Experimental and theoretical investigation of ligand effects on the synthesis of ZnO nanoparticles

ZnO nanoparticles with highly controllable particle sizes(less than 10 nm) were synthesized using organic capping ligands in Zn(Ac)2 ethanolic solution. The molecular structure of the ligands was found to have significant influence on the particle size. The multi-functional molecule tris(hydroxymethyl)-aminomethane (THMA) favoured smaller particle distributions compared with ligands possessing long hydrocarbon chains that are more frequently employed. The adsorption of capping ligands on ZnnOn crystal nuclei (where n = 4 or 18 molecular clusters of(0001) ZnO surfaces) was modelled by ab initio methods at the density functional theory (DFT) level. For the molecules examined, chemisorption proceeded via the formation of Zn...O, Zn...N, or Zn...S chemical bonds between the ligands and active Zn2+ sites on ZnO surfaces. The DFT results indicated that THMA binds more strongly to the ZnO surface than other ligands, suggesting that this molecule is very effective at stabilizing ZnO nanoparticle surfaces. This study, therefore, provides new insight into the correlation between the molecular structure of capping ligands and the morphology of metal oxide nanostructures formed in their presence

The role of the formamide/zirconia system in the synthesis of nucleobases and biogenic carboxylic acid derivatives

We describe the one-pot synthesis of a large variety of nucleic acid bases and related compounds from formamide in the presence of zirconium minerals as catalysts. The major products observed are: purine, 2-hydroxy pyrimidine, 5-hydroxy pyrimidine, isocytosine, adenine, urea, and carbodiimide. The synthesis of low molecular weight amides and carboxylic acid derivatives (intermediates of extant metabolism) was also observed: glyoxylamide, glycolic-, lactic-, succinic-, oxalic-, fumaric-, and maleic acids. As the major problem in the origin of informational polymers is the instability of their precursors, we also investigated the effects of zirconia minerals on the stability of ribooligonucleotides in formamide and in water. The relevance of these findings with respect to the origin of informational polymers and primordial metabolism is discussed. © 2010 Springer Science+Business Media, LLC