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.