Reduction of nitric oxide by acetylene on Ir surfaces with different morphologies: comparison with reduction of NO by CO

Ultra-small iridium nanoparticles as active catalysts for the selective and efficient reduction of nitroarenes

The ultra-small noble metal iridium nanoparticles (IrNPs) possessing super catalytic activity can be applied in the efficient and selective catalytic reduction of nitroarenes under mild reaction conditions for the first time.

Fluorescent iridium nanoclusters for selective determination of chromium(VI)

Fluorescent iridium nanoclusters (IrNCs) consisting of up to 7 Ir atoms were prepared by heating IrCl₃ in N,N-dimethylformamide. No other reagents are required. High resolution transmission electron microscopy (HRTEM) shows the IrNCs to be monodispersed with an average size of 0.9 ± 0.2 nm. They are well soluble in polar solvents and stable in these solvents for at least 6 months. Under photoexcitation with 365 nm light, they emit strong bluish green fluorescence with peaks that depend on the excitation wavelength and range from 530 to 650 nm. The fluorescence lifetime typically is 2.2 ns and the quantum yield is 8.3%. Fluorescence is quenched by Cr(VI) ion (chromate), and the emission peak is gradually red-shifted. According to the absorbance spectra of IrNCs in the presence and absence of Cr(VI) and Stern-Volmer quenching behavior study, static quenching is involved. Based on these findings, a selective assay was developed for the determination of Cr(VI). It has a linear response in the 0.1 to 100 μM chromate concentration range and a 25 nM detection limit. Graphic abstract Fluorescent iridium nanoclusters (IrNCs), consisting of up to 7 Ir atoms, were prepared in N,N-dimethylformamide (DMF) solution without using any other reagents. Their fluorescence is statically quenched by Cr(VI).

Theoretical and experimental studies of hydrogen adsorption and desorption on Ir surfaces

We report adsorption and desorption of hydrogen on planar Ir(210) and faceted Ir(210), consisting of nanoscale {311} and (110) facets, by means of temperature programmed desorption (TPD) and density functional theory (DFT) in combination with the ab initio atomistic thermodynamics approach. TPD spectra show that only one H2 peak is seen from planar Ir(210) at all coverages whereas a single H2 peak is observed at around 440 K (F1) at fractional monolayer (ML) coverage and an additional H2 peak appears at around 360 K (F2) at 1 ML coverage on faceted Ir(210), implying structure sensitivity in recombination and desorption of hydrogen on faceted Ir(210) versus planar Ir(210), but no evidence is found for size effects in recombination and desorption of hydrogen on faceted Ir(210) for average facet sizes of 5-14 nm. Calculations indicate that H prefers to bind at the two-fold short-bridge sites of the Ir surfaces. In addition, we studied the stability of the Ir surfaces in the presence of hydrogen at different H coverages through surface free energy plots as a function of the chemical potential, which is also converted to a temperature scale. Moreover, the calculations revealed the origin of the two TPD peaks of H2 from faceted Ir(210): F1 from desorption of H2 on {311} facets while F2 from desorption of H2 on (110) facets.