Síntese de nanopartículas de prata estabilizadas por carboximetilcelulose e avaliação da atividade catatílica

Abstract

The use of nanomaterials is increasingly expanding, mainly the use of metallic nanoparticles (M-NPs), in the application of industrial catalytic processes or in laboratory research. Silver nanoparticles (AgNPs) have excelled as excellent nanocatalysts due to their diverse properties of high surface area, low cost and easy procedure of synthesis. Thus, the main objective of this work is the preparation and characterization of AgNPs, through of the Green Synthesis, using stabilizing and reducing agents, which are benign to the human and environment, for further evaluation of the catalytic capacity of the same. The catalytic evaluation will be by reducing the p-nitrophenol (4-Nip). To achieve this objective, carboxymethylcellulose (CMC) used as a stabilizing agent and glucose as a reducing agent. Univariate experimental design was applied and based on the information obtained from the Surface Plasmon Resonance band (SPR) characteristic of AgNPs, the best conditions for the synthesis of AgNPs / CMC were defined. The synthesized AgNPs/CMC were characterized by UV-Vis absorption spectrometry, transmission electronic microscopy (TEM) and total reflection X-ray fluorescence spectrometry (TXRF). As a result UV-Vis and MET, were obtained AgNPs/CMC with absorbance of approximately 400 nms, with sizes of 19 and 14 nm, before and after the purification process, respectively, and good polydispersity. As a result of TXRF was obtained a concentration of 0.2746 mmol L-1 AgNPs/CMC. In the evaluation of the catalytic efficiency of the NPs in the 4-Nip reduction reaction with sodium borohydride (NaBH4), the AgNPs/CMC obtained the value of 0.18 s-1 m2 L as catalytic constant kL (rate constant normalized to the surface area of the NPs per volume unit), which is considered a good. In the study of the 4-Nip reduction reaction kinetics, it is suggested that the new synthesized nanocatalyst follows the Langmuir-Hinshelwood heterogeneous catalysis kinetic model, where the reagents participating in the reaction are adsorbed on the catalyst surface before the reaction occurs, however, the AgNPs/CMC did not show a good value for the catalytic constant kL.