Low-Platinum-Content Exchange-Coupled CoPt Nanoalloys with Enhanced Magnetic Properties.

Bimetallic colloidal CoPt nanoalloys with low platinum content were successfully synthesized following a modified polyol approach. Powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) studies were performed to estimate the crystal structure, morphology, and surface functionalization of the colloids, respectively, while the room-temperature magnetic properties were measured using a vibrating sample magnetometer (VSM). The particles exhibit excellent uniformity, with a narrow size distribution, and display strong room-temperature hysteretic ferromagnetic behavior even in the as-made form. Upon annealing at elevated temperatures, progressive formation and co-existence of exchange coupled, of both chemically ordered and disordered phases significantly enhanced the room-temperature coercivity.

LAPONITE® nanodisk-"decorated" Fe3O4 nanoparticles: a biocompatible nano-hybrid with ultrafast magnetic hyperthermia and MRI contrast agent ability.

Magnetic Fe3O4 nanoparticles "decorated" by LAPONITE® nanodisks have been materialized utilizing the Schikorr reaction following a facile approach and tested as mediators of heat for localized magnetic hyperthermia (MH) and as magnetic resonance imaging (MRI) agents. The synthetic protocol involves the interaction between two layered inorganic compounds, ferrous hydroxide, Fe(OH)2, and the synthetic smectite LAPONITE® clay Na0.7+[(Si8Mg5.5Li0.3)O20(OH)4]0.7-, towards the formation of superparamagnetic Fe3O4 nanoparticles, which are well decorated by the diamagnetic clay nanodisks. The latter imparts high negative ζ-potential values (up to -34.1 mV) to the particles, which provide stability against flocculation and precipitation, resulting in stable water dispersions. The obtained LAPONITE®-"decorated" Fe3O4 nanohybrids were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy, dynamic light scattering (DLS) and vibrating sample magnetometry (VSM) at room temperature, revealing superior magnetic hyperthermia performance with specific absorption rate (SAR) values reaching 540 W gFe-1 (28 kA m-1, 150 kHz) for the hybrid material with a magnetic loading of 50 wt% Fe3O4/LAPONITE®. Toxicity studies were also performed with human glioblastoma (GBM) cells and human foreskin fibroblasts (HFF), which show negligible to no toxicity. Furthermore, T2-weighted MR imaging of rodent brain shows that the LAPONITE®-"decorated" Fe3O4 nanohybrids predominantly affected the transverse T2 relaxation time of tissue water, which resulted in a signal drop on the MRI T2-weighted imaging, allowing for imaging of the magnetic nanoparticles.

Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction.

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids' surface functionalization in a nonpolar solvent.

Functionalization effects on HKUST-1 and HKUST-1/graphene oxide hybrid adsorbents for hydrogen sulfide removal.

HKUST-1, a Cu-based metalorganic framework (MOF), was synthesized solvothermally, functionalized with polyethyleneimine (PEI), and hybridized with graphene oxide (GO) and functionalized GO for H2S removal. MOF synthesis approach, molecular weight of amines, and the content of GO in the hybrid adsorbents were systematically varied. The adsorbent materials were characterized by XRD, FTIR, SEM, elemental analysis, liquid N2 adsorption-desorption, water vapor and oxygen sorption, and subsequently tested for H2S adsorption in a breakthrough column. The MOF in the composite adsorbents consisting of in-situ grown HKUST-1 on GO that was pre-functionalized with low molecular weight PEI exhibited the highest H2S adsorption uptake at ambient conditions (0.9 mmol S g-1 MOF) in comparison to 0.5 mmol S g-1 MOF for the parent HKUST-1, thus showing an 80 % increase in uptake, while this material also exhibited significantly enhanced sorption kinetics. H2S adsorption at higher temperature (150 °C) was also performed, and at this temperature a HKUST/GO hybrid adsorbent resulted in the highest MOF capacity, i.e. 2.1 mmol S g-1 MOF, which is 27 % higher than that of the parent MOF at the same conditions. Formation of hybrid adsorbents with GO coupled to tunable functionalization of both GO support and the MOF crystallites can contribute in optimizing H2S capture performance of MOFs.

Iron carbide nanoplatelets: colloidal synthesis and characterization.

Iron carbide nanoplatelets with an orthorhombic Fe3C structure were synthesized following a simple liquid chemical approach. The formation of the carbide phases was shown to depend on the presence of a long chain diol and the reaction temperature. Confirmation of the iron carbide phases and structural characterization was made by X-ray diffraction (XRD) and Mössbauer spectroscopy. Particle morphology was characterized by transmission electron microscopy (TEM) and HR-TEM and the magnetic properties were measured with magnetometry (VSM). The sample with the Fe3C phase shows a ferromagnetic behavior with a magnetization of 139 emu g-1 under a 30 kOe applied field. The simple methodology presented here for producing iron carbide nanoplatelets has promising application in the biomedical and catalyst industries.

Sulfur-oleyl amine platelet derivatives with liquid crystalline behavior.

A novel sulfur-based platelet derivative was synthesized by reacting elemental sulfur with oleyl amine. The sulfur-oleyl amine (S-OA) derivative has an ionic salt form, layered morphology and forms a highly lamellar structure. Polarized optical microscopy (POM) clearly shows the birefringent lyotropic liquid crystalline behavior of the S-OA platelets dispersions.

One pot synthesis and characterization of ultra fine CeO2 and Cu/CeO2 nanoparticles. Application for low temperature CO oxidation.

Ultra fine cerium oxide and copper doped cerium oxide nanoparticles are prepared in a one-step reaction by thermal decomposition of Ce acetate in commercial oleylamine. The products are highly crystalline and were characterized by XRD, Raman spectroscopy, XPS, TEM and BET. The TEM images show that the CeO2 particles prepared are uniformly nanosized. The size of the nanoparticles can be controlled in the sub-10 nm range by the presence of other capping agent in the reaction mixture such as tri-octylphosphine oxide and oleic acid. The copper doped cerium oxide nanoparticles show high specific surface area (up to 299 m2/gr) and high catalytic activity for the low temperature CO oxidation even at low copper loading such as 9 at.%.

Immobilization of magnetic iron oxide nanoparticles on laponite discs - an easy way to biocompatible ferrofluids and ferrogels.

Magnetic nanocomposites containing iron oxide (maghemite) nanoparticles, well embedded in a synthetic clay matrix (laponite) were prepared by a new one step chemical route and characterized by TEM, XRD, magnetization measurements, Mössbauer spectroscopy, DLS, and MRI measurements. The synthetic procedure leads to non-stoichiometric γ-Fe(2)O(3) with a controllable content in the nanocomposite. Magnetic nanoparticles incorporated in the diamagnetic clay matrix exhibit a mean diameter of 13 nm, superparamagnetic behavior with a high saturation magnetization achievable at low applied magnetic fields. In-field Mössbauer spectra and ZFC/FC magnetization curves reveal a perfect ferrimagnetic ordering within nanoparticles with negligible spin frustration and interparticle interactions due to the complete coating of maghemite surfaces by the nanocrystalline laponite matrix. Magnetic iron oxide nanoparticles embedded in laponite matrix exhibit strong T(2) weighted MRI contrast. The maghemite/laponite composite particles have 200 nm hydrodynamic diameter and form very stable hydrosols and/or hydrogels depending on their concentration in water.