Photocatalytic Characteristics Research Articles

Surface, structural, energy band-gap, and photocatalytic features of an emulsion-derived B-doped TiO2 nano-powder

Different amounts of boron-doped TiO2 (BDT) (B=0–10wt.%) nano-powders were prepared by following an emulsion-based sol-gel (EBSG) route and were calcined at 550°C for 6h. These calcined nano-powders were then thoroughly characterized by means of various techniques including XRD, XPS, SEM, FT-IR, FT-Raman, DRS, BET surface area, zeta-potential, and photocatalytic degradation of methylene blue (MB) in order to establish the effects of B-doping on structural, surface, band-gap energy, and photocatalytic characteristics of TiO2 nano-powder formed in the EBSG route. These characterization results revealed that after calcination, the pure TiO2 nano-powder formed in the EBSG route was in the form of a mixture of anatase and rutile phases in 70:30 ratio, whereas, the 0.2wt.% B-doped TiO2 nano-powder formed in the same route was in the form of a single anatase phase. These BDT nano-powders were also found to possess negative zeta-potentials (ζ) (<−55mV), high specific surface areas (up to >65m2/g), and low band-gap energies (<3.161eV). The photocatalytic results revealed that BDT nano-powders adsorbed considerable amounts MB (up to 50%) from aqueous solutions of 0.01mM, 0.02mM and 0.03mM MB during 30min stirring in the dark, whereas, the commercial Degussa P-25 TiO2 nano-powder did not adsorb any MB. Owing to adsorption of MB on the surface of photocatalyst, the quantum efficiency values determined did not match with those of total photocatalytic MB concentration reduction. Among various photocatalysts investigated in this study, the highest activity was noted over pure TiO2 nano-powder formed in the EBSG route.

Effect of Eu Doping on the Physical, Photoluminescence, and Photocatalytic Characteristics of ZnO Thin Films Grown by Sol–Gel Method

Eu doping concentration driven effect on the morphological, electrical, and optical properties of ZnO films prepared by sol gel method have been studied systematically. The properties of the films were studied using various experimental tools such as XRD, AFM, XPS, photoconductivity, UV–vis spectroscopy, photoluminescence (PL), and photocatalytic activity. Eu incorporation into the ZnO lattice was confirmed by XPS analysis. A decrease in crystallite size with increasing Eu concentration was observed. PL spectra showed that Eu‐ related light emission intensity reached a maximum at 6 wt.%. Photoconductivity measurements showed maximum photosensitivity for 4 wt.% Eu doped film. The photocatalytic activity of Eu‐ doped films was evaluated for methylene blue degradation and is found to be maximum for 6 wt.% Eu doped film.

Photocatalytic, hydrophobic and antimicrobial characteristics of ZnO nano needle embedded cement composites

In this work, ZnO nanoneedles were synthesized employing a co-precipitation method. Further, white cement composites were prepared with ZnO filler of 5%, 10% and 15% by weight ratio. With the increasing concentration of ZnO in cement matrix the synergetic effect between ZnO and white cement matrix was observed through FE-SEM and UV–visible. We studied the photocatalytic degradation of pollutant (Rhodamine 6G) using ZnO nano-needles embedded in white cement matrix under ultraviolet irradiation (UV) along with enhanced hydrophobic nature and the antimicrobial property of the cement. The pseudo-first order kinetics was found in a photocatalytic process, and degradation rate constant was enhanced up to 0.147 min−1 for ZnO modified cement which was significantly higher than the pure cement (0.037 min−1). Antimicrobial studies were performed using bacterial strains Escherichia.coli (JM109, Promega Gram negative), Bacillus subtilis (MTCC121, Gram-positive) and fungal strain Aspergillus niger (MTCC281) for all the composites. A significant improvement in bacterial and fungal degradation was observed in ZnO modified cement than control and pure cement in a dose-dependent manner.

Structural, photoluminescence, electrical, anti cancer and visible light driven photocatalytic characteristics of Co doped WO3 nanoplates

In this study, soft chemical route has been adopted for the synthesis of Co doped WO3 nanoplates. The prepared samples are crystallized into monoclinic phase of WO3 and composed of two dimensional (2-D) nanoplates. The substitution of Co2+ ions on the sites of W6+ ions has been confirmed through X-ray photoelectron spectroscopy (XPS) analysis. The presence of functional groups and chemical bonding has been verified through FTIR and Raman spectra. Narrowing of the optical gap with Co doping has been observed which is linked with formation defects levels in the band of WO3. The Co doping has been found to be very effective in enhancing the visible light driven photodegradation activity of WO3 nanoplates up to 90% which is attributed to trapping photo-generated electrons by defects. Furthermore, Co doped WO3 nanoplates have also shown good anticancer activities against human breast (MSF-7) and lever (Hep-2) cancer cells.

