Effluent toxicity study using biomarkers for ciprofloxacin photoelectrocatalytic degradation by bismuth-doped titanium dioxide nanotubes

Ciprofloxacin hydrochloride (CIP) is a broad-spectrum synthetic antibiotic often found in domestic sewage and industrial waste due to the inefficiency of conventional treatments. Given the potential risk of drug accumulation, this study presents coatings of titanium dioxide nanotubes (TiO2) doped with different bismuth (Bi) concentrations to degrade CIP through photocatalytic and photoelectrochemical processes. Characterization studies revealed that bismuth (Bi) doping affected the morphology of the materials, with concentrations of 0.01 and 0.05 mol L-1, resulting in collapsed materials with a smaller active surface area. Photocatalysis tests for all the materials exhibited a similar degree of efficiency to photolysis, approximately 33%. Ecotoxicity tests using the biomarkers Lactuca sativa L., Lemna minor, and Artemia salina indicated that, although they were similar to photolysis in terms of efficiency, the effluents generated when employing the doped catalysts showed lower levels of toxicity, with the best results achieved for the material doped with 0.005 mol L-1 of Bi, with a toxicity level approximately 40% lower. Photoelectrocatalysis proved to be the most efficient CIP degradation technique. The highest degradation rate was observed for materials doped with 0.005 mol L-1 of Bi, with an efficiency of 46%, which is 1.4 times more efficient than photolysis. These results demonstrate that materials doped with low amounts of Bi can be effectively used as photoanodes for drug degradation, as their performance is superior, and the final product generated exhibits low toxicity to living organisms.

A High-Performing Nanostructured Ir Doped-TiO2 for Efficient Photocatalytic Degradation of Gaseous Toluene

TiO2-based photocatalysts still have some limitations such as large bandgap and low surface area, leading to low efficiency in the photocatalytic degradation of VOCs and limiting it to use in sunlight. Here we report that the nanostructured Ir-doped TiO2 as an efficient photocatalyst generates an excellent risk-reduction material of gaseous toluene. We have succeeded in developing a nanostructured Ir-doped TiO2 and initially found that excellent efficient photocatalytic VOC decomposition can be achieved in our materials The nanostructured Ir-doped TiO2 was synthesized by a one pot, low temperature hydrothermal process with different ratios of Ir doped into the TiO2. It exhibited a high surface area, uniformly spherical morphology of 10–15 nm. Its activity for the photocatalytic degradation of gaseous toluene exhibited up to 97.5% under UV light. This enhancement could be explained by iridium doping which created a high concentration oxygen vacancy and changed the recombination rate of the photogenerated charge carriers. More generally, our study indicates a strategic way to develop the novel nanostructured material for numerous applications.

Photocatalytic membranes: a new perspective for persistent organic pollutants removal

The presence of conventional and emerging pollutants infiltrating into our water bodies is a course of concern as they have seriously threatened water security. Established techniques such as photocatalysis and membrane technology have proven to be promising in removing various persistent organic pollutants (POP) from wastewaters. The emergence of hybrid photocatalytic membrane which incorporates both photocatalysis and membrane technology has shown greater potential in treating POP laden wastewater based on their synergistic effects. This article provides an in-depth review on the roles of both photocatalysis and membrane technology in hybrid photocatalytic membranes for the treatment of POP containing wastewaters. A concise introduction on POP's in terms of examples, their origins and their effect on a multitude of organisms are critically reviewed. The fundamentals of photocatalytic mechanism, current directions in photocatalyst design and their employment to treat POP's are also discussed. Finally, the challenges and future direction in this field are presented.

Comparative visible-light driven selective oxidation to aldehydes of phenylmethanol (benzyl alcohol) and 4-pyridinylmethanol (4-pyridinecarbinol) on N-TiO2 and some commercial TiO2 samples

