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TiO₂ sol was prepared by a sol-gel method. Sodium polymethacrylate (PMAA) was added to TiO₂ sol, resulting in a stable TiO₂-PMAA. The copper(II) phthalocyanine tetrasulfonate (CuPcTs) was used to sensitize nanocrystalline TiO₂ photocatalyst. The hybrid nanoparticles had an average particle size of 35 nm and core-shell type morphology was observed using a TEM. For the preparation of TiO₂-CuPcTs, TiO₂ was directly complexed with CuPcTs, leading to a particle size of 100 nm by a sonication treatment. The photodegradation of the hybrid type photosensitizer was measured using AO7 as an indicator with He-Ne laser with wavelength 633 nm. The efficiency of singlet oxygen generation was also measured by the reduction ratio of concentration of trans-1-(2′-methoxyvinyl) pyrene (MVP) responding to the change of fluorescene emission at 420 nm, depending on the irradiation time.

In this study an easy access for modification of properties of porphyrin covered TiO₂ electrodes by post-assembling metal insertion was investigated. Therefore a new type of phosphonic acid terminated porphyrin was synthesized and immobilized on mesoporous TiO₂ electrodes by self-assembling. Surface concentrations in a range of 1.5–3.3 × 10^-8 mol.cm^-2, based on the geometric area, were obtained by two independent techniques, UV-vis and cyclic voltammetry. Co(II), Zn(II), Pd(II) and Mn(III) ions could be inserted into the immobilized porphyrin by exposing the electrode to a boiling solution of metal chloride in methanol. The electrode surface was characterized by UV-vis spectroscopy and cyclic voltammetry before and after metal insertion. The electrocatalytic activity towards the reduction of molecular oxygen in acidic solution was examined, further confirming metal insertion into immobilized porphyrin monolayer.

New methods for water treatment are required as a result from an increasing awareness in the reduction of the pollution impact in the environment. In the perspective of the photo-oxidation of organic pollutants present in water, the principal incentive for the preparation of heterogeneous photocatalysts is their easy recovery from the reaction mixture, which allows their reuse in successive runs, minimizing the loss of their original photocatalytic properties. Different types of supports can be used in the immobilization of photoactive species, such as porphyrins (Pors) and phthalocyanines (Pcs). This mini-review will consider the different methodologies for the immobilization of Pors and Pcs and their photocatalytic performance in the photodegradation of organic pollutants in water, addressing also their recycling ability in successive water treatments.

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$K_a$ 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.

Two surface-anchored aluminum(III) porphyrin (AlPorF${}_3)$ stacks, AlPorF₃(Py)-COO/TiO₂ and AlPorF₃(Ph)-COO/TiO₂, have been constructed to investigate the interfacial electron injection from the AlPorF₃ into the conduction band of the TiO₂ nanoparticles as a function of stacking topology. The Lewis acid properties of AlPorF₃ were combined with the electronic and surface properties of TiO₂ to obtain the investigated porphyrin stacks. The axial Lewis base, pyridyl (Py) unit, in AlPorF₃(Py)-COO/TiO₂ directs the porphyrins to stack on the TiO₂ surface in a layered fashion. The absence of a Lewis base in AlPorF₃(Ph)-COO/TiO₂ is unable to form such defined stacks. The AlPorF₃(Py)-COO/TiO₂ and AlPorF₃(Ph)-COO/TiO₂ were characterized by steady-state and transient spectroscopic techniques. Transient absorption spectral studies show that surface-stacked hybrids exhibit electron injection from AlPorF₃ to the conduction band of TiO₂. However, the injection efficiencies and kinetics are not very different in the investigated stacks AlPorF₃(Py)-COO/TiO₂ and AlPorF₃(Ph)-COO/TiO₂ indicating that the axial self-assembly does not alter the electronic communication within the AlPorF₃ layer to a significant level to perturb the photodynamics.

In this study, we utilized a hydrothermal method to coat TiO₂ nanoparticles onto Haematococcus pluvialis (H. pluvialis) cells. Various methods were employed to investigate the morphology, structure, and photoelectrocatalytic activity of the synthesized Ys/TiO₂ composites. Results indicated that, owing to the dye-sensitization effect of astaxanthin within H. pluvialis cells, the electron-hole pairs in Ys/TiO₂ composites achieved efficient charge separation, leading to superior photoelectrocatalytic CO₂ reduction performance. The composites also exhibited a broader wavelength absorption range with a Faradaic efficiency of up to 61.28%, and a liquid product yield of ethanol reaching 29.47 μmol·h⁻¹·cm⁻². Furthermore, the H. pluvialis/TiO₂ composites maintained high photoelectrocatalytic activity and stability even after four cycles.