Porous-C3N4 with High Ability for Selective Adsorption and Photodegradation of Dyes Under Visible-Light

Porous-C3N4 with high photocatalytic activity of anionic dyes was successfully synthesized by a SiO2-template method. Its photocatalytic selectivity could easily be switched to cationic dye via a simple post-treatment in NaOH solution. Through careful investigation of influencing parameters (the photocatalytic performances, the structure and surface characteristics of the catalysts), the selective degradation of various dyes is closely related to the adsorption selectivity of the porous g-C3N4 catalysts, which originated from the different surface charge. This study provides a new insight into developing metal-free g-C3N4 photocatalyst with high efficiency and selectivity in environmental purification.

Surfactant-free synthesis of ellipsoidal and spherical shaped TiO2 nanoparticles and their comparative photocatalytic studies

The work presents surfactant-free synthesis of ellipsoidal and spherical TiO2 nanoparticles (NPs) and their photocatalytic activities are compared with commercially available cubic shaped titania. The ellipsoidal TiO2 NPs having average length of ∼21nm and width ∼10nm were synthesized via a facile solvothermal method. The spherical TiO2 NPs were prepared by the solvent evaporation method having average diameter of ∼8nm. We effectively control the shape and size of TiO2 NPs under mild reaction conditions without using any surfactant. XRD patterns show diffraction peak at 25.3° corresponding to (101) crystalline plane, which confirmed the anatase phase of TiO2 NPs. BET surface area of the ellipsoidal and spherical TiO2 NPs are 2.22 and 1.85 times higher than cubic TiO2, respectively. Kubelka–Munk plots demonstrate significant decrease in the band gap of ellipsoidal (3.0eV) and spherical (3.17eV) NPs as compared to cubic shaped TiO2 (3.24eV). The photocatalytic activities of these materials investigated by decolorization/removal of rhodamine-6G (R6G) and methylene blue (MB) under UV–visible light irradiation. In first 15min of photo-degradation experiments, the results indicated 98, 86 and 71% decolorization and 90, 80 and 60% total organic carbon (TOC) removal of R6G by ellipsoidal, spherical, and cubic shaped TiO2 NPs, respectively. Similar findings were obtained for the photo-degradation of MB solution. This confirms the superior photocatalytic characteristics of the ellipsoidal NPs among the reported TiO2 shapes.

Carbon nanodots-based nanocomposites with enhanced photocatalytic performance and photothermal effects

Carbon nanomaterials with variable bandgaps exhibit wide spectral absorption, and photoluminescent nanodots have attracted much interest. In this work, carbon nanodots (CNDs) are grafted onto the surface of TiO2 nanotubes to enhance the photocatalytic properties. The CNDs increase light absorption, trap and shuttle photo-generated electrons, and enhance the pollutant adsorptivity. In addition, the synergistic photothermal effect of the CNDs-based nanocomposite facilitates photocatalysis. The CNDs-based nanocomposites with improved photothermal performance and efficient photocatalytic characteristics have large potential in environment and energy applications.

Synthesis, structure, optical and photocatalytic properties of copper-activated ZnO

The Zn 1– x Cu x O (0 x ≤ 0.1) solid solutions and Zn 1– x Cu x O: CuO composite materials have been synthesized by a precursor technology using Zn 1– x Cu x (HCOO) 2 ·2H 2 O (0 x ≤ 0.2) mixed formates as precursors, and their structural, optical and photocatalytic characteristics have been ascertained.

Preparation of coal-based C-Dots/TiO2 and its visible-light photocatalytic characteristics for degradation of pulping black liquor

