Boosted charge separation via Ce2S3 over dual Z-scheme ZnO-Ce2S3-MnO2 core double-shell nanocomposite for the degradation of diverse dye pollutants

Herein, core double-shell direct dual Z-scheme ZnO-Ce2S3-MnO2 nanocomposite was synthesized via a hydrothermal route along with pure ZnO, Ce2S3, MnO2, and characterized by numerous characterization tools for application in synthetic dyes degradation. The XRD, Raman, and FTIR analyses have confirmed the nanocomposite formation. TEM images exhibited the core double-shell morphology with an average particle diameter of 81 nm and stacking of ZnO, Ce2S3, and MnO2. EDX confirmed the existence of desired elements in the grown composition. The varied oxidation states, presence of defects, and fast charge transfer were also revealed from XPS, PL, and EIS. The ZnO-Ce2S3-MnO2 nanocomposite has an optical energy bandgap of 2.84 eV, capable of decomposing harmful dyes with excellent efficiency, 99.81% MB, 97.62% MO, 88.5% MR, and 58.9% EY in 40 min sunlight exposure. The effect of several operating parameters is also observed and obtained results showed the optimal catalyst dose was 20 mg, pH of 8, and dye concentration of 10 ppm. The scavenger's experiment suggests that •O2- and •OH are the main active radicals in the photodegradation reaction which is also evident in the dual Z-scheme formation. The MnO2 and ZnO layers covered the Ce2S3 (core) and dual Z-scheme formation allows rapid kinetics of redox reaction and provides plenteous channels for transfer of photo-generated charge carriers during photocatalysis. Thus, core double-shell direct dual Z-scheme photocatalysts having inorganic components could be an excellent choice for photocatalysis at the industrial level, particularly for water purification.

Synergistic effect of a bamboo-like Bi2S3 covered Sm2O3 nanocomposite (Bi2S3-Sm2O3) for enhanced alkaline OER

The availability of hydrogen energy from water splitting through the electrocatalytic route is strongly dependent on the efficiency, durability, and cost of the electrocatalysts. Herein, a novel Bi2S3-covered Sm2O3 (Bi2S3-Sm2O3) nanocomposite electrocatalyst was developed by a hydrothermal route for the oxygen evolution reaction (OER). The electrochemical properties were studied in 1.00 mol KOH solution after coating the target material on the stainless-steel substrate (SS). Physical analysis via XRD, FTIR, IV, TEM/EDX, and XPS revealed that the Bi2S3-Sm2O3 composite possesses metallic surface states, thereby displaying unconventional electron dynamics and purity of phases. The Bi2S3-Sm2O3 composite shows outstanding OER activity with a low overpotential of 197 mV and a Tafel slope of 74 mV dec-1 at a 10 mA cm-2 current density as compared to pure Bi2S3 and Sm2O3. Meanwhile, the composite catalyst retains high stability even after 100 h of the chronoamperometry test. Thus, this work unveils a new avenue for the speedy flow of electrons, which is attributed to the synergetic effect between Bi2S3 and Sm2O3, as well as enriched interfacial defects, which exhibit greater oxygen adsorption capability with improved electronic assemblies in the active interfacial region. In addition, the introduced porous structure in core-shell Bi2S3-Sm2O3 provides extraordinary electrical properties. Thus, this article offers a realistic framework for electrochemical energy generation.

Fabrication of fullerene-supported La2O3-C60 nanocomposites: dual-functional materials for photocatalysis and supercapacitor electrodes

Nowadays, water pollution and energy crises worldwide force researchers to develop multi-functional and highly efficient nanomaterials. In this scenario, the present work reports a dual-functional La₂O₃-C₆₀ nanocomposite fabricated by a simple solution method. The grown nanomaterial worked as an efficient photocatalyst and proficient electrode material for supercapacitors. The physical and electrochemical properties were studied by state-of-the-art techniques. XRD, Raman spectroscopy, and FTIR spectroscopy confirmed the formation of the La₂O₃-C₆₀ nanocomposite with TEM nano-graphs, and EDX mapping exhibits the loading of C₆₀ on La₂O₃ particles. XPS confirmed the presence of varying oxidation states of La³⁺/La²⁺. The electrochemical capacitive properties were tested by CV, EIS, GCD, ECSA, and LSV, which indicated that the La₂O₃-C₆₀ nanocomposite can be effectively used as an electrode material for durable and efficient supercapacitors. The photocatalytic test using methylene blue (MB) dye revealed the complete photodegradation of the MB dye under UV light irradiation after 30 min by a La₂O₃-C₆₀ catalyst with a reusability up to 7 cycles. The lower energy bandgap, presence of deep-level emissions, and lower recombination rate of photoinduced charge carriers in the La₂O₃-C₆₀ nanocomposite than those of bare La₂O₃ are responsible for enhanced photocatalytic activity with low-power UV irradiation. The fabrication of multi-functional and highly efficient electrode materials and photocatalysts such as La₂O₃-C₆₀ nanocomposites is beneficial for the energy industry and environmental remediation applications.

