Organic Methylene Blue Research Articles

TiO2 nanorods decorated Si nanowire hierarchical structures for UV light activated photocatalytic application

Water remediation techniques like photolysis have recently piqued the interest of many researchers due to water contamination resulting from heavy industrialization and urbanization. In the current work, as-synthesized TiO2 nanorod decorated vertically aligned silicon nanowire (SiNW) leads to a hierarchical morphological structure formation. The photocatalytic nature of the fabricated SiNW/TiO2 nanoheterojunction is examined by the dye degradation of textile pollutants like methylene blue (MB), rhodamine B (RhB), and eosin B (EB). The catalytic dye degradation investigations revealed that 4 h hydrothermal synthesis of TiO2 on the surface of SiNW (ST4) exhibited excellent catalytic behaviour. In the presence of H2O2 and UV irradiation, the ST4 nanoheterostructure can degrade 98.89% of the model pollutant methylene blue (MB) in 15 min, demonstrating remarkable photocatalytic performance. The direct Z-scheme heterojunction exhibited by the SiNW/TiO2 structure facilitates a more efficient charge transfer mechanism with higher reducing and oxidizing ability leading to enhanced photocatalytic behaviour. The degradation pathway examined by LC-MS studies demonstrated the complete breakdown of the organic MB dye molecules ultimately mineralizing into CO2, H2O, and other inorganic substances. The photocatalyst ST4 exhibited excellent reusability and stability after multiple cycles of dye degradation enabling its use in practical water purification purposes.

Gamma irradiation effect on photocatalytic properties of Cu and Sr ions codoped PbS

Gamma-irradiation effects on photocatalytic action of PbS nanocrystallites codoped with Cu and Sr ions were performed for organic dye degradation. The physical and chemical characterizations of these nanocrystallites were examined employing X-ray diffraction, Raman, and field emission electron microscopic analysis. The optical bandgaps of gamma-irradiated PbS with co-dopants have shifted from 1.95 eV (pristine PbS) to 2.45 eV in the visible spectrum. Under direct sunlight, the photocatalytic action of these compounds against methylene blue (MB) was investigated. Observations indicated that gamma-irradiated Pb(0.98)Cu0.01Sr0.01S nanocrystallite sample exhibits a higher photocatalytic degradation activity of 74.02% in 160 min and stability of 69.4% after three cycles, suggesting that gamma irradiation could potentially influence organic MB degradation. This is due to combined action of high-energy gamma irradiation (at an optimzed dose), which causes sulphur vacancies, and defects created by dopant ions, which alter the crystal structure by inducing strain in the crystal lattice, hence altering the crystallinity of PbS.

Optimization of green biosynthesized visible light active CuO/ZnO nano-photocatalysts for the degradation of organic methylene blue dye

Herein, CuO/ZnO nanocomposites at different ratios were successfully synthesized through a green biosynthesis approach. This was performed by harnessing the fungal-secreted enzymes and proteins during the sol-gel process for nanocomposites seed growth. All fabricated nanoparticles/nanocomposites were characterized using Fourier Transform Infra-Red (FT-IR) Spectroscopy, X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM-EDX) and X-ray Photoelectron Spectroscopy (XPS) analyses. The photocatalytic degradation efficacy of the synthesized nanocomposites was evaluated using a cationic methylene blue (MB) dye as a model of reaction. Results obtained from the FT-IR and EDX analyses revealed that CuO-NPs, ZnO-NPs, CuO/ZnO50/50, CuO/ZnO80/20, and CuO/ZnO20/80 were successfully prepared by harnessing the biomass filtrate of Penicillium corylophilum As-1. Furthermore, XRD and TEM revealed the variation in the particle size of the nanocomposites (10–55 nm) with the ratio of the nanoparticles. Notably, the size of the nanocomposites was proportionally increased with an increasing ratio of ZnO-NPs. XPS analysis affirmed the presence of both Cu and Zn in the nanocomposites with varying binding energies compared with individual nanoparticles. Furthermore, a high photo-degradation efficacy was achieved by increasing the ratio of ZnO-NPs in the nanocomposite formulation, and 97% of organic MB dye was removed after 85 min of irradiation using the CuO/ZnO20/80 nanocomposite.

