Preparation of mesoporous ThO2 nanoparticles: Influence of calcination on morphology and visible-light-driven photocatalytic degradation of indigo carmine and methylene blue.

The present article reports the synthesis of thoria nanoparticles (ThO2 NPs) via sol-gel process and examines the effect of calcination temperature of ThO2 on the morphology and photocatalytic degradation of indigo carmine (IC) and methylene blue (MB) under visible-light. As-synthesized white crystals of ThO2 were subjected to calcination at different temperatures, viz. 700 °C (TH-700), 800 °C (TH-800), and 900 °C (TH-900). The effect of calcination temperature on the structural, morphological, thermal, surface area-porosity, and optical properties of ThO2 NPs were investigated by diverse analytical techniques. XRD patterns show the cubic-space group Fm-3m (225) with parameter a = 5.597 Å and reveals crystallite sizes increased with calcination temperature. The bandgap energy was found to be 1.85 eV, 2.33 eV, and 2.71 eV for TH-700, TH-800, and TH-900 NPs, respectively, calculated by Kubelka-Munk (KM) plot. SEM and TEM unveil that the sample TH-700 calcined at a low temperature of 700 °C yields assembled nanosheets, while at higher temperatures, i.e., 800 °C (TH-800) and 900 °C (TH-900), produces agglomerated nanomaterials. Further, TH-700 sample exhibits enhanced photocatalytic degradation within 120 min for both IC and MB dye than TH-800 and TH-900 counterparts. Among the dyes, IC shows improved photocatalytic efficiency than MB for TH-700, owing to the increased optical absorption and improved separation of photogenerated charge carriers. The reusability study of TH-700 reveals that the catalysts were stable up to four successive cycles with no drastic changes in photocatalytic efficiency. Also, systematic photodisintegration of IC was investigated by Liquid chromatography-mass spectrometry (LC-MS).

Biosynthesized δ-Bi2O3 Nanoparticles from Crinum viviparum Flower Extract for Photocatalytic Dye Degradation and Molecular Docking.

Bioinspired delta-bismuth oxide nanoparticles (δ-Bi2O3 NPs) have been synthesized using a greener reducing agent and surfactant via co-precipitation method. The originality of this work is the use of Crinum viviparum flower extract for the first time for the fabrication of NPs, which were further calcined at 800 °C to obtain δ-Bi2O3 NPs. Physicochemical studies such as FTIR spectroscopy and XPS confirmed the formation of Bi2O3 NPs, whereas XRD and Raman verified the formation of the cubic delta (δ) phase of Bi2O3 NPs. However, HRTEM revealed the spherical shape with diameter 10-20 nm, while BET studies expose mesoporous nature with a surface area of 71 m2/gm. The band gap for δ-Bi2O3 NPs was estimated to be 3.45 eV, which ensured δ-Bi2O3 to be a promising photocatalyst under visible-light irradiation. Therefore, based on the results of physicochemical studies, the bioinspired δ-Bi2O3 NPs were explored as active photocatalysts for the degradation of toxic dyes, viz., Thymol blue (TB) and Congo red (CR) under visible-light irradiation. The study showed 98.26% degradation of TB in 40 min and 69.67% degradation of CR in 80 min by δ-Bi2O3 NPs. The photogenerated holes and electrons were found responsible for this enhancement. Furthermore, molecular docking investigations were also performed for δ-Bi2O3 NPs to understand its biological function as New Delhi metallo-ß-lactamase 1 (NDM-1) [PDB ID 5XP9] enzyme inhibitor, and studies revealed good interaction with various amino acid residues and found good hydrogen bonding with a fine pose energy of -3.851 kcal/mole.

Biogenic Synthesis of Metal/Metal Oxide Nanostructured Materials.

Nanotechnology is an emerging outlet of nanoscience in which the atoms are encompassed in nanoscale dimensions and become more receptive compared with their distinctive counterparts. Recently, the utilization of synthetic designs and physicochemical approaches has received special attention; nevertheless, the generation of noxious impressions on the eco-system has raised serious concerns of the scientific community worldwide. Presently, environment-friendly green synthesis routes are promising venues for the arrangement of Metal/Metal Oxide (M/MO) nanostructured materials by using plants and their corresponding alliances. This revolution is predominantly recompensing as far as the reduction of toxic emissions and wastes is concerned. Accordingly, material scientists have adopted various renewable naturally-occurring eco-friendly materials, and biogenic processes to fabricate the functional M/MO nanostructured materials. The current review article recapitulates and assimilates the present state of knowledge on different strategies for biogenic fabrication of M/MO nanostructured materials.