Dual Z-scheme core-shell PANI-CeO2-Fe2O3-NiO heterostructured nanocomposite for dyes remediation under sunlight and bacterial disinfection

Nowadays, environmental pollution due to discharge of organic pollutants from food, textile, and pharmaceutical industries into clean water and development of contagious diseases due to pathogenic organisms provide impetus to material researcher to fabricate novel design for efficient photocatalyst and antimicrobial agents. In this regard, designing a core-shell heterojunction catalyst based on metal oxides is considered an auspicious approach. In present study, combating the problems of singular oxides, core-shell PANI-CeO₂-Fe₂O₃-NiO nanocomposite (PCFN) and CeO₂-Fe₂O₃-NiO nanocomposite (CFN) was synthesized through sol-gel and oxidative polymerization route with cetyletrimethylammonium bromide (CTAB) as surfactant. The XRD, FTIR, and Raman confirmed the formation of nanocomposites with core-shell morphology composed of PANI (shell) and oxides (Core) in PCFN with a particle size of 52 nm (TEM). Surprisingly, PCFN has lower band gap, e^-/h⁺ recombination, and larger charge transfer character than CFN. The decomposition test using MB and MO dyes showed that PCFN degraded 99%, 98%, while CFN degraded only 73% and 54%, respectively, under 50 min sunlight illumination. The reusability was assessed up to 7th cycle for PCFN. The influence of operational parameters (catalyst dose, dye concentration, pH) was tested for PCFN. Further, the antimicrobial action against S. aureus (gram + ve), E. coli (gram -ve) were also tested. The supreme performance of PCFN has been credited to heterostructure dual Z-scheme formation and core-shell morphology supported with PANI, which suppresses the e^-/h⁺ recombination process by promoting their separation. The present finding indicated that the PCFN is a promising modifier for bacterial disinfection and acts as a superb photocatalyst through core-shell formation with PANI support.

Transition metal-doped SnO2 and graphene oxide (GO) supported nanocomposites as efficient photocatalysts and antibacterial agents

In the present work, pristine and transition metal (TM) (W, Ag, Zn)-doped SnO₂ nanocrystals using a facile sol-gel approach were synthesized. The grown products were anchored on graphene oxide (GO) sheets via a simple ultrasonication technique to fabricate binary nanocomposites. The structural, optical, and morphological properties of as-synthesized samples were studied by XRD, FTIR, Raman, EDX, UV-Visible, PL, and FE-SEM. The charge transferability of graphene oxide-based samples was investigated by EIS. The XRD exhibited the TM doping in SnO₂ and the development of GO-based nanocomposite. FTIR data evidenced the existence of the metal-oxygen bonds. Raman spectra presented the optical phonon modes of SnO₂ and the existence of oxygen vacancy defects. FE-SEM images demonstrated the anchoring of particles on the GO sheet, and EDX further approved the existence of desired dopants. The integration of SnO₂ with TM doping remarkably reduced optical bandgap (3.65-3.10 eV), which was further decreased (3.10-2.99 eV) by making composite with GO. The photodegradation results exhibited that GO-based nanocomposites have the higher potential to degrade synthetic dyes (methyl red (MR), and methyl orange (MO) and SnZnO₂/GO have shown superb photocatalytic performance after 80-min sunlight illumination (99.9% MR and 95.0% MO dyes) with the higher rate constant and superior stability up to 6th cycle against MR dye. The grown samples were tested for bacterial disinfection, and SnZnO₂/GO sample showed a higher zone of inhibition towards S. aureus and K. pneumoniae bacteria strains. The greater charge transfer rate and lower recombination of charge carriers in GO-based composites were also observed by EIS and PL analysis. Moreover, the present article ascribed that the photocatalytic and antibacterial properties of bare SnO₂ could be improved by TM doping and fabricating their composite with GO.

