Cysteine modified anatase TiO2 hollow microspheres with enhanced visible-light-driven photocatalytic activity

Efficient NiO/F-TiO2 nanocomposites for 4-chlorophenol photodegradation

This work aimed to study NiO/F-TiO₂ composites in the photocatalytic degradation of 4-chlorophenol. F-TiO₂ support was prepared by in-situ fluorination of TiO₂ using the sol-gel method. The heterostructured materials were prepared by wet impregnation method, varying NiO content (0.5, 1.0, and 2.0% wt). The solids were characterized by X-ray fluorescence, X-ray diffraction, nitrogen physisorption, diffuse reflectance UV-Vis spectrophotometry, infrared spectroscopy, and X-ray photoelectron spectroscopy. The characterization studies showed that the coupling of TiO₂ with fluoride ions promoted the generation of ≡Ti-F surface species that could be responsible for the decrease in the recombination frequency of charge carriers and the increased photoactivity. In addition, it was found that the coupling of NiO/F-TiO₂ semiconductors improved the photocatalytic properties of the fluorinated support, obtaining higher percentages of degradation and mineralization of the phenolic contaminant. These results are possibly a consequence of factors such as the formation of larger crystallites, lower band gap energies, and the generation of p-n type interfacial heterojunctions that potentiate the proper separation of electron-hole pairs. An effect of NiO content on photoactivity was observed, being a percentage of 1.0% wt the optimum in this photocatalytic treatment.

Photocatalytic activity of visible-light-driven L-Proline-TiO2/BiOBr nanostructured materials for dyes degradation: The role of generated reactive species

L-Proline (2%)-TiO₂/BiOBr (30%) nanocomposite was synthesized to obtain high photocatalytic performance in the visible light region and infrared radiation(IR) for methylene blue (MB) and congo red (CR) removal from the contaminated wastewater. L-Proline (2%)-TiO₂/BiOBr (30%) photocatalyst with strong absorption near IR wavelength and high charge separation ability was fabricated for the first time. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field-emission scanning electron microscope (FESEM)/Energy Dispersive X-ray (EDX), UV-Vis diffuse reflectance spectrum (DRS), photoluminescence (PL) and Brunauer-Emmett-Teller (BET) characterization techniques show that the visible driven nanocomposite was successfully synthesized. According to the UV-DRS analysis, the estimated band gaps for the L-proline (2%)-TiO₂ and L-Proline (2%)-TiO₂/BiOBr (30%) nanostructures were respectively 2.3 eV and 2.1 eV.The nanoparticles exhibited enhanced photocatalytic activity (93-100%) and high mineralization efficiency (71-89% TOC removal) for both the dyes. The best photocatalytic activity was achieved by adding 2 wt% of L-Proline and 30 wt% of BiOBr into TiO₂ sol. Response surface methodology (RSM) was employed to find significant parameters and their optimum values for maximum degradation, which show pH, dye concentration, irradiation time, and catalyst dosage for both the dyes are significant. The best photocatalytic degradation efficiency was achieved at the optimum conditions of pH = 7.7, catalyst dosage = 0.71 g/L, irradiation time = 142 and dye concentration = 11 mg/L for MB. Scavenger study showed that •OH radicals are responsible for the degradation process.

Properties of CuFeS2/TiO2 Nanocomposite Prepared by Mechanochemical Synthesis

CuFeS₂/TiO₂ nanocomposite has been prepared by a simple, low-cost mechanochemical route to assess its visible-light-driven photocatalytic efficiency in Methyl Orange azo dye decolorization. The structural and microstructural characterization was studied using X-ray diffraction and high-resolution transmission electron microscopy. The presence of both components in the composite and a partial anatase-to-rutile phase transformation was proven by X-ray diffraction. Both components exhibit crystallite size below 10 nm. The crystallite size of both phases in the range of 10-20 nm was found and confirmed by TEM. Surface and morphological properties were characterized by scanning electron microscopy and nitrogen adsorption measurement. Scanning electron microscopy has shown that the nanoparticles are agglomerated into larger grains. The specific surface area of the nanocomposite was determined to be 21.2 m^2·g^-1. Optical properties using UV-Vis and photoluminescence spectroscopy were also investigated. CuFeS₂/TiO₂ nanocomposite exhibits strong absorption with the determined optical band gap 2.75 eV. Electron paramagnetic resonance analysis has found two types of paramagnetic ions in the nanocomposite. Mössbauer spectra showed the existence of antiferromagnetic and paramagnetic spin structure in the nanocomposite. The CuFeS₂/TiO₂ nanocomposite showed the highest discoloration activity with a MO conversion of ~ 74% after 120 min irradiation. This study has shown the possibility to prepare nanocomposite material with enhanced photocatalytic activity of decoloration of MO in the visible range by an environmentally friendly manner.

