RESUMO
Based on a green chemistry mechanism, small silver clusters were obtained by using biosynthesis with alfalfa (medicago sativa), controlling the size of the nanoparticles base don different pH conditions. The analysis of the samples was made with help of transmission electron microscopy methods, mainly with high angle annular dark field and high resolution transmission electron microscopy. The optimal conditions were identified when the sample was obtained at pH10, which allowed obtaining an average size of 4.09 nm and a standard deviation of 1.59, mainly based on cubic like structures.
Assuntos
Química Verde/métodos , Nanopartículas Metálicas/química , Prata/química , Interpretação Estatística de Dados , Concentração de Íons de Hidrogênio , Medicago sativa/química , Medicago sativa/metabolismo , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Transmissão , Oxirredução , Prata/metabolismoRESUMO
Bimetallic Pd/Pt nanoparticles were synthesized by bio-reduction method. The structural characterizations were performed by high resolution transmission electron microscope and energy dispersive spectroscopy. The size distribution, shapes, structures and elemental distribution were studied for the synthesized samples. Molecular simulation methods based on quantum mechanics have been applied to acquire the further information on their structural stability, electronic properties etc. The results show that the particle size for the pH = 4 was bimodal with an average particle size of 3.2 nm and a variance of 1.8 nm. While for pH is 7 the average is 3.9 nm about the variance increase up to 3.7 nm, and larger particles can be found. By the HREM micrographs, it is identified fcc-like clusters with a few planar defects, which may be pure Pd or Pt, or bimetallic Pd/Pt. Theoretically the most stable configuration corresponds to the Pd18Pt37 eutectic-like structure, which implies a cluster in cluster form.
