UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .

Advanced Nanoarchitectures for Solar Photocatalytic Applications

The tremendous interest in magnetic nanoparticles (MNPs) is reflected in published research that ranges from novel methods of synthesis of unique nanoparticle shapes and composite structures to a large number of MNP characterization techniques, and finally to their use in many biomedical and nanotechnology-based applications. The knowledge gained from this vast body of research can be made more useful if we organize the associated results to correlate key magnetic properties with the parameters that influence them. Tuning these properties of MNPs will allow us to tailor nanoparticles for specific applications, thus increasing their effectiveness. The complex magnetic behavior exhibited by MNPs is governed by many factors; these factors can either improve or adversely affect the desired magnetic properties. In this report, we have outlined a matrix of parameters that can be varied to tune the magnetic properties of nanoparticles. For practical utility, this review focuses on the effect of size, shape, composition, and shell-core structure on saturation magnetization, coercivity, blocking temperature, and relaxation time.

http://lee.chem.uh.edu/2013/Int.%20J.%20Mol.%20Sci.%202013,%2014,%2015977.pdf

Tuning the Magnetic Properties of Nanoparticles

Highly crystalline single-domain magnetite Fe3O4 nanoparticles (NPs) are important, not only for fundamental understanding of magnetic behaviour, but also for their considerable potential applications in biomedicine and industry. Fe3O4 NPs with sizes of 10–300 nm were systematically investigated to reveal the fundamental relationship between the crystal domain structure and the magnetic properties. The examined Fe3O4 NPs were prepared under well-controlled crystal growth conditions using a large-scale liquid precipitation method. The crystallite size of cube-like NPs estimated from X-ray diffraction pattern increased linearly as the particle size (estimated by transmission electron microscopy) increased from 10 to 64.7 nm, which indicates that the NPs have a single-domain structure. This was further confirmed by the uniform lattice fringes. The critical size of approximately 76 nm was obtained by correlating particle size with both crystallite size and magnetic coercivity; this was reported for the first time in this study. The coercivity of cube-like Fe3O4 NPs increased to a maximum of 190 Oe at the critical size, which suggests strong exchange interactions during spin alignment. Compared with cube-like NPs, sphere-like NPs have lower magnetic coercivity and remanence values, which is caused by the different orientations of their polycrystalline structure.

/pdf/correlation-between-particle-size-domain-structure-and-8wklos383f.pdf

Correlation between particle size/domain structure and magnetic properties of highly crystalline Fe3O4 nanoparticles

Superparamagnetic ferrite nanoparticles (MFe2O4, where M = Fe, Co, Mn) were synthesized through a novel one-step aqueous coprecipitation method based on the use of a new type of alkaline agent: the alkanolamines isopropanolamine and diisopropanolamine. The role played by the bases on the particles’ size, chemical composition, and magnetic properties was investigated and compared directly with the effect of the traditional inorganic base NaOH. The novel MFe2O4 nanomaterials exhibited high colloidal stability, particle sizes in the range of 4–12 nm, and superparamagnetic properties. More remarkably, they presented smaller particle sizes (up to 6 times) and enhanced saturation magnetization (up to 1.3 times) relative to those prepared with NaOH. Furthermore, the nanomaterials exhibited improved magnetic properties when compared with nanoferrites of similar size synthesized by coprecipitation with other bases or by other methods reported in the literature. The alkanolamines were responsible for these achievem...

Superparamagnetic MFe2O4 (M = Fe, Co, Mn) Nanoparticles: Tuning the Particle Size and Magnetic Properties through a Novel One-Step Coprecipitation Route

Iron oxide nanoparticles (NPs) hold great promise for future biomedical applications because of their magnetic properties as well as other intrinsic properties such as low toxicity, colloidal stability, and surface engineering capability. Numerous related studies on iron oxide NPs have been conducted. Recent progress in nanochemistry has enabled fine control over the size, crystallinity, uniformity, and surface properties of iron oxide NPs. This review examines various synthetic approaches and surface engineering strategies for preparing naked and functional iron oxide NPs with different physicochemical properties. Growing interest in designed and surface-engineered iron oxide NPs with multifunctionalities was explored in in vitro/in vivo biomedical applications, focusing on their combined roles in bioseparation, as a biosensor, targeted-drug delivery, MR contrast agents, and magnetic fluid hyperthermia. This review outlines the limitations of extant surface engineering strategies and several developing strategies that may overcome these limitations. This study also details the promising future directions of this active research field.

Designed synthesis and surface engineering strategies of magnetic iron oxide nanoparticles for biomedical applications

Magnetic iron oxide nanoparticles in the 10−40 nm size range and with a reduced distribution in size have been synthesized under argon by using ammonium bases R4NOH (R = CH3, C2H5, C3H7) and a hydrothermal treatment. The size is tuned owing to the base to iron ratio and to the length of the alkyl chain R. We precipitate first ferric hydroxides at pH 1.5−2, then ferrous hydroxide at pH 5.5−6. The rapid increase of pH up to basic pH leads to the formation of magnetic iron oxide particles of 12 nm. For [base] to [Fe] ratio above 3.5, a homogeneous growth occurs during further hydrothermal treatment at 250 °C. The higher the quantity of base added and the longer the alkyl chain used, the smaller the particle size produced. For sizes above 20 nm, the Verwey transition at 120 K, characteristic of magnetite, is observed on the field cooling−zero field cooling magnetization curve. The nanoparticles can be described by a core−shell model, that is, a magnetite core surrounded by an oxidized layer close to maghemite...

Jaime Santoyo Salazar

Papers

Magnetic Iron Oxide Nanoparticles in 10−40 nm Range: Composition in Terms of Magnetite/Maghemite Ratio and Effect on the Magnetic Properties