Visible Light Photocatalytic Dye Degradation Research Articles

Chemical spray deposited SnO2:MoO3 composite thin films for visible light photocatalytic dye degradation application

Chemical spray deposited SnO2:MoO3 composite thin films for visible light photocatalytic dye degradation application

Visible light photocatalytic dye degradation, antimicrobial activities of green synthesized Ag/TiO2 nanoparticles

The co-precipitation approach was used in this study to synthesize Ag/TiO2 nanoparticles (NPs) using an extract of the flowers from C. pulcherrima. As a reducing agent and a stabilizer during the synthesis process, the flower extract performed a dual function. The surface plasmon resonance in the diffuse reflectance spectroscopy spectrum provided assurance that the Ag+, and Ti4+ ions were significantly reduced. The bandgap study of the Ag/TiO2 NPs revealed that they are suitable for optical and catalytic applications. The NPs were analyzed using X-ray diffraction (XRD) to assess their size and crystal structure. Through scanning and transmission electron microscopy (SEM and TEM), the shape and size changes of the Ag/TiO2 NPs were studied. Energy-dispersive X-ray spectroscopy (EDX) analysis was employed to investigate the elements' chemical composition in the produced NPs. A Fourier transform infrared spectroscopy (FTIR) study was carried out to identify functional groups that might be present in the plant extract and might be involved in the chemical reduction, stabilization, and bonding processes. The photocatalytic disintegration of the hazardous organic dye pollutant methylene blue was studied for 40 min while being exposed to visible light. The flower extract was used to create Ag/TiO2 NPs efficiency degradation rate of 94 %. Additionally, then NPs antimicrobial capacity was assessed, and it was discovered that they were most effective against the infections P. aeruginosa and E. coli.

Novel MgO and Ag/MgO nanoparticles green-synthesis for antibacterial and photocatalytic applications: A kinetics-mechanism & recyclability

The present study identifies the novel nano production of MgO nanoparticles as well as the Ag decoration of MgO nanoparticles using Morinda tinctoria plant extract. Green compounds are used to reduce zero valent atoms and to decorate metal oxide surfaces. X-ray Diffractometer analysis (XRD) was used to examine the cubic structure of MgO (28 nm) and Ag/MgO (21 nm) nanoparticles. Fourier transform infrared spectroscopy (FTIR) analysis was used to determine the reactive functional groups, metal–oxygen bonding, and OH molecules. Ultra-Violet Diffuse Reflectance Spectroscopy (UV-DRS) analysis revealed the optical entity and their orbital electron shift. Using the Kubelka-Munk relation, the optical defect of MgO (4.68 eV) and Ag/MgO (3.18 eV) nanoparticles was calculated. Scanning Electron Microscope (SEM) indicated surface decorations and their pure MgO nanoparticles rod-like shape, and Energy-Dispersive X-Ray Spectroscopy (EDX) identified their elements. TEM analysis confirmed the poly-dispersive nature of the Ag decorations on the MgO surface. X-Ray Photoelectron Spectroscopy (XPS) was used to determine the valency of metal (Ag-3d) and metal oxide (Mg-2 s&O-1 s). MgO and Ag/MgO were used in visible light photocatalytic dye degradation of Rh-B dye. The biological properties were tested against S.aureus and E.coli. The plasmonic decoration on the MgO surface accelerated photodegradation and increased biological susceptibility. The innovative characteristics of this work squeeze the green synthesis of Ag/MgO nanoparticles, their improved photocatalytic and antibacterial performance, and their potential applications in water remediation and biomedicine.

Synergistic interaction of three-dimensional ZnCdS@MoS2 heterostructures for high-efficiency visible-light photocatalytic degradation of dyes

High-performance photocatalysts should urgently be developed to efficiently solve serious environmental problems. Herein, we successfully synthesized a novel, visible-light activated, three-dimensional ZnCdS@MoS2 photocatalyst using a simple, two-step hydrothermal process. Based on reaction time-dependence, the growth mechanism of “oriented attachment” of the ZnCdS@MoS2 heterostructure is described in detail. The photodegradation of methylene blue (MB) indicated that the prepared sample has an outstanding photocatalytic activity owing to the accelerated photogenerated electron production rate, inhibited electron–hole pair recombination, improved visible light–utilization rate, and increased specific surface area. According to our experimental results, the degradation rate of MB using the ZnCdS@MoS2 nanocomposite was as high as 99.3% after 100 ​min of visible-light irradiation. The photocatalyst remained stable without any obvious decrease in activity even after three cycles of use. This study provides a strong support for the design of high-performance photocatalysts and their application in optoelectronic devices.

