Aqueous Aggregation and Surface Deposition Processes of

Article

Aqueous Aggregation and Surface Deposition Processes of Engineered Superparamagnetic Iron Oxide Nanoparticles for Environmental Applications Wenlu Li, Di Liu, Jiewei Wu, Changwoo Kim, and John Dyer Fortner Environ. Sci. Technol., Just Accepted Manuscript • Publication Date (Web): 15 Sep 2014 Downloaded from http://pubs.acs.org on September 29, 2014

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Environmental Science & Technology

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Aqueous Aggregation and Surface Deposition

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Processes of Engineered Superparamagnetic Iron

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Oxide Nanoparticles for Environmental Applications

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Wenlu Li, Di Liu, Jiewei Wu, Changwoo Kim, and John D. Fortner*

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Department of Energy, Environmental, and Chemical Engineering

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Washington University in St. Louis

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St. Louis, Missouri 63130, USA

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Submitted to

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Environmental Science and Technology

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July 31th, 2014

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*To whom correspondence should be addressed:

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John D. Fortner: Tel: +1-314-935-9293; Fax: +1-314-935-5464; Email: [email protected]

ACS Paragon Plus Environment

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ABSTRACT

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Engineered, superparamagnetic, iron oxide nanoparticles (IONPs) have significant potential as

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platform materials for environmental sensing, imaging and remediation due to their unique size,

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physicochemical and magnetic properties.

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chemistry of the materials is crucial for such applications in the aqueous phase, and in particular,

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for porous matrixes with particle-surface interaction considerations.

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superparamagnetic, highly monodispersed 8 nm IONPs were synthesized and transferred into

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water as stable suspensions (remaining monodispersed) by way of an interfacial oleic acid

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bilayer surface.

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interactions (deposition and release) were quantitatively investigated and described

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systematically as a function of ionic strength (IS) and type with time-resolved dynamic light

28

scattering (DLS), zeta potential, and real-time quartz crystal microbalance with dissipation

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monitoring (QCM-D) measurements. The critical coagulation concentration (CCC) for oleic

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acid bilayer coated iron oxide nanoparticles (OA-IONPs) were determined to be 710 mM for

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NaCl (matching DLVO predictions) and 10.6 mM for CaCl2, respectively. For all conditions

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tested, surface deposition kinetics showed stronger, more favorable interactions between OA-

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IONPs and polystyrene surfaces compared to silica, which is hypothesized to be due to increased

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particle-surface hydrophobic interactions (when compared to silica surfaces).

To this end, controlling the size and surface

In this study,

Once stabilized and characterized, particle-particle and model surface


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KEYWORDS

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Iron oxide nanoparticles (IONPs), nanoparticle aggregation, nanoparticle deposition,

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nanoparticle stability, environmental sensing, hydrophobic interactions, Quartz Crystal

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Microbalance with Dissipation (QCM-D)


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INTRODUCTION

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The vision of applying finely divided materials, or even nanoscale materials for simultaneous

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sensing, mapping and remediating of targeted, complicated environments has recently gained

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increasing attention, concurrent with advances in related material sciences.1-4 In particular,

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magnetic based nanoparticles (magnetite and maghemite) provide unique advantages to such

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applications due to their size (2 to 100 nm) and tunable physicochemical properties. To this

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point, engineered magnetite (Fe3O4) based nanostructures, differ substantially from it’s bulk

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phase counterpart due to greatly enhanced specific surface area, reactivity, and magnetic

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response (e.g., superparamagnetic properties are observed for single domain particles within a

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size range of ca. 6-20 nm compared to bulk phase ferromagnetism).5 Such properties underpin

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this class of materials’ potential in therapeutic, biological and environmental imaging,6-10

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remediation11-15 and sensing technologies.1, 2, 4, 16-19

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Ultimately though, for many of these applications to be successful, engineered materials such

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as these must not only process intrinsic, novel functionality but must also allow for controlled

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physical placement (e.g., within a desired volume or at a specific target interface). As an

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example, single domain, superparamagnetic iron oxide (magnetite) based nanoparticles have

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significant potential as T2 type nuclear magnetic resonance (NMR) imaging contrast agents7, 20

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and are being explored for enhanced environmental (subsurface) imaging.4,

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technologies are aimed at extending and refining hydrocarbon detection in oil-field rocks and

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even for NAPL (nonaqueous phase liquids) sensing (and remediation) in contaminated systems.2,

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3, 23

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nanoscale materials can be transported through low porosity media,2, 22, 24 potentially reaching

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non-aqueous liquid phases/interface targets (e.g., oil-water-interfaces), at which point they can

10, 21, 22

Such

Further, based on material size (< 20 nm) and dispersivity, it is possible that monodispersed


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be responsive and potentially even functional.22-24 However, to date, the bottleneck for such

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applications is largely due to particle (in)stability challenges.10, 24-26 As the aggregation state

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changes (based on the surface energy of suspended nanoparticles), transportation of

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nanoparticles through low porous media is increasingly limited and final deposition ‘misses the

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mark’. Normally, the stability of the nanoparticles is controlled by the surface chemistries

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involved27 and in particular, the coatings and charge of the particle surface, the matrix surface

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chemistries, the ionic strength or salinity of the water, and the interactions with other substances,

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such as natural organic matter (NOM).28 Therefore, quantitatively understanding the aggregation

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and deposition/adsorption behavior of (surface)stabilized iron oxide nanoparticles (IONPs) under

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different water chemistries is crucial for use in any potential in-situ, subsurface technologies.

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The development of low defect, single domain nanoscale IONPs has drawn considerable

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attention from a number of research communities over the past two decades.5, 7, 29-31 In contrast

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to aqueous preparation routes, high temperature organic solution phase methods, in particular,

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allow for the preparation and control of highly uniformed nanoparticles due to the successful

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separation of nucleation and the growth phases during synthesis.5 For this work, monodisperse

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IONPs with controlled sizes were synthesized by decomposition of iron carboxylate salts in

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high-temperature boiling solvent.29,

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organic solvent, a favorable stabilizing surface is required for aqueous suspensions, and thus

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applications. Here, we use a stable, oleic acid bilayer surface coating allowing for the efficient

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transfer33 of the nanoparticles from nonpolar solvent to water, forming stable, nonaggregating,

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monodispersed suspensions.

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available (oleic acid is a major component in a number of natural oils including olive oil and

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magnetite is a widely found natural mineral), such a “green” core-shell structure may be

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As the aforementioned materials are synthesized in

Further, as both materials are widely naturally occurring and


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desirable for actual environmental applications.33

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superparamagnetic properties29 of the iron oxide core does not provide attractive magnetic forces

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between nanoparticles, unlike ferromagnetic particles, unless an external magnetic field is

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applied, thus simplifying aggregation observations and discussion.

