Unveiling the charge transfer behavior within ZSM-5 and carbon nitride composites for enhanced photocatalytic degradation of methylene blue

Highly Active Carbon Material Derived from Carica papaya Fruit Juice: Access to Efficient Photocatalytic Degradation of Methylene Blue in Aqueous Solution under the Illumination of Ultraviolet Light

Herein, we describe a cost-effective, efficient, sustainable, and environmentally friendly pyrolytic method for the synthesis of highly active carbon materials from Carica papaya fruit juice for the photodegradation of various pollutants, such as methylene blue (MB), in aqueous solutions using ultraviolet (UV) light. Various analytical techniques were used to examine the morphology, crystal quality, functional group chemistry, particle size distribution, and optical properties of the materials. For evaluating the performance of the newly prepared carbon material, various photocatalyst parameters were investigated, including initial dye concentration, catalyst dose, pH of dye solution, cyclic stability, and scavenger studies. The obtained findings attest that the optimal degradation efficiency of carbon material for high MB concentrations (2.3 × 10−5 M) is around 98.08%, whereas at low concentrations of MB (1.5 × 10−5 M) it reaches 99.67%. Degradation kinetics indicate that MB degrades in a first-order manner. Importantly, as the pH of the dye solution was adjusted to ~11, the degradation rate increased significantly. The scavenger study indicated that hydroxyl radicals were the predominant species involved in the degradation of MB. In addition, active surface site exposure and charge transfer were strongly associated with efficient MB degradation. On the basis of its performance, this newly developed carbon material may prove to be an excellent alternative and promising photocatalyst for wastewater treatment. Furthermore, the synthetic approach used to produce carbon material from Carica papaya fruit juice may prove useful for the development of a new generation of photoactive materials for environmentally friendly applications, as well as for the production of hydrogen from solar energy.

Synergistic effect of modified pore and heterojunction of MOF-derived α-Fe2O3/ZnO for superior photocatalytic degradation of methylene blue

Mesoporous heterojunction MOF-derived α-Fe₂O₃/ZnO composites were prepared by a simple calcination of α-Fe₂O₃/ZIF-8 as a sacrificial template. The optical properties confirm that coupling of both the modified pore and the n-n heterojunction effectively reduces the possibility of photoinduced charge carrier recombination under irradiation. The mesoporous Fe(25)ZnO with 25% loading of α-Fe₂O₃ exhibited the best performance in MB degradation, up to ∼100% after 150 minutes irradiation, higher than that of pristine ZnO and α-Fe₂O₃. Furthermore, after three cycles reusability, mesoporous Fe(25)ZnO still showed an excellent stability performance of up to 95.42% for degradation of MB. The proposed photocatalytic mechanism of mesoporous Fe(25)ZnO for the degradation of MB corresponds to the n-n heterojunction system. This study provides a valuable reference for preparing mesoporous MOF-derived metal oxides with an n-n heterojunction system to enhance MB photodegradation.

A portable architectonics of Al/carbon nitride/metal-organic frameworks anchored Ag nanoparticles for SERS detection and photocatalytic degradation of fungicide

In recent years, it is urgent to develop bi-functional materials for highly sensitive SERS detection and photocatalytic degradation of contaminants in water of fish pond. Herein, using 5-mercapto-1-methyltetrazole as the ligand, the tree-trunk like zeolitic imidazolate framework (ZIF-8) is induced and in-situ grown on the surface of aluminum/flower carbon nitride (Al/f-C₃N₄). Then, AgNPs are tightly anchored in ZIF-8 of Al/f-C₃N₄/ZIF-8 by strong Ag-N and Ag-S bonds, and a portable architecture of Al/f-C₃N₄/ZIF-8/Ag is successfully prepared. Results indicate that the Al/f-C₃N₄/ZIF-8/Ag architecture exhibits excellent SERS activity and the detection limit can as low as 2.15 × 10^-11 mol⋅L^-1 for crystal violet (CV, a typical fungicide). Also, the Al/f-C₃N₄/ZIF-8/Ag substrate presents good photocatalytic activity for CV molecule, and the degradation efficiency reaches 98.58% after illumination for 90 min. This is mainly due to the good adsorption capacity of ZIF-8 which can enrich more CV molecules and pull them to "hot spots" generated by Ag in Al/f-C₃N₄/ZIF-8/Ag, and thus SERS response are enhanced significantly. Besides, the strong synergistic effect of f-C₃N₄, ZIF-8 and AgNPs is also important which facilitates the separation of photogenerated electrons and holes. Thus, the designed portable and bi-functional substrate could be used as a potential material for the detection and removal of CV in practical application.

Facile synthesis of a luminescent carbon material from yogurt for the efficient photocatalytic degradation of methylene blue

The present study is focused on yogurt as a simple, inexpensive, abundant, and green source for the preparation of luminescent carbon material for enhancing the photodegradation of methylene blue (MB). It introduces an ecological and sustainable approach for the large-scale production of carbon material using the direct thermal annealing of yogurt in a muffle furnace. The size of the as-prepared carbon material is about 200–300 nm, with average particle size distribution of 355 nm. The material exhibits clear luminescence under illumination with ultraviolet light. The synthesized carbon material shows an outstanding degradation functionality of MB under the irradiation of ultraviolet (UV) light in aqueous media. Various dye degradation parameters such as initial dye concentration, catalyst dose, pH of dye solution, and scavenger effects have been investigated. The optimum MB concentration was found to be 2.3 × 10⁻⁵ M with a degradation efficiency of 94.8%. The degradation was highly enhanced at pH 11 with a degradation efficiency of 98.11%. The degradation of MB under highly alkaline conditions was mainly governed by the high amount of hydroxyl radicals. Furthermore, the scavenger study confirmed that the hydroxyl radicals were mainly involved in the degradation process. The degradation kinetics of MB followed first order kinetics with large values of rate constant. The reusability was also studied to ensure the stability of the as-prepared carbon material during the degradation of MB. The preparation of carbon materials with efficient photosensitivity for the degradation of organic dyes from yogurt shows a green and innovative methodology. Therefore, it can be of great interest for future studies related to energy and environmental applications.

Left hand side: structural and optical aspects of the as-prepared carbon material from yogurt. Right hand side: the absorbance spectra of methylene blue degradation using the as-prepared carbon material from yogurt.