Investigation on structural, particle size of nano particles for visible light photocatalytic dye degradation

The sol–gel approach is used to prepare the undoped TiO2 and Zr/P doped nano photo catalysis. The XRD pattern reveals that the lattice parameters of all the samples are almost comparable, indicating that no structural changes have occurred. E-Dax spectrums of photo catalysis confirm that the Weight% and Atomic% of every element in each nanoparticle exactly match the desired Weight% of every element in the preparation of nanoparticles. TEM exhibits the average particle size of the 0.25Zr1PT is 8.023 nm and this size of various particles in 0.25Zr1PT is in accordance with the Gaussian distribution described. The absorbance of undoped TiO2 with Rose Bengal dye is very high hence most of the light is absorbed in undoed TiO2. The absorbance of 0.25Zr1PT photo catalysis falls more due to smaller particle size among the various weight percentages of Zr and P doped in TiO2 nanoparticles. Among all photo catalysis, 0.25Zr1PT has a higher percentage of photo degradation of Rose Bengal. The percentage of degradation is higher at 50 mgL−1 than at other catalyst dosages. Kinetic studies that suit pseudo first order reactions provided the rate constant for all doped TiO2 nanoparticles.

Visible-light photocatalytic degradation of dyes by TiO[formula omitted]–Au inverse opal films synthesized by Atomic Layer Deposition

TiO2–Au composite planar films and inverse opals were synthesized by Atomic Layer Deposition (ALD) using Direct Liquid Injection for TiO2 deposition and for the injection of preformed Au nanoparticles (NPs). A few nanometers thick layer of TiO2 was deposited after the Au NPs. Thermal annealing at 380 °C allowed to remove the polystyrene beads template and to form anatase TiO2.The obtained inverse opals have a layered structure of hollow TiO2 spheres interconnected by channels formed at the template beads contacts. Au NPs are homogeneously distributed on the surface. Their localized surface plasmon resonance (SPR) at 587 nm confirm that they are embedded in TiO2. These photocatalysts were tested for the degradation of methylene blue solutions under visible-light illumination. A significant photocatalytic effect is reported with a 95% degradation after 7 h of exposure only for the composite inverse opal. This results from the transfer of hot electrons from the NPs excited at their SPR to the conduction band of TiO2. They generate reactive oxygen species at the surface of TiO2 which are involved in the initial stage of MB degradation. These results highlight the potential of ALD for the fabrication of complex composite structures for application in photocatalysis.

La, Zr co-doped Ag3PO4 for enhanced visible-light photocatalytic degradation of dyes and Cr(VI) photoreduction

Visible light-driven photocatalysts have attracted considerable attention as these photocatalysts can effectively utilize visible light and are cost-effective. This study reports the synthesis of silver phosphate (Ag3PO4) and 1, 3, and 5% La, Zr co-doped Ag3PO4 via precipitation method. The synthesized materials were characterized using powder X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), UV-Visible diffuse reflectance spectra (DRS), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). No impurities were observed in all the synthesized materials as shown by the XRD analysis. FTIR measurements of the synthesized materials displayed the presence of several functional groups in the synthesized materials. The band gap energy of Ag3PO4 decreases as more La and Zr were incorporated into the Ag3PO4 lattice. The SEM images of Ag3PO4 displayed tetrapod-shaped particles whereas La, Zr co-doped Ag3PO4 showed irregular particles. The photocatalytic activities of the synthesized materials were determined through photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes as well as photoreduction of Cr(VI). Results showed that 1% La, Zr co-doped Ag3PO4 exhibited superior photocatalytic properties in both photocatalytic processes when compared to Ag3PO4.

Two-Step Visible Light Photocatalytic Dye Degradation Phenomena in Ag2O-Impregnated ZnO Nanorods via Growth of Metallic Ag and Formation of ZnO/Ag0/Ag2O Heterojunction Structures.

