Silver oxide particles/silver nanoparticles interconversion: susceptibility of forward/backward reactions to the chemical environment at room temperature

Abstract

The thermal stability of the silver oxide particles (Ag 2 O)/metallic silver nanoparticles (AgNPs) system in aqueous and gaseous environments is investigated with UV-Visible spectroscopy, TEM, SEM and DLS as characterisation techniques, and with calculations using electromagnetic theory. Thermal decomposition of aqueous Ag 2 O colloids to produce AgNPs is conclusively demonstrated and used as a base reaction to produce clean AgNPs without any external reducing agent. Such a spontaneous character of Ag 2 O decomposition in alkaline aqueous/water-enriched environments at room temperature makes the formation of silver oxide films on silver nanoparticles/nanostructures unlikely, keeping the silver surface oxide-free, a crucial feature in determining the silver catalytic and Raman enhancing properties. The synthetic suitability of this reaction to develop new routes to produce AgNPs is explored by analyzing the effect of temperature, complexing agents, and environment polarity on the AgNPs size/shape control. Thermal decomposition of Ag 2 O colloids in aqueous/ water-enriched environments offers the possibility to produce AgNPs at low cost, with easy, clean, safe and green chemistry procedures.

Synthesis of fibrinolytic active silver nanoparticle using wheat bran xylan as a reducing and stabilizing agent

“…Heating the alkaline solution of WB-xylan with silver nitrate produces a color change from pale brown to yellowish brown indicating the formation of AgNPs. The obtained result indicates that the treatment of AgNO 3 with NaOH might produce Ag 2 O which on subsequent heating produces the AgNPs (Gallardo et al, 2012). The absorption spectrum of AgNPs showed a SPR at 405 nm, indicating the formation of AgNPs, which is consistent with previous literature (Otari, Patil, Ghosh, Thorat, & Pawar, 2015).…”

Imposed Environmental Stresses Facilitate Cell-Free Nanoparticle Formation by Deinococcus radiodurans

“…Cells were grown to stationary phase, and AgNO 3 was added either to the isolated cell-free supernatant or directly to the culture (for cell-mediated experiments) and was reacted for 48 h. Nanoparticle production was observed under both conditions, as indicated by peaks at ϳ426 nm in the UV-visible (UV-vis) absorption spectrum, demonstrating that cell-free synthesis of silver nanoparticles using D. radiodurans supernatant was possible. The presence of a peak at ϳ426 nm also confirmed that the silver nanoparticles were elemental silver and not silver oxides, which exhibit a characteristic maximum near 650 nm (34). Uninoculated tryptone-glucose-yeast (TGY) medium was treated with AgNO 3 as a control, to ensure that silver reduction was exclusively due to cellular reducing factors, and it showed no evidence of nanoparticle formation.…”

Synthetic Routes for the Preparation of Silver Nanoparticles

“…Moreover, addition of NaOH is necessary to obtain the silver colloids [33]. Then, the silver species reacting could be Ag 2 O that has been recently reported as a good AgNP precursor by thermal decomposition [34].…”