A reusable visible driven N and C-N doped TiO2 magnetic nanocomposites for photodegradation of direct red 16 azo dye in water and wastewater

The visible active N-doped TiO₂/ZnFe₂O₄ (urea-TiO₂/ZnFe₂O₄) and CN-codoped TiO₂/ZnFe₂O₄ (L-asparagine-TiO₂/ZnFe₂O₄) nanocomposites were successfully synthesized by the sol-gel-hydrothermal method for direct red 16 (DR16) photodegradation. Their properties of the prepared nanocomposites were analysed using XRD, FT-IR, FE-SEM, EDX, DRS and PL tests. The DRS and PL results confirmed a narrow band-gap energy and low recombination rate of photo-produced electron and hole pairs, respectively. The effect of adding various dopant agents (urea and L-asparagine) with different loadings and magnetic nanoparticle (ZnFe₂O₄) into TiO₂ sol on the photodegradation of DR16 was also evaluated. As a result, the L-asparagine (2 wt. %)-TiO₂/ZnFe₂O₄ is the best photocatalyst compared to the other modified TiO₂ nanocomposites due to its narrow band gap and high quantum efficiency. The catalyst concentration (1-2 g/L), DR16 concentration (25-45 ppm), initial pH (4-10), and irradiation time (30-90 min) as numerical variables were also considered for photocatalytic process analysis and moulding by central composite design (CCD). The increase in the pH and dye concentration reduces the photodegradation efficiency while irradiation time and catalyst concentration effectively improved its photodegradation efficiency. The DR16 was completely removed at 25 ppm of DR16, initial pH of 4 and 1.5 g/L of photocatalyst after 90-min irradiation. The photoactivity test was also repeated four times by reused L-asparagine-TiO₂/ZnFe₂O₄ photocatalyst at optimum conditions. The decrease of dye degradation and loss of photocatalyst were not significant which was approved by the good performance and high recovery capability of the prepared nanocomposite.

Caffeine photocatalytic degradation using composites of NiO/TiO2-F and CuO/TiO2-F under UV irradiation

The interest in the removal of emerging contaminants has increased in the last decade. Photocatalytic degradation using p-n heterojunctions could effectively provide the degradation of these type of substances that are persistent in the environment. In this work, the synthesis, characterization, and photocatalytic evaluation of TiO₂-F as well as CuO/TiO₂-F and NiO/TiO₂-F composite materials were studied in the photo-assisted degradation of caffeine using UV radiation. The fluorination of titanium dioxide induced changes in some physicochemical properties of the materials, which contributed to a decrease in surface area and bandgap energy as well as an increase in crystallite size as compared to pristine TiO₂. ≡Ti-F species were evidenced to be formed, which could favor charge separation processes. A highest segregation of CuO species in comparison with NiO on the surface of TiO₂-F could be formed, which could increase defect sites and decrease the band gap. The formation of a heterojunction between the semiconductors was evidenced, responsible for the observed improvements in photocatalytic properties of the composite materials. The photocatalytic tests evidenced an important degradation of caffeine; however, mineralization was incomplete. The stability of the composite materials and their potential use in the photocatalytic treatment of caffeine was evaluated by reuse tests.

Atomic Layer Deposition of Mixed-Layered Aurivillius Phase on TiO2 Nanotubes: Synthesis, Characterization and Photoelectrocatalytic Properties

For the first time, one-dimensional phase-modulated structures consisting of two different layered Aurivillius phases with alternating five and six perovskite-like layers were obtained by atomic layer deposition (ALD) on the surface of TiO2 nanotubes (Nt). It was shown that the use of vertically oriented TiO2 Nt as the substrate and the ALD technology of a two-layer Bi2O3-FeOx sandwich-structure make it possible to obtain a layered structure due to self-organization during annealing. A detailed study by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the coating is conformal. Raman spectroscopic analysis indicated the structure of the layered Aurivillius phases. Transient photocurrent responses under Ultraviolet-Visible (UV-Vis) light irradiation show that the ALD coating benefits the efficiency of photon excitation of electrons. The results of the photoelectrocatalytic experiments (PEC) with methyl orange degradation as a model demonstrate the significant potential of the synthesized structure as a photocatalyst. Photoluminescent measurement showed a decrease in the probability of recombination of photogenerated electron-hole pairs for ALD-coated TiO2 Nt, which demonstrates the high potential of these structures for use in photocatalytic and photoelectrochemical applications.

