RESUMEN
InP/ZnSe/ZnS quantum dots (QDs) stand as promising candidates for advancing QD-organic light-emitting diodes (QLED), but low emission efficiency due to their susceptibility to oxidation impedes applications. Structural defects play important roles in the emission efficiency degradation of QDs, but the formation mechanism of defects in oxidized QDs has been less investigated. Here, we investigated the impact of diverse structural defects formation on individual QDs and propagation during UV-facilitated oxidation using high-resolution (scanning) transmission electron microscopy. UV-facilitated oxidation of the QDs alters shell morphology by the formation of surface oxides, leaving ZnSe surfaces poorly passivated. Further oxidation leads to the formation of structural defects, such as dislocations, and induces strain at the oxide-QD interfaces, facilitating In diffusion from the QD core. These changes in the QD structures result in emission quenching. This study provides insight into the formation of structural defects through photo-oxidation, and their effects on emission properties of QDs.
RESUMEN
The delaminated gadolinium hydroxide layers doped with Eu(3+) ions were assembled on the surface of silica spheres and annealed at high temperatures, resulting in the formation of fluorescent and MR active GdPO(4) : Eu nanoparticles at the surface.
Asunto(s)
Medios de Contraste/química , Gadolinio/química , Nanopartículas del Metal/química , Dióxido de Silicio/química , Imagen por Resonancia Magnética , Espectrometría de FluorescenciaRESUMEN
The assembly of NiO nanoparticles at the surface of magnetic silica resulted in a hybrid superstructure which has utility as a carrier for a magnetically separable biocatalyst system.
Asunto(s)
Biocatálisis , Óxido Ferrosoférrico/química , Magnetismo , Níquel/química , Dióxido de Silicio/química , Enzimas Inmovilizadas/química , Enzimas Inmovilizadas/genética , Enzimas Inmovilizadas/metabolismo , Epóxido Hidrolasas/química , Epóxido Hidrolasas/genética , Epóxido Hidrolasas/metabolismo , Escherichia coli/genética , Óxido Ferrosoférrico/síntesis química , Nanopartículas/química , Rhodotorula/enzimología , Propiedades de SuperficieRESUMEN
A layered gadolinium hydroxychloride (LGdH), [Gd2(OH)5(H2O)x]Cl, was synthesized from an aqueous solution of GdCl3.6H2O. The X-ray diffraction (XRD) and the selected area electron diffraction (SAED) studies showed that this compound crystallizes in the orthorhombic structure (a = 12.88(4) A, b = 7.30(2) A, and c = 8.46(3) A) which is isostructural with [Eu2(OH)5(H2O)x]Cl. Interestingly, this layered material was readily dispersed and led to a stable colloidal nanosheet in aqueous medium. The obtained colloidal solutions were characterized by the evaluation of their stability in acidic solution, their in vitro cytotoxicity, and their magnetic resonance imaging (MRI) relaxation properties. It is reported that the relaxometry analysis of LGdH suspensions exhibits a sufficient contrast effect for T1 weighted magnetic resonance imaging.
Asunto(s)
Medios de Contraste/síntesis química , Gadolinio/química , Hidróxidos/síntesis química , Imagen por Resonancia Magnética , Coloides/síntesis química , Coloides/química , Medios de Contraste/química , Hidróxidos/química , Tamaño de la Partícula , Suspensiones/síntesis química , Suspensiones/química , Temperatura , Agua/químicaRESUMEN
The decoration of iron oxide nanoparticles with Ni2+ ions provided the superparamagnetic nanoparticles with a binding site for His-tagged proteins, allowing their selective binding and convenient separation from a multi-component solution with an appropriately applied magnetic field.