Porous lanthanide oxides via a precursor method: morphology control through competitive interaction of lanthanide cations with oxalate anions and amino acids.

Porous lanthanide oxides were fabricated by a precursor-thermolysis method. The precursors were synthesized by a hydrothermal reaction with lanthanide (La, Ce, Pr and Nd) salts, sodium oxalate and asparagine (or glutamine). Under hydrothermal conditions asparagine and glutamine exhibited greatly different complexation abilities with lanthanide cations. The competitive interactions of lanthanide cations with oxalate anions and asparagine (or glutamine) gave rise to the formation of precursors with different structures and morphologies. ESI-MS detection further confirmed the different complexation abilities of asparagine or glutamine with lanthanide cations at the molecular level. Variation of oxalate anion concentration or the pH value of the reaction solution could tune the morphology of the products. After calcination, porous lanthanide oxides were obtained with the morphologies of their corresponding precursors. Our work suggests that the complexation ability of organic molecules with metal cations could be a crucial factor for morphological control of the precursors. Moreover, considering the diversity of organic additives and metal salts, other metal oxides with complex composition and morphology could be fabricated via this organic molecule-modified precursor method.

Fabrication of lanthanide oxide microspheres and hollow spheres by thermolysis of pre-molding lanthanide coordination compounds.

A series of lanthanide oxide microspheres and hollow spheres have been fabricated by thermolysis of corresponding lanthanide coordination compounds formed via bottom-up self-assembly.

Effect of alcohol on morphology and mesostructure control of anionic-surfactant-templated mesoporous silica (AMS).

In the synthesis of anionic-surfactant-templated mesoporous silica (AMS), the effects of alcohols have been investigated for the first time. Without the addition of extra alcohols, spherical mesoporous silica with radially oriented mesopores could be obtained through the anionic surfactant templating route. By using alcohols with different carbon chain length such as ethanol, n-butanol, hexanol and 1-octanol as the additives, different morphologies and mesostructures of mesoporous silica were obtained. It was found that both the types and concentrations of alcohols in the synthesis solution could tune the morphologies and mesostructures of the AMS, giving rise to the formation of hexagonal mesoporous discs and particles with novel multi-layered inner structure. In general alcohol with appropriate carbon chain length such as n-butanol and hexanol could act as the co-surfactant in the synthesis of mesoporous silica templated by anionic surfactant.

Anionic surfactant-templated mesoporous silica (AMS) nano-spheres with radially oriented mesopores.

Mesoporous silica nano-spheres with pore size larger than 3 nm were synthesized using an anionic surfactant as the template. These nano-spheres possess centrosymmetric radial mesopores (emanating from the spherical center to the exterior surface) and form stable suspension. The spherical size and mesostructure can be finely tuned by changing the pH value of the synthetic system in the range of 8.8 to 6.4. In addition, when the pH value was decreased to 5.8, instead of spheres, anisotropic morphologies such as elliptical, peanutlike and trifurcate particles were obtained, exhibiting core/shell structure due to the different orientations of the mesopores in the core and the shell of the particles. It is proposed that the evolution of the morphologies and mesostructures of the products templated by anionic surfactants strongly depend on the pH value of the synthetic system.