
DOIs
StatePublished - Nov 5 2015

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Keywords

  • Controlled synthesis
  • Formation mechanism
  • Layered double hydroxide nanoparticle
  • Phase separation
  • Surface energy

ASJC Scopus subject areas

  • Surfaces, Coatings and Films
  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Colloid and Surface Chemistry

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