A novel eco-friendly procedure was developed to produce safer, stable and highly pure zinc oxide nanoparticles (ZnO NPs) using microalgae Chlorella extract. The ZnO NPs were synthesized simply using zinc nitrate and microalgae Chlorella extract which conducted at ambient conditions. In this recipe, microalgae Chlorella extract acted as the reducing agent and a stabilizing layer on fresh ZnO NPs. UV–visible spectrum was confirmed the formation of ZnO NPs showing an absorption peak at 362 nm. XRD results demonstrated that prepared ZnO NPs has a high-crystalline hexagonal (Wurtzite) structure, with average size about 19.44 nm in diameter. FT-IR spectral analysis indicated an active contribution of algae-derived biomolecules in zinc ions bioreduction. According to SEM and TEM observations, ZnO NPs are well dispersed and has a hexagonal shape with the average size of 20 ± 2.2 nm, respectively. Based on gas chromatography analyses, the optimum 0.01 g/L dosage of ZnO catalyst revealed an effective photocatalytic activity toward the degradation (97%) of Dibenzothiophene (DBT) contaminant as an organosulfur model in the neutral pH at the mild condition. Rapid separation and facile recyclability at five consecutive runs were demonstrated high efficiency and durability of green ZnO nanophotocatalyst. The possible mechanisms of green ZnO NPs formation and the photo-desulfurization of DBT were also proposed.

The present study reports the synergistic antibacterial activity of biosynthesized silver nanoparticles (AgNPs) with the aid of a combination of chitosan and seaweed-derived polyphenols as a green synthetic route. Under optimum synthesis conditions, the rapid color change from yellowish to dark brown and UV–visible absorption peak at 425 confirmed the initial formation of AgNPs. DLS, TEM, XRD, and EDX analyses revealed the spherical shape of pure biogenic AgNPs with a mean diameter size of 12 nm ± 1.5 nm, and a face-centered cubic crystal structure, respectively. FTIR and TGA results indicated the significant contribution of chitosan and polyphenol components into silver ions bioreduction and thermal stability of freshly formed AgNPs. Long-term colloidal stability of AgNPs was obtained after 6-month storage at room temperature. The bio-prepared AgNPs possessed a negative surface charge with a zeta potential value of − 27 mV. In contrast to naked chemical silver nanoparticles, the green Ag nanosamples demonstrated the distinct synergistic antibacterial in vitro toward all selected human pathogens presumably due to the presence of high content of biomolecules on their surface. The results show that synergy between chitosan and polyphenol results in the enhancement of bactericidal properties of biogenic AgNPs. We also highlighted the underlying mechanism involved in AgNPs formation based on nucleophile–electrophile interaction.

A facile novel green methodology is presented for the synthesis of highly stable and well-dispersed copper oxide nanoparticles using aqueous wheat seed extract. Under optimal reaction conditions, the wheat seed extract-derived electron-rich biomolecules were functioned as a reducing and capping/ stabilizing agent. The ultraviolet-visible absorption peak at 300 nm was confirmed the formation of copper oxide nanoparticles. Fourier-transform infrared spectroscopy analysis determined Cu–O bonds in nanosample, indicating the active role of functional groups in the wheat seed extract in bio-reduction of Cu cations. X-ray diffraction pattern results demonstrated the monoclinic structure of highly pure biosynthesized copper oxide nanoparticles with a crystallite size of 20.76 nm. The stability of copper oxide nanoparticles was confirmed after 3 months’ storage of product with no sedimentation or suspension. Transmission electron microscopy results showed the spherical shape of nano-particle with an average size of 22 ± 1.5 nm. X-ray photo-electron spectroscopy analyses revealed only copper and oxygen elements in the sample, confirming the purity of copper oxide nanoparticles. Bio-assisted copper oxide nanoparticles demonstrated significant catalytic efficiency and reusability toward 4-nitrophenol removal by an average of 97.6% from aqueous solutions after successive 5 days’ exposure to UV irradiation.

A facile green recipe was developed to synthesise highly pure, safe and durable zinc oxide nanoparticles (ZnO Nps) using homemade starch-rich potato extract. The ZnO Nps were synthesised using zinc nitrate and potato extract, and the whole reaction is carried out for 30 min at 80 C. In the synthesis, starch-rich potato extract acted as the reducing agent and as a stabilising layer on freshly formed ZnO Nps. Hexagonal (wurtzite) shaped ZnO Nps with size about 20 § 1.2 nm were synthesised and characterised using X-ray diffraction, transition electron microscope and scanning microscopy analyses. Fourier transform infrared spectral analysis indicated that highly pure ZnO nanopowders were obtained at higher temperatures. The use of environmentally benign and renewable material as the respective reducing and protecting agents, starch-rich potato extract, as well as a gentle solvent medium (H 2 O), offered a simple and quite efficient procedure for the synthesis of ZnO Nps in neutral medium with promising potential for biological and biomedical applications.

This research presents a novel biological route for the biosynthesis of nickel oxide nanoparticles (NiO NPs) using marine macroalgae extract as a reducing and coating agent under optimized synthesis conditions. XRD and TEM analyses revealed that phytosynthesized NiO NPs are crystalline in nature with a spherical shape having a mean particle size of 32.64 nm. TGA results indicated the presence of marine-derived organic constituents on the surface of NiO NPs. It is found that biogenic NiO NPs with BET surface area of 45.59 m2g−1 is a highly efficient catalyst for benign one-pot preparation of pyridopyrimidine derivatives using aqueous reaction conditions. This environmentally friendly procedure takes considerable advantages of shorter reaction times, excellent product yields (up to 96%), magnetically viable nanocatalyst (7 runs), low catalyst loadings, and free toxic chemical reagents.