Visible light photocatalytic activity follows the single-slope pseudo-first-order reaction kinetics in pristine ZnO nanorods, while for pure Ag2O, a two-slope paradigm is pursued with a higher slope at a later period. For the Ag2O-impregnated ZnO heterostructured nanorod photocatalyst, the two-step photocatalysis phenomena proceed with dye degradation rate constants emerging higher than those of individual ZnO and Ag2O, at both time zones. Improved performance of ZnO/Ag2O heterostructures arises initially from the reduced e-/h+ recombination rate by the synergistic effect between ZnO and Ag2O. At a later phase, metallic Ag is produced, which traps the valence electrons of Ag2O nanoparticles and advances the e-/h+ separation across the ZnO/Ag0/Ag2O heterojunction structures, rendering them promptly accessible for dye degradation. At an increased Ag2O loading, the photodegradation rate constants boost up in both time zones, and the corresponding crossover time (tC) between the two phases steadily diminishes, leading toward a unique photocatalytic phenomenon that prevails with a superior rate constant. The optimized ZAO25 heterostructure photocatalyst demonstrates ∼96.24% photodegradation of methylene blue (MB) dye within 30 min of visible light exposure, and its degradation rate constant is ∼0.24848 min-1, which is ∼26.75 times superior than that of pristine ZnO samples. The metal-induced biphasic photocatalysis phenomena have never been reported earlier.

Charge separation effect in the nanocomposites of Co3O4-QDs: visible light photocatalytic dye degradation in aqueous solutions.

Photo-treatment of water is a promising environmentally friendly process that provides clean water and makes wastewater reusable in industry. Thus, efforts toward finding highly efficient photocatalysts have gained a huge attention to remove the organic contaminants in water. Quantum dots (QDs) are extensively utilized for photocatalytic remediation regarding their prominent optical, electrical, and chemical properties. Herein, we report the highly efficient and environmentally friendly synthesis of Co3O4-QDs-based graphene quantum dots (GQDs) and infinite coordination polymer comprising Zn nodes (Zn-ICP) nanocomposites as active and robust photocatalysts for photo-assisted water treatment. The pristine Co3O4-QDs, GQDs, and Zn-ICP showed lower activity under visible light. However, after functionalization of GQDs and Zn-ICP with Co3O4-QDs, the activity increased, and more photocatalytic efficiency was achieved. For instance, Zn-ICP, GQDs, Co3O4-QDs, Co3O4-QDs/Zn-ICP, and Co3O4-QDs/GQD degraded 21, 19, 52, 73, and 83% of rhodamine B (RhB) and 34, 46, 50, 73, and 76% of methylene blue (MB) after 60min. The high photocatalytic efficiency was ascribed to the conjugation of Co3O4-QDs with GQDs and Zn-ICP which causes efficient absorption of visible light. The existence of Co3O4-QDs was found to be essential not only for effective charge separation but also widening the region of light absorption followed by increase in photocatalytic performances. Charge separation in photocatalytic reactions, energy levels of nanocomposites, and mechanism of the photocatalytic process were investigated by photoluminescence spectra (PL), Mott-Schottky, electrochemical impedance (EIS), and diffuse reflectance UV-Vis spectroscopy (DRS).

N-SrTiO3 nanoparticle/BiOBr nanosheet as 0D/2D heterojunctions for enhanced visible light photocatalytic dye degradation

A novel 0D/2D heterojunction N-SrTiO3/BiOBr (NSTO/BiOBr) was constructed by uniform dispersing of N-SrTiO3 nanoparticles on BiOBr nanosheets through a facial one-step precipitation method. All the synthesized NSTO/BiOBr composite photocatalysts with different N-SrTiO3 content were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflection spectroscopy (UV–Vis DRS), photoluminescence (PL) spectra, photocurrent response, electrochemical impedance spectra (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption. The visible light rhodamine B degradation results revealed that the formation of 0D/2D heterojunction NSTO/BiOBr results in improved photodegradation activity as compared with N-SrTiO3 and BiOBr, and NSTO/BiOBr with the 18% weight percentage of N-SrTiO3 is most effective among all the NSTO/BiOBr nanocomposites. The activity comparison of 18% NSTO/BiOBr with that of pure NSTO and BiOBr also conforms to their corresponding photoelectric response and electron transfer impedance measurements. Finally, RhB degradation mechanism over NSTO/BiOBr composite catalyst were proposed.

Insight into the kinetics and mechanism of visible-light photocatalytic degradation of dyes onto the P doped mesoporous graphitic carbon nitride

In this study, Phosphorus-doped mesoporous graphitic carbon nitride (P-mpg-C3N4) was successfully prepared by a facile simple thermal method. Microstructure and chemical properties of catalyst were studied by a series of characterization methods, the results showed that the P atoms were successfully doped on the structure of graphitic carbon nitride and uniformly distributed on the whole mesoporous nanostructure. And specific surface area of P-mpg-C3N4 can reach 198.3 m2/g, which is almost 10.7 times more than that of g-C3N4 (18.6 m2/g), pore diameter of P-mpg-C3N4 is mainly distributed in 2–20 nm and the average pore size is 11.3 nm. Photocatalytic degradation performance of the catalyst for brilliant ponceau 5R (BP-5R) in solution were studied under dark and visible light irradiation. The photocatalytic activity of P-mpg-C3N4 is about 31.1 times higher compared with that of g-C3N4, and about 3.9 times and 2.4 times than that of mpg-C3N4 and P-g-C3N4, respectively. Mechanism of its enhanced photocatalytic performance was mainly attributed to the synergistic effect of P-doping and fragmented mesoporous structure, on the one hand, which can extend visible light absorption range. On the other hand, it's can also promote the separation of photo-generated electron-hole pairs and accelerate the transfer of photo-generated electrons.

