Photodegradation Activity of Nitrogen‐rich Graphitic Carbon Nitride Intercalated ZnO\Mg‐Al Layered Double Hydroxide Ternary Nanocomposites on Methylene Blue Dye

Indulgent of the physiochemical features of MgCr-LDH nanosheets towards photodegradation process of methylene blue

In the present work, we report the preparatory strategy of MgCr-layered double hydroxide (LDH) nanosheets with 90% degree of delamination by employing a formamide-assisted co-precipitation and mild hydrothermal route for the degradation of methylene blue (MB) under solar light exposure. The as-synthesized MgCr-LDH nanosheets were characterized by assorted characterization techniques such as powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Raman, thermogravimetric analysis (TGA), N₂ adsorption-desorption measurement, X-ray photoelectron spectroscopy (XPS) and UV-Visible diffused reflectance spectroscopy (UV-DRS). The XRD pattern of MgCr-LDH nanosheets quantified the strain (ε) and dislocation density (δ) of 1.371 lines^-2 m^-4 and 0.5723 lines m^-2 related to the (110) plane with d-spacing value of 1.6169 Ȧ. With a minimum band gap of ∼2.63 eV, the as-synthesized MgCr-LDH nanosheets displayed 90.6% MB photodegradation under the experimental protocols such as catalyst dosage of 30 mg/L, initial MB concentrations of 20 ppm, pH of 7 and time duration of 2 h under solar light exposure. Further, the recyclability test of the photocatalyst signifies material stability up to four successive cycles with 90% retention of MB degradation under sunlight exposure. The superior catalytic performances of the MgCr-LDH nanosheets could be ascertained to the suppression of excitonic recombination and effective light harvestation properties, synergistically contributed by the porous structural aspects via association of uni/multi-lamellar nanosheets, surface defect sites and photoactive Cr³⁺ cations. Additionally, the surface -OH groups of LDH contributed towards the generation of ^•OH radicals for triggering the catalytic performances. This type of work advances the novel ideas for establishing highly potent photocatalysts via synergizing structural and surface properties, paving towards effective wastewater treatment.

A Novel Composite of Zinc-based Metal Organic Framework Embedded with SnO2 Nanoparticle as a Photocatalyst for Methylene Blue Dye Degradation as well as Fluorometric Probe for Nitroaromatic Compounds Detection

A facile bottom up synthesis technique is opted for the preparation of novel composite SnO₂@Zn-BTC. This synthesized composite is fully characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and Elemental mapping techniques. Optical analysis was performed using UV-Visible absorption spectroscopy and fluorescence studies. Further this composite was utilized for the first time as a photocatalyst for methylene blue (MB) dye degradation under sunlight irradiation. This photocatalyst shows degradation efficiency of 89% within 100 min of exposure of sunlight. In addition to that, the synthesized composite can be utilized as a fluorescence probe for detection of NACs via 'turn-off" quenching response. This composite is extremely sensitive towards 3-NA in aqueous medium with quenching efficiency of 75.42%, which is highest quenching rate till reported. There occurs no interference for detecting 3-NA in the presence of other NACs. The linear fitting of the Stern-Volmer plot for 3-NA shows large quenching constant (K_SV) of 0.0115 ppb^-1 with correlation coefficient R² = 0.9943 proves higher sensitivity of composite in sensing process. The outstanding sensitivity of composite for 3-NA is certified by the low detection limit (LOD) of 25 ppb (0.18 µM). Photoinduced Electron Transfer (PET) and Fluorescence Resonance Energy Transfer (FRET) are the mechanisms used for clarification of quenching response of PL intensity by NACs via density functional theory (DFT) calculations and extent spectral overlap, respectively. Hence, synthesized composite is verified as multi-component system to act as excellent photocatalyst as well as fluorescent sensor.

Photocatalytic Degradation of Malachite Green by Layered Double Hydroxide Based Composites

Studies of LDH materials to be applied as photocatalyst for dye pollutant degradation have been developed. These interesting efforts are inseparable from the investigation of degradation performance and competitive synthetic methods. Composites based on Zn/Al and Mg/Al layered double hydroxides (LDHs) with ZnO and TiO2 were prepared by coprecipitation-impregnation method following by calcination at 300 °C to forms Zn/Al-ZnO, Mg/Al-ZnO, Zn/Al-TiO2, and Mg/Al-TiO2. Composites were characterized by XRD, FTIR, SEM and UV-DRS. Photodegradation of malachite green (MG) was carried out, after optimization of pH, catalyst loading and contact time in batch system under UV irradiation. XRD and spectroscopic data shows composites were successfully formed indicated by formation of both pristine materials. Degradation of malachite green showed that composites as photocatalyst have higher catalytic activity than pristine LDHs. LDH-ZnO composite have better activity, energy band gap and degradation reusability than LDH-TiO2. The Zn/Al-ZnO and Zn/Al-TiO2 composites degraded 97.1% and 96.3% MG, whereas the Mg/Al-ZnO and Mg/Al-TiO2 composites were able to degrade 99.8% and 98.6% MG, respectively. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Strategic combination of metal-organic frameworks and C3N4 for expeditious photocatalytic degradation of dye pollutants

