Stratified Assemblies of Magnetite Nanoparticles and Montmorillonite Prepared by the Layer-by-Layer Assembly

Abstract

Hybrid thin films are prepared from 8 to 10 nm Fe3O4 nanoparticles and exfoliated montmorillonite clay by using layer-by-layer assembly on poly(diallyldimethylammonium bromide), PDDA. Distinct stratification of the Fe3O4/PDDA/clay films is obtained due to the sheetlike structure of the clay particles. This feature distinguishes these assemblies from their polyelectrolyte-polyelectrolyte analogues, where the layers of individual polyelectrolytes are strongly interdigitated. Being adsorbed on PDDA strictly parallel to the substrate surface, montmorillonite produces a dense layer of overlapping alumosilicate sheets, which virtually flawlessly separates one magnetite layer from another. The difference in magnetic properties between assemblies of various architectures is attributed to the insulation effect of clay layers inserted between magnetic layers. The montmorillonite sheets disrupt the electron exchange interactions between the magnetite nanoparticles in adjacent layers, thereby limiting the magnetization reversal to two dimensions. Some optical properties of Fe3O4/PDDA films are investigated as well. When they are deposited on thin plastic substrate, oscillations of optical density were observed in the red part of the UV-vis spectrum. This effect, which was never been observed for conventional, thick substrates such as glass slides, stems from the interference of the light beams passed through and reflected off of the assembled film.

Freestanding Nanostructures via Layer‐by‐Layer Assembly

“…[94][95][96][97][98] Spasova et al have synthesized optically tunable microspheres with magnetic/gold particle shells using LbL assembly. [85] Such microspheres can be assembled into chains up to 1 mm in length by deposition in a magnetic field.…”

“…[33,94,[110][111][112][113][114] The synthesis of artificial nacre by LbL assembly provides a striking example of the potential of LbL fabrication. The internal structure of these artificial nacre films mimics seashell nacre, with the organic and inorganic layers forming multilayered nanostructures.…”

Magnetic/gold nanoparticle functionalized biocompatible microcapsules with sensitivity to laser irradiation

“…[4][5][6][7][8] The LbL assembly method is based on the bottom-up principle used in the fabrication of composite materials, 9 which makes it possible to achieve a significant control over the physical properties of nanodimensional shells 10,11 or planar layers. [12][13][14][15][16] A study of the control of microcapsule properties by varying shell composition and physicochemical parameters of the surrounding medium for encapsulation of substances and their controlled release was already published. 17 However, many applications also require remote control over the permeability of the microcapsule shell.…”

Challenges and breakthroughs in recent research on self-assembly

“…Because of the simplicity of the assembly process, there is a vast choice of materials available. Various types of polymers including conventional polyelectrolytes [770][771][772][773][774], conductive polymers [775,776], block-copolymers, dendrimers [777,778]; biomaterials such as proteins [780][781][782][783][784][785], nucleic acids [786,787], saccharides [788][789][790][791][792], virus particles [793], and other biomaterials [795]; inorganic materials such as colloidal particles [795][796][797][798][799], quantum dots [800], clay plates [801,802], nanosheet [803][804][805][806][807][808][809], nanorods and nanowires [810,811], various nanotubes [812,813], and other inorganic substances [814][815]…”