Abstract
We describe herein the significance of a sodium citrate and tannic acid mixture in the synthesis of spherical silver nanoparticles (AgNPs). Monodisperse AgNPs were synthesized via reduction of silver nitrate using a mixture of two chemical agents: sodium citrate and tannic acid. The shape, size and size distribution of silver particles were determined by UV–Vis spectroscopy, dynamic light scattering (DLS) and scanning transmission electron microscopy (STEM). Special attention is given to understanding and experimentally confirming the exact role of the reagents (sodium citrate and tannic acid present in the reaction mixture) in AgNP synthesis. The oxidation and reduction potentials of silver, tannic acid and sodium citrate in their mixtures were determined using cyclic voltammetry. Possible structures of tannic acid and its adducts with citric acid were investigated in aqueous solution by performing computer simulations in conjunction with the semi-empirical PM7 method. The lowest energy structures found from the preliminary conformational search are shown, and the strength of the interaction between the two molecules was calculated. The compounds present on the surface of the AgNPs were identified using FT-IR spectroscopy, and the results are compared with the IR spectrum of tannic acid theoretically calculated using PM6 and PM7 methods. The obtained results clearly indicate that the combined use of sodium citrate and tannic acid produces monodisperse spherical AgNPs, as it allows control of the nucleation, growth and stabilization of the synthesis process.Graphical abstractᅟ
Highlights
IntroductionThe synthesis of nanoparticles (NPs) has been an important topic of research in material science due to the applications of NPs in electronics (Kamyshny et al 2011), optoelectronics (Tanabe 2007), information storage (Gupta et al 2012) as well as drug delivery systems and biosensors
We present the method of synthesis to control the size, size distribution and shape of AgNPs in a chemical reduction method using a combination of sodium citrate and tannic acid
UV–Vis spectroscopy is a sensitive method for detecting colloidal silver, because AgNPs exhibit a characteristic absorption peak at about 400 nm, which is attributed to surface plasmon excitation
Summary
The synthesis of nanoparticles (NPs) has been an important topic of research in material science due to the applications of NPs in electronics (Kamyshny et al 2011), optoelectronics (Tanabe 2007), information storage (Gupta et al 2012) as well as drug delivery systems and biosensors The preparation of AgNPs by chemical reduction is probably the most versatile method, great care must be exercised to make a stable and reproducible colloid containing spherical NPs. A typical AgNP chemical synthesis uses either tannic acid or citrate as a reducing and stabilizing agent. Control over the shape and size of AgNPs in chemical reduction is possible with the combined use of citrate and tannic acid in one synthesis (Bastus et al 2014; Rainville et al 2013). The results confirm that only with the use of two reagents—tannic acid and sodium citrate—is it possible to obtain monodisperse, spherical AgNPs. AgNPs were prepared in water by a chemical reduction method. The syntheses at room temperature were carried out by the addition of a sodium citrate and tannic acid mixture to the aqueous solution of silver nitrate. A sample was placed dropwise on a gold substrate, and following solvent evaporation, it was put on an ATR crystal, and measurements were taken
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