Lastly, within this size range, the

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To the best of our knowledge, this is the first study systematically quantifying the aggregation

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kinetics of engineered superparamagnetic IONPs and their deposition behaviors onto different

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model environmental surfaces in the presence of sodium and calcium cations. IONP suspensions

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were developed, synthesized and characterized with size of 8 nm as stable, monodispersed

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aqueous suspensions by way of an oleic acid surface bilayer. Particle-particle and model surface

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interactions were quantitatively investigated and described as a function of ionic strength/type

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with time resolved dynamic light scattering (DLS), zeta (ζ) potential and real-time quartz crystal

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microbalance with dissipation monitoring (QCM-D) measurements (surface deposition and

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release), using two model environmental surfaces (hydrophilic vs. hydrophobic).

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MATERIALS AND METHODS

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Materials: Iron(III) oxide (hydrated, catalyst grade), 1-octadecene (technical grade, 90%),

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oleic acid (technical grade, 90%), sodium chloride (ACS reagent, ≥99.0%), calcium chloride

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dihydrate (ACS reagent, ≥99%), sodium hydroxide (ACS reagent, ≥97.0%) , sodium bicarbonate

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(ACS reagent, 99.7-100.3%) and nitric acid (trace metal grade) were all purchased from Sigma-

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Aldrich. All materials were used without any further purification.

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Preparation of Oleic Acid Bilayer Coated Iron Oxide Nanoparticles (OA-IONPs):

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Detailed synthesis of IONPs and phase transfer method for OA-IONPs are given in the

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Supporting Information (SI). The concentration of the water stable OA-IONPs stock suspension


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was 50 mg/L as determined by inductively coupled plasma mass spectrometry (ICP-MS, Agilent

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7500ce).

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Solution Chemistry: Various concentrations of NaCl and CaCl2 electrolyte stock solutions

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were prepared and filtrated (pore size of 0.2 um, Millipore) before use. All DLS and QCM-D

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measurements were conducted at pH 7.2 ± 0.2 buffered by 0.15 mM NaHCO3 and at room

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temperature (22 °C).

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Dynamic Light Scattering: The DLS measurements were performed on a Zetasizer (Nano

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ZS, Malvern). The OA-IONPs stock solution was diluted 50 times to 1 mg/L for the DLS

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experiments and pH was adjusted to 7.2. For each measurement, a predetermined volume of

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diluted nanoparticle suspension was added into a vial. After that, a certain amount of electrolyte

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stock solution was injected into the vial to make the total volume of sample to be 1 mL. After a

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short time of vortex (1.5 s), samples were quickly put into the DLS chamber and measured

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immediately. The scattered light intensity was detected by a photodetector at a scattering angle

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of 173°. Data points were measured every 15 s and recorded continuously. DLS samples were

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left to aggregate between 20 to 60 min, depending on the aggregation rate of each sample. The

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attachment efficiency (α) of the OA-IONP aggregates in the presence of various electrolyte

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concentrations was calculated by the following equation34

124

1

α= W = k

k fast

(1)

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where k is the initial aggregation rate constant at different salt concentrations and kfast is the

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aggregation rate constant under diffusion-limited (fast) aggregation conditions.

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Quartz Crystal Microbalance with Dissipation: QCM-D measurements were performed

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with a Q-Sense E4 (Q-sense AB, Sweden) unit by simultaneously monitoring the changes in

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frequency (∆f) and energy dissipation (∆D) of a 5 MHz silica (SiO2) coated QCM-D crystal


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(QSX-303, Q-sense) and a 5 MHz polystyrene (PS) coated QCM-D crystal (QSX-305, Q-sense).

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Protocols used to clean the sensors and detailed deposition experiment conditions are described

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in the Supporting Information (SI). All deposition measurements were allowed to proceed for a

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period between 10 to 30 min to determine the nanoparticle deposition rates. As deposition of

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OA-IONPs occurred onto the silica or polystyrene sensor surfaces, the increase in the mass of the

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crystal induced a continuous shift in the frequency (f), as described by the Sauerbrey

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relationship.35

∆ = − ∆

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(2)

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where n is the overtone number (1, 3, 5, 7, 9, etc…) and C is the crystal constant (17.7 ng/(Hz

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cm2)). The deposition process on the crystal surface will also enhance the crystal’s ability to

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dissipate energy, as shown in the increase in the energy dissipation (D) via the following

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equation: E

dissipated D= 2πE

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stored

(3)

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where Edissipated is the energy loss in one oscillation cycle and Estored is the total energy stored in

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the oscillator. Since deposited mass is linear to the frequency shift, the nanoparticle deposition

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rate can be calculated from the initial slope of frequency change.

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normalized frequency at the third overtone in a given period (t) was used to quantify the

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deposition rate (rd):34

148 149

d =

d∆ d

The initial change of

(4)

In order to obtain the deposition attachment efficiency (αD) as shown in equation 5,

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favorable deposition conditions were conducted by coating the silica sensor with a positively

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charged poly-L-lysine (PLL) layer as described elsewhere:36


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= "

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∆ ⁄ ∆ ⁄ #fav

(5)

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RESULTS AND DISCUSSION

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IONPs Stabilization and Characterization

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IONPs of 8 nm were synthesized and used specifically for this study as shown in TEM

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micrograph in Figure 1a. These nanoparticles are highly uniform in size, with size distribution

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variability well under 10 %; the size distribution histograms are shown in Figure S1a. The HR-

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TEM image (SI Figure S1b) of 8 nm IONPs shows that they are highly crystallized and the

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lattice fringe was indexed to (440) plane of the inverse spinel iron oxide structure.29, 37 Once

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synthesized, all nanoparticles used for this work were capped with an oleic acid layer with

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hydrophobic tail pointing outside, rendering them stable in the non-polar solvent (in this case,

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hexanes). A water stabilizing, surface bilayer was achieved by mixing a small amount of

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additional oleic acid with water and the iron oxide suspension in hexane (creating a liquid-liquid

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system) and then using a sonication probe to facilitate phase transfer.38-40 Corresponding TEM

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micrographs (Figure 1b) along with DLS measurements discussed below, indicate aqueous

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transferred IONPs remain monodisperse with no core size change. The stable, homogenous

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bilayer, as described by others, is formed when the hydrophobic oleic acid tail of the second

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layer aligns with the original hydrophobic tail of the first layer (via hydrophobic and dispersive

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Van der Waals forces),41 and the hydrophilic head group (carboxylic acid functionality) of the

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second layer aligns at the aqueous interface, rendering the nanoparticles water stable.33 The

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number-weighted hydrodynamic diameter of the OA-IONPs was measured to be 15.6 ± 1.3 nm

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for 8 nm IONPs originally dispersed in hexane (SI Figure S2). The DLS value for 8 nm IONPs

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is consistent with the value reported before (14.2 ± 2.6 nm) which takes into account the


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thickness of the bilayer.33 For all aqueous suspensions, no significant change in hydrodynamic

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diameter was observed after 3 months and the OA-IONPs did not precipitate over 6 months.

