Nonuniform Growth of Composite Layer-by-Layer Assembled Coatings via Three-Dimensional Expansion of Hydrophobic Magnetite Nanoparticles

Abstract

Nanocomposite coatings are promising for a range of practical applications, and layer-by-layer assembly (LbL) is a versatile tool for nanocomposite formation. However, conventional LbL is a quite laborious procedure taking a lot of time to reach a sufficient thickness of the coatings required for practical applications. Herein, we proposed a novel variant of the LbL approach based on the deposition of hydrophilic polyelectrolyte molecules from a polar solvent and hydrophobic magnetite nanoparticles (NPs) from a nonpolar dispersion medium with an intermediate washing in the same polar solvent. The composite multilayers formed in this way exhibit exponential growth of the thickness and mass. On the basis of quartz crystal microbalance (QCM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and surface profile measurements, we propose a model describing the driving force of multilayer formation and the factors leading to nonlinear growth of their mass and thickness. The results allow one to expand the understanding of the mechanism of the LbL assembly in order to form multifunctional nanocomposites in a more efficient way.

Innovation in Layer-by-Layer Assembly

“…Similarly, having a biphasic solution of immiscible liquids with the coating liquid on top allows for low-volume coating of large planar substrates during immersion . Alternatively, deposition from alternating polar and nonpolar solvents can be used to control the film morphology and thickness . Finally, a different approach to expedite manual immersive assembly is to use a magnetic stirrer bar to mix the polymer solution during layering, which greatly speeds up the assembly kinetics (Figure ).…”

Rational Surface Design of Upconversion Nanoparticles with Polyethylenimine Coating for Biomedical Applications: Better Safe than Brighter?

“…With the intention to limit the cytotoxic effects of PEI, six additional surface modifications of the particles were performed to create single (L1) or double (L1, L2) external polymer layers on the surface of the UCNP@PEI particles (see Figure ). Multilayer-structured nanomaterials are known in the field of polymeric nanoparticles; however, this attractive technique is not fully recognized in the area of inorganic nanoparticles, and only a few relevant reports are available for PEI-modified inorganic nanomaterials . Likewise, the reports on the L-b-L assembling of polymer surface coatings on UCNPs are scarce.…”

“…Multilayer-structured nanomaterials are known in the field of polymeric nanoparticles; 53 however, this attractive technique is not fully recognized in the area of inorganic nanoparticles, and only a few relevant reports are available for PEI-modified inorganic nanomaterials. 54 Likewise, the reports on the L-b-L assembling of polymer surface coatings on UCNPs are scarce. For example, (Gd 3+ )-doped UCNPs coated with polyethylene glycol and successively coated with one or two layers of PEI were synthesized in a study where PEI was applied for cell transfection.…”

Inorganic/Organic Multilayer Capsule Composition for Improved Functionality and External Triggering

“…Hence, the capsules sensitive to ultrasound can be used for biomedicine application such as drug delivery. [71] Second approach is based on the control over mechanical properties of microcapsules. The first one is related to preferable nucleation of gas bubbles on the hydrophobic surfaces.…”

“…[129] It is necessary to remark that intensity of cavitation threshold is increasing with frequency increasing, for example, at 0.5 MHz the threshold intensity is 0.25 W cm −2 , at 5 MHz the threshold intensity is 3.33 W cm −2 . [71,142] Interestingly, this approach can be applied in preparation of capsules with terminated hydrophobic layer making them responsive to ultrasound as well as controlling its other properties such as adsorption and possibly permeability. [140] Interface energy formed as results of cavitation bubble collapse at higher frequency is significantly lower compare with low-frequency one.…”