Vivek Sheel Jaswal

In the current work, a novel green and sustainable method was developed to prepare CaO-CoO nanocomposites using onion peel extract as a stabilising and reducing agent. A thorough characterization of structure, morphology, elemental, and optical properties of the synthesized nanocomposite was performed with the help of methods including XRD, FTIR, XPS, FESEM, EDS, as well as fluorescence spectroscopy. XRD analysis established the successful development of crystalline CaO and CoO phases, while FTIR and XPS studies verified the existence of characteristic metal-oxygen bonds and surface functional groups. FESEM analysis revealed an agglomerated quasi-spherical nanomaterial with a mean particle size of 23 nm. Fluorescence studies demonstrated strong emission behaviour in the 350-450 nm region, with significant quenching upon the addition of Zn2+ ions. CaO-CoO nanocomposite exhibited excellent sensitivity towards Zn2+ ions detection with concentration from 0-50 nM with a lower detection limit of 5nM. Additionally, the synthesized nanocomposite showed concentration- dependent antimicrobial activity against Bacillus sp., S. aureus, and E. coli. These results suggest that the green-synthesized CaO-CoO nanocomposite can be used as a potential multifunctional material that serves very well for environmental sensing and antimicrobial applications.

La-doped ZrO2 nanomaterial were designed as an efficient fluorescent probe for the selective detection of Hg2+ ions in aqueous media. The synthesized material was systematically analyzed using XRD, SEM, XPS and FTIR analysis. XRD results confirmed the highly crystalline nature of the La-doped ZrO2 while the SEM images demonstrate a rough surface morphology with agglomerated particulates. FTIR and XPS studies verified the successful integration of La3+ions into the ZrO2 matrix and the presence of oxygen-rich surface functional groups. The optical properties of the fabricated material were examined using UV-Vis and fluorescence spectroscopy was employed to investigate the quenching behavior. The fluorescence studies demonstrated a strong and selective quenching response toward Hg2+ ions compared to other competing metal ions, including Zn2+, Ba2+, As3+, Ag2+, Cr3+, Fe3+, K+, Al3+, Ni2+, Ca2+, Cd2+and Mn2+, Co2+, Cu2+, Pb2+. The limit of detection (LOD) for Hg2+ ions was determined to be 12.7nM within the studied concentration range. These findings suggest that La-doped ZrO2 nanomaterial are promising candidate for the selective detection of Hg2+ ions in the environmental analysis of water samples.