Bioinspired Reduced Graphene Oxide Based Nanohybrids for Photocatalysis and Antibacterial Applications.

Ultra-thin graphene has been receiving significance in the diverse sections of material science, owing to its exceptional physicochemical and thermo-mechanical characteristics. Currently, the fabrication of high-grade graphene in an economical target and green procedures area is a massive concern. Among the diverse techniques, chemical-mediated fabrication is believed to be the finest process since it is simple, scalable, and of low-cost; however, it involves noxious or hazardous chemical reducers for producing functional graphene-based Nanocomposites (NCs). Therefore, around the globe, scientists are endeavoring to adopt the bioinspired techniques to manufacture the functional reduced Graphene Oxide (rGO) and reduced Graphene Oxide-Metal/Metal Oxide (rGO-M/MO) NCs. Hence, keeping this issue in mind, the present review article summarize and integrates the current state of knowledge about the diverse bioinspired strategies developed to obtain rGO and rGO-M/MO NCs and their photocatalytic, antibacterial, and cytotoxic assessments.

Mesoporous Octahedron-Shaped Tricobalt Tetroxide Nanoparticles for Photocatalytic Degradation of Toxic Dyes.

The present article reports a facile approach to fabrication of mesoporous octahedron-shaped tricobalt tetroxide nanoparticles (Co3O4 NPs) with a very narrow size distribution for eco-friendly remediation of toxic dyes. Co3O4 NPs were fabricated by a sol-gel process using cobalt chloride hexahydrate (CoCl2·6H2O) and monosodium succinate (C4H5O4Na) as a chelating/structure-directing agent and sodium dodecyl sulfate as a surfactant. Moreover, the phase structure, elemental composition, and thermal and morphological facets of Co3O4 NPs were investigated using XRD, FT-IR, EDS, Raman, XPS, TGA, SEM, and TEM techniques. The face-centered cubic spinel crystalline structure of the Co3O4 NPs was confirmed by XRD and SEM, and TEM analysis revealed their octahedron morphology with a smooth surface. Moreover, the narrow pore size distribution and the mesoporous nature of the Co3O4 NPs were confirmed by Brunauer-Emmett-Teller measurements. The photocatalytic activity of Co3O4 NPs for degradation of methyl red (MR), Eriochrome Black-T (EBT), bromophenol blue (BPB), and malachite green (MG) was examined under visible light irradiation, and the kinetics of the dye degradation was pseudo-zero-order with the rate constant in the order of MR > EBT > MG > BPB. Furthermore, the mechanism of photo-disintegration mechanism of the dye was examined by a scavenging test using liquid chromatography-mass chromatography, and its excellent photodegradation activities were attributed to the photogenerated holes (h+), superoxide (O2 -) anions, and hydroxyl (·OH) radicals. Finally, the synergistic effect of the nano-interconnected channels with octahedron geometry, mesoporous nature, and charge transfer properties along with photogenerated charge separations leads to an enhanced Co3O4 photocatalytic activity.

Metal/Metal Oxide Nanoparticles: Toxicity, Applications, and Future Prospects.

The ever-growing resistance of pathogens to antibiotics and crop disease due to pest has triggered severe health concerns in recent years. Consequently, there is a need of powerful and protective materials for the eradication of diseases. Metal/metal oxide nanoparticles (M/MO NPs) are powerful agents due to their therapeutic effects in microbial infections. In this context, the present review article discusses the toxicity, fate, effects and applications of M/MO NPs. This review starts with an introduction, followed by toxicity aspects, antibacterial and testing methods and mechanism. In addition, discussion on the impact of different M/MO NPs and their characteristics such as size, shape, particle dissolution on their induced toxicity on food and plants, as well as applications in pesticides. Finally, prospective on current and future issues are presented.