Rida Atif

Bio: Rida Atif is an academic researcher from Georgetown University. The author has contributed to research in topics: Lanthanide & Nanoparticle. The author has an hindex of 1, co-authored 2 publications receiving 4 citations.

Single-Source Precursors for Lanthanide Diselenide Nanosheets

Abstract: A series of complexes of the type [Ln(Se2P(phenyl)2)3(CH3CN)x] (x = 1 or 2) have been synthesized and structurally characterized for Ln = La–Lu (excluding Pm). The complexes are straightforward to ...

Synthesis of Mixed-Valent Lanthanide Sulfide Nanoparticles.

Abstract: In targeting reduced valent lanthanide chalcogenides, we report the first nanoparticle synthesis of the mixed-valent ferromagnets Eu3 S4 and EuSm2 S4 . Using divalent lanthanide halides with bis(trimethylsilyl)sulfide and oleylamine, we prepared nanoparticles of EuS, Eu3 S4 , EuSm2 S4 , SmS1.9 , and Sm3 S4 . All nanoparticle phases were identified using powder X-ray diffraction, transmission electron microscopy was used to confirm morphology and nanoparticle size, and magnetic susceptibility measurements for determining the ordering temperatures and valence. The UV/Vis, Raman and X-ray photoelectron spectroscopies for each phase were compared. Surprisingly, the phase is influenced by the halide and the reaction temperature, where EuCl2 formed EuS while EuI2 formed Eu3 S4 , highlighting the role of kinetics in phase stabilization. Interestingly, at lower temperatures EuI2 initially forms EuS, and converts over time to Eu3 S4 .

Rare-Earth Sulfide Nanocrystals from Wet Colloidal Synthesis: Tunable Compositions, Size-Dependent Light Absorption, and Sensitized Rare-Earth Luminescence.

Abstract: We report the synthesis of colloidal EuS, La2S3, and LaS2 nanocrystals between 150 and 255 °C using rare-earth iodides in oleylamine. The sulfur source dictates phase selection between La2S3 and LaS2, which are stabilized for the first time as colloidal nanocrystals. The indirect bandgap absorption of LaS2 shifts from 635 nm for nanoellipsoids to 365 nm for square-based nanoplates. Er3+ photoluminescence in La2S3:Er3+ (10%) is sensitized by the semiconducting host in the 390-450 nm range. The synthetic route yields tunable compositions of rare-earth sulfide nanocrystals. Interaction of light with these novel semiconducting nanostructures hosting rare-earth emitters should be attractive for applications that require broadband sensitization of RE emitters.

Synthesis of Mixed-Valent Lanthanide Sulfide Nanoparticles.

Abstract: In targeting reduced valent lanthanide chalcogenides, we report the first nanoparticle synthesis of the mixed-valent ferromagnets Eu3 S4 and EuSm2 S4 . Using divalent lanthanide halides with bis(trimethylsilyl)sulfide and oleylamine, we prepared nanoparticles of EuS, Eu3 S4 , EuSm2 S4 , SmS1.9 , and Sm3 S4 . All nanoparticle phases were identified using powder X-ray diffraction, transmission electron microscopy was used to confirm morphology and nanoparticle size, and magnetic susceptibility measurements for determining the ordering temperatures and valence. The UV/Vis, Raman and X-ray photoelectron spectroscopies for each phase were compared. Surprisingly, the phase is influenced by the halide and the reaction temperature, where EuCl2 formed EuS while EuI2 formed Eu3 S4 , highlighting the role of kinetics in phase stabilization. Interestingly, at lower temperatures EuI2 initially forms EuS, and converts over time to Eu3 S4 .

Superconductivity in S-rich phases of lanthanum sulfide under high pressure

Abstract: Pressure, a fundamental thermodynamic variable, enables phase transitions to exotic phases with unique physical properties, such as superconductivity. In this work we perform a complete study of crystal structures and relevant electronic properties of La--S crystalline systems in a pressure range of 0--200 GPa. A structural search based on first-principles swarm-intelligence identifies two hitherto unknown pressure-stabilized stoichiometries, namely, ${\mathrm{LaS}}_{3}$ and ${\mathrm{LaS}}_{5}$, in addition to the previously reported compounds. We find that the S-S bonding patterns in La--S compounds evolve in the following sequence with increasing S content and pressure: Atomic S, ${\mathrm{S}}_{2}$ dimers, one-dimensional linear S chains, and two-dimensional S ladders. Further electron-phonon calculations show that both ${\mathrm{LaS}}_{3}$ and ${\mathrm{LaS}}_{5}$ are superconductors with critical temperatures of 13.6 K at 100 GPa and 11 K at 120 GPa, respectively. The softened acoustic phonon branches are responsible for their superconductivity. Our current work is expected to guide future experimental studies investigating superconductivity and structural features of La--S system and more, in general, of other rare-earth chalcogenides.