Abstract
M.Sc. (Chemistry)
An eco-friendly synthesis of silver (Ag) and platinum (Pt) nanoparticles (NPs) using aqueous extracts from both fresh and dried leaves of water hyacinth plant as efficient reducing and stabilizing agents is presented. The optical properties of the as-synthesised material from both extracts were studied at different pH and reaction time and were characterized using UV-visible, transmission electron microscopy (TEM), Fourier Transform infra-red spectroscopy (FTIR), Dynamic light scattering (DLS), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). The colour changes from light yellow to brown with the presence of the silver surface plasmon resonance (SPR) band indicated the formation of Ag-NPs while the disappearance of the peak intensity at 260 nm confirmed the formation of Pt-NPs. TEM analysis showed that the as-synthesised materials from both extracts were of different sizes and spherical in shape while DLS analysis revealed their hydrodynamic sizes in the hydrated state. FTIR indicated that, the presence of polyphenols, alkaloids and polysaccharides groups present in both water hyacinth leaf extract were responsible for the reduction and capping of Ag-NPs and Pt-NPs. The presence of elemental silver as well as platinum and the purity of the as-synthesised sample were confirmed by EDS analysis.
This study demonstrates the feasibility of using water hyacinth leaf extract from fresh and dried leaves for the synthesis of Ag-NPs and Pt-NPs. However, fresh leaves extract was more preferred than dried leaves extract as it retains most of the phytochemicals that could influence the formations of the nanoparticles. The as-synthesised materials were further used for colorimetric sensing of heavy metals in aqueous solution (Hg2+, Ca2+, Cr3+, Ba2+ Li+, K+, Ni2+, Co2+, Pb2+, Mn2+) and only Ag-NPs shows a sensitive response towards these metal ions as indicated by the shift in the position of the surface plasmon resonance (SPR) band with a more selective response to Hg2+. Pt-NPs on the other hand show no response towards these metal ions and hence cannot act as a colorimetric probe...