Desorption and subsequent rehydrogenation of Mg(BH4)2 with and without 5 mol % TiF3 and ScCl3 have been investigated. Temperature programmed desorption (TPD) experiments revealed a significant increase in the rate of desorption as well as the weight percentage of hydrogen released with additives upon heating to 300 °C. Stable Mg(B x H y ) n intermediates were formed at 300 °C, whereas MgB2 was the major product when heated to 600 °C. These samples were then rehydrogenated and subsequently characterized with powder X-ray diffraction (pXRD), Raman, and NMR spectroscopy. We confirmed significant conversion of MgB2 to fully hydrogenated Mg(BH4)2 for the sample with and without additives. TPD and NMR studies revealed that the additives have a significant effect on the reaction pathway during both dehydrogenation and rehydrogenation reactions. This work suggests that the use of additives may provide a valid pathway for improving intrinsic hydrogen storage properties of magnesium borohydride.

An improved synthetic method has been designed and demonstrated to reproducibly generate hollow gold nanospheres (HGNs) with strong surface plasmon resonance (SPR) absorption in the near infrared (NIR). The HGNs have been synthesized via galvanic replacement of cobalt with gold while utilizing different amounts of poly(vinylpyrrolidone) (PVP) as a template stabilizing agent. Ninety percent of syntheses performed by this modified method resulted in HGNs with an SPR near 800 nm, which is highly desirable for biomedical applications such as photothermal ablation (PTA) therapy, while other polymers (PAA and PEG) did not. Based on absorption and TEM measurements, PVP stabilizes the cobalt template particles via carbonyl-induced stabilization that slows nucleation and growth of the gold shell allowing for the generation of a reproducibly thin shell, thereby inducing a significant red shift of the SPR to 800 nm. The results are significant to various potential applications of HGNs, e.g. cancer therapy and sensing.

Ultrafast pump−probe spectroscopy was used to characterize coherent vibrational oscillations of hollow gold nanospheres (HGNs) composed of a polycrystalline Au shell and a hollow, solvent-filled interior. Different HGN samples show heavily damped radial breathing mode oscillations with a period ranging from 28 ± 2 to 33 ± 3 ps. We theoretically modeled the oscillation period of HGNs while varying both the shell thicknesses and particle radii. Creation of a hollow cavity was predicted to increase the oscillation period relative to solid gold nanoparticles, and this result was verified experimentally. Our theoretical predictions of oscillation period are significantly lower than the experimental measurements. We propose that this difference is due to the polycrystalline nature of HGNs that softens the vibration of the lattice compared with a single-crystalline shell. We compare our system to solid Au nanoparticles and Au nanoparticle aggregates and find a general trend of longer oscillation period with increasing particle polycrystallinity.