Synthesis, Characterization and Sun Light-Driven Photocatalytic Activity of Zinc Oxide Nanostructures.

Low-temperature growth of nanostructures with large yield is a basic requirement for fulfilling the demand of large-scale applications of nanomaterials. The synthesis of nanoscale materials has gained considerable attention due to their excellent properties also in photocatalysis. Catalyst and Dopant free, solar active ZnO nanostructures photocatalysts with vacancy richness were synthesized in large quantities (in grams) through the co-precipitation growth process using ZnNi₂·6H₂O as the zinc source at room temperature. This method has advantages such as low temperature with high yield (>8 grams per liter) at atmospheric pressure synthesis. The experimental results confirm that synthesized ZnO samples were crystallized into a wurtzite hexagonal structure. Under direct sunlight energy examined degradation of organic dye methylene blue (MB) for photocatalytic activity using ZnO nanostructures. The photocatalytic performance depends on the different defects as well as the specific surface area. After photocatalytic degradation of MB dye in 60 min under natural sunlight irradiation colorless matrix was observed. The repeatability assessments for reusability of ZnO nanostructures after photocatalytic activity was also studied and reported for degradation of organic MB dye.

Investigation on the Magnetically Separable Zn Substituted CoFe₂O₄ Nanoparticles with Enhanced Photo-Fenton Degradation.

We report the influence of Co1-xZnxFe2O4 nanoferrites for the photodegradation of organic pollutant present in the aqueous solution. A series of Co1-xZnxFe2O4 (x = 0.01, 0.03, 0.05 and 0.10) nanoferrites have been synthesized via a facile and economically viable coprecipitation technique and investigated the effect of zinc dopant in their structural, optical, electrical and magnetic properties. X-ray diffraction and Fourier Transform Infrared spectral studies reveal the spinel phase formation of the as-synthesized nanoferrites. Photoluminescence and UV-visible spectral studies show the bandgap of nanoferrites increase from 2.47-2.67 eV and exhibited a blue shift in the band edge emission with respect to increase in Zn content. Phase transition of the samples from weak ferromagnetic to superparamagnetic nature has been observed by Vibrating Sample Magnetometer at room temperature. Furthermore, the Co1-xZnxFe2O4 was assessed for the degradation of Methylene Blue (MB) dye and the sample with Co1-0.10Zn0.10Fe2O4 showed better photocatalytic degradability of organic MB due to its enhanced adsorption in the visible region and the existence of lower concentration charge-carriers.

Eco-friendly seeded Fe3O4-Ag nanocrystals: a new type of highly efficient and low cost catalyst for methylene blue reduction.

Hybrid Fe3O4-Ag nanocrystals, a new type of highly efficient and reusable catalyst for methylene blue (MB) reduction, are fabricated by a novel seed deposition process. X-ray diffraction and Mössbauer spectroscopy results show that the developed iron oxides are in a pure magnetite Fe3O4 phase. Upon manipulating the amount of Ag seeds capsuled on the modified surfaces of Fe3O4 nanocrystals, the catalytic capacities on the reduction of MB can be precisely adjusted with a tunable fabrication cost control. The linear correlation of the reduced MB concentration versus reaction time catalyzed by our developed hybrid Fe3O4-Ag nanocrystals is coherent with pseudo first order kinetics. Importantly, with remarkable recyclability features, the hybrid Fe3O4-Ag nanocrystals can be easily separated by applying an external magnetic field. The tailored catalytic performances of the hybrid Fe3O4-Ag nanocrystals during MB reduction are attributed to the optimized dynamic electron transfer process, which dominates the electrochemical mechanism wherein the nucleophilic BH4− ions donate electrons to electrophilic organic MB through Ag seeds in a regulated amount. Such developed hybrid Fe3O4-Ag nanocrystals pave the way towards the mass production of highly efficient and low cost catalysts for methylene blue reduction.