Preparation of Fe3O4Spherical Nanoporous Particles Facilitated by Polyethylene Glycol 4000

Much interest has been attracted to the magnetic materials with porous structure because of their unique properties and potential applications. In this report, Fe3O4nanoporous particles assembled from small Fe3O4nanoparticles have been prepared by thermal decomposition of iron acetylacetonate in the presence of polyethylene glycol 4000. The size of the spherical nanoporous particles is 100–200 nm. Surface area measurement shows that these Fe3O4nanoporous particles have a high surface area of 87.5 m2/g. Magnetization measurement and Mössbauer spectrum indicate that these particles are nearly superparamagnetic at room temperature. It is found that the morphology of the products is greatly influenced by polyethylene glycol concentration and the polymerization degree of polyethylene glycol. Polyethylene glycol molecules are believed to facilitate the formation of the spherical assembly

Size-Tailored Physicochemical Properties of Monodisperse Polystyrene Nanoparticles and the Nanocomposites Made Thereof

The latex monodisperse polystyrene (PS) colloids are important for different advanced applications (e.g. in coating, biotechnology etc.). However, the size dependency of their structural properties that impacts the characteristics of the nanocomposites composed thereof is largely unknown. Here, monodisperse PS nanoparticles (MPNPs) are synthesized via emulsion polymerization in five sizes (50, 150, 300, 350, and 450 nm). The size of the PS MPNPs is tailored by controlling the reaction time, temperature, and amount of surfactant and initiator. The correlation between the particle size and structural properties of the PS MPNPs is established by different thermomechanical and optical characterizations. The smaller particles (50 and 150 nm) show a lower glass transition (Tg) and thermal decomposition temperature and a lower Raman peak intensity. Yet, they trigger a higher IR absorption, thanks to a larger surface area. When incorporated in a polyvinyl alcohol (PVA) matrix, the smaller particles impart the resulting nanocomposite a higher tensile strength, and elastic and storage moduli. Whereas, they decline the elongation and loss factor. The very few examples of the MPNPs incorporated polymeric nanocomposites have been unstudied from this perspective. Thus, these tangible knowledge can profit scalable production of this kind of nanocomposite materials for different applications in a cost/energy efficient manner.Peer reviewe

Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed

Size-Dependent Structure and Dynamics of CdS Nanoclusters

CdS nanoparticles with diameters from 14 - 120 Å and very narrow size distributions are studied by x-ray absorption fine structure spectroscopy between 5 and 296 K. Clear trends in the Cd-S distance as a function of size and surface stabilization of the nanoparticles could be observed. Particles with thiols as ligands show an expansion of the Cd-S distance with decreasing particle size whereas polyphosphate stabilized samples are slightly contracted with respect to CdS bulk. The static disorder of the nanoparticles is enlarged with respect to the bulk. In contrast, the dynamic behavior of the nanoparticles shows a slight stiffening of the Cd-S vibration with decreasing particle size. Measurements of the third moment of the pair distribution function indicate the possibility to distinguish between cubic and hexagonal structures in CdS nanoparticles

Size dependence of the pressure-induced gamma to alpha structural transition in iron oxide nanocrystals

The size trend for the pressure-induced gamma-Fe2O3 (maghemite) to alpha-Fe2O3 (hematite) structural phase transition in nanocrystals has been observed. The transition pressure was found to increase with decreasing nanocrystal size: 7 nm nanocrystals transformed at 272GPa, 5 nm at 343GPa and 3 nm at 372GPa. Annealing of a bulk sample of gamma-Fe2O3 was found to reduce the transition pressure from 352 to 242GPa. The bulk modulus was determined to be 2626GPa for 7 nm nanocrystals of gamma-Fe2O3, which is significantly higher than for the value of 1906 GPa that we measured for bulk samples. For alpha-Fe2O3, the bulk moduli for 7 nm nanocrystals (3365) and bulk (30030) were found to be almost the same within error. The bulk modulus for the gamma phase was found to decrease with decreasing particle size between 10 and 3.2 nm particle size. Values for the ambient pressure molar volume were found within 1 percent to be: 33.0 cm3/mol for bulk gamma-Fe2O3, 32.8 cm3/mol for 7 nm diameter gamma-Fe2O3 nanocrystals, 30.7 cm3/mol for bulk alpha-Fe2O3 and 30.6 cm3/mol for alpha-Fe2O3 nanocrystals

Size dependence of the pressure-induced gamma to alpha structural transition in iron oxide nanocrystals

The size trend for the pressure-induced gamma-Fe2O3 (maghemite) to alpha-Fe2O3 (hematite) structural phase transition in nanocrystals has been observed. The transition pressure was found to increase with decreasing nanocrystal size: 7 nm nanocrystals transformed at 272GPa, 5 nm at 343GPa and 3 nm at 372GPa. Annealing of a bulk sample of gamma-Fe2O3 was found to reduce the transition pressure from 352 to 242GPa. The bulk modulus was determined to be 2626GPa for 7 nm nanocrystals of gamma-Fe2O3, which is significantly higher than for the value of 1906 GPa that we measured for bulk samples. For alpha-Fe2O3, the bulk moduli for 7 nm nanocrystals (3365) and bulk (30030) were found to be almost the same within error. The bulk modulus for the gamma phase was found to decrease with decreasing particle size between 10 and 3.2 nm particle size. Values for the ambient pressure molar volume were found within 1 percent to be: 33.0 cm3/mol for bulk gamma-Fe2O3, 32.8 cm3/mol for 7 nm diameter gamma-Fe2O3 nanocrystals, 30.7 cm3/mol for bulk alpha-Fe2O3 and 30.6 cm3/mol for alpha-Fe2O3 nanocrystals

Soft X-ray spectroscopy of single sized CdS nanocrystals : size confinement and electronic structure

Soft X-ray spectroscopy of CdS nanocrystals within their crystalline superlattice allows to relate unambiguously, changes of the electronic structure with the particle size and shape which is known from single crystal X-ray diffraction. We find that the valence and conduction band edge shift contribute to the same extent to the total band gap opening of about 2 eV with respect to CdS bulk as the particle size decreases to 10 Å. Taking a finite height of the potential walls into account, we can reproduce these results within an effective mass approximation model