Intermediate state created by dopant ions (Mn, Co and Zr) into TiO 2 nanoparticles for degradation of dyes under visible light

The degradation of bisphenol-A organic pollutant using the dispersal of TiO2 nanorods onto the partial reduction of graphene oxide nanosheets

The notion of innovative combinations of semiconducting metal oxides for photocatalytic destruction is a key factor in the removal of environmental contaminants. However, for the first time, the combination was made possible for the aforementioned reason by embedding one-dimensional titanium dioxide (TiO2) semiconductor nanorods on two-dimensional rGO (reduced graphene oxide) nanosheets utilizing hydrothermal and a modified Hummers' method. By applying several sophisticated procedures, the properties of these catalysts were found, and then the degradation of BPA (bisphenol-A) was examined with UV and visible light sources. Further, all the analyses were performed on pure TiO2 material. As a result of the synergistic interaction between TiO2 and rGO, the rGO-TiO2 catalyst produced a favorable photocatalytic outcome. The structural investigation of rGO-TiO2 has confirmed that the TiO2 was in anatase phase along with GO and rGO peaks, and the morphological characterization showed that the TiO2 nanorods were integrated randomly into the rGO nanosheets along with defective sites. Also, adding rGO to TiO2 causes charge separation, and π-π interactions to improve the visible light absorption range. In this study, the main model organic component in the photocatalytic degradation is bisphenol-A (BPA). During visible light irradiation, the OH radicals were finally produced by the redox reactions. Furthermore, the rGO surface adsorbs the phenol molecules due to graphene π-π interactions, thus narrowing the band gap and increasing the efficiency of BPA degradation.

Ginsenoside Rk1-Loaded Manganese-Doped Hollow Titania for Enhancing Tumor Sonodynamic Therapy via Upregulation of Intracellular Reactive Oxygen Species

Amplifying the intracellular reactive oxygen species (ROS) level remains an urgent challenge for efficient sonodynamic therapy (SDT) of tumors. Herein, by loading ginsenoside Rk1 with manganese-doped hollow titania (MHT), a Rk1@MHT sonosensitizer was conceived to strengthen the outcome of tumor SDT. The results verify that manganese-doping remarkably elevates the UV-visible absorption and decreases the bandgap energy of titania from 3.2 to 3.0 eV, which improves ROS production under ultrasonic irradiation. Immunofluorescence and Western blot analysis demonstrate that ginsenoside Rk1 can block the critical protein of the glutathione synthesis pathway, glutaminase, thus enhancing intracellular ROS by eliminating the endogenous glutathione-depleted pathway of ROS. Manganese-doping confers the nanoprobe T₁-weighted MRI function (r₂/r₁ = 1.41). Moreover, the in vivo tests confirm that Rk1@MHT-based SDT eradicates liver cancer in tumor-bearing mice via dual upregulation of intracellular ROS production. In summary, our study provides a new strategy for designing high-performance sonosensitizer to achieve noninvasive cancer treatment.

The influence of heterostructured TiO2/ZnO nanomaterials for the removal of azo dye pollutant

In recent times, there has been an inspired research on combining semiconducting metal oxides for improved industrial applications. Significantly, wastewater removal is concerned and the researchers are finding new methodologies for removing azo dyes that possess a high level of carcinogenic effects. In this connection, this work investigates the photocatalytic activity of synthesized TiO2/ZnO nanocomposite irradiated under UV and visible light. The application of the work involves the removal of methylene blue (MB) dye solution. Initial work begins with the novel synthesis of TiO2/ZnO coupled system by integrated sol-gel and thermal decomposition methods. Then, various characterization techniques brought out the existing properties of the prepared TiO2/ZnO catalyst. The X-ray diffraction measurements showed the assorted tetragonal and hexagonal structures. The spherical shape mixed with hexagonal shaped particles were perceived via transmission electron microscopy (TEM). Besides, from photoluminescence spectrum (PL) results, the TiO2/ZnO coupled system displayed slowing down of charge recombination, because of the intermediate states that helps in intensifying the photocatalytic activity. The dual absorption bands corresponding to UV region were deep-rooted from UV-vis spectroscopy. Further, the valuable application of the catalyst in removing methylene blue (MB) dye under both UV and visible light was carried out. The catalyst had displayed 90% of degradation within 40 min under UV light conditions. The other hand, visible light illumination of the catalyst provides divergent results as it possess lesser light absorption. Therefore, this catalyst was unable to yield visible light photocatalytic activity. Hence, this captivating research would bring the wastewater treatment progression using UV light.