Abstract Coal-based carbon-dots (C-Dots) with a graphene-like structure is prepared from the coal mined of Xinjiang Wucaiwan by an acid/ultrasonic mixed oxidation technique. Subsequently, the C-Dots is combined with the in-situ synthesized TiO 2 particles, yielding C-Dots/TiO 2 nanoparticles. These were characterized by TEM, XRD, TG, Raman, BET, XPS, EDS, UV–vis DRS and PL, respectively. It was found that the C-Dots/TiO 2 are subsphaeroidal particles formed by the deposition of C-Dots on the surface of TiO 2 . Those particles are linked to various functional groups such as C C, C OH/C O C, C O, Ti O, and are 30–50 nm in diameter and evenly distributed without agglomeration. After combination with C-Dots, the band gap of C-Dots/TiO 2 decreases from 3.2 eV in the case of pure TiO 2 to 2.9 eV, the PL intensity of C-Dots/TiO 2 centered at 400 nm dropped significantly, indicates stronger visible light photocatalytic activity. The photocatalytic activities of the nanocomposites are evaluated by the photocatalytic degradation of cotton pulp cooking black liquor in the presence of visible light irradiation. The composite catalysts exhibited higher photocatalytic activity for the degradation of organic pollutants than pure TiO 2 and coal-based C-dots, which is due to the synergistic effect of C-Dots.

Synthesis, structure, and photocatalytic properties of Zn1–x Cu x O: CuO composites with various morphologies of aggregates

Using mixed copper zinc carboxylates as precursors, Zn1–x Cu x O: CuO composite materials with various morphologies and microstructures of aggregates were synthesized. Their structural, optical, and photocatalytic characteristics were determined.

Enhanced photocatalytic performance of Ag2O/BiOF composite photocatalysts originating from efficient interfacial charge separation

Previous studies have well established that the photocatalytic performance of BiOF is greatly inhibited by its inherent drawbacks, which are the wide band gap and high recombination of photo-generated charge carriers. Therefore, it is necessary to promote the photocatalytic activity of BiOF. In this work, a series of novel Ag2O/BiOF composites were prepared by a facile precipitation method and characterized by X-ray diffractometry (XRD), UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), surface photovoltage (SPV) spectroscopy, and electron spin-resonance (ESR) spectroscopy. The photocatalytic characteristics of Rhodamine B (RhB) discoloration under simulated sunlight and visible-light irradiation were studied. The results revealed that the sample with 1.0% molar ratio of Ag/Bi displayed the best photocatalytic performance towards RhB discoloration and all the studied composites in this work displayed a higher photocatalytic activity than the bare BiOF. Based on the results of “band edge potential” of Ag2O and BiOF, SPV and ESR, charge separation and transportation mechanisms are suggested. Under simulated sunlight illumination, the charge separation and transport mechanism of the photo-induced charge pairs followed a Z-scheme.

Effects of phosphorus-doping on energy band-gap, structural, surface, and photocatalytic characteristics of emulsion-based sol-gel derived TiO2 nano-powder

Different amounts of phosphorus (P)-doped TiO2 (PDT) nano-powders (P=0–10wt.%) were synthesized by following a new emulsion-based sol-gel (EBSG) route and calcined at 400°C–800°C for 6h. These calcined PDT powders were then thoroughly characterized by means of XRD, XPS, SEM, FT-IR, FT-Raman, DRS, BET surface area, zeta-potential, cyclic-voltammetry and photocatalytic evaluation using methylene blue (MB) as a model-pollutant and established the effects of phosphorous doping on structural, surface, band-gap energy, and photocatalytic characteristics of TiO2 nano-powder formed in EBSG route. The characterization results suggest that the EBSG derived TiO2 nano-powder after calcination at 400°C for 6h is in the form of anatase phase when it was doped with <8wt.% P, and it is in the amorphous state when doped with >8wt.% P. Furthermore, these EBSG derived PDT powders own high negative zeta-potentials, high specific surface areas (up to >250m2/g), and suitable band-gap energies (<3.34eV). Surprisingly, these PDT powders exhibit very high MB adsorption (up to 50%) from its aqueous 0.01mM, 0.02mM and 0.03mM solutions during 30min stirring in the dark, whereas, the commercial Degussa P-25 TiO2 nano-powder shows no adsorption. Among various photocatalysts investigated in this study, the 1wt.% P-doped TiO2 nano-powder formed in EBSG route exhibited the highest photocatalytic activity for MB degradation reaction.

Simple route for preparation cobalt tungstate nanoparticles with different amino acids and its photocatalyst application

Nanoparticles sphere-like cobalt tungstate (CoWO4) have been successfully synthesized via the co-precipitation method process by using cobalt (II) nitrate hexahydrate and Na2WO4⋅2H2O. Capping agents are frequently used in colloidal synthesis to inhibit nanoparticle overgrowth and aggregation as well as to control the structural characteristics of the resulted nanoparticles in a precise manner; therefore, valine, glycine, and alanine were applied as capping agents. Besides, the effect of valine, glycine, and alanine on the morphology and size of final products were investigated by SEM analysis. According to the vibrating sample magnetometer, cobalt tungstate nanoparticles indicated a paramagnetic behavior at room temperature. The morphology and particle size of products were investigated by SEM images, XRD patterns, UV–Vis and EDS spectroscopy. The photocatalytic characteristics of as-obtained nanocrystalline cobalt tungstate were also examined by degradation of methyl orange (MeO) dye as water contaminant.

