We report the first synthesis of highly stable and efficiently recyclable multifunctional adsorbents containing FeCo/GC nanoparticles with the strongest magnetic properties.
We have synthesized ultra-small and uniform Fe(x)Co(1-x)/graphitic carbon shell (Fe(x)Co(1-x)/GC) nanocrystals (x=0.13, 0.36, 0.42, 0.50, 0.56, and 0.62, respectively) with average diameters of <4 nm by thermal decomposition of metal precursors in approximately 60 nm MCM-41 and methane CVD. The composition of the Fe(x)Co(1-x)/GC nanocrystals can be tuned by changing the Fe:Co ratios of the metal precursors. The Fe(x)Co(1-x)/GC nanocrystals show superparamagnetic properties at room temperature. The Fe(0.50)Co(0.50)/GC, Fe(0.56)Co(0.44)/GC, and Fe(0.62)Co(0.38)/GC nanocrystals have a single bcc FeCo structure, whereas the Fe(0.13)Co(0.87)/GC, Fe(0.36)Co(0.64)/GC, and Fe(0.42)Co(0.58)/GC nanocrystals have a mixed structure of bcc FeCo and fcc Co. The single bcc-phased Fe(x)Co(1-x)/GC nanocrystals functionalized with phospholipid-poly(ethylene glycol) (PL-PEG) in phosphate buffered saline (PBS) are demonstrated to be excellent T(1) MRI contrast agents.
We have developed a highly stable and magnetically recyclable nanocatalyst system for alkene hydrogenation. The materials are composed of mesoporous silica spheres (MSS) embedded with FeCo/graphitic shell (FeCo/GC) magnetic nanoparticles and Pt nanocatalysts (Pt-FeCo/GC@MSS). The Pt-FeCo/GC@MSS have superparamagnetism at room temperature and show type IV isotherm typical for mesoporous silica, thereby ensuring a large enough inner space (surface area of 235.3 m(2) g(-1), pore volume of 0.165 cm(3) g(-1), and pore diameter of 2.8 nm) to undergo catalytic reactions. We have shown that the Pt-FeCo/GC@MSS system readily converts cyclohexene into cyclohexane, which is the only product isolated and Pt-FeCo/GC@MSS can be seperated very quickly by an external magnetic field after the catalytic reaction is finished. We have demonstrated that the recycled Pt-FeCo/GC@MSS can be reused further for the same hydrogenation reaction at least four times without loss in the initial catalytic activity.
Covalently functionalized water-soluble FeCo/ graphitic shell nanocrystals (fÀFeCo/GC NCs) were synthesized via 1,3-dipolar cycloaddition of azomethine ylides generated in situ from sarcosine and glucose. The FeCo core has superparamagnetic properties at room temperature, and the graphitic shell exhibits near-infrared optical absorbance. Acetylation of the hydroxyl groups on the fÀFeCo/GC NCs gives doubly functionalized FeCo/GC (ffÀFeCo/GC) NCs that are soluble only in organic solvents such as ethyl acetate. The fÀFeCo/GC NCs were shown to be excellent T 1 or T 2 MRI contrast agents. Especially, due to the hydrophilic and compact surface functionalization, fÀFeCo/GC NCs exhibit a doubled r 1 relaxivity and half r 2 /r 1 ratio compared to those of the non-covalently PL-PEG-functionalized FeCo/GC NCs. This work shows not only the first synthesis of covalently functionalized highly water-soluble metal NCs coated with a single-layered graphitic shell, but also for the first time the MR enhancing properties of the covalently functionalized magnetic NCs.[a] Dr.
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