A Review on Metal Ions Modified TiO2 for Photocatalytic Degradation of Organic Pollutants

TiO2 is a semiconductor material with high chemical stability and low toxicity. It is widely used in the fields of catalysis, sensing, hydrogen production, optics and optoelectronics. However, TiO2 photocatalyst is sensitive to ultraviolet (UV) light; this is why its photocatalytic activity and quantum efficiency are reduced. To enhance the photocatalytic efficiency in the visible light range as well as to increase the number of the active sites on the crystal surface or inhibit the recombination rate of photogenerated electron–hole pairs electrons, various metal ions were used to modify TiO2. This review paper comprehensively summarizes the latest progress on the modification of TiO2 photocatalyst by a variety of metal ions. Lastly, the future prospects of the modification of TiO2 as a photocatalyst are proposed.

Use of Nanocellulose extracted from grass for adsorption abatement of Ciprofloxacin and Diclofenac removal with phyto, and fish toxicity studies

The present study deals with the adsorption of antibiotic Ciprofloxacin (CPXO) and anti-inflammatory agent Diclofenac (DCF) on Grass nanocellulose (GNC) extracted from Cyprus rotundas grass. The adsorbent GNC was characterised using various microscopic, elemental and spectroscopic analysis to monitor the physicochemical alterations of the surface before and after adsorption. The size of the converted nanocellulose was found to be 40-50 nm. The experimental measures influencing the adsorption of CPXO and DCF that were optimised are initial solution pH, GNC dosage, temperature and initial concentration of the adsorbate. Halsey isotherm model and pseudo-second order kinetic model agreed best with the experimental outcome for both the adsorbate. The maximum adsorption capacity of GNC were 227.223 and 192.307 mg/g for CPXO and DCF respectively. Phytotoxicity studies were performed using 6 different types of seeds to evaluate the effect of GNC treated effluent on plants. Similarly, acute fish toxicity on zebra fish analysis showed to have lesser mortality rate of the effluent after adsorption of CPXO and DCF on GNC.

Present applications of titanium dioxide for the photocatalytic removal of pollutants from water: A review

The evolution of modern technology and industrial processes has been accompanied by an increase in the utilization of chemicals to derive new products. Water bodies are frequently contaminated by the presence of conventional pollutants such as dyes and heavy metals, as well as microorganisms that are responsible for various diseases. A sharp rise has also been observed in the presence of new compounds heretofore excluded from the design and evaluation of wastewater treatment processes, categorized as "emerging pollutants". While some are harmless, certain emerging pollutants possess the ability to cause debilitating effects on a wide spectrum of living organisms. Photocatalytic degradation has emerged as an increasingly popular solution to the problem of water pollution due to its effectiveness and versatility. The primary objective of this study is to thoroughly scrutinize recent applications of titanium dioxide and its modified forms as photocatalytic materials in the removal and control of several classes of water pollutants as reported in literature. Different structural modifications are used to enhance the performance of the photocatalyst such as doping and formation of composites. The principles of these modifications have been scrutinized and evaluated in this review in order to present their advantages and drawbacks. The mechanisms involved in the removal of different pollutants through photocatalysis performed by TiO2 have been highlighted. The factors affecting the mechanism of photocatalysis and those affecting the performance of different TiO2-based photocatalysts have also been thoroughly discussed, thereby presenting a comprehensive view of all aspects involved in the application of TiO₂ to remediate and control water pollution.

Impact of Titanium Dioxide (TiO2) Modification on Its Application to Pollution Treatment—A Review

A high-efficiency method to deal with pollutants must be found because environmental problems are becoming more serious. Photocatalytic oxidation technology as the environmentally-friendly treatment method can completely oxidate organic pollutants into pollution-free small-molecule inorganic substances without causing secondary pollution. As a widely used photocatalyst, titanium dioxide (TiO2) can greatly improve the degradation efficiency of pollutants, but several problems are noted in its practical application. TiO2 modified by different materials has received extensive attention in the field of photocatalysis because of its excellent physical and chemical properties compared with pure TiO2. In this review, we discuss the use of different materials for TiO2 modification, highlighting recent developments in the synthesis and application of TiO2 composites using different materials. Materials discussed in the article can be divided into nonmetallic and metallic. Mechanisms of how to improve catalytic performance of TiO2 after modification are discussed, and the future development of modified TiO2 is prospected.

Surfactant-assisted synthesis of copper oxide nanorods for the enhanced photocatalytic degradation of Reactive Black 5 dye in wastewater

In this study, copper oxide nanorods were synthesized via surfactant-assisted chemical precipitation method and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV-Visible spectrometer. XRD result reveals that CuO nanorods were structured in the monoclinic phase. SEM image suggested that synthesized CuO were shaped like nanorod with approximately 20-40 nm width and 500-800 nm length. The observed band gap calculated from UV-Visible absorption studies is 1.45 eV. As-prepared CuO nanorods were applied as a photocatalyst for the degradation of textile dye Reactive Black 5 (RB-5) in aqueous solution under the presence of visible light. The result exhibited that an enhanced degradation of RB-5 was achieved around 98% within 300 min and the experimental values were well matched with the linear fit model (R² = 0.97) and the observed rate constant found to be 5 × 10^-3 min^-1. Therefore, as-synthesized CuO nanorods can be applied as a potential photocatalyst material for the degradation of organic pollutants in the wastewater.

