Dissecting Colloidal Stabilization Factors in Crowded Polymer Solutions by Forming Self-Assembled Monolayers on Gold Nanoparticles

Abstract

An ideal colloidal system should be highly stable in a diverse range of buffer conditions while still retaining its surface accessibility. We recently reported that dispersing citrate-capped gold nanoparticles (AuNPs) in polymers such as polyethylene glycol (PEG) can achieve such a goal due to contributions from depletion stabilization. Since AuNPs can weakly adsorb PEG to exert steric stabilization and the remaining citrate can impart charge stabilization, the extent of the contribution of depletion stabilization is unclear. In this work, we aim to dissect the contribution of each stabilizing factor. This is achieved by coating AuNPs with a layer of thiolated compound, which inhibits the adsorption of PEG and also allows the control of surface charge. We found that depletion stabilization alone was insufficient to stabilize AuNPs at room temperature. However, when working together with other stabilization mechanisms, ultrahigh stability can be achieved. The size of both AuNPs and PEG was systematically varied and the trend was compared with theoretical calculations. Finally, we report the importance of the surface chemistry of commercial AuNPs.

Parts-per-Million of Polyethylene Glycol as a Non-Interfering Blocking Agent for Homogeneous Biosensor Development

“…24 Unmodified PEG has the advantage of being cost-effective and easy to use, but it is under-explored as a surface blocker. 25,26 We recently reported the use of PEG as a stabilizer for nanoparticles, [27][28][29] and PEG is also a commonly used artificial crowding agent. [30][31][32] With the common perception that PEG is an anti-fouling molecule, unmodified PEG appears to be a poor blocker.…”

Polymeric Stabilization of Nano‐Scale HMX Suspensions During Wet Milling

“…The depletion mechanism is characterized by the presence of free (non-adsorbed) polymer due to the creation of high-energy depletion zones between closely interacting particle surfaces. The origin of depletion repulsion is related to the transport of polymers trapped between the particles against a deep osmotic pressure gradient [11][12][13][14].…”

“…If the polymer chains remain in solution, they may not adhere to the surface and the depletion stabilization is achieved by the free polymer existing in the suspension as illustrated in Figure 2. The origin of depletion repulsion is related to the transportation of the polymers trapped between the particles against a deep osmotic pressure gradient [11][12][13][14].…”

Cu2+-catalyzed and H2O2-facilitated oxidation strategy for sensing copper(ii) based on cysteine-mediated aggregation of gold nanoparticles

“…With a few percent of PEG, AuNPs are stable even under extreme conditions such as with very high salt and extreme pH values. 26,27 Therefore, PEG is a suitable polymer surfactant employed in our experiment. In our study, the addition of only 0.125% PEG caused no aggregation of AuNPs with increasing the amount of NaCl up to 200 mM (Fig.…”