Influence of capping agents additives on morphology of cadmium tungstate nanoparticles and study of their photocatalytic properties

In this investigation, a facile precipitation route has been developed for the preparation of cadmium tungstate (CdWO4) nanoparticles by using cadmium nitrate hexahydrate and sodium tungstate dehydrate as cadmium and vanadate precursor, respectively. The effect of different capping agents such as glycine, valine, and alanine on the morphology and particle size of the products has been investigated. Facile preparation and separation are important features of this route. This work has provided a general, simple, and effective method to control the composition and morphology of cadmium tungstate in aqueous solution, which will be important for inorganic synthesis methodology. The morphology and particle size of products were investigated by scanning electron microscopy images, X-ray diffraction patterns, ultraviolet–visible and electron dispersive X-ray spectroscopy spectroscopy. The photocatalytic characteristics of as-obtained nanocrystalline cadmium tungstate were also examined by degradation of methyl orange dye as water contaminant.

Mechanical, Thermal and Photocatalytic Properties of Hybrid TiO&lt;sub&gt;2&lt;/sub&gt;/PET Fiber Composite

This study investigates the effects of the hybrid TiO2 polymerin PET fiber on the mechanical properties, thermal properties, and self-cleaning properties. The results showed that the tensile strength of the hybrid TiO2/PET composite fibers decreased with the increasing contents of TiO2 in polymer matrix. The contents of TiO2 in the composite fibers had no impact on the thermal properties of the fibers, but the %Crystalline of the composite fibers increased with the contents of TiO2 in the composite fibers. The photocatalytic characteristics of the composite fibers were studied through self-cleaning properties. The presence of contents of hybrid TiO2 in the PET fiber significantly showed the improvement of the self-cleaning properties under UV-A radiation. The hybrid TiO2/PET fibers in the presence of TiO2 10wt% showed the best results of self-cleaning under the 24 hours of UV radiation exposure period.

Chemical synthesis, structural, optical, magnetic characteristics and enhanced visible light active photocatalysis of Ni doped CuS nanoparticles

In this paper, we report systematic investigations on the effects of Ni doping on the structural, optical, magnetic and photocatalytic characteristics of CuS nanoparticles synthesized by simplistic wet chemical co-precipitation route via EDTA molecules as templates. XRD studies confirmed that accurate phase formation of synthesized nanoparticles and chemical composition were obtained by EDX. Magnetic measurements revealed that 3% Ni doped CuS nanoparticles show signs of good ferromagnetism at room temperature and transition of magnetic signs from ferromagnetic to paramagnetic nature by increasing the Ni dopant concentration in CuS host matrix. The photocatalytic degradation efficiency of the prepared pure and Ni doped CuS nanoparticles were evaluated as a function of simulated sunlight irradiation via RhB organic dye pollutant as a test molecule. Particularly, in the presence of 3% Ni doped CuS nanoparticles in pollutant solution 98.46% degradation efficiency was achieved within 60 min of sunlight irradiation; meanwhile bare CuS attained only 83.22%. Further, after five cycles 3% Ni doping CuS nanoparticles exhibit good photocatalytic stability with very negligible catalyst loss. We believe that the investigations in this study provides adaptable pathway for the synthesizing of various diluted magnetic semiconductor nanoparticles and their applications in spintronic devices as well as sunlight-driven photocatalysts intended for wastewater purification.

Photocatalytic Degradation of Humic Acid with Metal-Doped TiO&lt;sub&gt;2&lt;/sub&gt; under Near-Visible Irradiation

The improvement of photocatalytic activity of TiO2 has been explored. TiO2 has been doped with some transition metal elements for new photocatalytic materials. They were prepared using nitrates of Fe, Cu and Zn. Their photocatalytic activities were investigated by conducting a semi-batch experiment. The degradation of aqueous humic acid was performed under near-visible irradiation. For examining the photocatalytic characteristics of the new materials, the dissolved organic carbon and the UV254 absorption of humic acid were analyzed. The new metal-doped photocatalysts showed higher photoactivities than the synthesized pure TiO2. And photodegradation result of humic acid by the new metal-doped material was even better than by the commercial Degussa P-25 TiO2 at wavelengths of 315 nm - 400 nm.

