Vanadium(V) oxide clusters synthesized by sublimation from bulk under fully inert conditions

Abstract

While laser ablation in combination with electron impact mass spectroscopy yield numerous fragments and reaction products, helium-mediated mass analysis reveals the sublimation from bulk in units of (V2O5)2.

Synthesis of nanosized vanadium(v) oxide clusters below 10 nm

“…24,25 In this paper we employ a different strategy to synthesise nanoparticles which is based on the accumulation of V 2 O 5 oligomers in helium nanodroplets. The present work expands our previous experiments from the in situ characterisation of V 2 O 5 oligomers in a helium droplet beam, 26 towards the formation of nanoparticle films comprising of individually deposited particles with diameters below 10 nm. After deposition, several ex situ measurement techniques can be applied to the particles in order to reveal their characteristics on different supports.…”

“…As documented in ref. 26, small oligomers of vanadium pentoxide, preferably units of V 4 O 10 , tend to evaporate from the V 2 O 5 powder upon heating. After collision with a helium droplet, these units of sublimated V 2 O 5 remain attached and agglomerate to V 2 O 5 clusters inside the droplet.…”

Metal clusters synthesized in helium droplets: structure and dynamics from experiment and theory

“…Probably the more indirect ionization through a charge hopping process inside the droplets and the high cooling rate of the surrounding helium are reasons for this softer process, which allowed us recently to measure a distribution of unfragmented V 2 O 5 clusters. 69 As latest improvement of the apparatus, another laser interaction region was added with an optical detection channel to measure integrated or wavelength selected laser induced fluorescence in a scheme previously employed in our other helium droplet experiments, see e.g. ref.…”

“…1, almost any core@shell nanoparticle of an atomic or molecular composition can be synthesized if the constituents can be provided in a pickup cell at a vapour pressure of 10 À5 to 10 À4 mbar. Due to the helium mediated soft ionization, [67][68][69] the TOF-MS shows the element specific loading of the droplet. The ultrahigh vacuum (UHV) in the deposition chamber guarantees almost contamination-free samples.…”

“…In order to produce V 2 O 5 nanoparticles and deposit them on solid substrates, we heated V 2 O 5 powder with a purity of 99.9%, kept in a small quartz crucible (Kurt Lesker EVC2Q), to temperatures between 1000 and 1200 K, which yielded a vapour pressure of about 10 À3 mbar. 69 Helium droplets were generated at 20 bar stagnation pressure and various nozzle temperatures for different droplet size distributions. The TOF-MS served as diagnostic tool for the observation of aggregation products formed in the droplets.…”