Deposition Kinetics of Quantum Dots and Polystyrene Latex Nanoparticles onto Alumina: Role of Water Chemistry and Particle Coating

Abstract

A clear understanding of the factors controlling the deposition behavior of engineered nanoparticles (ENPs), such as quantum dots (QDs), is necessary for predicting their transport and fate in natural subsurface environments and in water filtration processes. A quartz crystal microbalance with dissipation monitoring (QCM-D) was used to study the effect of particle surface coatings and water chemistry on the deposition of commercial QDs onto Al2O3. Two carboxylated QDs (CdSe and CdTe) with different surface coatings were compared with two model nanoparticles: sulfate-functionalized (sPL) and carboxyl-modified (cPL) polystyrene latex. Deposition rates were assessed over a range of ionic strengths (IS) in simple electrolyte (KCl) and in electrolyte supplemented with two organic molecules found in natural waters; namely, humic acid and rhamnolipid. The Al2O3 collector used here is selected to be representative of oxide patches found on the surface of aquifer or filter grains. Deposition studies showed that ENP deposition rates on bare Al2O3 generally decreased with increasing salt concentration, with the exception of the polyacrylic-acid (PAA) coated CdTe QD which exhibited unique deposition behavior due to changes in the conformation of the PAA coating. QD deposition rates on bare Al2O3 were approximately 1 order of magnitude lower than those of the polystyrene latex nanoparticles, likely as a result of steric stabilization imparted by the QD surface coatings. Adsorption of humic acid or rhamnolipid on the Al2O3 surface resulted in charge reversal of the collector and subsequent reduction in the deposition rates of all ENPs. Moreover, the ratio of the two QCM-D output parameters, frequency and dissipation, revealed key structural information of the ENP-collector interface; namely, on bare Al2O3, the latex particles were rigidly attached as compared to the more loosely attached QDs. This study emphasizes the importance of considering the nature of ENP coatings as well as organic molecule adsorption onto particle and collector surfaces to avoid underestimating ENP mobility in natural and engineered aquatic environments.

Interpreting Deposition Behavior of Polydisperse Surface-Modified Nanoparticles Using QCM-D and Sand-Packed Columns

“…In experiments conducted in KCl at the maximum IS (100 mM KCl), we also observe a decrease in r d for particles capped with C 3 and C 7 , as compared with experiments conducted at 30 mM KCl (Table 3). In agreement with these results, other QCM-D studies have reported that when particle aggregation is highly favorable, a lessened convective-diffusive transport of aggregated particles to the surface can result in lower measured r d values (Chen and Elimelech, 2006;Quevedo and Tufenkji, 2009;Quevedo et al, 2013). To better understand this phenomenon, experimental deposition rates (r d ) were normalized by the theoretical particle deposition rate (r d SL ) based on purely convective-diffusive transport (Adamczyk and van de Ven, 1981) (Fig.…”

QCM-D study of nanoparticle interactions

“…Many studies on interactions between a few selected types of nanoparticles and QCM-D sensor surfaces are summarized in Table 6. Attachment of other type of nanoparticles, such as quantum dots (QDs) [19,55], silica [153], laponite [154][155] and polymer-coated nanoparticles [19,156] [156] Under the favorable conditions, spherical nanoparticles showed a remarkably higher deposition rate than rod-shape nanoparticles.…”

“…Compared with other techniques the volume of the flow chamber in a typical QCM-D cell can be as small as 0.05 cm 3 , suitable for systems of only limited volume (about a few milliliters) of samples. [13][14] In the past ten years, we witnessed an exponential increase in the number of research groups who use QCM-D as one of main research tools for their research in liquid systems, covering a wide range of disciplines such as adsorption of lipid bilayer, [15][16] interactions of nanoparticles with clean or functionalized surfaces in aqueous solutions, [17][18][19] and adsorption kinetics of polymers, DNA and proteins on various probing substrates or immobilized bio-surfaces. [20][21][22][23][24][25][26][27][28][29] In a series of studies on the adsorption of polymers onto different solid surfaces using QCM-D [27][28][29], Guzmán et al.…”

Tailoring adhesion of anionic surfaces using cationic PISA-latexes – towards tough nanocellulose materials in the wet state

“…Two examples are colloidal probe atomic force microscopy (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D). AFM can able to image the surface but also to measure adhesion between two surfaces in the wet state, whereas the adsorption kinetics and adsorbed amount onto different substrates can be quantified in detail with the aid of the QCM-D. [21][22][23][24][25] Given the increasing expectations of greener chemistry, it is attractive to use water-borne chemistry to produce hydrophobic polymers for direct mixing with nanocellulose dispersions. Inspired by the well-established industrial and academic production of latexes, emulsion polymerization [26][27][28] has received intensified interest lately.…”