Exploring a surface-capping role of carboxymethyl cellulose for the synthesis of silver nanoparticles via the induction period in a catalytic hydrogenation

The present study reported a dual role as a reducing agent and a stabilizer of carboxymethyl cellulose (CMC), a natural origin biopolymer, for the synthesis of silver nanoparticles (AgNPs) via a chemical reduction method. The operating parameters were optimized and established involving pH, reaction time, reaction temperature, AgNO3 molar concentration, CMC/Ag molar ratio. The formation of monodisperse AgNPs in the assistance of a CMC surface-capping agent thanks to an electrostatic stabilization effect were evidenced by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscope (TEM). The aqueous solution consisting of AgNPs in roughly spherical shape with a mean particle size of 24.3 nm was stable in ambient condition at least 2 months. The role of CMC as a surface-capping agent was also explored via the catalytic hydrogenation of methyl orange (MO) towards aromatic amines in the presence of NaBH4 at room temperature, revealing the induction period of 12 min before accelerating reaction rate in the next 18 min. At room temperature, such a catalytic hydrogenation of MO in water obeyed the pseudo first-order kinetic model with a rate constant of 0.2435 min−1 using 2.5 ppm CMC-capped AgNPs catalyst, and the reuse performance was remained in 5 consecutive cycles. To sum up, the present work shed light on a surface-capping role of carboxymethyl cellulose for the synthesis of silver nanoparticles by both physicochemical and catalytic studies.