Smallest Bimetallic CoPt₃ Superparamagnetic Nanoparticles

Abstract

We present for the first time a nonaqueous sol-gel route to produce ultrasmall (<2 nm) magnetic bimetallic CoPt nanoparticles (NPs). The one-pot procedure is carried out at low temperature (180 °C) using benzyl alcohol, acting as both reducing agent and solvent. The highly monodisperse CoPt NPs were investigated with innovative advanced X-ray methods (whole powder pattern modeling), HR-STEM, XPS, and SQUID magnetometry. XPS showed Co was mostly in metallic form, but with a very small amount of CoO on the NP surface. The spherical NPs had an ultrasmall diameter of 1.6 nm and could self-assemble in aligned linear chains, or nanobelts, of single NPs. They are superparamagnetic, with blocking temperature of ∼20 K and coercivity at 10 K of 27.9 kA m (∼350 Oe). However, there is evidence of a second magnetic phase (probably CoO) in the ZFC magnetization curve, which enhances their magnetization values, without significantly affecting their superparamagnetism.

Plasmonic properties of an Ag@Ag2Mo2O7 hybrid nanostructure easily designed by solid-state photodeposition from very thin Ag2Mo2O7 nanowires

“…42 As already described, 27,28 a combination of energy X-ray dispersive spectroscopy (EDS) and HR-TEM techniques, which is a powerful tool to extract structural and chemical information at the nanoscale. 43,44 The EDS spectra were recorded on the NPs and compared to those obtained on the NWs (Figure 3c). While the NWs show the presence of Ag, O and Mo lines (and also Cu coming from the TEM grid), only the Ag line is observed for the NPs.…”

Hybrid Noble-Metals/Metal-Oxide Bifunctional Nano-Heterostructure Displaying Outperforming Gas-Sensing and Photochromic Performances

“…To get more information on the nature of the NPs, they were investigated by a combination of energy dispersive X-ray spectroscopy (EDS) and high-resolution TEM (HR-TEM) techniques, that is, a powerful tool to extract structural and chemical information at the nanoscale. 25 A darker contrast in STEM–HAADF images highlights materials having lower atomic number and/or lower mass density and/or lower thickness. Thus, these NPs showing a darker contrast correspond to TiO 2 NPs.…”

Increased UV absorption properties of natural hydroxyapatite‐based sunscreen through laser ablation modification in liquid

“…The microstructural features were analyzed via the whole powder pattern modeling (WPPM) method, through the PM2K software; this novel technique exploits XRD by describing each observed peak profile as a convolution of instrumental and sample‐related physical effects, and by refining the corresponding model parameters directly on the observed data . Therefore, adopting the WPPM formalism, microstructure information such as crystalline domain shape and size (ie, the size of coherently scattering domains), size distribution, defect type, and content, can be obtained quantitatively . The shape of the crystalline domains was approximated to be spherical, with diameter distributed according to a log‐normal curve.…”