IRON OXIDE NANOPARTICLES IN DRUG DELIVERY SYSTEMS

The geometry and electronic structure of iron oxide Fe 3 O 4 with di-glucose and pentapeptide CREKA complex compound have been studied by the semiempirical molecular mechanics MM + and quantum chemistry РМ3 methods. The geometrical and energy parameters, characterizing the low energy states of the complex, were calculated using the HyperChem 8.03 program. A synthetic macromolecule, aminodextran-coated iron oxide nanoparticles conjugated with CREKA peptide, was then synthesized as a nanocarrier, which was detectable using magnetic resonance imaging. The synthesis process began with a two-step reaction that attached a high density of amino groups to a dextran backbone. The aminodextran-coated iron oxide nanoparticles thus synthesized were characterized using Fourier transform infrared spectroscopy. Also, the morphology of this synthetic macromolecule was studied by scanning electron microscopy

Tailoring Plasmonic Enhanced Upconversion in Single NaYF4:Yb3+/Er3+ Nanocrystals

By using silver nanoplatelets with a widely tunable localized surface plasmon resonance (LSPR), and their corresponding local field enhancement, here we show large manipulation of plasmonic enhanced upconversion in NaYF4:Yb(3+)/Er(3+) nanocrystals at the single particle level. In particular, we show that when the plasmonic resonance of silver nanolplatelets is tuned to 656 nm, matching the emission wavelength, an upconversion enhancement factor ~5 is obtained. However, when the plasmonic resonance is tuned to 980 nm, matching the nanocrystal absorption wavelength, we achieve an enhancement factor of ~22 folds. The precise geometric arrangement between fluorescent nanoparticles and silver nanoplatelets allows us to make, for the first time, a comparative analysis between experimental results and numerical simulations, yielding a quantitative agreement at the single particle level. Such a comparison lays the foundations for a rational design of hybrid metal-fluorescent nanocrystals to harness the upconversion enhancement for biosensing and light harvesting applications

Controlling the emission rate of Er3+ ions by dielectric coupling with thin films

The variation of local density of states and/or excitation of surface plasmons in proximity of a metal surface can be used to control the emission rate of Er-doped materials for optical and optoelectronic devices. In the present work we studied the modification of the radiative lifetime of Er3+ ions incorporated in silica layers by magnetron cosputtering, due to the interaction with metal (Ag, Au, Ti, and Cr) and semiconductor (Si) thin films. Photoluminescence measurements have shown in both cases a strong decrease of the erbium lifetime for the radiative transition at 1540 nm and a clear dependence on the distance between the film and the emitter up to 250 nm. A comparison between the effect of homogeneous thin films and nanostructured layers (nanohole arrays) has also been carried out. The results demonstrated that a high control over the radiative efficiency of the emitter can be achieved by a proper choice of the overlayer properties, and an increase of the radiative decay rate up to 300% has been experimentally measured