Contradictory Dual Effects: Organothiols Can Induce Both Silver Nanoparticle Disintegration and Formation under Ambient Conditions

Abstract

Using propanethiol (PrT), 2-mercaptoethanol (ME), glutathione (GSH), and cysteine (Cys) as model thiols, we demonstrated herein that organothiols can induce both silver nanoparticle (AgNP) disintegration and formation under ambient conditions by simply mixing organothiols with AgNPs and AgNO 3 , respectively. Mechanistically, organothiols induce AgNP disintegration by chelating silver ions produced by ambient oxygen oxidizing the AgNPs, while AgNP formation in AgNO 3 / organothiol mixtures is the result of organothiols serving as the reducing agent. Furthermore, surface-plasmon-and fluorescent-active AgNPs can be interconverted by adding excess Ag + or ME into the AgNP-containing solutions. Organothiols can also reduce gold ion in HAuCl 4 /organothiol solutions into fluorescence-and surfaceplasmon-active gold nanoparticles (AuNPs), but no AuNP disintegration occurs in the AuNP/organothiol solutions. This work highlights the extraordinary complexity of organothiol interactions with gold and silver nanoparticles. The insights from this work will be important for AgNP and AuNP synthesis and applications.

Kinetic monitoring of glutathione-induced silver nanoparticle disintegration

“…After adding GSH to the silver nanoparticles in a molar ratio of 1 to 5 (silver atoms to GSH molecules), the mixture was incubated at a temperature of 21°C. According to literature, 11 we expected that GSH continuously etches the silver nanoparticles, resulting in a decreasing radius and finally in their dissolution. SAXS was employed to follow the etching process over a period of 240 h. Radii distributions of the particles and their volume concentrations were determined from SAXS data with the help of a Monte Carlo method.…”

“…Furthermore, GSH was also found to induce the disintegration of silver nanoparticles. 11 Unfortunately, the role of GSH in particle formation, stabilisation, and disintegration is presently unclear and, therefore, a subject of current research. In this context, it is the aim of our study to understand the fate of silver nanoparticles in the presence of GSH.…”

“…It has been reported in literature that silver nanoparticles can be nucleated from silver-GSH salts, which are formed by combination of silver ions and GSH in aqueous solution. 11 Similarly, this model can be adapted for the generation of GSH-stabilised silver particles through etching of p large and subsequent silver nanoparticle formation of p small . The change of the specific surface area of p small as a function of time can be quantified with the exponential function S V;small ðtÞ ¼ S V;small ð1Þ Á ð1 À e ÀkÁt Þ ð 3Þ…”

“…22 The observed increase of the specific surface area can be explained mechanistically in analogy to silver nanoparticle formation from aqueous solutions of GSH and silver nitrate reported in literature. 11 For consistency check, it is of interest to calculate the theoretically possible maximum value of the particle surface as…”

PEI/Ag as an Optical Gas Nano-Sensor for Intelligent Food Packaging

“…The following immersion of modified PEI to a silver nitrite solution results in the exchange of the potassium ions to silver ions [6]. When the PEI substrate with adsorbed silver ions is exposed to 2-ME, the organothiols can reduce silver ions to Ag NPs [9]. The change of the color of the PEI/Ag film and absorbance were monitored and recorded for three hours.…”