Thin films of metal oxide nano-particles (NPs) are used in nano-technological applications, such as semiconductors and solar cells, as these films can potentially give the desired optical and electrical properties. Films of NPs with a controlled packing can be made by forming Langmuir films of NPs at an air-aqueous interface and then by depositing and sintering these films to a substrate. However, Langmuir films of metal oxide NPs (SiO2 or TiO2) cannot form at air-water interfaces, as their high hydrophilicity makes them instable at the air-water interface. A common method to overcome this problem is to hydrophobically modify the NPs by using surfactants or polymers. In this talk, we will discuss an alternate way of making non-modified metal oxide NPs stable at air-aqueous interfaces, which involves the addition of inorganic salts to the aqueous phase. We will also discuss how to modify the physical properties (roughness and surface charge) of the transferred films by mixing NPs of different sizes and types at the air-aqueous interface.

Magnetite nanoparticles (MNPs) show unique properties important for nanomedicine such as small size, nontoxicity, wide chemical affinity, and intrinsic superparamagnetism. These properties make them attractive nanomaterials for application in magnetic resonance imaging, targeted drug delivery, and hyperthermia-based cancer therapy. Moreover, their functionalisation with biopolymers can improve their biocompatibility, biodegradability, and bioadhesivity. Numerous types of MNPs for medical applications have been synthesised, but only a few of them have been introduced on the market. One of the reasons behind this is the limited knowledge of the effect of MNPs on biological cells. Native biological membranes are dynamic and complex systems, which hinders understanding of interactions between nanomaterials and components of these membranes through studies based on cell lines. Such a kind of research also provides information only on the collective response of whole cells. Hence, complementary methods based on simplified models of cell membranes and delivering information about the influence of nanomaterials at the molecular level have attracted a great deal of attention. A useful tool for studying the interaction between nanomaterials and phospholipids in model cell membranes is a Langmuir technique. A single Langmuir monolayer made of phospholipids at the air-water interface constitutes a simplified model of a native cell membrane consisting of two weakly coupled phospholipid monolayers with embedded peptides, cholesterol, sugars, etc. The presented research demonstrates the use of the Langmuir method to study the effect of MNPs functionalized with different biopolymers on the stability, phase state, viscoelastic properties, and morphology of the model cell membranes.