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Figure 2 shows ζ-potential measurements of 8 nm OA-IONPs under various NaCl and CaCl2

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electrolyte concentrations. Due to the dissociation of carboxylate groups at pH 7.2, OA-IONPs

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exhibit negatively charged surfaces (OA pKa = 4.95).42 ζ-potentials of OA-IONPs were negative

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for the entire range of NaCl and CaCl2 concentrations examined in this study.

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conditions, as expected, the nanoparticle ζ-potentials become less negative with increasing ionic

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strength due to the basic charge screening effect.43 ζ-potential values of OA-IONPs became less

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negative from -53.4 mV to -46.5 mV as NaCl concentration increased from 10 to 300 mM. As

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low as 0.05 mM of CaCl2 significantly increased the ζ-potential values of OA-IONPs to -30.7

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mV, indicating the enhanced effect of charge neutralization from divalent cations, as observed in

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other studies.34, 43, 44

Under all

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Aggregation Kinetics

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Extensive studies, focused mostly on carbon based material and metal/metal oxides, have been

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conducted to evaluate the aqueous aggregation behavior(s) of a number of engineered

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nanomaterials.27 By monitoring effective particle size change via dynamic light scattering (DLS),

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aggregation kinetics (as a function of one variable) can be determined. For most studies, such

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aggregation behaviors of engineered materials can be described by Derjaguin-Landau-Verwey-

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Overbeek (DLVO) theory27 and exhibit reaction-limited (slow) and diffusion-limited (fast)

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regimes.45 Further, previous reports primarily focus on the effects of Na+ and Ca2+, as sodium

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and calcium are the most abundant cations in most natural aquifers and even deep saline water

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resevoirs.46


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Here, the aggregation of OA-IONPs was also studied in the presence of NaCl and CaCl2 at pH

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7.2. The aggregation rate of OA-IONPs increased with increasing NaCl concentrations below

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700 mM (SI Figure S3a). This is consistent with zeta potential measurements as an increase in

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NaCl concentration, nanoparticle zeta potential became less negative (Figure 2). However, at

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higher NaCl concentrations (800 and 1000 mM), the increase in electrolyte concentration has a

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negligible effect on the aggregation rate. Similarly, the aggregation kinetics of OA-IONPs in the

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presence of CaCl2 follows the same trend (SI Figure S3b), but at lower concentrations as

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expected with divalent Ca2+.34, 44, 47 Figure 3 shows the aggregation attachment efficiencies of

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OA-IONPs as a function of both electrolyte concentrations. For these systems, aggregation

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kinetics can also be classically divided into two regimes: reaction-limited (slow) and diffusion-

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limited (fast) aggregation.

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concentration screens the surface charge, thus effectively reducing the energy barriers to

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aggregation (SI and SI Figure S4).27,

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However, when the electrolyte concentrations increase to the critical coagulation concentration,

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the energy barrier is completely eliminated, leading to diffusion-controlled aggregation. Figure

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S5 shows good agreement between prediction of DLVO theory (calculated) and experimental

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data. The critical coagulation concentrations (CCC) for OA-IONPs are 710 mM for NaCl and

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10.6 mM for CaCl2. Tombácz et al. reported a CCC value of 500 mM NaCl for poly(acrylic acid)

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– PAA coated magnetite nanoparticles with primary size under 10 nm at pH 6.5.48 Considering

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the different preparation methods for IONPs and surface modifications, our CCC value for OA-

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IONPs is comparable. The ratio of CCC values calculated (10.6/710) is proportional to z-6.07,

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where z is the valence of the calcium counterion (i.e. z=2). This is in good agreement with the

In the reaction-limited regime, an increase in the electrolyte

34

As a result, the aggregation sizes increase rapidly.


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empirical Schulze-Hardy rule that the CCC ratio for CaCl2 and NaCl should be z-6 for particles

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with large ζ-potentials.49

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Deposition Kinetics

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Quartz crystal microbalance with dissipation (QCM-D) enables the real-time, high sensitivity

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surface (interaction) analysis (here as particle deposition and release) for fluid suspended

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particles and even macromolecules.50, 51 Recently, QCM-D has proven to be useful and powerful

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in evaluating solution based interfacial behaviors of engineered nanomaterials.27,

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Representative studies of note include: Chen et al. who examined the deposition of fullerene

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nanoparticles onto silica surfaces and found a decreased deposition rate at higher electrolyte

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concentrations;34 Fatisson et al.52 employed this technique to compare the deposition behavior of

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bare and CMC-modified nanoscale zerovalent iron (nZVI) particles onto silica surfaces over a

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wide range of solution chemistries; Saleh et al. found the lowest deposition rates from the

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triblock copolymer coated nanoscale zerovalent iron (nZVI) compared to bare and other

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surfactant-modified nZVI from QCM-D experiment.53 Further, QCM-D based analyses can be

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tailored as quartz crystal (sensor) surfaces can be modified via a number of methods to mimic

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particle or environmental surfaces36 for enhancing the technique’s applicability. As done in this

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work, interfacial surface interactions can be quantitatively investigated with QCM-D using both

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(relatively) hydrophilic (as silica) and (relatively) hydrophobic (as polystyrene)54-57 sensor

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surfaces.

36, 52

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A representative normalized frequency shift at the third overtone ( ∆"%# ) for OA-IONPs

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deposition onto a polystyrene surface is shown in Figure S6. The deposition kinetics for OA-

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IONPs were studied as a function of nanoparticle concentration ranging from 2.5 mg/L to 40

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mg/L (measured as Fe). In order to have a sufficient frequency shift for all deposition studies,


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we chose 7.5 mg/L as the concentration for all QCM-D measurements, above this concentration

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(40 mg/L maximum) no change in deposition kinetics was observed. Figure S7 presents a

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typical deposition study of 8 nm OA-IONPs in the presence of 0, 300, 500, and 800 mM NaCl

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onto a silica sensor surface. To begin, there was no deposition of OA-IONPs onto silica sensor

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surface in the absence of salt.

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electrostatic interactions between OA-IONPs and the silica surface.

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silica58 are both negatively charged pH 7.2, the strong repulsive force simply inhibits deposition.

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When OA-IONPs do interact with the sensor surface, the decrease in the frequency shift

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indicates the continuous deposition of nanoparticles and as nonlinear deposition behavior34 is

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observed at high ionic strength (e.g., 800 mM NaCl on silica), where the initial slope is used to

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calculate the unsaturated (surface) deposition rate. The deposition behaviors of 8 nm OA-IONPs

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onto silica and polystyrene sensor surfaces were examined over a wide range of NaCl and CaCl2

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concentrations, as shown in Figure 4. As electrolyte concentrations increased, deposition rates

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correspondingly increased as the electric double layers were compressed by the charge screening

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from the additional salt. Further increase in electrolyte concentrations close to or higher than the

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CCC values, resulted in diffusion limited transport, and the deposition rate then decreased as

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expected and observed by others.34 From Figure 4a, nanoparticles reach a maximum deposition

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rate on silica at around 500 mM NaCl, while on the more hydrophobic polystyrene surface, the

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fastest deposition rate was observed for NaCl concentrations between 200-400 mM.

