Thermally induced anchoring of a zinc-carboxyphenylporphyrin on rutile TiO2 (110)

Abstract

Functionalization of surfaces has become of high interest for a wealth of applications such as sensors, hybrid photovoltaics, catalysis, and molecular electronics. Thereby molecule-surface interactions are of crucial importance for the understanding of interface properties. An especially relevant point is the anchoring of molecules to surfaces. In this work, we analyze this process for a zinc-porphyrin equipped with carboxylic acid anchoring groups on rutile TiO2 (110) using scanning probe microscopy. After evaporation, the porphyrins are not covalently bound to the surface. Upon annealing, the carboxylic acid anchors undergo deprotonation and bind to surface titanium atoms. The formation of covalent bonds is evident from the changed stability of the molecule on the surface as well as the adsorption configuration. Annealed porphyrins are rotated by 45° and adopt another adsorption site. The influence of binding on electronic coupling with the surface is investigated using photoelectron spectroscopy. The observed shifts of Zn 2p and N 1s levels to higher binding energies indicate charging of the porphyrin core, which is accompanied by a deformation of the macrocycle due to a strong interaction with the surface.

Self‐Metalation of Anchored Porphyrins on Atomically Defined Cobalt Oxide Surfaces: In situ Studies by Surface Vibrational Spectroscopy

“…The development of the ν s (O‐C‐O) band during sample heating allows us to follow the anchoring of the MCTPP layer with increasing temperature. Previously, a strong temperature dependence of the anchoring reaction was also observed for MCTPP on Co 3 O 4 (111) and ZnDCPP on TiO 2 (110) . The isothermal experiments at 300 and 450 K, further suggest that a reorientation of the porphyrins takes place in the first layer concomitant with the anchoring reaction.…”

Adsorption and self-assembly of porphyrins on ultrathin CoO films on Ir(100)

“…The research revealed numerous ways to steer self-assembly and on-surface reactions by a careful choice of functionalization and substrates [2]. Despite its importance for applications, the investigation of the structure and binding of porphyrins on semiconducting and, notably, metal oxide surfaces remains scarce [3][4][5][6][7][8][9][10][11][12][13]. We chose here to investigate two different porphyrins on thin films of cobalt(II) oxide (CoO).…”

“…Cobalt(II) oxide not only is a semi-conducting oxide, it is also an anti-ferromagnet due to electron correlation effects and it shows catalytic activity [14][15][16][17]. As a thin film grown on Ir(100), the oxide is of extremely high quality [18][19][20] avoiding the complexity that arises from atomicscale defects in bulk materials [5][6][7][8]. The atomic structure of these films has been investigated in detail by diffraction methods [18][19][20][21].…”

Comparing a porphyrin- and a coumarin-based dye adsorbed on NiO(001)

“…In contrast to TiO 2 [3–11], wide-bandgap p-type semiconductors, such as NiO, and their functionalization with sensitizers, have been less extensively studied by using SPM [12–15]. NiO was the first reported p-type wide-bandgap semiconductor [16], and can be used for the fabrication of p-type DSSCs with photoactive cathodes, a first step towards the design of tandem solar cells with two photoactive electrodes [17–18].…”