In order to increase antibacterial abilities and avoid aggregation of Ag nanoparticles, Ag−SiO2 nanocomposites were studied to achieve hybrid structure. SiO2 nanoparticles synthesized by the Stöber method served as seeds for immobilization of Ag. The chemical binding structure and morphology of Ag−SiO2 nanocomposites and SiO2 nanoparticles were investigated with X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The antibacterial properties of Ag−SiO2 nanocomposites were examined with disk diffusion assay and minimum inhibitory concentration (MIC). Results showed that Ag nanoparticles are homogeneously formed on the surface of SiO2 nanoparticles without aggregation and showed excellent antibacterial abilities.

Cu deposition on the surface of spherical SiO2 nanoparticles was studied to achieve the hybrid structure of Cu-SiO2 nanocomposite. SiO2 nanoparticles served as seeds for continuous Cu metal deposition. The chemical structure and morphology were studied with X-ray photoelectron spectroscopy (XPS), scanning electron microscope energy dispersive X-ray (SEM-EDX), and a transmission electron microscope (TEM). The antibacterial properties of the Cu-SiO2 nanocomposite were examined with disk diffusion assays. The homogeneously formed Cu nanoparticles on the surface of SiO2 nanoparticles without aggregation of Cu nanoparticles showed excellent antibacterial ability.

Although several methods (e.g., self-assembly, spin coating, etc.) have been explored for making a monolayer film of nanoparticles, the monolayer on a substrate is typically smaller than 1 micromx1 microm in certain regions. The approach is not ideally suitable for generating a highly ordered and close-packed homogeneous vast monolayer of nanoparticles, which is potentially important for applications. In this report, the preparation of the vast monolayer films of Fe3O4 nanoparticles with a wide range such as that over 3.25 micromx3.95 microm is reported. Their TEM images showed a two-dimensional assembly of Fe3O4 nanoparticles, demonstrating the uniformity of these nanoparticles. The formation of a Langmuir monolayer of the oleic acid-coated Fe3O4 nanoparticles mixed with stearic acid molecules at the air/water interface and its stability were studied with a pressure-area isotherm curve. TEM and BAM studies demonstrated that increasing surface pressure resulted in a transition from well-separated domains of nanoparticles complex to well-compressed, monoparticulate layers.

The Langmuir layer behavior of arachidic acid/γ-Fe2O3 nanoparticle complexes was studied at the air/water interface. The subphase was an aqueous colloidal solution (hydrosol) of γ-Fe2O3 nanoparticles with an average diameter of 8.3 nm and with a standard deviation of ±1.4 nm. Formation of the complex between arachidic acid and γ-Fe2O3 nanoparticles was studied with surface pressure−area isotherms, surface potential−area isotherms and Brewster angle microscopy. Increasing surface pressure resulted in a transition from well-separated domains of the complex to well-compressed, nanoparticulate layers and, ultimately, to multiparticulate layers. The magnetic nanoparticles and layers of nanoparticles on solid substrates were studied with FTIR, Mössbauer spectroscopy and vibrating sample magnetometry (VSM). The γ-Fe2O3 nanoparticles and Langmuir−Blodgett films with the nanoparticles showed superparamagnetic properties. The stability of the γ-Fe2O3 nanoparticle hydrosol solution was studied by ζ potential measurements. Positively charged γ-Fe2O3 nanoparticles in aqueous hydrosol solution at pH 3.5−5 showed excellent long-term colloidal stability.

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Nanocomposite Langmuir-Blodgett films of poly(maleic monoester) (PMA)/Fe 3 O 4 nanoparticles were prepared by transferring PMA/iron oxide nanoparticles complex monolayers in a hydrosol subphase of Fe 3 O 4 nanoparticles onto solid substrates. A Mo ¨ssbauer spectrum of the nanoparticles showed the highly crystalline nature of the magnetite structure. Homogeneous dispersion of Fe 3 O 4 nanoparticles between poly(maleic monoester) layers was observed with transmission electron microscopy (TEM), and surface morphology of the nanocomposite film was studied with atomic force microscopy (AFM). The magnetic properties of the Fe 3 O 4 nanoparticles and the nanocomposite Langmuir-Blodgett film of poly(maleic monoester) (PMA)/ Fe 3 O 4 nanoparticles were studied with vibrating magnetometry (VSM) by obtaining magnetic hysteresis loops. The PMA is a polymeric surfactant and interacts with Fe 3 O 4 nanoparticles by electrostatic attraction between carboxylate groups of PMA and the charged Fe 3 O 4 nanoparticles. This interaction stabilizes the homogeneous dispersion of nanoparticles between the PMA polymer layers. The surface morphology, as shown by AFM images, gives well-formed surface structures that were evenly spaced by iron oxide nanoparticles. The average height of one layer of the PMA/iron oxide nanocomposite film is determined to be 12.9 nm and this is approximately consistent with the summation of the PMA thickness and the average iron oxide diameter with an average roughness of 3.3 nm. The cross sectional AFM image also shows homogeneous distinct single domains of Fe 3 O 4 nanoparticles in the nanocomposite film.

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In the present study, metal nanocrystals were obtained by the very easy, economical, and nontoxic thermal decomposition method and stabilized by coating oleate without any solvent. These nanocrystals have a highly crystalline structure due to a high decomposition temperature (~563-573 K) at low pressure and very narrow distribution. The prepared Fe3O4 nanocrystals were controlled by the annealing time and vacuum pressure. A TEM image of monodispersed Fe3O4 nanocrystals showed the 2D assembly of nanocrystals, demonstrating their uniformity. The particle size is 10.6 +/- 1.2 nm. TEM images of silver nanocrystals a showed 2D assembly with 9.5 +/- 0.7 nm. An electron diffraction image and X-ray diffraction of the nanocrystals showed the highly crystalline nature of metal nanocrystals.