Controlled synthesis of mesoporous codoped titania nanoparticles and their photocatalytic activity

The photocatalytic (PC) activity of anatase titania nanoparticles can be improved through codoping with transition metals and nitrogen. In addition, the PC activity can also be improved by creating monodisperse, mesoporous nanoparticles of titania. The question naturally arose as to whether combining these two characteristics would result in further improvement in the PC activity or not. Herein, we describe the synthesis and photocatalytic characteristics of codoped, monodisperse anatase titania. The transition metals tested in the polydisperse and the monodisperse forms were Mn, Co, Ni, and Cu. In each case, it was found that the monodisperse version had a higher PC activity compared to the corresponding polydisperse version.

Best compromise for photocatalytic activity and hydrophilicity: N-doped TiO2 films under UV light

This study seeks to determine the best compromised parameters for photoluminescence performance and hydrophilicity of nitrogen-doped titanium dioxide coatings deposited on glass substrates using radio frequency reactive magnetron sputtering. Rf power (W), process pressure (mtorr), Ar/O2/N2 flow ratios and substrate temperature (°C) were optimized with reference to the structure and photocatalytic characteristics of TiO2. An L9 (34) orthogonal array, the signal-to-noise ratio and analysis of variance were employed for determination of the compromise deposition settings of nitrogen-doped titanium dioxide thin films, annealed in Ar ambient (10 mtorr) at temperatures of 250, 350 and 450 °C, for a period of 30 min. The results demonstrate that for Ar/O2/N2 flow ratios of 80/20/0, 75/20/5, 70/20/10, and 65/20/15, the respective corresponding methylene blue absorbance is 0.412, 0.406, 0.385, and 0.355, which depicts a greater photocatalytic activity with a larger N2 flow ratio. For the morphological properties, the nitrogen-doped titanium dioxide films with a larger N2 flow ratio show a homogenous structure, smaller grain sizes and more spherical particles with Ra roughness of 1.394–0.362 nm. The effects of annealing temperature, duration of ultraviolet and visible light irradiation were also analyzed. The films annealed at higher temperature (450 °C) under ultraviolet and visible light irradiation of 240 min exhibit coexistence of the anatase (101) and rutile (004) structures, which appears to imbue the nitrogen-doped titanium dioxide film with greater photocatalytic activity and photo-induced hydrophilicity. Novelty Statement 1. This study seeks to determine the best compromised parameters for photoluminescence performance and hydrophilicity. 2. The ANOVA results show that the rf power has the major effect on methylene blue (MB) absorbance and the process pressure ranks the second. 3. This study determines the effect of Ar/O2/N2 flow ratios and post annealing treatment on the morphology, hydrophilicity and photocatalytic activity of N-TiO2 thin films. The results demonstrate that a greater photocatalytic activity for N-TiO2 thin films can be achieved by using a greater N2 flow ratio. 4. The film that is annealed at 450 °C exhibits the coexistence of the anatase (101) and rutile (004) structures, which appears to imbue the N-doped TiO2 film with greater photocatalytic activity and photoinduced hydrophilicity under UV and visible light illumination.

Synthesis and photocatalytic performance of yttrium-doped CeO2 with a hollow sphere structure

We report a facile and novel approach to prepare yttrium-doped CeO2 with a hollow sphere hierarchical structure by a simple hydrothermal method with cerium nitrate hexahydrate and yttrium nitrate hexahydrate as original materials and polystyrene microsphere as a soft-template. Through systematic experiments, the effects of experimental parameters such as doping and morphology on photocatalytic characteristics of the ceria were examined in detail. The morphology and element distribution of the as-prepared samples were characterized by field emission scanning electron microscopy and high-resolution transmission electron microscopy. Structure information with Rietveld refined data were obtained by using an X-ray diffractometer. Intrinsic oxygen vacancies and extrinsic oxygen vacancies caused by doping were analyzed from Raman spectra. Analyses of elements and chemical valence analysis were carried out by X-ray photoelectron spectroscopy, and changes in reactive oxygen species were determined by calculation. Based on structural information, element valence states, and the results of photocatalytic decomposition of acetaldehyde, we can draw the conclusion that Y-doped CeO2 with a hollow sphere hierarchical structure has high photocatalytic activity, attributed to more oxygen vacancies and surface active oxygen species. Yttrium doped ceria with hollow sphere structure has a maximum rate constant of 0.0267h−1 and an oxidation quantum efficiency of 0.3610%, which are about 2 times as high as that of pure CeO2 with octahedral structure.