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separate peaks in the deposition rates of silica and polystyrene surfaces indicate the higher

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affinity of (this particular) OA-IONPs deposition onto polystyrene, a relatively more

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hydrophobic surface. In addition, the maximum deposition rate on polystyrene is around 6.5

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Hz/min, which is significantly higher than the deposition rate on silica surface (2.5 Hz/min).

This observation can be explained based on the repulsive Since OA-IONPs and

The


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From Figure 4b, nanoparticles reach a maximum deposition rate on silica around 5 to 7.5 mM

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CaCl2, while on the polystyrene surface, the fastest deposition concentration for CaCl2 is

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between 2-3 mM. The concentrations at which the nanoparticles reach highest deposition rate in

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the presence of NaCl are significantly higher than that in the presence of CaCl2. In addition to

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the similar charge screening effect as Na+, Ca2+ can also form complexes with the carboxyl

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groups and thus further neutralize their surface charge.34 Furthermore, carboxyl groups do not

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form inner sphere complexes with Na+ (i.e. Na+ can only screen the charges of nanoparticles).59

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For these reasons, Ca2+ ions are significantly more effective in reducing the energy barrier to

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OA-IONPs deposition than Na+, which is in line with observations made by others.34, 43, 53, 60

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Favorable deposition onto PLL coated silica sensor surfaces was also conducted under the

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same conditions as for the unfavorable conditions.27, 34 Insets from Figure 4 show the deposition

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rates (frequency shift rates) of OA-IONPs in the presence of NaCl and CaCl2 onto PLL coated

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sensor surfaces at pH 7.2. Generally, on PLL coated sensor surfaces, deposition rates decreased

277

with increasing ionic strength in both NaCl and CaCl2 solutions.

278

explained due to the significant formation of large aggregates36,

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concentrations as shown for previous DLS measurements (SI Figure S3). By normalizing the

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particle deposition rates at unfavorable conditions to the corresponding particle deposition rates

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at favorable conditions, deposition attachment efficiencies (αD) of OA-IONPs are shown in

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Figure 5. For deposition onto silica sensor surfaces, αD increased with the increasing IS until the

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energy barrier is completely eliminated, resulting in αD of 1 (SI Figure S8). The critical

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deposition concentration36 (CDC) was determined to be 485 mM for NaCl and 5.1 mM for CaCl2.

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While the deposition kinetics on silica surfaces clearly shows typical unfavorable and favorable

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regimes, deposition kinetics on polystyrene surfaces do not follow classical deposition behaviors

The observation can be

43, 58

at elevated electrolyte


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of engineered particles,27 suggesting that hydrophobic interactions mainly influence the

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attachment of engineered OA-IONPs onto polystyrene surfaces.61 Xiao and Wiesner found that

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aqu-nC60, a moderately hydrophobic nanoparticle, has the highest retention on the most

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hydrophobic BSA-coated glass beads, indicating the hydrophobic interaction contributes to the

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particle attachment.62 A recent study by Song et al.61 suggested hydrophobic interactions are

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responsible for the increased deposition onto hydrophobic surfaces with increasing

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hydrophobicity of Ag nanoparticles. As oleic acid bilayer coating is actually amphiphilic,33 we

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propose that the increased deposition rate onto polystyrene is due to the additional hydrophobic

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interactions55 between the hydrophobic portion of the coating with the polystyrene sensor surface

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(which also has less surface charge than silica).56 However, the exact mechanisms behind the

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hydrophobic interactions (nanoparticle-surface) are still not fully understood.63-65 The relative

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higher deposition attachment efficiencies of engineered OA-IONPs onto the polystyrene surface

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indicate that the transport and fate of these nanoparticles will be greatly influenced by the

300

hydrophobic surfaces in the environment (e.g. oil, NAPL or natural organic matter). In another

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word, if transportation of these engineered IONPs in the subsurface could reach to a target

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volume, favorable in-situ partitioning at oil / NAPL is likely.

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Deposited Layer Stiffness and Stability

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Along with measuring frequency changes, thus mass deposition changes, QCM-D can also

305

measure the change in dissipated energy during and after particle deposition events.60 The slope

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of D to f (&∆'"%# ⁄∆"%# &) can be used as an estimation of the induced energy dissipation per

307

coupled mass change – which is a measure of particle size and particle-surface contact stiffness

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for films of discrete nanoparticles.55, 66-68 Here, the slope of D to f exhibited a linear relationship

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(R2 ≥ 0.99, SI Figure S9) for most cases except at very low ionic strength due to negligible


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Therefore, &∆'"%# ⁄∆"%# & was calculated for all the

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deposition mass on the sensor surface.

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deposition experiments except for deposition at very low electrolyte concentrations. The trends

312

of &∆'"%# ⁄∆"%# & as a function of NaCl and CaCl2 are presented in Figure 6. For nanoparticle

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deposition onto the silica surface, &∆'"%# ⁄∆"%# & increased with increasing electrolyte

314

concentration for both NaCl and CaCl2. The interactions of aggregated nanoparticles with the

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silica surface become increasingly dissipative and therefore, &∆'"%# ⁄∆"%# & values increase – in

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other words, the layer becomes more loosely attached to silica with increasing ionic strength due

317

to formation of large aggregates.69

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coated surfaces are lower than the values on silica surfaces. Interestingly, the &∆'"%# ⁄∆"%# & of

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nanoparticle deposition on the polystyrene surface is much lower than for a silica surface in the

320

presence of NaCl and CaCl2, indicating the nanoparticles were more rigidly attached onto the

321

polystyrene surface as compared to the silica surface. This phenomenon is hypothesized to be in

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part, due to stronger hydrophobic interactions,55,

323

attachment of aggregated nanoparticles onto the polystyrene surface.

