RESUMEN
Tungsten and molybdenum carbides have shown great potential in catalysis and superconductivity. However, the synthesis of ultrathin W/Mo carbides with a controlled dimension and unique structure is still difficult. Here, inspired by the host-guest assembly strategy with single-walled carbon nanotubes (SWCNTs) as a transparent template, we reported the synthesis of ultrathin (0.8-2.0 nm) W2C and Mo2C nanowires confined in SWCNTs deriving from the encapsulated W/Mo polyoxometalate clusters. The atom-resolved electron microscope combined with spectroscopy and theoretical calculations revealed that the strong interaction between the highly carbophilic W/Mo and SWCNT resulted in the anisotropic growth of carbide nanowires along a specific crystal direction, accompanied by lattice strain and electron donation to the SWCNTs. The SWCNT template endowed carbides with resistance to H2O corrosion. Different from normal modification on the outer surface of SWCNTs, such M2C@SWCNTs (M = W, Mo) provided a delocalized and electron-enriched SWCNT surface to uniformly construct the negatively charged Pd catalyst, which was demonstrated to inhibit the formation of active PdHx hydride and thus achieve highly selective semihydrogenation of a series of alkynes. This work could provide a nondestructive way to design the electron-delocalized SWCNT surface and expand the methodology in synthesizing unusual 1D ultrathin carbophilic-metal nanowires (e.g., TaC, NbC, ß-W) with precise control of the anisotropy in SWCNT arrays.
RESUMEN
Parathyroid hormone (PTH1-34)-loaded dry powders were fabricated from aqueous solution for pulmonary administration using supercritical fluid assisted atomization introduced by a hydrodynamic cavitation mixer (SAA-HCM). Herein, chitosan oligosaccharide (CSO) was selected as a carrier in an effort to enhance transmucosal absorption of the drug. Well-defined, separated and spherical PTH(1-34)/CSO composite microparticles were obtained, and the particles size could be well controlled with narrow distribution. Aerodynamic performance was determined using next generation impactor (NGI), and the mass median aerodynamic diameter (MMAD) ranged strictly 1-5⯵m range with fine particle fraction (FPF) up to 63.51%. The structural integrity of coprecipitated PTH(1-34) was validated by HPLC, FT-IR and circular dichroism, and a high loading efficiency up to 92.8% was obtained. TGA analyses revealed its thermal stability was preserved and XRD patterns showed amorphous structure of particles. The SAA-HCM process is proposed as a green technique for preparation of inhalable protein/polymer composite dry powders without use of any organic solvents.
