Ultrasonication-assisted synthesis of CN-TiO2 and its photocatalytic degradation of diclofenac under visible light irradiation

In this study, CN codoped TiO2 nanoparticles (CN-TiO2) were fabricated by solvothermal and low temperature calcination methods with the aid of ultrasonication. According to the number of ultrasonic treatments used in the preparation process, the samples were named NN, YN, NY and YY. The characteristics of transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectroscopy (UV-vis) were employed to analyse the effect of the ultrasonic treatment step in the synthetic process. The results showed that ultrasonication can increase the CN content in TiO2, reduce the band gap energy, and improve the catalytic performance of the CN-TiO2, and the effect of secondary ultrasound is particularly obvious. The YY obtained by two-step ultrasonication with the lowest band gap energy of 3.07 eV. The photocatalytic activity of the CN-TiO2 was evaluated using the degradation of diclofenac (DCF) under visible light irradiation (white LED strips with an emission wavelength of 450 nm). It was observed that the YY exhibited significantly superior DCF degradation activity. When using 0.4 g L-1 of YY, an excellent DCF degradation of 97% could be reached, which is 1.4 times that of NN (without ultrasonication). Moreover, YY had good visible light photocatalytic activity, and the degradation efficiency of YY for DCF under visible light was comparable to that of a xenon lamp. Therefore, ultrasonication played a critical role in the enhancement of photocatalytic activity during the synthesis of CN-TiO2.

C-,N- and S-Doped TiO2 Photocatalysts: A Review

This article presents an overview of the reports on the doping of TiO2 with carbon, nitrogen, and sulfur, including single, co-, and tri-doping. A comparison of the properties of the photocatalysts synthesized from various precursors of TiO2 and C, N, or S dopants is summarized. Selected methods of synthesis of the non-metal doped TiO2 are also described. Furthermore, the influence of the preparation conditions on the doping mode (interstitial or substitutional) with reference to various types of the modified TiO2 is summarized. The mechanisms of photocatalysis for the different modes of the non-metal doping are also discussed. Moreover, selected applications of the non-metal doped TiO2 photocatalysts are shown, including the removal of organic compounds from water/wastewater, air purification, production of hydrogen, lithium storage, inactivation of bacteria, or carbon dioxide reduction.

Photocatalytic Reactivity of Carbon–Nitrogen–Sulfur-Doped TiO2 Upconversion Phosphor Composites

Sol–gel synthesized N-doped and carbon–nitrogen–sulfur (CNS)-doped TiO2 solutions were deposited on upconversion phosphor using a dip coating method. Scanning electron microscopy (SEM) imaging showed that there was a change in the morphology of TiO2 coated on NaYF4:Yb,Er from spherical to nanorods caused by additional urea and thiourea doping reagents. Fourier transform infrared (FTIR) spectroscopy further verified the existence of nitrate–hyponitrite, carboxylate, and SO42− because of the doping effect. NaYF4:Yb,Er composites coated with N- and CNS-doped TiO2 exhibited a slight shift of UV-Vis spectra towards the visible light region. Photodecomposition of methylene blue (MB) was evaluated under 254 nm germicidal lamps and a 300 W Xe lamp with UV/Vis cut off filters. The photodegradation of toluene was evaluated on TiO2/NaYF4:Yb,Er and CNS-doped TiO2/NaYF4:Yb,Er samples under UV light illumination. The photocatalytic reactivity with CNS-doped TiO2/NaYF4:Yb,Er surpassed that of the undoped TiO2/NaYF4:Yb,Er for the MB solution and toluene. Photocatalytic activity is increased by CNS doping of TiO2, which improves light sensitization as a result of band gap narrowing due to impurity sites.

Highly Crystalline Ordered Cu-dopedTiO2Nanostructure by Paper Templated Method: Hydrogen Production and Dye Degradation under Natural Sunlight

A highly crystalline ordered Cu-TiO2 nanostructure was synthesized using a simple paper template method using cupric nitrate and titanium isopropoxide as precursors. The structural study by XRD confirmed the formation of highly crystalline anatase phase of Cu-TiO2. The broad diffraction peaks of Cu-TiO2 exhibit the nanocrystalline nature of the product. The optical study by UV-DRS indicated the red shift in absorption wavelength with an increase in Cu doping, i.e., towards the visible region. The FE-SEM and FE-TEM study validated the formation of spherical shaped nanoparticles of Cu-TiO2 having sizes in the range of 20–30 nm. Considering the absorption in the visible region, the photocatalytic study was performed for water splitting and rhodamine-B (RhB) dye degradation under natural sunlight. The 2% Cu-doped TiO2 showed the highest photocatalytic hydrogen evolution, i.e., 1400 µmol·g−1·h−1 from water, among the prepared compositions. The photocatalytic performance of Cu-TiO2 conferred complete degradation of RhB dye within 40 min. The higher activity in both cases was attributed to the formation of highly crystalline ordered nanostructure of Cu-doped TiO2. This synthesis approach has potential to prepare other highly crystalline ordered nanostructured semiconductors for different applications.

Sunlight mediated degradation of spent wash using hydrothermally synthesized orthorhombic shaped Cu–TiO2 nanoparticles

This method is suitable for the selective growth of orthorhombic shaped Cu–TiO₂, which shows an excellent performance for the degradation of sugar industry waste.