Core-shell structured TiO2 as highly efficient visible light photocatalyst for dye degradation

Abstract TiO2 is one of the most important photocatalysts, but it is inefficient for visible light photocatalysis due to its large band gap. Herein, the unique core-shell structured TiO2 photocatalyst was synthesized by a one-step hydrogen treatment at temperature of 400–600 °C. The novel catalyst exhibited excellent performance for visible light photocatalytic dye degradation at room temperature. Even under weak visible light (40 mW cm−2) illumination, its degradation efficiency for methylene blue dye was 400% higher than that of pristine TiO2. Such a large enhancement can be attributed to the stable Ti3+ centers inside the core for visible light photocatalytic activity and the disordered shell for dye adsorption.

Doping effect on monolayer MoS2 for visible light dye degradation - A DFT study

The electronic and optical properties of, Nitrogen (N), Cobalt (Co), and Co-N co-doped monolayers of MoS2 has been studied by using density functional theory (DFT) for visible light photocatalytic activity. From the calculations, it has been observed that the band gap of monolayer MoS2 has been reduced while doping. However, the band gaps of pristine and N doped MoS2 monolayers only falls in the visible region while for Co and Co-N co-doped systems, the band gap shifted to IR region. The optical calculation also confirms the results. The formation energy values of the doped system reaveal that MoS2 monolayer drops its stability while doping. To evaluate the photocatalytic response, band edge potentials of pristine and N-MoS2 are calculated, and the observed results show that compared to N-doped MoS2 monolayer, pure MoS2 is highly suitable for visible light photocatalytic dye degradation.

Facile synthesis of magnetically separable CoFe2O4/Ag2O/Ag2CO3 nanoheterostructures with high photocatalytic performance under visible light and enhanced stability against photodegradation

We have developed magnetically separable and reasonably stable visible light active photocatalysts containing CoFe2O4 and mixture of Ag2O/Ag2CO3 nanoheterostructures. Obtained ternary nanoheterostructures outperform previously reported magnetically separable visible light photocatalysts, showing one of the highest visible light photocatalytic dye degradation activities in water by a magnetically separable photocatalyst. Photocatalytically active part is Ag2O/Ag2CO3 whereas the CoFe2O4 mainly has stabilizing and magnetic separation functions. The Ag2CO3 phase junction on Ag2O nanoparticle surface were obtained by straightforward phase transformation from silver oxide to silver carbonate in air due to ambient CO2. The phase transformation was followed using X-ray diffraction (XRD), and hard X-ray photoelectron spectroscopy (HAXPES) measurements.

Rapid and efficient visible light photocatalytic dye degradation using AFe2O4 (A = Ba, Ca and Sr) complex oxides

Photocatalytic activity of spinel type complex oxides has been investigated in this study. Alkaline earth ferrites AFe2O4 (A = Ba, Ca, Sr) were synthesized by sol–gel method. Structural characterizations reveal that the synthesized ferrites have orthorhombic crystal structures with different space groups and cell dimensions when they have different alkaline earth metals in their A site. All the synthesized ferrites exhibited their bandgap in the range 2.14–2.19 eV. Their photocatalytic activities were studied using congo red dye under sunlight and xenon lamp radiation. The substitution of Ba, Ca and Sr at A site of these ferrites had varying impact on dye degradation process. Under xenon lamp irradiation, BaFe2O4 exhibited the highest percentage of dye degradation (92% after 75 min). However, CaFe2O4 showed the fastest degradation of the dye (70% within 15 min). In the absence of irradiation, SrFe2O4 showed the highest dye adsorption (44% after 75 min).

Three way electron transfer of a C–N–S tri doped two-phase junction of TiO2nanoparticles for efficient visible light photocatalytic dye degradation

C–N–S tridoped TiO2nanoparticles were synthesized by a sol–gel method using thiourea as a compound source of carbon (C), nitrogen (N) and sulphur (S).