Synthesis of iron oxide nanoparticles by the recently developed green approach is extremely promising because of its non-toxicity and environmentally friendly behavior. In this study, nano scaled iron oxide particles (α-Fe2O3) were synthesized from hexahydrate ferric chloride (FeCl3.6H2O) with the addition of papaya (Carica papaya) leaf extract under atmospheric conditions. The synthesis of iron oxide nanoparticles was confirmed by systematic characterization using FTIR, XRD, FESEM, EDX and TGA studies. The removal efficiency of remazol yellow RR dye with the synthesized iron oxide nanoparticles as a photocatalyst was determined along with emphasizing on the parameters of catalyst dosage, initial dye concentration and pH. Increasing the dose of iron oxide nanoparticles enhanced the decolorization of the dyes and a maximum 76.6% dye degradation was occurred at pH 2 after 6 h at a catalyst dose of 0.8 g/L. Unit removal capacity of the photocatalyst was found to be 340 mg/g at dye concentration of 70 ppm and at a catalyst dose of 0.4 g/L. The synthesized nanoparticles showed moderate antibacterial activity against Klebsiella spp., E.Coli, Pseudomonas spp., S.aureus bacterial strains. Although the cytotoxic effect of nanoparticles against Hela, BHK-21 and Vero cell line was found to be toxic at maximum doses but it can be considered for tumor cell damage because it showed excellent activity against the Hela and BHK-21 cell lines.

Nanostructured particles offer outstanding diversities of applications in the fields of nanotechnology, nano-engineering, nano-biotechnology, etc. Morphological structure, size distribution, electronic behavior including intrinsic characteristics of nanoparticles depend on the source and synthesis methods. Here, an eco-friendly approach using microwave irradiation for the synthesis of zinc oxide (ZnO) nanoparticles has been reported. Zinc nitrate was used as a precursor whereas starch and D-glucose were used as capping and reducing agent, respectively. The synthesized nanoparticles were characterized by different instrumental methods including Ultraviolet-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and field emission scanning electron microscopy (FE-SEM). The characteristic λ_max at 373 nm for ZnO nanoparticles was recorded from UV-Vis absorption spectrum in aqueous system. FT-IR spectrum showed a very sharp peak at 476.62 cm^-1 which confirmed the presence of Zn-O bond. The prepared ZnO was highly crystalline having wurtzite structure and the crystallite size was calculated to be 24.41 nm obtained from XRD analysis. FE-SEM images showed that the synthesized ZnO nanoparticles had near- spherical morphology and particle size was found in the range of 40–90 nm. The antibacterial and anti-biofilm application of ZnO nanoparticles were studied and inhibition zones of Gram negative Salmonella typhi (S. typhi), Klebsiella spp., Escherichia coli (E. coli) and Gram positive Staphylococcus aureus (S. aureus)- 8a were found to be 11 mm, 12 mm, 11.5 mm and 13.5 mm, respectively. Besides, ZnO nanoparticles also showed excellent photocatalytic activity against methylene blue dye solution. The easy and eco-friendly fabrication method would play vital role in other nanoparticles synthesis to meet the demand in textile industry, agriculture and medical sectors.

Functionalization of indigenous materials improves inherent physicochemical properties that depend mainly on their fabrication techniques. Here, pH triggered biocomposites using different proportions of kaolinite and chitosan were fabricated. It was revealed that the biocomposites were formed in 1M acetic acid and stabilized after dropwise addition of the mixture of kaolinite and chitosan solution in 3M NaOH. Binding of kaolinite and chitosan at their interface through functional groups was studied using Fourier transform infrared (FT-IR) spectroscopy and dynamic light scattering (DLS). The average particle size of the biocomposite in aqueous system having 80% w/w kaolinite and 20% w/w chitosan was determined to be 400.8 nm. Crystallinity disappearance of chitosan in the biocomposite, as shown in x-ray diffraction (XRD) spectrum, supports the wrapping of kaolinite with soft and flexible chitosan. Differential scanning calorimetry (DSC) showed the thermal stability of the biocomposites and it was found that the biocomposite fabricated from 50% w/w kaolinite and 50% w/w chitosan was stabled up to 318°C. Morphological studies were carried out using scanning electron microscopy (SEM), where a progressive tendency towards granular morphology was evidenced with increase in kaolinite content. These functionalized materials in bionanocomposite structure would play a vital role in advanced research in analytical and environmental science.

Advanced engineering of naturally occurring materials opens new doors in nanoscience and nanotechnology for the separation and/or removal of environmental hazards. Here, a series of nanocomposites containing kaolinite and chitosan varying in the range of 20 to 80% (w/w) kaolinite were used for the adsorptive removal of a reactive textile dye, Remazol Red, from an aqueous solution. Batch experiments were carried out to investigate the effects of pH, contact time, and initial dye concentration on the adsorption capacity. Nanocomposites containing 80% kaolinite (w/w) and 20% chitosan (w/w), i.e., NK₈₀C₂₀, showed an equilibrium adsorption capacity of 371.8 mg/g at pH 2.5, which was 5.2 times higher than that of commercial activated charcoal. Moreover, NK₈₀C₂₀ was regenerated instantly up to 99.9% at pH 10. Therefore, NK₈₀C₂₀ can be effectively utilized as a potential adsorbent for the separation of Remazol Red and homologous azo dyes from industrial effluents. We expect that the findings from this study will play a vital role in environmental research leading to advanced applications in water purification.