Green Synthesis of Silver Nanoparticles with Size Distribution Depending on Reducing Species in Glycerol at Ambient pH and Temperatures

Abstract

With an increase in biodiesel demand, a large surplus of glycerol is expected, and there is interest regarding the usage of glycerol as a value-added product. One such idea is to use glycerol as a “green solvent” to replace petroleum-based organic solvents. Glycerol is nontoxic to humans, and its vapor pressure is sufficiently high for the chemical reaction to be performed at high temperatures under ambient atmospheric pressures. Its dielectric constant is between those of water and organic solvents, and it dissolves widely varying materials, spanning between salts and organic molecules. Metal nanoparticles have been known to be synthesized in glycerol within limited experimental conditions, including high temperatures, alkaline pH conditions, and the irradiance of ultraviolet light. Herein, we report that silver nanoparticles have been formed in glycerol under completely green conditions (e.g., room temperature, neutral pH conditions, and without irradiance of ultraviolet light). We suggest that aldehydes and free radicals are generated in glycerol, which is operating as reducing species.

Room-Temperature Polyol Synthesis of Ag/SiO2 Nanocomposite as a Catalyst for 4-Nitrophenol Reduction

“…Figure 6 shows that when there is no SiO 2 , the reduction of Ag + ions occurs at a very slow speed. Although it was reported that silver ions are reduced by solely glycerol at RT [25], our result indicates that the presence of SiO 2 facilitates the formation of AgNP. is means there are interactions between SiO 2 and glycerol that contributed to the reduction of silver ions and stabilization of the produced AgNP/ SiO 2 nanocomposite.…”

“…UV-vis spectrum of SiO 2 dispersion shows strong absorption in the UV region due to the presence of SiO 2 . e spectrum of the reaction mixture after 2 h shows a broad peak developing at 400 nm, indicating the formation of AgNP [25].…”

“…However, most of them require harsh conditions, such as high temperatures, UV irradiation, or alkaline medium. Our literature survey found only one published comprehensive research dealing with the polyol synthesis of AgNP at RT and pH [25]. e authors concluded that there can be two possible reducing species in glycerol: (i) glyceraldehyde in old glycerol, which produced Advances in Materials Science and Engineering a grey solution with large and polydispersed AgNP (94 ± 36 nm) and (ii) free radicals in new glycerol, which produced a yellow solution with small and monodispersed AgNP (24 ± 11 nm).…”

“…Most AgNP syntheses using the polyol approach require high temperatures, ultraviolet irradiation, or alkaline medium [22][23][24]. Very few studies use the polyol synthesis at ambient pH and temperature, which are desirable conditions for green processes [25].…”

Enhanced Reaction Rate via Different Mechanisms for the Synthesis of Silver Nanoparticles in Glycerol by Eco‐friendly Manipulations

“…It has been reported that various metal nanoparticles ( e.g ., gold, silver, copper, and platinum) can be synthesized in glycerol at high temperatures, 6–11 or at room temperature under highly alkaline conditions 12–18 . In a recent study, we demonstrated that high temperatures and alkaline conditions are not necessary for the synthesis of silver nanoparticles in glycerol 19 . We discovered that silver nanoparticles can be synthesized at room temperature (~298 K) with neutral pH conditions and without exposure to light (termed in “ambient conditions” hereinafter) by simply dissolving silver nitrate in glycerol and waiting for a certain period of time (usually several days).…”