324

electrolyte concentrations and types, the &∆'"%# ⁄∆"%# & value on the polystyrene surface remains

325

constant, which suggests the stiffness of the nanoparticles’ attachment is independent to the

326

addition of salt and surface chemistry. These observations are in good agreement with Chang et

327

al.’s study which highlights the role of sensor surface chemistry with regard to nanoparticles

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deposition.55

Under non-repulsive conditions, &∆'"%# ⁄∆"%# & on PLL

61

as discussed above, leading to the rigid Moreover, under all

329

To further evaluate the properties of the sorbed layer, experiments were designed to measure

330

the effective particle release after favorable deposition60 had occurred. OA-IONPs were first

331

deposited onto the silica surface at favorable deposition rate conditions (500 mM NaCl and 7.5

332

mM CaCl2, respectively) and then the (flowing) aqueous solution chemistry over the deposited


16

Page 17 of 32


333

layer was changed (termed the rinse solution) to investigate the stability of the sorbed layer and

334

release of nanoparticles back into solution. For silica surfaces (Figure 7a), the rinse solutions

335

used here include the corresponding buffer, 1 mM NaCl, water buffered at pH 7.2 and water

336

buffered at pH 12. A partial increase of frequency is observed in Figure 7a where the rinse

337

solution is changed from 500 mM NaCl (step D) to 1 mM NaCl (step E), indicating release of

338

sorbed particles when the solution chemistry changed. However, with the initial 7.5 mM CaCl2

339

based suspension, no obvious frequency change is observed (less than 2 % of mass change

340

calculated with Sauerbrey model, Figure 7b and SI Table S1), thus indicating a stable deposition

341

layer regardless of the changes in water chemistry. As discussed, previous studies have shown

342

that Ca2+ can bind to two adjacent carboxyl groups, acting as a bridge, which leads to a more

343

stable deposited layer.43, 70, 71 The negative frequency shift in step G was due to the increase in

344

viscosity/density in water solution buffered at high pH.34 These results indicate that the sorbed

345

layer properties can also be functions of both ionic type71 and surface, and that the initial

346

conditions are critical, as we observed the majority of sorbed layers, for all cases, remain (mass

347

retained) even after the rinse solution changed back to MilliQ water. Such observations are

348

important when considering particle transport over long distances or times as heterogeneities

349

with regard to local ionic strength/type and surfaces may act as effective surface (particle) sinks.

350

On the other hand, if a stable, rigid (deposition) layer is desirable, divalent or even trivalent

351

cations may be useful in application.

352

In summary, this work fundamentally describes the role of two typical cations, Na+ and Ca2+,

353

on the aggregation, deposition and corresponding release of engineered iron oxide nanoparticles

354

(IONPs) with two model surface types (hydrophilic vs. hydrophobic).

355

quantitatively describe and discern the effects of different cations and ionic strength, which

Measurements


17


Page 18 of 32

356

strongly affect the stability of nanoparticles and thus their function with regard to particle

357

deposition and release onto/from different, model environmental surfaces. Data sets indicate

358

these OA-IONPs will be relatively stable in groundwater conditions as the Na+ is typically 1-10

359

mM and Ca2+ is typically 0.1-2 mM.53 However, based on this and other studies, it is still

360

difficult to control the stability and deposition of engineered IONPs under extreme conditions,

361

particularly at high salinity (IS > 1 M) as found, for example in brine aquifers or some petroleum

362

reservoirs.46 Additionally, sensor surface (coatings) also proved to be critical factors governing

363

the deposition rates of these nanoparticles onto environmental surfaces.

364

observed a greater affinity, in all cases, for these nanoparticles to associate with the more

365

hydrophobic surface and that oleic acid coatings are quite sensitive to the presence of calcium.

366

In particular, we

To conclude, aqueous application (e.g. sensing, remediation, etc.) of highly controlled,

367

magnetic engineered nanoparticles remains relatively nascent.

This work provides new

368

fundamental knowledge and understanding for such applications and beyond, while underscoring

369

complexities associated with nanoparticle behavior in multiphase systems (here as water-solid

370

interfaces). The authors certainly recognize that natural environments will be more complicated

371

than systems presented, based on the presence of NOM, redox reactions (resulting in particle

372

aging), (bio) molecules, among others, which all add to the uncertainty of extrapolation with

373

regard to real world understanding and accurate prediction of aggregation and deposition

374

processes.27

375

specifically discerning the role of environmental aging and the presence of NOM for similar

376

IONPs aggregation and deposition behaviors.

Accordingly, ongoing research is being conducted to investigate such factors,


18

Page 19 of 32


377 378

Figure 1. TEM micrographs of the as-prepared 8 nm IONPs in (a) hexane and (b) water. All

379

scale bars are 50 nm.


19


Page 20 of 32

380 381

Figure 2. Zeta potentials of OA-IONPs over a range of NaCl and CaCl2 concentrations under pH

382

7.2. Each data point shows the mean of 30 measurements of triplicate samples, where the error

383

bars represent standard deviations.


20

Page 21 of 32


384 385

Figure 3. Attachment efficiency (α) of OA-IONPs as functions of (a) NaCl and (b) CaCl2

386

concentrations at pH 7.2.

387

measurements is 710 mM NaCl and 10.6 mM CaCl2 for OA-IONPs. The lines are extrapolated

388

from the reaction-limited and diffusion-limited regimes, and the intersections show the

389

respective CCC values.

The critical coagulation concentration (CCC) based on the


21


Page 22 of 32

390 391

Figure 4. Deposition rates (frequency shift rates) of OA-IONPs in the presence of (a) NaCl and

392

(b) CaCl2 onto silica and polystyrene sensor surfaces. Insets: deposition rates under favorable

393

conditions. Each data point shows the average of duplicate or triplicate measurements, where the

394

error bars represent standard deviations.


22

Page 23 of 32


395 396

Figure 5. Deposition attachment efficiency (αD) of OA-IONPs in the presence of (a) NaCl and (b)

397

CaCl2 onto silica and polystyrene sensor surfaces. The lines are extrapolated from the

398

unfavorable and favorable deposition regimes, and the intersections show the respective critical

399

deposition concentration (CDC) values.


23


Page 24 of 32

400 401

Figure 6. &∆'"%# ⁄∆"%# & of OA-IONPs deposition in the presence of NaCl and CaCl2 onto PLL,

402

silica and polystyrene surfaces.


24

Page 25 of 32


403 404

Figure 7. Stability of deposited OA-IONPs layer over different rinse solutions when the layer

405

was formed in the presence of (a) 500 mM NaCl and (b) 7.5 mM CaCl2. Baseline was first

406

established in MilliQ water (A) and corresponding electrolytes (B), before the nanoparticles are

407

deposited onto the silica surface (C). The system is then rinsed in the respective electrolytes (D),

408

1 mM NaCl at pH 7.2 (E), MilliQ water at pH 7.2 (F), and finally, MilliQ water with pH adjusted

409

to 12 (G).


25


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Page 26 of 32

ASSOCIATED CONTENT

411

Supporting Information. Detailed synthesis and phase transfer of iron oxide nanoparticles,

412

QCM-D sensor cleaning protocols, QCM-D deposition experiment, DLVO calculations, nine

413

figures (nanoparticle size distribution, DLS size of nanoparticles, aggregation profiles, DLVO

414

interaction energy profiles, DLVO predictions, QCM-D deposition experiments, and

415

representative D/f ratio) and one table are available free of charge via the Internet at

416

http://pubs.acs.org.

417

AUTHOR INFORMATION

418

Corresponding Author

419

*To whom correspondence should be addressed:

420

John D. Fortner: Tel: +1-314-935-9293; Fax: +1-314-935-5464; Email: [email protected]

421

Funding Sources

422

The authors would like to thank the American Chemical Society’s Petroleum Research Fund

423

(#52640-DNI10) and the National Science Foundation (CBET, #1236653) for supporting this

424

work.

