Photoelectrochemical properties and reactivity of supported titanium NTs for bacterial inactivation and organic pollutant removal.

In this work, we report on the effect of anodization time on the morphology, optical, and photocatalytic properties of TiO2 nanotubes (NTs) allowing bacterial inactivation and two organic pollutant degradation under low-intensity solar-simulated light. Scanning electron microscopy (SEM) showed that the length of the TiO2 NTs increased from 2.8 to 25.8 µm as anodization time was increased from 15 to 300 min at 60 V, respectively. The X-ray diffraction (XRD) patterns showed that all samples crystallize in the anatase phase after annealing at 400 °C for 3 h. Samples anodized for 30 and 60 min exhibit low diffuse reflection at 400 nm, which was attributed to the disorder-induced exciton scattering at the molecular level. The intensity of the photoluminescence (PL) spectra was found to increase as the length of the NTs increases up to a maximum anodization time of 300 min, revealing the contribution of bulk excitonic states. A maximum photoelectric conversion efficiency of 0.55% was obtained at a potential of - 0.5 V vs. Ag/AgCl for TiO2 NTs anodized for 60 min. The optimized NTs (anodized for 60 min) showed a photocatalytic bacterial inactivation of a magnitude of 6 log within 360 min and a degradation of indole and methylene blue (MB) under low-intensity solar-simulated light (50 mW/cm2). The stability of the prepared catalyst was tested over several cycles.

Photocatalytic Activity of Silicon Nanowires Decorated with PbS Nanoparticles Deposited by Pulsed Laser Deposition for Efficient Wastewater Treatment.

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.

Synthesis and Characterization of TiO2 Nanotubes (TiO2-NTs) Decorated with Platine Nanoparticles (Pt-NPs): Photocatalytic Performance for Simultaneous Removal of Microorganisms and Volatile Organic Compounds.

This work reports on the effect of TiO2 nanotubes (TiO2-NTs), decorated wih platinum nanoparticles (Pt-NPs), on the removal of bacteria and volatile organic compounds (VOCs). The Pt-NPs were loaded onto the TiO2-NTs using the electrodeposition method at four decoration times (100, 200, 300, and 600 s). The realized Pt-NPs/TiO2-NTs nanocomposites were used for the degradation of cyclohexane, a highly toxic and carcinogenic VOC pollutant in the chemical industry. The achieved Pt-NPs/TiO2-NTs nanocomposites were characterized using X-ray diffraction (XRD), photoluminescence (PL), diffuse reflectance spectroscopy (UV-Vis), and scanning (SEM) and transmission (TEM) electron microscopy. To understand the photocatalytic and antibacterial behavior of the Pt-NPs/TiO2-NTs, simultaneous treatment of Escherichia coli and cyclohexane was conducted while varying the catalyst time decoration. We noticed a complete bacterial inactivation rate with 90% VOC removal within 60 min of visible light irradiation. Moreover, the Langmuir-Hinshelwood model correlated well with the experimental results of the photocatalytic treatment of indoor air.

Effect of the Helium Background Gas Pressure on the Structural and Optoelectronic Properties of Pulsed-Laser-Deposited PbS Thin Films.

This work focuses on the dependence of the features of PbS films deposited by pulsed laser deposition (PLD) subsequent to the variation of the background pressure of helium (PHe). The morphology of the PLD-PbS films changes from a densely packed and almost featureless structure to a columnar and porous one as the He pressure increases. The average crystallite size related to the (111) preferred orientation increases up to 20 nm for PHe ≥ 300 mTorr. The (111) lattice parameter continuously decreases with increasing PHe values and stabilizes at PHe ≥ 300 mTorr. A downshift transition of the Raman peak of the main phonon (1LO) occurs from PHe = 300 mTorr. This transition would result from electron-LO-phonon interaction and from a lattice contraction. The optical bandgap of the films increases from 1.4 to 1.85 eV as PHe increases from 50 to 500 mTorr. The electrical resistivity of PLD-PbS is increased with PHe and reached its maximum value of 20 Ω·cm at PHe = 300 mTorr (400 times higher than 50 mTorr), which is probably due to the increasing porosity of the films. PHe = 300 mTorr is pointed out as a transitional pressure for the structural and optoelectronic properties of PLD-PbS films.

Morphological influence of BiVO4 nanostructures on peroxymonosulfate activation for highly efficient catalytic degradation of rhodamine B.

Bismuth vanadate (BiVO4) nanostructured films were prepared and successfully applied for peroxymonosulfate (PMS) activation for the degradation of rhodamine B (RhB) in aqueous solution. The BiVO4 thin films were obtained by thermal reaction between electrodeposited bismuth (Bi) films and vanadium precursor. The as-prepared BiVO4 porous, nanoflowers, and cluster nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and BET analysis. The catalytic performance of BiVO4 nanostructures has been carefully evaluated in activating PMS for the degradation of RhB. The nanoflower-like BiVO4 nanostructures exhibit the best catalytic activity. Under optimized conditions, the complete catalytic degradation of RhB using BiVO4 nanoflowers/PMS system was achieved in 17 min at room temperature as revealed by high-performance liquid chromatography (HPLC) analysis. Quenching experiments suggested that sulfate radicals are the main active species in the degradation process. Additionally, BiVO4 catalyst remained stable without any apparent activity loss after five cycling runs.

Enhanced photocatalytic activities of silicon nanowires/graphene oxide nanocomposite: Effect of etching parameters.

Homogeneous and vertically aligned silicon nanowires (SiNWs) were successfully fabricated using silver assisted chemical etching technique. The prepared samples were characterized using scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Photocatalytic degradation properties of graphene oxide (GO) modified SiNWs have been investigated. We found that the SiNWs morphology depends on etching time and etchant composition. The SiNWs length could be tuned from 1 to 42 µm, respectively when varying the etching time from 5 to 30 min. The etchant concentration was found to accelerate the etching process; doubling the concentrations increases the length of the SiNWs by a factor of two for fixed etching time. Changes in bundle morphology were also studied as function of etching parameters. The SiNWs diameter was found to be independent of etching time or etchant composition while the size of the SiNWs bundle increases with increasing etching time and etchant concentration. The addition of GO was found to improve significantly the photocatalytic activity of SiNWs. A strong correlation between etching parameters and photocatalysis efficiency has been observed, mainly for SiNWs prepared at optimum etching time and etchant concentrations of 10 min and 4:1:8. A degradation of 92% was obtained which further improved to 96% by addition of hydrogen peroxide. Only degradation efficiency of 16% and 31% has been observed for bare Si and GO/bare Si samples respectively. The obtained results demonstrate that the developed SiNWs/GO composite exhibits excellent photocatalytic performance and could be used as potential platform for the degradation of organic pollutants.

Photocatalytic activity of Cr-doped TiO2 nanoparticles deposited on porous multicrystalline silicon films.

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.