This work deals with the deposition of Cr-doped TiO2 thin films on porous silicon (PS) prepared from electrochemical anodization of multicrystalline (mc-Si) Si wafers. The effect of Cr doping on the properties of the TiO2-Cr/PS/Si samples has been investigated by means of X-ray diffraction (XRD), atomic force microcopy (AFM), photoluminescence, lifetime, and laser beam-induced current (LBIC) measurements. The photocatalytic activity is carried out on TiO2-Cr/PS/Si samples. It was found that the TiO2-Cr/PS/mc-Si type structure degrades an organic pollutant (amido black) under ultraviolet (UV) light. A noticeable degradation of the pollutant is obtained for a Cr doping of 2 at. %. This result is discussed in light of LBIC and photoluminescence measurements.

Cu-doped TiO₂ films were synthesized directly on FTO glass with a spin coating method. With a variation in copper amount, samples were prepared with 0%, 1%, 2%, 4% and 8% of dopant concentrations. Morphological and structural characterization of undoped and Cu-doped TiO₂ samples were investigated and the obtained results showed the small, spherical shapes of the nanoparticles forming a thin film on top of FTO glass and their preferred orientation of TiO₂ anatase (101), which is the same for each sample. However, this peak exhibited a slight shift for the 2% sample, related to the inflation of the microstrain compared to the other samples. For the optical properties, the 4% sample displayed the highest transmittance whereas the 2% sample exhibited the lowest band gap energy of 2.96 eV. Moreover, the PL intensity seems to be at its highest for the 2% sample due to the present peaking defects in the structure, whereas the 8% sample shows a whole new signal that is related to copper oxide. These properties make this material a potential candidate to perform as an electron transport layer (ETL) in solar cells and enhance their power conversion efficiency.

The present work aims to study the photocatalytic properties of nanohybrids composed of silicon nanowires (SiNWs) decorated with PbS nanoparticles (NPs). The elaborated material was intended to be utilized in wastewater treatment. The SiNWs were elaborated from the Metal Assisted Chemical Etching route (MACE), while the PbS NPs were deposited at room temperature onto SiNWs using the pulsed laser deposition (PLD) technique. The influence of decorating SiNWs (having different lengths) with PbS-NPs on their structural, morphological, optoelectronic, and photocatalytic properties was scrutinized. PbS/SiNWs nanohybrids exhibited enhanced photocatalytic degradation towards Black Amido (BA) dye for 20 µm SiNWs length and 0.2% of BA volume concentration. These optimized conditions may insinuate that this nanocomposite-like structure is a promising efficient photocatalytic systems contender, cost-effective, and recyclable for organic compound purification from wastewaters.

In the present study, the adhesion of TiO₂ nanotubes (TiO₂-NTs) to thicker substrates was improved by decorating them with metallic Ag nanoparticles (NPs) using the photo-reduction process. The obtained coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM). X-ray diffraction (XRD) confirmed that all TiO₂-NTs crystallized in anatase after annealing at 400°C regardless of the anodization potential. The scanning electron microscopy (SEM) indicated that the TiO₂-NTs were uniformly distributed on the substrate with an ordered and vertically aligned morphology. It also revealed that the diameter of the TiO₂-NTs reached~100 nm. The decoration of TiO₂-NTs surface with silver nanoparticles was assessed by transmission electron microscopy (TEM). Moreover, a new scratch test mode called ‘wear mode’ was performed to evaluate the wear resistance of the coatings. Results obtained by the scratch tests proved that the decorated coating with Ag nanoparticles improved the interfacial adhesion. The friction coefficient decreased from 0.65 to 0.45 when pure TiO₂ was decorated with 10 min-Ag-NPs.The wear behavior was studied using a multi-pass scratch test. It was found that the wear volume reduced with the incorporation of Ag nanoparticles. The study of the damage mechanisms showed visco-elastic plastic deformation in the pure TiO₂ coating.