Energy-levels well-matched direct Z-scheme ZnNiNdO/CdS heterojunction for elimination of diverse pollutants from wastewater and microbial disinfection

Energy-levels well-matched direct Z-scheme ZnNiNdO/CdS heterojunction was successfully fabricated using facile co-precipitation and ultra-sonication techniques and characterized with XRD, FTIR, Raman, PL, UV-vis, and FE-SEM. The XRD diffractograms confirmed the co-doping of Ni-Nd in ZnO and the formation of heterostructured nanocomposite. FTIR and Raman data showed the presence of metal-oxygen vibration and optical phonon modes of ZnO and CdS. FE-SEM images exhibited the network type morphology. The energy bandgap was redshifted by co-doping (3.37-2.9 eV) and was further reduced (2.6 eV) by making a composite with CdS. The ZnNiNdO/CdS catalyst degraded 99.7, 49, 96.6, 98.6, and 98.6% methylene blue (MB), p-nitroaniline (P-Nitro), methyl orange (MO), methyl red (MR), and rhodamine B (RhB) dyes under 50 min sunlight irradiation. Moreover, ZnNiNdO/CdS showed intense inhibition activity towards Staphylococcus aureus, Escherichia coli, Proteus vulgaris, and Pseudomonas aeruginosa bacterial strains with maximum inhibition zone diameters 30, 33, 27, and 31 mm, respectively. The synergistic effects arising from band alignment can lead to efficient vectorial charge separation, transportation, and lower recombination of photoinduced charge carriers, ultimately boosting photocatalytic and antibacterial performance. The ZnNiNdO/CdS photocatalyst has higher stability up to the 7th cycle towards MB dye with ~ 5% deficit in degradation efficiency. The higher generation of superoxide and hydroxyl radical was confirmed by species trapping experiments responsible for photodegradation of dyes molecules. Furthermore, the results showed that the photocatalytic and antibacterial performance of pristine ZnO can be enhanced by co-doping and tuning energy bandgap.

Sunlight-induced photocatalytic degradation of various dyes and bacterial inactivation using CuO-MgO-ZnO nanocomposite

Novel tri-phase CuO-MgO-ZnO nanocomposite was prepared using the co-precipitation technique and investigated its physical properties using characterization techniques including XRD, FTIR, Raman, IV, UV-vis, PL, and SEM. The application of grown CuO-MgO-ZnO nanocomposite for the degradation of various dyes under sunlight and antibacterial activity against different bacteria were studied. The XRD confirmed the existence of diffraction peaks related to CuO (monoclinic), MgO (cubic), and ZnO (hexagonal) with CuO phase 40%, MgO 24%, and ZnO 36%. The optical energy gap of nanocomposite was 2.9 eV, which made it an efficient catalyst under sunlight. Raman and FTIR spectra have further confirmed the formation of the nanocomposite. SEM images revealed agglomerated rod-shaped morphology. EDX results showed the atomic percentage of a constituent element in this order Cu>Zn>Mg. PL results demonstrate the presence of intrinsic defects. The photocatalytic activity against methylene blue (MB), methyl orange (MO), rhodamine-B (RhB), cresol red (CR), and P-nitroaniline (P-Nitro) dyes has shown the excellent degradation efficiencies 88.5%, 93.5%, 75.9%, 98.8%, and 98.6% at 5 ppm dye concentration and 82.6%, 83.6%, 64.3%, 93.1%, and 94.3% at 10 ppm dye concentration in 100 min, respectively, under sunlight illumination. The higher degradation is due to the generation of superoxide and hydroxyl radicals. The recyclability test showed the reusability of catalyst up to the 5th cycle. The antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Proteus Vulgaris, Staphylococcus aureus, and Pseudomonas aeruginosa bacteria with the zone of inhibition 30, 31, 30, 30, and 30 mm, respectively, was achieved.

Fractionation of Biomolecules in Withania coagulans Extract for Bioreductive Nanoparticle Synthesis, Antifungal and Biofilm Activity

Withania coagulans contains a complex mixture of various bioactive compounds. In order to reduce the complexity of the plant extract to purify its phytochemical biomolecules, a novel fractionation strategy using different solvent combination ratios was applied to isolate twelve bioactive fractions. These fractions were tested for activity in the biogenic synthesis of cobalt oxide nanoparticles, biofilm and antifungal activities. The results revealed that plant extract with bioactive fractions in 30% ratio for all solvent combinations showed more potent bioreducing power, according to the observed color changes and the appearance of representative absorption peaks at 500-510 nm in the UV-visible spectra which confirm the synthesis of cobalt oxide nanoparticles (Co3O4 NPs). XRD diffraction was used to define the crystal structure, size and phase composition of the products. The fractions obtained using 90% methanol/hexane and 30% methanol/hexane showed more effectiveness against biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus so these fractions could potentially be used to treat bacterial infections. The 90% hexane/H2O fraction showed excellent antifungal activity against Aspergillus niger and Candida albicans, while the 70% methanol/hexane fraction showed good antifungal activity for C. albicans, so these fractions are potentially useful for the treatment of various fungal infections. On the whole it was concluded that fractionation based on effective combinations of methanol/hexane was useful to investigate and study bioactive compounds, and the active compounds from these fractions may be further purified and tested in various clinical trials.