Gas phase vibrational spectroscopy of cold (TiO2)n− (n = 3–8) clusters

Abstract

We report infrared photodissociation (IRPD) spectra for the D2-tagged titanium oxide cluster anions (TiO2)n− with n = 3–8 in the spectral region from 450 to 1200 cm−1. The IRPD spectra are interpreted with the aid of harmonic spectra from BP86/6-311+G* density functional theory calculations of energetically low-lying isomers. We conclusively assign the IRPD spectra of the n = 3 and n = 6 clusters to global minimum energy structures with Cs and C2 symmetry, respectively. The vibrational spectra of the n = 4 and n = 7 clusters can be attributed to contributions of at most two low-lying structures. While our calculations indicate that the n = 5 and n = 8 clusters have many more low-lying isomers than the other clusters, the dominant contributions to their spectra can be assigned to the lowest energy structures. Through comparison between the calculated and experimental spectra, we can draw conclusions about the size-dependent evolution of the properties of (TiO2)n− clusters, and on their potential utility as model systems for catalysis on a bulk TiO2 surface.

The ratio law of the structure evolution and stability for TinOm (n = 3–18, m = 1–2n) clusters

“…In fact, many works have been done on the stable structures of (TiO2)n (n=2-24) and most geometries listed in Figs. 3 and 4 can be found in literature , except (TiO2)15 , whose energy is 2.0 eV lower than earlier reports [8,9,12,14,15]. In the third column of Fig.…”

“…Owing to its technological importance, numerous experimental and theoretical investigations have been carried out on isolated titanium oxide clusters to correlate their structures and properties with their bulk counterparts. [6][7][8][9][10][11][12][13][14][15][16][17][18] Yu and Freas produced isolated positive titanium/oxygen clusters by sputtering titanium dioxide powder and titanium foil (exposed to oxygen) with an energetic xenon atom beam (~8 keV). [7] The form of titanium/oxygen cluster ions from their results is [TinO2n-δ] + , where n equals 1 to 8 and δ ranges from 0 to 4.…”

“…At present, theoretical studies on titanium oxide mainly aimed at (TiO2)n (n≤24) [8,9,11,12,[14][15][16] and experimental researches focused on TinOm (n=1-7, m=2n-3, 2m+1) [7,13,14]. A clear, systemic and an in-depth understanding for the geometries of TinOm particles have not yet emerged.…”

Dissociative Water Adsorption on Gas-Phase Titanium Dioxide Cluster Anions Probed with Infrared Photodissociation Spectroscopy

“…In this paper, we explore water splitting on TiO 2 in molecular detail by measuring vibrational spectra of cryogenically-cooled [(TiO 2 ) n (D 2 O) m ] − cluster anions. This work stands as a follow-up to our prior characterization of the bare (TiO 2 ) n − anions [13] as we move towards more explicit cluster-based models of catalytic reaction mechanisms.…”

“…While there is a growing body of work on the gas-phase spectroscopy of bare titanium dioxide clusters [13,[42][43][44][45][46], studies probing their interactions with water are more sparse. Early work from the Castleman group reported on the mass spectrum of the water-solvated TiO + cation [47].…”