Molecular damage in bi-isonicotinic acid adsorbed on rutile TiO2(110)

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Zinc-protoporphyrin, adsorbed on the rutile TiO(2)(110) surface, has been studied using photoemission spectroscopy and near-edge absorption fine structure spectroscopy to deduce the nature of the molecule-surface bonding and the chemical environment of the central metal atom. To overcome the difficulties associated with sublimation of the porphyrin molecules, samples were prepared in situ using ultrahigh vacuum electrospray deposition, a technique which facilitates the deposition of nonvolatile and fragile molecules. Monolayers of Zn protoporphyrin are found to bond to the surface via the oxygen atoms of the deprotonated carboxyl groups. The molecules initially lie largely parallel to the surface, reorienting to an upright geometry as the coverage is increased up to a monolayer. For those molecules directly chemisorbed to the surface, the interaction is sufficiently strong to pull the central metal atom out of the molecule.

Section: Methodssupporting

confidence: 59%

X-ray absorption and photoemission spectroscopy of zinc protoporphyrin adsorbed on rutile TiO2(110) prepared by in situ electrospray deposition

Rienzo

Mayor

Magnano

et al. 2010

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“…The latter is shown magnified in the inset. As with previous studies, 11 we have assigned the lower binding energy peak (∼268 eV) to the carbon atoms in the pyridine ring and the higher binding energy peak (∼289.5 eV) to the carboxylic group. The low intensity satellite at ∼293 eV is attributed to a shakeup feature.…”

Section: Fig 2: O 1s Xps Spectra For A) Multilayer and B) Monolayer supporting

confidence: 62%

“…For the monolayer film, molecules were deposited until the peak ratios in the XPS and the lineshape of the valence band region were consistent with monolayer and sub-monolayer data for these molecules on other surfaces. 4,11 This method was chosen over that of annealing a multilayer 4,11 in order to avoid the potential damage of the molecules through excessive heating as previously observed in the N 1s XAS for bi-isonicotinic acid on the Au(111) surface. 4 …”

Section: Methodsmentioning

confidence: 99%

Adsorption and charge transfer interactions of bi-isonicotinic acid on Ag(111)

Temperton

Gibson

Handrup

et al. 2017

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The adsorption and charge transfer dynamics of the organic molecule bi-isonicotinic acid (4,4-dicarboxy-2,2-bipyridine) on single crystal Ag(111) has been studied using synchrotron radiation-based photoemission, x-ray absorption and resonant core spectroscopies. Measurements for multilayer and monolayer coverage are used to determine the nature of the molecule-surface interactions and the molecular orientation. An experimental density of states for the monolayer with respect to the underlying metal surface is obtained by combining x-ray absorption spectroscopy at the N 1s edge and valence photoemission to measure the unoccupied and occupied valence states, respectively. This shows that the lowest unoccupied molecular orbital in the core-excited state lies energetically below the Fermi level of the surface allowing charge transfer from the metal into this orbital. Resonant photoelectron spectroscopy was used to probe this charge transfer in the context of super-spectator and super-Auger electron transitions. The results presented provide a novel interpretation of resonant core-level spectroscopy to explore ultra-fast charge transfer between an adsorbed organic molecule and a metal surface through the observation of electrons from the metal surface playing a direct role in the core-hole decay of the core-excited molecule.

“…Previous studies on the bi-isonicotinic acid ligand and on the Ru 535 dye complex have shown that the N 1s NEXAFS is dominated by pyridinelike π * orbitals. 9,38,39 The lowest binding energy peak in the valence photoemission spectra corresponds to the HOMO. For each dye complex the HOMO is present within the substrate bandgap which prevents back transfer of electrons from the substrate.…”

Section: B Electronic Structurementioning

confidence: 99%

Charge transfer dynamics of model charge transfer centers of a multicenter water splitting dye complex on rutile TiO2(110)

Weston

Britton

O’Shea

2011

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Charge transfer dynamics between an adsorbed molecule and a rutile TiO(2)(110) surface have been investigated in three organometallic dyes related to multicenter water splitting dye complexes: Ru 535 (cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)-ruthenium(II)), Ru 455 (cis-bis(2,2'-bipyridyl)-(2,2'-bipyridyl-4,4'-dicarboxylic acid)-ruthenium(II)), and Ru 470 (tris(2,2'-bipyridyl-4,4'-dicarboxylic acid)-ruthenium(II)). The adsorption of the dye molecules on the rutile TiO(2)(110) surface has been studied using core-level and valence photoemission. Dye molecules were deposited in situ using ultrahigh vacuum electrospray deposition. Core-level photoemission spectra reveal that each complex bonds to the surface via deprotonation of two carboxylic groups. All three dye complexes show evidence of ultrafast charge transfer to the TiO(2) substrate using the core-hole clock implementation of resonant photoemission spectroscopy.