Life Cycle Assessment of the Sustainability of Enhancing the Photodegradation Activity of TiO2 with Metal-Doping

While TiO2 nanoparticles have shown potential as photocatalysts in the degradation of organic contaminants, their inability to absorb efficiently visible light has limited their industrial application. One strategy for solving this problem is monodoping TiO2 photocatalysts with transition metals, which has worked in the degradation of several pollutants. However, it is not clear if this improvement is enough to offset the potential environmental impacts of adding metal ions to the synthesis of TiO2. Herein, we have used Life Cycle Assessment (LCA) to determine the sustainability of monodoping TiO2 with transition metals (Fe, Co, Mn and Ni, with a 1% weight ratio) to enhance the photocatalytic properties of the photocatalyst toward the degradation of Carbamazepine and Methyl Orange, under UV-A and visible light irradiation. We found that the addition of transition-metals has no significant effect on the environmental impacts associated with the synthesis of TiO2, when a weight-based functional unit was considered. However, when photocatalytic activity was considered, major differences were found. Thus, our results demonstrate that the sustainability of monodoping with different transition metals is solely determined by their ability to enhance (or not) the photocatalytic activity of TiO2. Our data also demonstrated that isopropyl alcohol constitutes a critical point in the synthesis of TiO2 photocatalysts, with ethanol being a potential substitute.

Photocatalytic mineralization and degradation kinetics of sulphamethoxazole and reactive red 194 over silver-zirconium co-doped titanium dioxide: Reaction mechanisms and phytotoxicity assessment

The photodegradation and phytotoxicity of the pharmaceutical antibiotic, sulphamethoxazole (SMX) and the azo-dye reactive-red-194 (RR194) under visible-light irradiation of TiO₂ nanoparticles modified by silver and zirconium was investigated. The results indicated that sulphamethoxazole and its toxic degradation by product, 3-amino-5-methylisoxazole and RR-194 could be degraded efficiently by the co-doped Zr/Ag-TiO₂ catalyst. PL studies and ROS generation results suggested that the effective charge separation was carried out while irradiation of the modified TiO₂ nanoparticles. Phytotoxicity tests demonstrated lower percentage of germination in P. vulgaris (40%), V. radiata (30%) and P. lunatus (30%) of the seeds treated with 50 ppm of SMX, compared to the seeds treated with the degradation products (100%). The results with 50 ppm of RR-194 also showed lower percentage of germination in P. vulgaris (40%), V. radiata (50%) and P. lunatus (30%) compared to the degradation products (100%). Furthermore, significant increase in root and shoot development was observed in the seeds treated with the degraded products when compared with SMX and RR-194. Overall, this study contributes to further understanding the photodegradation mechanisms, degradation products and environmental fate of SMX and RR-194 in water which helps in the evaluation and mitigation of the environmental risk of SMX and RR-194 for water reuse and crop irrigation.

Visible light photocatalytic mineralization of 17α-ethinyl estradiol (EE2) and hydrogen evolution over silver and strontium modified TiO2 nanoparticles: mechanisms and phytotoxicity assessment

This study focusses on the novel synthesis of silver and strontium modified TiO₂ nanocomposite through a sol–gel method, which was then utilized for visible light degradation of EE2 and hydrogen production for the first time.

Laser synthesized TiO2-based nanoparticles and their efficiency in the photocatalytic degradation of linear carboxylic acids

Titanium dioxide nanoparticles were synthesized by laser pyrolysis, their surface and electronic properties were modified by gold and/or nitrogen. These materials were characterized by different techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Time resolved conductivity (TRMC) was used to study the charge separation of electron/hole pairs. Altogether (XPS, EPR, TRMC), the physicochemical characterizations are well correlated with chemical photoactivity of the different samples. Their photocatalytic activity was evaluated for the degradation of linear carboxylic acids (C2-C3) under UV and visible illumination. The decomposition rate of acids was measured, it shows that the modification with gold increases the photoactivity while the presence of nitrogen slows down the process. Such observations are in good agreement with evolution of TRMC signals. A degradation pathway has been determined by identification of intermediate products by chromatography and EPR, results show different intermediate species. In particular EPR confirms the presence of NO^2- paramagnetic centers and shows two novel N centered paramagnetic centers. A decrease of the degradation rate is observed with increase of carboxylic acid chain length.

Ag@SrTiO3 nanocomposite for super photocatalytic degradation of organic dye and catalytic reduction of 4-nitrophenol

Ag@SrTiO₃ nanocomposite was constructed for super photocatalytic degradation of organic dye and catalytic reduction of 4-nitrophenol.

Hybrid CuxO–TiO2 porous hollow nanospheres: preparation, characterization and photocatalytic properties

A series of CuxO–TiO₂ hollow nanospherical composites with different mass percents of copper element were prepared, and the composites displayed high photocatalytic activities towards acetaldehyde degradation to CO₂ under visible-light irradiations.