Visible light (λ > 420 nm) selective photooxidation of phenylmethanol and 4-pyridinylmethanol in CH₃CN to the corresponding aldehydes on N-TiO₂ is compared with homemade undoped TiO₂ (U-TiO₂) and commercial undoped anatase specimens (such as PC105, PC500). Significant differences observed between N-TiO₂ and undoped TiO₂ are neither directly related to the surface area nor to the adsorbed amount of alcohol in the dark by surface area unit. FTIR and EPR spectroscopies are used to study the surface of TiO₂ samples and to deeply understand the phenomena intervening in the visible-light photocatalytic activation of the doped vs the undoped oxides. In particular, it is shown that on N-TiO₂ (and also on undoped PC105) strong Lewis acid sites (LAS) exist. The favorable role of LAS on the photocatalytic activity is illustrated by the higher photooxidation of 4-pyridinylmethanol vs phenylmethanol over N-TiO₂ and PC105 in contrast to the other undoped samples, whose visible light sensitivity originates from a charge transfer between the alcohol and the solid. EPR spectra of N-TiO₂ point out the presence of paramagnetic centers related to nitrogen that disappear when the photocatalyst is irradiated with visible light in the presence of alcohol, which starts its oxidative process. On the basis of presented results, we propose that doping with N introduces new intraband gap states that not only contribute to LAS and adsorption of alcohol but also are directly involved in the photochemical process occurring under visible light irradiation.

A novel, mesoporous molybdenum doped titanium dioxide/reduced graphene oxide composite as a green, highly efficient solid acid catalyst for acetalization

A novel, mesoporous molybdenum doped titanium dioxide-reduced graphene oxide composite is synthesized as a highly efficient heterogeneous solid acid catalyst.

Structure and performance of a V2O5–WO3/TiO2–SiO2 catalyst derived from blast furnace slag (BFS) for DeNOx

The excellent DeNOx performances for a slag-based catalyst derived from its presence of proper amounts of Al₂O₃/Fe₂O₃/SO₄²⁻ as the catalyst dopants or impurities from processing Ti-bearing BFS in making the catalyst.

SnxTi1−xO2 solid-solution-nanoparticle embedded mesoporous silica (SBA-15) hybrid as an engineered photocatalyst with enhanced activity

Synthesis of hybrids of a porous host-material (with well-dispersed embedded nanoparticles inside the pore), wherein each nanoparticle has precisely controlled properties (size and composition) poses a generic challenge. To this end, a new strategy is proposed to form Sn_xTi_1−xO₂ solid-solution-nanoparticles inside the pores of sphere-like mesoporous silica (SBA-15), with different percentages of Sn in the nanoparticle (varying from 5 to 50 at%), for enhanced photocatalysis. X-ray diffraction confirms the formation of solid-solution nanoparticles in the porous silica hybrid, while the location of nanoparticles and elemental composition are identified using electron microscopy. The hybrid with 5 at% of Sn (Sn_0.05Ti_0.95O₂-sphere-like SBA-15) shows the maximum photocatalytic activity for degradation of rhodamine-B dye (first order rate constant for degradation, k = 1.86 h⁻¹), compared to both pure TiO₂-sphere-like SBA-15 (k = 1.38 h⁻¹) or pure SnO₂-sphere-like SBA-15 (k = 0.14 h⁻¹) or other hybrids in this series. XPS and PL spectra suggest the formation of more oxygen vacancies during the replacement of Ti⁴⁺ with Sn⁴⁺. Electrochemical studies reveal that there is a reduction of charge transfer resistance from 910 kΩ cm⁻² for TiO₂-sphere-like SBA-15, to 332 kΩ cm⁻² for Sn_0.05Ti_0.95O₂-sphere-like SBA-15. These results imply that the enhancement in photocatalytic performance is as a result of delay in recombination of charge carriers. Therefore, the approach followed in the present work to form solid-solution nanoparticles inside a porous host without causing pore blockage, would be a promising route towards increasing reaction rates in catalytic applications of hybrid materials.

Glucosamine-induced growth of highly distributed TiO2 nanoparticles on graphene nanosheets as high-performance photocatalysts

Ultrasmall TiO₂ nanoparticles@graphene composites with superior photocatalytic activity have been designed by a facile glucosamine-assisted hydrothermal strategy.

Enhanced photoelectric performance of PbS/CdS quantum dot co-sensitized solar cells via hydrogenated TiO2 nanorod arrays

The enhanced photoelectric performance of quantum dot sensitized solar cells via hydrogenated TiO2 is proposed. The best energy conversion efficiency is 1.5 times higher than cells without hydrogen treatment. We demonstrated that introducing oxygen vacancies by hydrogenation is an effective and feasible method for enhanced photoelectric performance.

