Dense arrays of zinc oxide nanorods with high specific surface areas were grown by hydrothermal method and functionalized by self-assembled monolayer (SAM) of porphyrins. The growth process was optimized to obtain dense arrays of nanorods with diameter of 60–80 nm and length up to 1.5 μm. The increase in the effective surface area was monitored by comparing the absorbances of SAM deposited both on the flat and nanorod surfaces of ZnO. To alter further semiconductor-organic SAM interactions, a 2 or 5 nm thick layer of either Al2O3 or TiO2 was deposited on the ZnO nanorods. The present results show that both carboxylic acid and triethoxysilane anchors can be used to form porphyrin SAMs on the studied metal oxide substrates, and the electronic interactions between the metal oxide and porphyrin SAM are strongly modified by a thin layer of Al2O3 or TiO2. These hybrid semiconductor-organic SAM constructions present promising model systems for advanced spectroscopy studies of semiconductor-organic interfaces with high degree of control over electronic interactions and system morphology.

The photoinduced electron transfer processes were studied for hybrid systems consisting of self-assembled monolayer of zinc phthalocyanine (ZnPc) assembled on ZnO nanorods and a film of organic hole transporting material (HTM) atop. Polythiophene (P3HT) or Spiro-OMeTAD were used as HTM. The study was carried out by ultrafast transient absorption spectroscopy technique with selective excitation of ZnPc at 680 nm or P3HT at 500 nm. Data analysis revealed that photoexcitation of ZnPc in the structure ZnO|ZnPc|P3HT results in a fast (1.8 ps) electron transfer from ZnPc to ZnO, which is followed by a hole transfer from the ZnPc cation to P3HT roughly in 30 ps. However, in the case of ZnO| ZnPc|Spiro-OMeTAD structure, the primary reaction upon excitation of ZnPc is a fast (0.5 ps) hole transfer from ZnPc to Spiro-OMeTAD, and the second step is electron injection from the ZnPc anion to ZnO in roughly 120 ps. Thus, we demonstrate two structurally very similar hybrid architectures that implement two different mechanisms for photoinduced charge separation found in dye-sensitized or in organic solar cells.

Terpyridine-substituted perylenes containing cyclic anhydrides in the peri position were synthesized. The anhydride group served as an anchor for assembly of the terpyridyl-crowned chromophores as monomolecular layers on metal oxide surfaces. Further coordination with Zn(2+) ions allowed for layer-by-layer formation of supramolecular assemblies of perylene imides on the solid substrates. With properly selected anchor and linker molecules it was possible to build high quality structures of greater than ten successive layers by a simple and straightforward procedure. The prepared films were stable and had a broad spectral coverage and high absorbance. To demonstrate their potential use, the synthesized dyes were employed in solid-state dye-sensitized solar cells, and electron injection from the perylene antennas to titanium dioxide was observed.

Perylene diimides (PDIs) substituted with a terpyridine moiety at the bay-region have been synthesized. These building blocks were used to construct supramolecular complexes in chloroform. A dimer and a trimer were built via the bay-region complexation with zinc. The PDI compounds were further modified to have silane anchors and PDI self-assembled monolayers (SAMs) were prepared on a quartz substrate. Complexation of metal ions was also done on the surface, and this was observed clearly in the absorption spectrum. These studies on the surface show possible progress in the study of supramolecular multilayer structures.

Formation of self-assembled monolayers (SAMs) of three porphyrin and one phthalocyanine derivatives on thin ZnO film was studied by monitoring absorption spectra of the samples. The compounds were equipped with carboxylic or phosphate groups to bind to the surface. The SAM formation was found to be fast. The layer was formed in less than 15 min for all studied porphyrins, and 30 min was sufficient to form phthalocyanine layer. For porphyrins with different anchor groups the SAM formation was too fast to see any difference between the anchoring groups. The stability of SAMs was tested then by immersing the samples into neat solvents. Upon immersion the SAMs were gradually losing the absorbance for all the compounds with degradation trends being in line with p[Formula: see text] values of the binding groups of the same type. However, even for the weakest binding group the SAM was relatively stable after a few tens of minutes of washing, which was sufficient to remove physisorbed compounds but the SAM was essentially not destroyed. Comparison of SAMs on thin films with SAMs on ZnO nanorods and TiO2 nanoparticle films indicated the same fast layer formation but relatively weaker SAMs stability, showing 20–40% faster absorption losses during the washing.

No abstract

Novel monoisomeric perylene imide derivatives with terpyridinyl and pyrrolidinyl substituents were synthesized and deposited onto solid substrates, such as a thin film of Al2O3 and mesoporous TiO2 nanoparticle layer, by using a simple dip‐by‐dip method. Arrays of up to 33 layers were built on Al2O3. In the case of mesoporous TiO2, the interstitial volume between the particles was filled up with dye assemblies. Deposition could produce either layers of microcrystals or molecular layers if an appropriate washing procedure was used. The resultant arrays were studied by means of scanning electron microscopy, X‐ray photoelectron spectroscopy measurements, and UV/Vis absorption.

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