Synthesis and characterization of vanadium-doped Mo(O,S)2 oxysulfide for efficient photocatalytic degradation of organic dyes

We developed simple and low cost synthesis methods at low temperature to synthesize V-doped Mo(O,S)₂ for the photocatalytic degradation of dyes.

A novel L-Histidine (C, N) codoped-TiO2-CdS nanocomposite for efficient visible photo-degradation of recalcitrant compounds from wastewater

The aim of current study is to synthesis novel visible driven photocatalysts (L-Histidine (C, N) codoped-TiO₂-CdS) with different loadings of L-Hisitdine (1, 2, and 3 wt.%) and CdS (1:9, 7:1, and 1:5 mass ratios of CdS to TiO₂). Then, their application for photo-degradation of methyl orange (MO) and biologically treated palm oil mill effluent (POME) were studied. The structure, optical properties, and morphology of the prepared nanocomposites were also characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR), photoluminescence spectroscopy (PL), and diffuse reflectance spectra (DRS). DRS results indicated that all the modified samples with different L-Hisitdine and CdS loadings showed a red shift to visible region. The results of photo-degradation experiments showed that L-Hisitdine with a weight fraction of 2% and mass ratio of TiO₂ to CdS of 7:1 were the optimum amount of the modifiers in the photocatalyst network. The PL intensity of the photocatalyst decreased with addition of L-Hisitdine and CdS nanoparticles due to a decrease in e^-/h⁺ recombination. The effects of organic pollutant concentration, initial pH, catalyst concentration, and irradiation time on the photo-degradation process of MO and POME were studied using full faced centered central composite design (CCFD) under response surface methodology (RSM). The obtained results showed that MO was completely removed at initial concentration of 10 mg/L, acidic pH, and catalyst loading of 1.5 g/L after 120 min. The complete degradation of biologically treated POME was achieved at original pH, 300 mg/L of chemical oxygen demand (COD) concentration, catalyst loading of 2 g/L, and irradiation time of 2 h.

N/Ti3+-codoped triphasic TiO2/g-C3N4 heterojunctions as visible-light photocatalysts for the degradation of organic contaminants

N/Ti³⁺-codoped triphasic TiO₂/g-C₃N₄ heterojunctions were successfully prepared by a one-step in situ hydrothermal method, and they demonstrated considerably enhanced photocatalytic performance.

Polymer Capsules for Enzymatic Catalysis in Confined Environments

Catalysis is at the base of a series of biological and technological application processes. In recent years, the tendency has developed to carry out catalyzed reactions within confined structures, thus forming systems called micro or nanoreactors. Compartmentalized structures are cavities delimited by a wall where specific functions are introduced with a defined concentration and in the desired sites. These containers are generally referred to as nano or microcapsules, assuming the function of reactors in the presence of chemical reactions. Among the various types of existing structures, one of the most interesting is represented by systems made with polymers. This review aims to highlight some of the current advances in the use of functionalized structures that are useful for catalysis reactions, paying particular attention to polymer capsules and enzymes. The built-up methods used for the production of polymer capsules, as well as the aspects that influence membrane permeability and reactivity to environmental conditions, are discussed. Recent advances on biocatalysis confined in polymeric capsules are illustrated, and the strengths and weaknesses of the principal nanoreactors are considered.

C–N–S tridoping into TiO2matrix for photocatalytic applications: observations, speculations and contradictions in the codoping process

C–N–S-tridoped TiO₂: behind and beyond the codoping process.