Eco-friendly carbon-nanodot-based fluorescent paints for advanced photocatalytic systems

Fluorescent carbon nanomaterials, especially zero-dimensional (0D) carbon nanodots (CDs), are widely used in broad biological and optoelectronic applications. CDs have unique characteristics such as strong fluorescence, biocompatibility, sun-light response, and capability of mass-production. Beyond the previous green CD obtained from harmful natural substances, we report a new type of fluid-based fluorescent CD paints (C-paints) derived from polyethylene glycol (PEG; via simple ultrasound irradiation at room temperatures) and produced in quantum yields of up to ~14%. Additionally, C-paints possess a strong, UV- and visible-light-responsive photoluminescent (PL) property. Most especially, C-paints, by incorporation into a photocatalytic system, show additional roles in the emission of fluorescent light for activation of TiO2 nanoparticles (NPs) and the resultant detoxification of most organic dyes, thus further enabling embarkation in advanced water purification.

A bilayer composite composed of TiO2-incorporated electrospun chitosan membrane and human extracellular matrix sheet as a wound dressing

We designed bilayer composites composed of an upper layer of titanium dioxide (TiO2)-incorporated chitosan membrane and a sub-layer of human adipose-derived extracellular matrix (ECM) sheet as a wound dressing for full-thickness wound healing. The dense and fibrous top layer, which aims to protect the wound from bacterial infection, was prepared by electrospinning of chitosan solution followed by immersion in TiO2 solution. The sponge-like sub-layer, which aims to promote new tissue regeneration, was prepared with acellular ECM derived from human adipose tissue. Using a modified drop plate method, there was a 33.9 and 69.6% reduction in viable Escherichia coli and Staphylococcus aureus on the bilayer composite, respectively. In an in vivo experiment using rats, the bilayer composites exhibited good biocompatibility and provided proper physicochemical and compositional cues at the wound site. Changes in wound size and histological examination of full-thickness wounds showed that the bilayer composites induced faster regeneration of granulation tissue and epidermis with less scar formation, than control wounds. Overall results suggest that the TiO2-incorporated chitosan/ECM bilayer composite can be a suitable candidate as a wound dressing, with an excellent inhibition of bacterial penetration and wound healing acceleration effects.

One-step synthesis of nanohybrid carbon dots and TiO2 composites with enhanced ultraviolet light active photocatalysis

Nano-hybrid composites of carbon dots (CDs) and titanium dioxide (TiO₂) were fabricated by a designed one-step solvothermal method.

Facile synthesis of ZnO–C nanocomposites with enhanced photocatalytic activity

ZnO–C nanocomposites exhibit excellent photocatalytic activity towards methylene blue degradation.

Adsorption and photocatalytic behavior of titanate nanotubes sensitized with zinc tetra(4-carboxyphenyl) porphyrin

Effect of calcination temperature and ZnTCPP sensitizer on the morphology of ZnTCPP–TNTS.

Highly crystalline Ti-doped SnO2 hollow structured photocatalyst with enhanced photocatalytic activity for degradation of organic dyes

We developed a facile infiltration route for synthesizing hollow-structured SnO₂ with an adjustable Ti doping content using SiO₂ microspheres as hard templates via an improved Stober method.

Electrically conductive polyaniline sensitized defective-TiO2 for improved visible light photocatalytic and photoelectrochemical performance: a synergistic effect

A proposed scheme for the synthesis of s-Pani@m-TiO₂ nanocomposites.

In situ encapsulation of germanium clusters in carbon nanofibers: high-performance anodes for lithium-ion batteries

Alloyed anode materials for lithium-ion batteries (LIBs) usually suffer from considerable capacity losses during charge-discharge process. Herein, in situ-grown germanium clusters are homogeneously encapsulated into porous nitrogen-doped carbon nanofibers (N-CNFs) to form Ge/N-CNFs hybrids, using a facile electrospinning method followed by thermal treatment. When used as anode in LIBs, the Ge/N-CNFs hybrids exhibit excellent lithium storage performance in terms of specific capacity, cycling stability, and rate capability. The excellent electrochemical properties can be attributed to the unique structural features: the distribution of the germanium clusters, porous carbon nanofibers, and GeN chemical bonds all contribute to alleviating the large volume changes of germanium during the discharge-charge process, while at same time the unique porous N-CNFs not only increase the contact area between the electrode and the electrolyte, but also the conductivity of the hybrid.

