Herein, we present a remarkable approach for developing highly efficient photo-catalytic H2 produ... more Herein, we present a remarkable approach for developing highly efficient photo-catalytic H2 production systems employing porphyrins as photocatalysts. Palladium and platinum tetracarboxy-porphyrins (PdTCP and PtTCP) were adsorbed/co-adsorbed onto TiO2 nanoparticles (NPs), which act as electron transport medium and as scaffold that promotes the self-organization of the porphyrinoids. The self-organization of PdTCP and PtTCP forming H- and J-aggregates, respectively, was the key element for H2 evolution, as in the absence of TiO2 NPs no catalytic activity was detected. Notably, J-aggregated PtTCPs were more efficient towards H2 production than H-aggregated PdTCPs. In our approach, a single porphyrin, which self-organizes onto TiO2 NPs, acts as light harvester and simultaneously as catalyst whereas TiO2 serves as the electron transport medium. Importantly, the concurrent adsorption of PdTCP and PtTCP onto TiO2 NPs, resulted in the most efficient catalytic system illustrating 22,733 turnover numbers (TONs) and 30,200 μmol (H2)/g (cat).
In this study, a series of diphenylalanine tetra-substituted porphyrin derivatives were synthesiz... more In this study, a series of diphenylalanine tetra-substituted porphyrin derivatives were synthesized and their self-assembly ability was extensively studied. Apart from investigating the impact of incorporating many peptide moieties onto a porphyrin molecule; another perspective was investigated as well, namely the connection of two different chromophore entities (porphyrin and BODIPY) onto the same diphenylalanine molecule. Interestingly, various supra-molecular nanostructures were observed depending on the solvent mixture as well as the protecting group of the peptides, namely spheres, plaques and fibrils. The obtained self-assemblies were studied via UV-vis absorption and emission spectroscopies. Mainly red shifting was observed, indicating the formation of [Formula: see text]-aggregates in the self-assembled state. However, in one case a blue shifted UV-vis spectrum was obtained suggesting the formation of [Formula: see text]-type aggregates. Concerning the porphyrin-diphenylalan...
Titanium dioxide (TiO2) has a strong photocatalytic activity in the ultra-violet part of the spec... more Titanium dioxide (TiO2) has a strong photocatalytic activity in the ultra-violet part of the spectrum combined with excellent chemical stability and abundance. However, its photocatalytic efficiency is prohibited by limited absorption within the visible range derived from its wide band gap value and the presence of charge trapping states located at the band edges, which act as electron–hole recombination centers. Herein, we modify the band gap and improve the optical properties of TiO2 via co-doping with hydrogen and halogen. The present density functional theory (DFT) calculations indicate that hydrogen is incorporated in interstitial sites while fluorine and chlorine can be inserted both as interstitial and oxygen substitutional defects. To investigate the synergy of dopants in TiO2 experimental characterization techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray and ultra-violet photoelectron spectroscopy (XPS/UPS), UV–Vis absorption and scanning ...
Herein, we present a remarkable approach for developing highly efficient photo-catalytic H2 produ... more Herein, we present a remarkable approach for developing highly efficient photo-catalytic H2 production systems employing porphyrins as photocatalysts. Palladium and platinum tetracarboxy-porphyrins (PdTCP and PtTCP) were adsorbed/co-adsorbed onto TiO2 nanoparticles (NPs), which act as electron transport medium and as scaffold that promotes the self-organization of the porphyrinoids. The self-organization of PdTCP and PtTCP forming H- and J-aggregates, respectively, was the key element for H2 evolution, as in the absence of TiO2 NPs no catalytic activity was detected. Notably, J-aggregated PtTCPs were more efficient towards H2 production than H-aggregated PdTCPs. In our approach, a single porphyrin, which self-organizes onto TiO2 NPs, acts as light harvester and simultaneously as catalyst whereas TiO2 serves as the electron transport medium. Importantly, the concurrent adsorption of PdTCP and PtTCP onto TiO2 NPs, resulted in the most efficient catalytic system illustrating 22,733 turnover numbers (TONs) and 30,200 μmol (H2)/g (cat).
In this study, a series of diphenylalanine tetra-substituted porphyrin derivatives were synthesiz... more In this study, a series of diphenylalanine tetra-substituted porphyrin derivatives were synthesized and their self-assembly ability was extensively studied. Apart from investigating the impact of incorporating many peptide moieties onto a porphyrin molecule; another perspective was investigated as well, namely the connection of two different chromophore entities (porphyrin and BODIPY) onto the same diphenylalanine molecule. Interestingly, various supra-molecular nanostructures were observed depending on the solvent mixture as well as the protecting group of the peptides, namely spheres, plaques and fibrils. The obtained self-assemblies were studied via UV-vis absorption and emission spectroscopies. Mainly red shifting was observed, indicating the formation of [Formula: see text]-aggregates in the self-assembled state. However, in one case a blue shifted UV-vis spectrum was obtained suggesting the formation of [Formula: see text]-type aggregates. Concerning the porphyrin-diphenylalan...
Titanium dioxide (TiO2) has a strong photocatalytic activity in the ultra-violet part of the spec... more Titanium dioxide (TiO2) has a strong photocatalytic activity in the ultra-violet part of the spectrum combined with excellent chemical stability and abundance. However, its photocatalytic efficiency is prohibited by limited absorption within the visible range derived from its wide band gap value and the presence of charge trapping states located at the band edges, which act as electron–hole recombination centers. Herein, we modify the band gap and improve the optical properties of TiO2 via co-doping with hydrogen and halogen. The present density functional theory (DFT) calculations indicate that hydrogen is incorporated in interstitial sites while fluorine and chlorine can be inserted both as interstitial and oxygen substitutional defects. To investigate the synergy of dopants in TiO2 experimental characterization techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray and ultra-violet photoelectron spectroscopy (XPS/UPS), UV–Vis absorption and scanning ...
Uploads
Papers by Eleni Agapaki