Evolution of Silver Nanoparticles within an Aqueous Dispersion of Nanosized Zeolite Y: Mechanism and Applications

Abstract

Stable aqueous dispersion of silver ion-exchanged nanozeolite Y was reacted with the three common dihydroxyphenols, hydroquinone, catechol and resorcinol. With hydroquinone and catechol, there was rapid reduction of the intrazeolitic silver to form metallic silver with complete destruction of the zeolite framework. Resorcinol, the weakest reducing agent amongst the group behaved differently. The formation of metallic silver was considerably slower, and the zeolite framework was mostly intact. This made it possible to examine the evolution of silver cluster formation with optical spectroscopy and transmission electron microscopy. In the first 135 min of reaction, extinction/fluorescence spectroscopy indicates the formation of Ag n<4 and Ag n>4 clusters. The smaller clusters disappear more rapidly with time. For the 1 hr reduced sample, transmission electron microscopy showed uniform distribution of 1.4 nm Ag particles throughout the zeolite.After 2 hr of reduction, the average size of the particles was 2.5 nm, and a fraction of these particles appeared on the zeolite surface. With further time of reduction (3-24 hr), more of the intrazeolitic Ag migrated to the surface, and Ostwald ripening into larger nanoparticles (> 3 nm) was observed at the zeolite-solution interface. We propose that the slow growth of the silver prevented the destruction of the zeolite framework. Two factors are considered important for the slow growth of silver with resorcinol. First, resorcinol is a weak reducing agent. Second, and more importantly, the intrazeolitic pH drops upon initial silver reduction, as measured by an acidochromic dye, which raises the reduction potential of resorcinol, thereby arresting further reduction and particle growth. By removing the resorcinol at any stage of the reduction, stable Ag nanoparticles on nanozeolite samples can be isolated. Such samples were investigated as SERS substrates as well as a heterogeneous

Nanosilver as a new generation of silver catalysts in organic transformations for efficient synthesis of fine chemicals

“…Besides, recent progress in this context further supported the importance of such a reaction in the evaluation of catalytic activity of silver nanoparticles, which showed great potential for practical application in water treatment. 15 Poly(ethylene oxide propylphosphonamidate) (PEOPPA)-supported nanosilvers, 16 metal-organic framework-based silver nanoparticles, 17 semi-IPN hydrogel-based silver nanoparticles, 18 bimetallic gold/silver core-shell nanoparticles or other Ag-based bimetallic nanoparticles, 19 zeolite Y-dispersed silver nanoparticles, 20 silver/reduced graphene oxide or N-doped graphene hybrid nanocomposites, 21 superparamagnetic silver/halloysite nanotube/Fe 3 O 4 nanocomposites, 22 silver nanoparticles supported on polymer material, 23 etc., have been designed and prepared for the reduction of 4-nitrophenol, which happens to be a hot topic for nanocatalysis. However, most of the research studies for this reaction only deal with the simple examination of various silver nanoparticles that supported various types of inorganic or organic supports.…”

Effect of Chlorine-Containing VOCs on Silver Migration and Sintering in ZSM-5 Used in a TSA Process

“…The instability of the nanometer-sized silver particles due to their tendency to migrate and aggregate irreversibly into larger nanoparticles is, however, a recurrent problem. The use of confining scaffolds, such as zeolite-type material, is often reported in the literature as an efficient solution to overcome particle migration at the surface and eventually grows, leading to a loss of performances [18,19]. Nevertheless, over the course of a pilot-scale study of the TSA process on site, we observed a drop in adsorption capacity that was concomitant with the appearance of AgCl and an apparent growth of silver nanoparticles at the zeolite surface.The objectives of this study are (i) to determine why xenon adsorption capacity decreases, with a special focus on understanding the origin and role of Cl; (ii) to study regeneration parameters that can restore the adsorption capacity; and (iii) to validate the regeneration process in the context of a cyclic TSA process in relevant conditions.…”

Fabrication of zeolite/polymer multilayer composite membranes for carbon dioxide capture: Deposition of zeolite particles on polymer supports

“…Zeolite Y particles of roughly two sizes, 200 nm and 40 nm, were synthesized. The procedures used to prepare and characterize these particles are detailed in the recent dissertation work conducted at The Ohio State University [39] and in the related publication [40]. The synthesis of smaller zeolite particles of roughly 40 nm size was based on prior work by Holmberg et al [41].…”