Enhanced photoelectrochemical properties of TiO2 nanorod arrays decorated with CdS nanoparticles

TiO₂ nanorod arrays (TiO₂ NRAs) sensitized with CdS nanoparticles were fabricated via successive ion layer adsorption and reaction (SILAR), and TiO₂ NRAs were obtained by oxidizing Ti NRAs obtained through oblique angle deposition. The TiO₂ NRAs decorated with CdS nanoparticles exhibited excellent photoelectrochemical and photocatalytic properties under visible light, and the one decorated with 20 SILAR cycles CdS nanoparticles shows the best performance. This can be attributed to the enhanced separation of electrons and holes by forming heterojunctions of CdS nanoparticles and TiO₂ NRAs. This provides a promising way to fabricate the material for solar energy conversion and wastewater degradation.

Synergistic effect on the visible light activity of Ti3+ doped TiO2 nanorods/boron doped graphene composite

TiO2/graphene (TiO2-x/GR) composites, which are Ti(3+) self-doped TiO2 nanorods decorated on boron doped graphene sheets, were synthesized via a simple one-step hydrothermal method using low-cost NaBH4 as both a reducing agent and a boron dopant on graphene. The resulting TiO2 nanorods were about 200 nm in length with exposed (100) and (010) facets. The samples were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, X-band electron paramagnetic resonance (EPR), X-ray photoelectron spectra (XPS), transmission electron microscope (TEM), Raman, and Fourier-transform infrared spectroscopy (FTIR). The XRD results suggest that the prepared samples have an anatase crystalline structure. All of the composites tested exhibited improved photocatalytic activities as measured by the degradation of methylene blue and phenol under visible light irradiation. This improvement was attributed to the synergistic effect of Ti(3+) self-doping on TiO2 nanorods and boron doping on graphene.

Facile synthesis of TiO2 hollow spheres composed of high percentage of reactive facets for enhanced photocatalytic activity

In this study, facile synthesis of hollow TiO₂ spheres composed of a high percentage of reactive facets (~85%) is successfully prepared with TiOSO₄ and HBF₄ by the hydrothermal method.

Alumina decorated TiO2 nanotubes with ordered mesoporous walls as high sensitivity NO(x) gas sensors at room temperature

Alumina (Al2O3) decorated anatase TiO2 nanotubes with ordered mesoporous pore walls (Al2O3/meso-TiO2 nanotubes) are successfully synthesized through vacuum pressure induction technology, and then combined with the thermal decomposition of a mesoporous TiO2 sol precursor, inside the cylindrical nanochannels of an anodic aluminium oxide (AAO) template. The decorated Al2O3 was formed by in situ deposition via direct reaction of the strong acid sol precursor and the nanochannel wall of the AAO template. The resultant Al2O3/meso-TiO2 nanotubes are characterized in detail by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and N2 adsorption-desorption. The experimental results reveal that the Al2O3/meso-TiO2 nanotubes have a tubular structure with an average diameter of ∼200 nm and highly ordered mesopores in the tubular walls. The Al2O3 is distributed evenly on the anatase TiO2 nanotubes. Moreover, the Al2O3/meso-TiO2 nanotubes possess a large specific surface area (136 m(2) g(-1)) and narrow mesopore size distribution (∼10 nm). By using NO(x) as a probe molecule, the Al2O3/meso-TiO2 nanotube films exhibit better sensing performance than that of mesoporous TiO2 nanotubes, in terms of their high sensitivity, fast response-recovery time, and good stability in air at room temperature. The outstanding performance in the gas sensing ability of Al2O3/meso-TiO2 nanotubes is a result of their one-dimensional tubular and mesoporous nanostructures, advantageous for the adsorption and diffusion of NO(x) gas. In addition, the sensing response is greatly improved by virtue of the decorated Al2O3 on the surfaces of the TiO2 nanotubes, which acts as an energy barrier to suppress charge recombination. The structural properties of the Al2O3/meso-TiO2 nanotubes makes them a viable novel gas sensor material at room temperature.

Effects of copper and vanadium deposition in multi-walled hydrogen trititanate and mixed-phase anatase/trititanate nanotubes

Metal incorporation and doping is one of the routes commonly explored to improve visible light photocatalytic activity of titania and related materials. In this work, we explore the effect of copper and vanadium deposition and incorporation in multi-walled hydrogen trititanate and mixed-phase anatase/trititanate nanotubes. The molecular designed dispersion method is used to introduce the metals in the materials. Electron paramagnetic resonance facilitates a full characterization of the metal sites before and after calcination and allows determining the UV- and visible-light-induced formation of paramagnetic intermediates. Vanadium or copper deposition on the tubes leads to increased formation of F(+) centres under visible or UV illumination. The EPR results are linked to the activity towards rhodamine 6G photobleaching of the different materials.