Gas phase synthesis of transition metal oxides

TOF-Mass Spectrum of Ti_xO_y⁺ Clusters

3 groups of stable Ti_xO_y⁺ clusters:

              (TiO₂)_n⁺

              (TiO)⁺(TiO₂)_n

              (TiO)₊(TiO₂)_nO₂

 

Photofragmentation spectra (@ 308 nm) —> explain the growth of the clusters from TiO⁺ and Ti₂O₃⁺ by sequential uptake of TiO₂ building blocks

Titanium oxide clusters - Photodissociation

Non-resonant photofragmentation is not very efficient

Photons are replaced with atoms => lead to fragmentation through collision

References:

 

M. Velegrakis et al  Applied Physics A 97 (2009) 765

 

Maria Jadraque, Borja Sierra, Antonis Sfounis, and Michalis Velegrakis, “Photofragmentation of mass-selected titanium oxide cluster cations”, Applied Physics B,   100  (2010)  587

 

 

· Important species with potential applications in the fields of:

           - Physics (magnetism, nanoelectronics, ...)

           - Chemistry (catalysis, ...)

           - Biology (antibacterial properties, ...)

· Their properties strongly depend on the local environment of the metal atoms such as the coordination number and the oxidation number.

· These change as the cluster size increases.

Transition metal oxide clusters-Examples

 

Ta: [Xe]5d³6s² ; Ta⁺: 5d³6s¹

Oxidation numbers

Ta:+5,+4,+3,+2,+1

Ta⁺:+4,+3,+2,+1

 

Oxidation number

Oxygen:     - 2

Metal:    + σ

 

 

Main Series:

[Ta⁺⁴O^-2₂]⁺ · [Ta⁺⁵₂O^-2₅]_n ,   

[Ta⁺⁴₂O^-2₄] ⁺· [Ta⁺⁵₂O^-2₅]_n

 

Zr:[Kr] 4d²5s²

Oxidation numbers

Zr: +4,+3,+2,+1

Zr⁺: +3,+2,+1

 

Main Series:

[Zr⁺²O^-2]⁺ · [Zr⁺⁴O^-2₂]_n

 

 

Stability Rule:

Neutral cluster   :  x · σ  =  y· 2

Cation(+1) :     x · σ  - 1 =  y· 2

Anion  (-1)    :     x · σ  + 1 =  y· 2