Ultrahigh Selective Room-Temperature Ammonia Gas Sensor Based on Tin-Titanium Dioxide/reduced Graphene/Carbon Nanotube Nanocomposites by the Solvothermal Method

Resistive-based gas sensors have been considered as the most favorable gas sensors for detection of toxic gases and volatile organic compounds (VOCs) because of their simple structure, low cost, high sensitivity, ease of use, and high stability. Unfortunately, wide application of resistive-based gas sensors is limited by their low selectivity. In this article, we present the fabrication of ultrahigh selective NH₃ gas sensor based on tin-titanium dioxide/reduced graphene/carbon nanotube (Sn-TiO₂@rGO/CNT) nanocomposites. The Sn-TiO₂@rGO/CNT nanocomposites with different molar ratios of Sn/Ti (1:10, 3:10, and 5:10) were synthesized via the solvothermal method. Characterizations by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy confirmed the decoration of Sn-TiO₂ nanoparticles on rGO/CNT nanocomposite surfaces. The Sn-TiO₂@rGO/CNT nanocomposite gas sensor exhibited high response and ultrahigh selectivity to NH₃ against toluene, dimethylformamide, acetone, ethanol, methanol, isopropanol, formaldehyde, hydrogen, carbon dioxide, acetylene, and VOCs in paint thinners at room temperature. The Sn-TiO₂@rGO/CNT nanocomposite gas sensor with molar ratio of Sn/Ti = 1:10 showed the highest response to NH₃ over other molar ratios of Sn/Ti as well as pure rGO/CNT and Sn-TiO₂ gas sensors. The ammonia-sensing mechanisms of the Sn-TiO₂@rGO/CNT gas sensor were proposed based on the formation of p-n heterojunctions of p-type rGO/CNT and n-type Sn-TiO₂ nanoparticles via a low-temperature oxidizing reaction process.

Photocatalytic Hydrogen Production: Role of Sacrificial Reagents on the Activity of Oxide, Carbon, and Sulfide Catalysts

Photocatalytic water splitting is a sustainable technology for the production of clean fuel in terms of hydrogen (H2). In the present study, hydrogen (H2) production efficiency of three promising photocatalysts (titania (TiO2-P25), graphitic carbon nitride (g-C3N4), and cadmium sulfide (CdS)) was evaluated in detail using various sacrificial agents. The effect of most commonly used sacrificial agents in the recent years, such as methanol, ethanol, isopropanol, ethylene glycol, glycerol, lactic acid, glucose, sodium sulfide, sodium sulfite, sodium sulfide/sodium sulfite mixture, and triethanolamine, were evaluated on TiO2-P25, g-C3N4, and CdS. H2 production experiments were carried out under simulated solar light irradiation in an immersion type photo-reactor. All the experiments were performed without any noble metal co-catalyst. Moreover, photolysis experiments were executed to study the H2 generation in the absence of a catalyst. The results were discussed specifically in terms of chemical reactions, pH of the reaction medium, hydroxyl groups, alpha hydrogen, and carbon chain length of sacrificial agents. The results revealed that glucose and glycerol are the most suitable sacrificial agents for an oxide photocatalyst. Triethanolamine is the ideal sacrificial agent for carbon and sulfide photocatalyst. A remarkable amount of H2 was produced from the photolysis of sodium sulfide and sodium sulfide/sodium sulfite mixture without any photocatalyst. The findings of this study would be highly beneficial for the selection of sacrificial agents for a particular photocatalyst.

Solar-light-active mesoporous Cr–TiO2 for photodegradation of spent wash: an in-depth study using QTOF LC-MS

A dark coloured effluent called “spent wash” is generated as an unwanted product in sugar based alcohol distillery which is degraded to less toxic compounds using visible light active Cr–TiO₂ photocatalyst under natural sunlight.

Recent Progress on Titanium Dioxide Nanomaterials for Photocatalytic Applications

Environmental and energy problems have drawn much attention owing to rapid population growth and accelerated economic development. For instance, photocatalysis, "a green technology", plays an important role in solar-energy conversion owing to its potential to solve energy and environmental problems. Recently, many efforts have been devoted to improving visible-light photocatalytic activity by using titanium dioxide as a photocatalyst as a result of its wide range of applications in the energy and environment fields. However, fast charge recombination and an absorption edge in the UV range limit the photocatalytic efficiency of TiO₂ under visible-light irradiation. Many investigations have been undertaken to overcome the limitations of TiO₂ and, therefore, to enhance its photocatalytic activity under visible light. The present literature review focuses on different strategies used to promote the separation efficiency of electron-hole pairs and to shift the absorption edge of TiO₂ to the visible region. Current synthesis techniques used to elaborate several nanostructures of TiO₂ -based materials, recent progress in enhancing visible photocatalytic activity, and different photocatalysis applications will be discussed. On the basis of the studies reported in the literature, we believe that this review will help in the development of new strategies to improve the visible-light photocatalytic performance of TiO₂ -based materials further.

Photodegradation of spent wash, a sugar industry waste, using vanadium-doped TiO2 nanoparticles

A sol–gel-derived V-TiO₂ photocatalyst exhibited high photocatalytic activity for the degradation of spent wash and Jakofix red dye under natural sunlight with high stability.

Hierarchical CdMoO4 nanowire–graphene composite for photocatalytic hydrogen generation under natural sunlight

Herein, a facile in situ solvothermal technique for the synthesis of a CdMoO₄/graphene composite photocatalyst for hydrogen generation under natural solar light.

Solar light active plasmonic Au@TiO2 nanocomposite with superior photocatalytic performance for H2 production and pollutant degradation

Spherically shaped plasmonic Au nanoparticles (NPs) of size 10 nm (±4 nm) have been decorated on TiO₂ NPs for the synthesis of Au@TiO₂ composites via an aqueous sol–gel method.