Thiourea-Modified TiO2 Nanorods with Enhanced Photocatalytic Activity

Semiconductor TiO₂ photocatalysis has attracted much attention due to its potential application in solving the problems of environmental pollution. In this paper, thiourea (CH₄N₂S) modified anatase TiO₂ nanorods were fabricated by calcination of the mixture of TiO₂ nanorods and thiourea at 600 °C for 2 h. It was found that only N element was doped into the lattice of TiO₂ nanorods. With increasing the weight ratio of thiourea to TiO₂ (R) from 0 to 8, the light-harvesting ability of the photocatalyst steady increases. Both the crystallization and photocatalytic activity of TiO₂ nanorods increase first and then decrease with increase in R value, and R2 sample showed the highest crystallization and photocatalytic activity in degradation of Brilliant Red X3B (X3B) and Rhodamine B (RhB) dyes under visible light irradiation (λ > 420 nm). The increased visible-light photocatalytic activity of the prepared N-doped TiO₂ nanorods is due to the synergistic effects of the enhanced crystallization, improved light-harvesting ability and reduced recombination rate of photo-generated electron-hole pairs. Note that the enhanced visible photocatalytic activity of N-doped nanorods is not based on the scarification of their UV photocatalytic activity.

Novel β-In2.77S4 nanosheet-assembled hierarchical microspheres: synthesis and high performance for photocatalytic reduction of Cr(vi)

A novel nanosheet-assembled hierarchical sulfur deficient β-In_2.77S₄ microsphere photocatalyst was prepared, and the β-In_2.77S₄ microsphere shown high visible light photocatalytic activity in the reduction of aqueous Cr(vi).

L-cysteine-induced fabrication of spherical titania nanoparticles within poly(ether-imide) matrix

In the presented study, a new L-cysteine-containing diamine is synthesized and fully characterized and its application for the in situ sol-gel fabrication of poly(ether-imide)/titania nano hybrid materials is investigated. The electron microscopic photographs (TEM, FE-SEM and AFM) of the resulted materials confirm the production of spherical nanoparticles with well dispersion and narrow particle size distribution which is a usual challenge in the sol-gel methods. In addition to the positive effects on the particles morphology, the existence of amino acid containing pendant groups in the structure of polymer chains led to the comprehensive interaction with titania phase. As a result, the improvement in the flexibility of polymer backbone (as one of the most serious difficulties in polyimides processing) is obtained while its thermal stability dose is not sacrificed (confirmed by TGA and DSC techniques).

Effect of TiO2 calcination temperature on the photocatalytic oxidation of gaseous NH3

Carbon-modified titanium dioxide (TiO2) was prepared by a sol-gel method using tetrabutyl titanate as precursor, with calcination at various temperatures, and tested for the photocatalytic oxidation (PCO) of gaseous NH3 under visible and UV light. The test results showed that no samples had visible light activity, while the TiO2 calcined at 400°C had the best UV light activity among the series of catalysts, and was even much better than the commercial catalyst P25. The catalysts were then characterized by X-ray diffractometry, Brunauer-Emmett-Teller adsorption analysis, Raman spectroscopy, thermogravimetry/differential scanning calorimetry coupled with mass spectrometry, ultraviolet-visible diffuse reflectance spectra, photoluminescence spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy. It was shown that the carbon species residuals on the catalyst surfaces induced the visible light adsorption of the samples calcined in the low temperature range (< 300°C). However, the surface acid sites played a determining role in the PCO of NH3 under visible and UV light over the series of catalysts. Although the samples calcined at low temperatures had very high SSA, good crystallinity, strong visible light absorption and also low PL emission intensity, they showed very low PCO activity due to their very low number of acid sites for NH3 adsorption and activation. The TiO2 sample calcined at 400°C contained the highest number of acid sites among the series of catalysts, therefore showing the highest performance for the PCO of NH3 under UV light.

Review on modified N–TiO2 for green energy applications under UV/visible light: selected results and reaction mechanisms

Modifications of the activity, band structure, morphology, optical and electronic properties of N–TiO₂ for energy and environmental applications.

Ti powder-assisted synthesis of Ti3+ self-doped TiO2 nanosheets with enhanced visible-light photoactivity

Visible-light responsive Ti³⁺ self-doped TiO₂ nanosheets with exposed high-energy (001) facets were fabricated using Ti powder as a reductant.

Celastrol-modified TiO2 nanoparticles: effects of celastrol on the particle size and visible-light photocatalytic activity

Celastrol-modified TiO₂ nanoparticles were synthesized by a mild hydrothermal method and the modification of CSL exhibited higher visible-light photocatalytic activity.

Effects of crystalline phase and morphology on the visible light photocatalytic H2-production activity of CdS nanocrystals

Optimized multi-armed CdS nanorods with a high percentage of wurtzite, prepared by a simple solvothermal route, exhibited high visible-light photocatalytic H₂-production performance.