Existence of a Precipitation Threshold in the Electrostatic Precipitation of Oppositely Charged Nanoparticles

Abstract

Oppositely charged nanoparticles precipitate rapidly only at the point of electroneutrality, wherein their charges are macroscopically compensated. We investigated the aggregation and precipitation of oppositely charged nanoparticles at concentrations ranging from 10 to 10−3 mm (based on gold atoms) by using UV/Vis measurements. We employed solutions of equally sized (4.6 nm) gold nanoparticles, which were functionalized and stabilized with either positively or with negatively charged alkanethiols. Results showed that oppositely charged nanoparticles do not precipitate if their concentration is below a certain threshold even if the electroneutrality condition is fulfilled. This finding suggests a universal behavior of chemical systems comprising oppositely charged building blocks such as ions and charged nanoparticles.

Turn-On Selectivity in Inherently Nonselective Gold Nanoparticles for Pb2+ Detection by Preferential Breaking of Interparticle Interactions

“…This is due to an ionic-like sharp precipitation of [+] and [−] AuNPs at the charge neutrality (i.e., when Σ Q[+] + Σ Q[−] = 0), confirming the formation of [+]–[−] Au nanoionic precipitates . The nanoionic precipitation occurred, under stirring, well beyond the threshold values as reported by Istvan and co-workers …”

Pattern Formation in Precipitation Reactions: The Liesegang Phenomenon

“…It was presented that banded structures can be obtained in the precipitation process of oppositely charged nanoparticles . Diffusion and electrostatic attraction (and vdW interaction) between the oppositely charged nanoparticles generate the periodic precipitation of nanoparticles showing the universality of this phenomenon. , Recently, it was proven for nanosystems that oppositely charged nanoparticles precipitate only if their concentration reaches a threshold (precipitation) concentration . The existence of this threshold is a key ingredient in producing spatially periodic precipitation structures in either ionic or nanoscopic systems.…”

Evolution of Micron-Spaced Patterns within Precipitating Patterns of In Situ Synthesized Silver Nanoparticles in a Nanodot-Embedded PVA/PVP Film

“…To overcome the above limitation present in ionic species, we wished to investigate a novel Liesegang mechanism involving the in situ formation of metallic nanoparticles in a thin polymer film. The precipitation behavior of presynthesized oppositely charged nanoparticles has been investigated in millimeter-thick agarose gel. , Very recently, the precipitation behavior of silver nanoparticles (Ag NPs) has been studied by enabling the contact of agarose gel doped with silver ions with the surface of gelatin containing a reducing agent . Moreover, periodic patterns of plasmonic nanoparticles are of greater importance due to their application in surface plasmon resonance (SERS)-based sensors, electrochemical energy storage, and others. , In this work, commonly used polymer films, polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), are chosen to investigate the pattern formation.…”

“…The precipitation behavior of presynthesized oppositely charged nanoparticles has been investigated in millimeter-thick agarose gel. 20,21 Very recently, the precipitation behavior of silver nanoparticles (Ag NPs) has been studied by enabling the contact of agarose gel doped with silver ions with the surface of gelatin containing a reducing agent. 22 Moreover, periodic patterns of plasmonic nanoparticles are of greater importance due to their application in surface plasmon resonance (SERS)-based sensors, electrochemical energy storage, and others.…”