425

ACKNOWLEDGMENT

426

This work was supported by American Chemical Society’s Petroleum Research Fund and the

427

National Science Foundation. TEM, DLS facilities were provided by the Nano Research Facility

428

(NRF) at Washington University in St. Louis, a member of the National Nanotechnology

429

Infrastructure Network (NNIN), which is supported by the National Science Foundation under

430

Grant No. ECS-0335765.). We also thank Mr. Carl H. Hinton for his contributions to this work.


26

Page 27 of 32


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REFERENCES

432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475

1. Hsu, R.-S.; Chang, W.-H.; Lin, J.-J., Nanohybrids of Magnetic Iron-Oxide Particles in Hydrophobic Organoclays for Oil Recovery. ACS Applied Materials & Interfaces 2010, 2, (5), 1349-1354. 2. Saleh, N.; Sirk, K.; Liu, Y. Q.; Phenrat, T.; Dufour, B.; Matyjaszewski, K.; Tilton, R. D.; Lowry, G. V., Surface modifications enhance nanoiron transport and NAPL targeting in saturated porous media. Environ. Eng. Sci. 2007, 24, (1), 45-57. 3. Saleh, N.; Phenrat, T.; Sirk, K.; Dufour, B.; Ok, J.; Sarbu, T.; Matyjaszewski, K.; Tilton, R. D.; Lowry, G. V., Adsorbed Triblock Copolymers Deliver Reactive Iron Nanoparticles to the Oil/Water Interface. Nano Letters 2005, 5, (12), 2489-2494. 4. Ingram, D. R.; Kotsmar, C.; Yoon, K. Y.; Shao, S.; Huh, C.; Bryant, S. L.; Milner, T. E.; Johnston, K. P., Superparamagnetic nanoclusters coated with oleic acid bilayers for stabilization of emulsions of water and oil at low concentration. Journal of Colloid and Interface Science 2010, 351, (1), 225-232. 5. Park, J.; An, K.; Hwang, Y.; Park, J.-G.; Noh, H.-J.; Kim, J.-Y.; Park, J.-H.; Hwang, N.M.; Hyeon, T., Ultra-large-scale syntheses of monodisperse nanocrystals. Nat Mater 2004, 3, (12), 891-895. 6. Gupta, A. K.; Gupta, M., Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications. Biomaterials 2005, 26, (18), 3995-4021. 7. Na, H. B.; Song, I. C.; Hyeon, T., Inorganic Nanoparticles for MRI Contrast Agents. Advanced Materials 2009, 21, (21), 2133-2148. 8. Cattoz, B.; Cosgrove, T.; Crossman, M.; Prescott, S. W., Surfactant-Mediated Desorption of Polymer from the Nanoparticle Interface. Langmuir 2011, 28, (5), 2485-2492. 9. Hu, F.; Jia, Q.; Li, Y.; Gao, M., Facile synthesis of ultrasmall PEGylated iron oxide nanoparticles for dual-contrast T 1 - and T 2 -weighted magnetic resonance imaging. Nanotechnology 2011, 22, (24), 245604. 10. Bagaria, H. G.; Xue, Z.; Neilson, B. M.; Worthen, A. J.; Yoon, K. Y.; Nayak, S.; Cheng, V.; Lee, J. H.; Bielawski, C. W.; Johnston, K. P., Iron Oxide Nanoparticles Grafted with Sulfonated Copolymers are Stable in Concentrated Brine at Elevated Temperatures and Weakly Adsorb on Silica. ACS Applied Materials & Interfaces 2013, 5, (8), 3329-3339. 11. Fan, Q.-h.; Li, P.; Chen, Y.-f.; Wu, W.-s., Preparation and application of attapulgite/iron oxide magnetic composites for the removal of U(VI) from aqueous solution. Journal of Hazardous Materials 2011, 192, (3), 1851-1859. 12. Yavuz, C.; Mayo, J. T.; Suchecki, C.; Wang, J.; Ellsworth, A.; D’Couto, H.; Quevedo, E.; Prakash, A.; Gonzalez, L.; Nguyen, C.; Kelty, C.; Colvin, V., Pollution magnet: nano-magnetite for arsenic removal from drinking water. Environ Geochem Health 2010, 32, (4), 327-334. 13. Yean, S.; Cong, L.; Yavuz, C. T.; Mayo, J. T.; Yu, W. W.; Kan, A. T.; Colvin, V. L.; Tomson, M. B., Effect of magnetite particle size on adsorption and desorption of arsenite and arsenate. Journal of Materials Research 2005, 20, (12), 3255-3264. 14. Yavuz, C. T.; Mayo, J. T.; Yu, W. W.; Prakash, A.; Falkner, J. C.; Yean, S.; Cong, L. L.; Shipley, H. J.; Kan, A.; Tomson, M.; Natelson, D.; Colvin, V. L., Low-field magnetic separation of monodisperse Fe3O4 nanocrystals. Science 2006, 314, (5801), 964-967. 15. Jiang, Y.; Wang, W.-N.; Biswas, P.; Fortner, J. D., Facile Aerosol Synthesis and Characterization of Ternary Crumpled Graphene–TiO2–Magnetite Nanocomposites for Advanced Water Treatment. ACS Applied Materials & Interfaces 2014, 6, (14), 11766-11774.


