Adsorption of cobalt ferrite nanoparticles within layer-by-layer films: a kinetic study carried out using quartz crystal microbalance

Abstract

The paper reports on the successful use of the quartz crystal microbalance technique to assess accurate kinetics and equilibrium parameters regarding the investigation of in situ adsorption of nanosized cobalt ferrite particles (CoFe 2 O 4 -10.5 nm-diameter) onto two different surfaces. Firstly, a single layer of nanoparticles was deposited onto the surface provided by the gold-coated quartz resonator functionalized with sodium 3-mercapto propanesulfonate (3-MPS). Secondly, the layer-by-layer (LbL) technique was used to build multilayers in which the CoFe 2 O 4 nanoparticle-based layer alternates with the sodium sulfonated polystyrene (PSS) layer. The adsorption experiments were conducted by modulating the number of adsorbed CoFe 2 O 4 /PSS bilayers (n) and/or by changing the CoFe 2 O 4 nanoparticle concentration while suspended as a stable colloidal dispersion. Adsorption of CoFe 2 O 4 nanoparticles onto the 3-MPS-functionalized surface follows perfectly a first order kinetic process in a wide range (two orders of magnitude) of nanoparticle concentrations. These data were used to assess the equilibrium constant and the adsorption free energy. Alternatively, the Langmuir adsorption constant was obtained while analyzing the isotherm data at the equilibrium. Adsorption of CoFe 2 O 4 nanoparticles while growing multilayers of CoFe 2 O 4 /PSS was conducted using colloidal suspensions with CoFe 2 O 4 concentration in the range of 10 À8 to 10 À6 (moles of cobalt ferrite per litre) and for different numbers of cycles n = 1, 3, 5, and 10. We found the adsorption of CoFe 2 O 4 nanoparticles within the CoFe 2 O 4 /PSS bilayers perfectly following a first order kinetic process, with the characteristic rate constant growing with the increase of CoFe 2 O 4 nanoparticle concentration and decreasing with the rise of the number of LbL cycles (n). Additionally, atomic force microscopy was employed for assessing the LbL film roughness and thickness. We found the film thickness increasing from about 20 to 120 nm while shifting from 3 to 10 CoFe 2 O 4 /PSS bilayers, using the 8.9 Â 10 À6 (moles of cobalt ferrite per litre) suspension.

Magnetic nanoparticle film reconstruction modulated by immersion within DMSA aqueous solution

“…For film fabrication the stock MF sample was diluted down to 5 × 10 13 particle/mL whereas the glass substrate was immersed into the MF for 3 minute. Typical AFM image of the fabricated film is shown in Figure 3S (see Supplementary ), revealing a high nanoparticle surface coverage, likely above 90% as expected from a first order kinetics film deposition process 39 . Subsequently, after drying out the solvent, the as-prepared MNP-based film was immersed into DMSA aqueous solutions prepared at three different molar concentration, namely 0.025, 0.050 and 0.100 mol/L to produce Sample-L, Sample-I and Sample-H, respectively.…”

Hybrid Nanoscale Magnetic Composites

“…It is observed a shoulder at 480 nm characteristic of maghemite, once PSS does not show any absorption in the visible range. 55 A representative cross-sectional high resolution transmission electron microscopy (HRTEM) micrograph of nanofilms comprised by polyaniline and maghemite (PANI/J-n-MAG) is shown in Figure 5 (a). Similar results are observed with other nanoparticle/polyelectrolyte systems when adsorption is driven by electrostatic attraction.…”

Combined quartz crystal microbalance with dissipation (QCM-D) and generalized ellipsometry (GE) to characterize the deposition of titanium dioxide nanoparticles on model rough surfaces

“…In recent years, the deposition of nanoparticles onto various surfaces has been investigated using quartz crystal microbalance with dissipation (QCM-D) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. A QCM-D sensor surface maintains resonant mechanical oscillations which cause shear motions of sheet layers of liquid within which the sensor is embedded.…”