The potential of fabricated silver and bismuth Co-N-doped imidazolate embedded into graphitic nitride BiO-Ag(0)/C₃N₄@ZIF-67 for the degradation of Methylene blue (MB) and Congo red (CR) dyes have been reported. The synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy photoluminescence (PL) spectroscopy, and electrochemical impedance spectroscopy (EIS). The band gaps of ZIF-67, C₃N₄ and composites were calculated using Tauc plot. Besides, it was revealed that incorporation of silver, bismuth, and C₃N₄ reduced the band gap energy to 2.2 eV. The introduction of metallic species in the precursors promoted better charge separation behavior towards photogenerated electron and hole in the heterojunction composite. Two perilous organic dyes; MB and CR were degraded under natural sunlight irradiation. The photocatalytic efficiency of BiO-Ag(0)/C₃N₄@ZIF-67 for the removal of CR and MB significantly increased compared to bare ZIF-67. The enhanced photocatalytic activity of BiO-Ag(0)/C₃N₄@ZIF-67 is attributed to the higher surface area and Plasmon effect of noble silver metal. The solar light-triggered degradation of MB and CR yielded efficient efficiency of 96.5 and 90% for 10 mg/L of dye solution each. Additionally, the effect of pH was evaluated for optimizing degradation of CR and MB dyes. The kinetics studies of both CR and MB were clarified according to Langmuir model. The reusability and quenching investigation of active species were carried out to discover find catalytic potential of the composite. Besides, possible dye degradation mechanism was proposed for BiO-Ag(0)/C₃N₄@ZIF-67. The obtained results indicated that solar-light triggered photocatalyst BiO-Ag(0)/C₃N₄@ZIF-67 can be employed as a promising approach for photocatalytic elimination of organic pollutants.

Hydrothermally activated TiO2 nanoparticles with a C-dot/g-C3N4 heterostructure for photocatalytic enhancement

Dye degradation via photocatalysis technology has been investigated intensively to tackle environmental issues and energy crisis concerns. In this study, a newly designed ternary photocatalyst was facilely prepared by a simple one-pot hydrothermal process by directly mixing TiO₂ nanoparticles with carbon dots (C-dots) and graphitic carbon nitride (g-C₃N₄). The optimized precursor treatments and heterostructure components show significantly enhanced photodegradation activity towards organic dyes Rhodamine B (RhB) and methylene blue (MB). Excellent photocatalytic activities were achieved owing to the better attachment of anatase-type TiO₂ nanoparticle-aggregations to the C-dots/g-C₃N₄ (CC) nanocomposite, which impressively displays superhydrophilicity by employing the hydrothermal activation process. FT-IR spectra revealed that the hydrothermal treatment could remarkably increase the coupling interactions between TiO₂ nanoparticles and the CC nanosheets within the ternary catalyst, enhancing the photocatalytic activity. Thus, it was concluded that this ternary photocatalyst is highly suitable for the remediation of dye-contaminated wastewater.

Visible light driven reduced graphene oxide supported ZnMgAl LTH/ZnO/g-C3N4 nanohybrid photocatalyst with notable two-dimension formation for enhanced photocatalytic activity towards organic dye degradation

In this study, 2D/2D/2D heterostructured r-GO/LTH/ZnO/g-C₃N₄ nanohybrid were synthesized through hydrothermal method. The strong electrostatic interaction between the negatively charged g-C₃N₄ and r-GO nanosheets with positively charged layered triple hydroxide (LTH) nanosheets are effectively influences the successful formation of heterojunction. The LTH nanosheets are well spread on the g-C₃N₄ nanosheets combined with r-GO. In particular, the as prepared heterojunction shows a better photocatalytic degradation activity compared to pristine samples and the significant enhancement in the photocatalytic performance is mainly accredited to the large interfacial charge transition of photogenerated charge carriers under the visible light irradiation. Although the 2D/2D/2D heterojunction effectively hinders the charge carrier recombination resulting high photocatalytic activity with good stability. In addition, the r-GO supported LTH/ZnO/g-C₃N₄ heterojunction shows high photo-stability after sequential experimental runs with no obvious change in the dye degradation process. Consequently, the role of active species was investigated over the r-GO/LTH/ZnO/g-C₃N₄ heterojunction with the help of different scavengers.