27


476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519

Page 28 of 32

16. Hua, L.; Zhou, J.; Han, H., Direct electrochemiluminescence of CdTe quantum dots based on room temperature ionic liquid film and high sensitivity sensing of gossypol. Electrochimica Acta 2010, 55, (3), 1265-1271. 17. Su, S.; Wu, W.; Lu, J.; Gao, J.; Fan, C., Nanomaterials-based sensors for applications in environmental monitoring. Journal of Materials Chemistry 2012. 18. Khan, S. D.; Jacobson, S., Remote sensing and geochemistry for detecting hydrocarbon microseepages. Geological Society of America Bulletin 2008, 120, (1-2), 96-105. 19. Strand, S.; Austad, T.; Puntervold, T.; Høgnesen, E. J.; Olsen, M.; Barstad, S. M. F., “Smart Water” for Oil Recovery from Fractured Limestone: A Preliminary Study. Energy & Fuels 2008, 22, (5), 3126-3133. 20. Park, Y.; Whitaker, R. D.; Nap, R. J.; Paulsen, J. L.; Mathiyazhagan, V.; Doerrer, L. H.; Song, Y.-Q.; Hürlimann, M. D.; Szleifer, I.; Wong, J. Y., Stability of Superparamagnetic Iron Oxide Nanoparticles at Different pH Values: Experimental and Theoretical Analysis. Langmuir 2012, 28, (15), 6246-6255. 21. Simpson, A. J.; Simpson, M. J.; Soong, R., Nuclear Magnetic Resonance Spectroscopy and Its Key Role in Environmental Research. Environmental Science & Technology 2012, 46, (21), 11488-11496. 22. Park, Y. C.; Paulsen, J.; Nap, R. J.; Whitaker, R. D.; Mathiyazhagan, V.; Song, Y.-Q.; Hürlimann, M.; Szleifer, I.; Wong, J. Y., Adsorption of Superparamagnetic Iron Oxide Nanoparticles on Silica and Calcium Carbonate Sand. Langmuir 2014, 30, (3), 784-792. 23. Berlin, J. M.; Yu, J.; Lu, W.; Walsh, E. E.; Zhang, L.; Zhang, P.; Chen, W.; Kan, A. T.; Wong, M. S.; Tomson, M. B.; Tour, J. M., Engineered nanoparticles for hydrocarbon detection in oil-field rocks. Energy & Environmental Science 2011, 4, (2), 505-509. 24. Yoon, K. Y.; Kotsmar, C.; Ingram, D. R.; Huh, C.; Bryant, S. L.; Milner, T. E.; Johnston, K. P., Stabilization of Superparamagnetic Iron Oxide Nanoclusters in Concentrated Brine with Cross-Linked Polymer Shells. Langmuir 2011, 27, (17), 10962-10969. 25. Ottofuelling, S.; Von Der Kammer, F.; Hofmann, T., Commercial Titanium Dioxide Nanoparticles in Both Natural and Synthetic Water: Comprehensive Multidimensional Testing and Prediction of Aggregation Behavior. Environmental Science & Technology 2011, 45, (23), 10045-10052. 26. Le, N. Y. T.; Pham, D. K.; Le, K. H.; Nguyen, P. T., Design and screening of synergistic blends of SiO 2 nanoparticles and surfactants for enhanced oil recovery in high-temperature reservoirs. Advances in Natural Sciences: Nanoscience and Nanotechnology 2011, 2, (3), 035013. 27. Petosa, A. R.; Jaisi, D. P.; Quevedo, I. R.; Elimelech, M.; Tufenkji, N., Aggregation and Deposition of Engineered Nanomaterials in Aquatic Environments: Role of Physicochemical Interactions. Environmental Science & Technology 2010, 44, (17), 6532-6549. 28. Li, X.; Lenhart, J. J., Aggregation and Dissolution of Silver Nanoparticles in Natural Surface Water. Environmental Science & Technology 2012, 46, (10), 5378-5386. 29. Yu, W. W.; Falkner, J. C.; Yavuz, C. T.; Colvin, V. L., Synthesis of monodisperse iron oxide nanocrystals by thermal decomposition of iron carboxylate salts. Chemical Communications 2004, (20), 2306-2307. 30. Sun, S.; Zeng, H., Size-Controlled Synthesis of Magnetite Nanoparticles. Journal of the American Chemical Society 2002, 124, (28), 8204-8205.


28

Page 29 of 32

520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564


31. Hyeon, T.; Lee, S. S.; Park, J.; Chung, Y.; Na, H. B., Synthesis of Highly Crystalline and Monodisperse Maghemite Nanocrystallites without a Size-Selection Process. Journal of the American Chemical Society 2001, 123, (51), 12798-12801. 32. Lee, S. S.; Zhang, C.; Lewicka, Z. A.; Cho, M.; Mayo, J. T.; Yu, W. W.; Hauge, R. H.; Colvin, V. L., Control over the Diameter, Length, and Structure of Carbon Nanotube Carpets Using Aluminum Ferrite and Iron Oxide Nanocrystals as Catalyst Precursors. The Journal of Physical Chemistry C 2012, 116, (18), 10287-10295. 33. Prakash, A.; Zhu, H.; Jones, C. J.; Benoit, D. N.; Ellsworth, A. Z.; Bryant, E. L.; Colvin, V. L., Bilayers as Phase Transfer Agents for Nanocrystals Prepared in Nonpolar Solvents. ACS Nano 2009, 3, (8), 2139-2146. 34. Chen, K. L.; Elimelech, M., Aggregation and Deposition Kinetics of Fullerene (C60) Nanoparticles. Langmuir 2006, 22, (26), 10994-11001. 35. Sauerbrey, G., Use of quartz vibrator for weighing thin layers and as a micro-balance. Z. Phys. 1959, 155, (2), 206-222. 36. Chen, K. L.; Elimelech, M., Interaction of Fullerene (C60) Nanoparticles with Humic Acid and Alginate Coated Silica Surfaces: Measurements, Mechanisms, and Environmental Implications. Environmental Science & Technology 2008, 42, (20), 7607-7614. 37. Teng, X.; Yang, H., Effects of surfactants and synthetic conditions on the sizes and selfassembly of monodisperse iron oxide nanoparticles. Journal of Materials Chemistry 2004, 14, (4), 774-779. 38. Xu, X. Q.; Shen, H.; Xu, J. R.; Li, X. J., Aqueous-based magnetite magnetic fluids stabilized by surface small micelles of oleolysarcosine. Applied Surface Science 2004, 221, (1– 4), 430-436. 39. Meerod, S.; Tumcharern, G.; Wichai, U.; Rutnakornpituk, M., Magnetite nanoparticles stabilized with polymeric bilayer of poly(ethylene glycol) methyl ether–poly(ɛ-caprolactone) copolymers. Polymer 2008, 49, (18), 3950-3956. 40. Maity, D.; Agrawal, D. C., Synthesis of iron oxide nanoparticles under oxidizing environment and their stabilization in aqueous and non-aqueous media. Journal of Magnetism and Magnetic Materials 2007, 308, (1), 46-55. 41. Shen, L. F.; Laibinis, P. E.; Hatton, T. A., Bilayer surfactant stabilized magnetic fluids: Synthesis and interactions at interfaces. Langmuir 1999, 15, (2), 447-453. 42. Morgan, L. J.; Ananthapadmanabhan, K. P.; Somasundaran, P., Oleate adsorption on hematite: Problems and methods. International Journal of Mineral Processing 1986, 18, (1–2), 139-152. 43. Yi, P.; Chen, K. L., Influence of Surface Oxidation on the Aggregation and Deposition Kinetics of Multiwalled Carbon Nanotubes in Monovalent and Divalent Electrolytes. Langmuir 2011, 27, (7), 3588-3599. 44. Chowdhury, I.; Duch, M. C.; Mansukhani, N. D.; Hersam, M. C.; Bouchard, D., Colloidal Properties and Stability of Graphene Oxide Nanomaterials in the Aquatic Environment. Environmental Science & Technology 2013, 47, (12), 6288-6296. 45. Lin, M. Y.; Lindsay, H. M.; Weitz, D. A.; Ball, R. C.; Klein, R.; Meakin, P., UNIVERSALITY IN COLLOID AGGREGATION. Nature 1989, 339, (6223), 360-362. 46. Hu, Y.; Ray, J. R.; Jun, Y.-S., Na+, Ca2+, and Mg2+ in Brines Affect Supercritical CO2– Brine–Biotite Interactions: Ion Exchange, Biotite Dissolution, and Illite Precipitation. Environmental Science & Technology 2012, 47, (1), 191-197.


