The tin dioxide nanoparticles (SnO₂ NPs) were fabricated via eco-friendly process using Daphne mucronata (D. mucronata) leaves extract as capping and reducing agent. The N₂ adsorption/desorption experiment was performed to determine the surface area by Brunauer–Emmett–Teller (BET) method and S_BET was found to be 147 m² g⁻¹. The crystalline nature and lattice parameter was studied by x-ray diffraction (XRD) and calculated crystallite size is 15.63 nm. The surface morphology was examined by scanning electron microscopy (SEM) and the estimated average particle size is 64 nm. The percentage composition and purity of the SnO₂ NPs was determined by energy dispersive x-ray (EDX). The raman active modes were identified by using raman spectroscopy while functional groups upon the surface were studied by using fourier transform infrared (FTIR) spectroscopy. The photocatalytic performance of SnO₂ NPs was examined against Rhodamine 6G (R6G) and 99.70% rhodamine 6G (R6G) were degraded in 390 min with the degradation rate of 0.0148 per min. The SnO₂ NPs were screened against the selected microorganisms and the order of antimicrobial activity is given as; Gram negative bacteria (GNB) > Gram positive bacteria (GPB) > fungi.

TiO₂nanoparticles were synthesized at room temperature by chemical precipitation method and were then heated at 120, 300, 600 and 900 °C temperatures. The phase transition and crystallite size variation were determined by X-rays diffraction (XRD) analysis. The surface area, pore volume and pore size were measured using Brunauer–Emmet–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods. The optical activity of heat treated and non-heat treated samples were carried out by diffuse reflectance (DR) spectroscopy. Four different methods were used to calculate band gap energy. The results obtained from thermogravimetric and differential thermal gravimetric (TG/TDG) analyses and Fourier transform infra-red (FTIR) spectroscopy agreed with each other. Agar well diffusion method has been applied to explore the antibacterial activity of nanoparticles against different bacterial strains such asBacillus subtilis,Staphylococcus Aureus, Escherichia coliandPseudomonas Aeruginosa. It was observed that TiO₂nanoparticles heated at 120 °C displayed maximum antibacterial activity while those heated at higher temperature showed no activity against the examined bacteria.

The cobalt oxide nanoparticles (Co₃O₄ NPs) were synthesized via the green method using Piper nigrum (P. nigrum) leaves extract and were calcined at different temperatures. The crystalline nature was studied through x-ray diffractometer (XRD). With increasing calcination, the amorphous phase transitioned to the crystalline phase. Diffuse reflectance spectroscopy (DRS) was used to observe UV-Visible light absorbance phenomenon, and Tauc’s plot was used to calculate the band gap energy, which was found to decrease with calcination. Scanning electron microscopy (SEM) was used to analyze the surface morphology, and Fourier transform infrared (FTIR) spectroscopy was used to classify the surface functional groups. The antibacterial efficacy of the Co₃O₄ NPs was examined against Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB), whereas its antioxidant potential was explored against ABTS free radicals. Antibacterial and antioxidant potentials of Co₃O₄ NPs were found to decrease with increasing calcination.