Origin and Quenching of Novel ultraviolet and blue emission in NdGaO3: Concept of Super-Hydrogenic Dopants.

In this study we report the existence of novel ultraviolet (UV) and blue emission in rare-earth based perovskite NdGaO3 (NGO) and the systematic quench of the NGO photoluminescence (PL) by Ce doping. Study of room temperature PL was performed in both single-crystal and polycrystalline NGO (substrates and pellets) respectively. Several NGO pellets were prepared with varying Ce concentration and their room temperature PL was studied using 325 nm laser. It was found that the PL intensity shows a systematic quench with increasing Ce concentration. XPS measurements indicated that nearly 50% of Ce atoms are in the 4+ state. The PL quench was attributed to the novel concept of super hydrogenic dopant (SHD)", where each Ce4+ ion contributes an electron which forms a super hydrogenic atom with an enhanced Bohr radius, due to the large dielectric constant of the host. Based on the critical Ce concentration for complete quenching this SHD radius was estimated to be within a range of 0.85 nm and 1.15 nm whereas the predicted theoretical value of SHD radius for NdGaO3 is ~1.01 nm

Design and Synthesis of Polymer-Functionalized NIR Fluorescent Dyes–Magnetic Nanoparticles for Bioimaging

The fluorescent probes having complete spectral separation between absorption and emission spectra (large Stokes shift) are highly useful for solar concentrators and bioimaging. In bioimaging application, NIR fluorescent dyes have a greater advantage in tissue penetration depth compared to visible-emitting organic dyes or inorganic quantum dots. Here we report the design, synthesis, and characterization of an amphiphilic polymer, poly(isobutylene-<i>alt</i>-maleic anhyride)-functionalized near-infrared (NIR) IR-820 dye and its conjugates with iron oxide (Fe₃O₄) magnetic nanoparticles (MNPs) for optical and magnetic resonance (MR) imaging. Our results demonstrate that the Stokes shift of unmodified dye can be tuned (from ∼106 to 208 nm) by the functionalization of the dye with polymer and MNPs. The fabrication of bimodal probes involves (i) the synthesis of NIR fluorescent dye (IR-820 cyanine) functionalized with ethylenediamine linker in high yield, >90%, (ii) polymer conjugation to the functionalized NIR fluorescent dye, and (iii) grafting the polymer-conjugated dyes on iron oxide MNPs. The resulting uniform, small-sized (<i>ca</i>. 6 nm) NIR fluorescent dye–magnetic hybrid nanoparticles (NPs) exhibit a wider emissive range (800–1000 nm) and minimal cytotoxicity. Our preliminary studies demonstrate the potential utility of these NPs in bioimaging by means of direct labeling of cancerous HeLa cells <i>via</i> NIR fluorescence microscopy and good negative contrast enhancement in <i>T</i>₂-weighted MR imaging of a murine model

Design and synthesis of polymer-functionalized NIR fluorescent dyes-magnetic nanoparticles for bioimaging

10.1021/nn401734tACS Nano786796-680