29


565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608

Page 30 of 32

47. Li, K.; Zhang, W.; Huang, Y.; Chen, Y., Aggregation kinetics of CeO2 nanoparticles in KCl and CaCl2 solutions: measurements and modeling. J Nanopart Res 2011, 13, (12), 64836491. 48. Tombácz, E.; Tóth, I. Y.; Nesztor, D.; Illés, E.; Hajdú, A.; Szekeres, M.; L.Vékás, Adsorption of organic acids on magnetite nanoparticles, pH-dependent colloidal stability and salt tolerance. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2013, 435, (0), 91-96. 49. Gregory, J., Particles in Water: Properties and Processes. 2006. 50. Zhang, X.; Yang, S., Nonspecific Adsorption of Charged Quantum Dots on Supported Zwitterionic Lipid Bilayers: Real-Time Monitoring by Quartz Crystal Microbalance with Dissipation. Langmuir 2011, 27, (6), 2528-2535. 51. Donahoe, C. D.; Cohen, T. L.; Li, W.; Nguyen, P. K.; Fortner, J. D.; Mitra, R. D.; Elbert, D. L., Ultralow Protein Adsorbing Coatings from Clickable PEG Nanogel Solutions: Benefits of Attachment under Salt-Induced Phase Separation Conditions and Comparison with PEG/Albumin Nanogel Coatings. Langmuir 2013, 29, (12), 4128-4139. 52. Fatisson, J.; Ghoshal, S.; Tufenkji, N., Deposition of Carboxymethylcellulose-Coated Zero-Valent Iron Nanoparticles onto Silica: Roles of Solution Chemistry and Organic Molecules. Langmuir 2010, 26, (15), 12832-12840. 53. Saleh, N.; Kim, H.-J.; Phenrat, T.; Matyjaszewski, K.; Tilton, R. D.; Lowry, G. V., Ionic Strength and Composition Affect the Mobility of Surface-Modified Fe0 Nanoparticles in WaterSaturated Sand Columns. Environmental Science & Technology 2008, 42, (9), 3349-3355. 54. Reimhult, K.; Petersson, K.; Krozer, A., QCM-D Analysis of the Performance of Blocking Agents on Gold and Polystyrene Surfaces. Langmuir 2008, 24, (16), 8695-8700. 55. Chang, X.; Bouchard, D. C., Multiwalled Carbon Nanotube Deposition on Model Environmental Surfaces. Environmental Science & Technology 2013. 56. Tammelin, T.; Saarinen, T.; Österberg, M.; Laine, J., Preparation of Langmuir/Blodgettcellulose Surfaces by Using Horizontal Dipping Procedure. Application for Polyelectrolyte Adsorption Studies Performed with QCM-D. Cellulose 2006, 13, (5), 519-535. 57. Wu, J.; Alemany, L. B.; Li, W.; Petrie, L.; Welker, C.; Fortner, J. D., Reduction of Hydroxylated Fullerene (Fullerol) in Water by Zinc: Reaction and Hemiketal Product Characterization. Environmental Science & Technology 2014, 48, (13), 7384-7392. 58. Jiang, X.; Tong, M.; Li, H.; Yang, K., Deposition kinetics of zinc oxide nanoparticles on natural organic matter coated silica surfaces. Journal of Colloid and Interface Science 2010, 350, (2), 427-434. 59. Nguyen, T. H.; Chen, K. L., Role of Divalent Cations in Plasmid DNA Adsorption to Natural Organic Matter-Coated Silica Surface. Environmental Science & Technology 2007, 41, (15), 5370-5375. 60. Fatisson, J.; Domingos, R. F.; Wilkinson, K. J.; Tufenkji, N., Deposition of TiO2 Nanoparticles onto Silica Measured Using a Quartz Crystal Microbalance with Dissipation Monitoring. Langmuir 2009, 25, (11), 6062-6069. 61. Song, J. E.; Phenrat, T.; Marinakos, S.; Xiao, Y.; Liu, J.; Wiesner, M. R.; Tilton, R. D.; Lowry, G. V., Hydrophobic Interactions Increase Attachment of Gum Arabic- and PVP-Coated Ag Nanoparticles to Hydrophobic Surfaces. Environmental Science & Technology 2011, 45, (14), 5988-5995.


30

Page 31 of 32

609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639


62. Xiao, Y.; Wiesner, M. R., Transport and Retention of Selected Engineered Nanoparticles by Porous Media in the Presence of a Biofilm. Environmental Science & Technology 2013, 47, (5), 2246-2253. 63. Faghihnejad, A.; Zeng, H., Hydrophobic interactions between polymer surfaces: using polystyrene as a model system. Soft Matter 2012, 8, (9), 2746-2759. 64. Meyer, E. E.; Rosenberg, K. J.; Israelachvili, J., Recent progress in understanding hydrophobic interactions. Proceedings of the National Academy of Sciences 2006, 103, (43), 15739-15746. 65. Zhuang, J.; Qi, J.; Jin, Y., Retention and transport of amphiphilic colloids under unsaturated flow conditions: Effect of particle size and surface property. Environmental Science & Technology 2005, 39, (20), 7853-7859. 66. Reviakine, I.; Johannsmann, D.; Richter, R. P., Hearing What You Cannot See and Visualizing What You Hear: Interpreting Quartz Crystal Microbalance Data from Solvated Interfaces. Analytical Chemistry 2011, 83, (23), 8838-8848. 67. Tellechea, E.; Johannsmann, D.; Steinmetz, N. F.; Richter, R. P.; Reviakine, I., ModelIndependent Analysis of QCM Data on Colloidal Particle Adsorption. Langmuir 2009, 25, (9), 5177-5184. 68. Olsson, A. L. J.; Quevedo, I. R.; He, D.; Basnet, M.; Tufenkji, N., Using the Quartz Crystal Microbalance with Dissipation Monitoring to Evaluate the Size of Nanoparticles Deposited on Surfaces. ACS Nano 2013, 7, (9), 7833-7843. 69. Quevedo, I. R.; Olsson, A. L. J.; Tufenkji, N., Deposition Kinetics of Quantum Dots and Polystyrene Latex Nanoparticles onto Alumina: Role of Water Chemistry and Particle Coating. Environmental Science & Technology 2013, 47, (5), 2212-2220. 70. Nguyen, T. H.; Elimelech, M., Plasmid DNA Adsorption on Silica: Kinetics and Conformational Changes in Monovalent and Divalent Salts. Biomacromolecules 2006, 8, (1), 2432. 71. Chowdhury, I.; Duch, M. C.; Mansukhani, N. D.; Hersam, M. C.; Bouchard, D., Deposition and Release of Graphene Oxide Nanomaterials Using a Quartz Crystal Microbalance. Environmental Science & Technology 2013, 48, (2), 961-969.


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