Abstract:
Advancement of environmentally friendly synthetic methods of nanoparticles is growing in the field of nanotechnology. Turbinaria
ornata is a brown alga which is highly abundant in coastal region of Sri Lanka and an excellent source of bioactive
compounds. The aim of this study is to synthesise silver nanoparticles (AgNPs) with Turbinaria ornata to use in antibacterial
activities. Sources contain Ag nanoparticles are being used for various applications such as photocatalytic degradation
and antimicrobial activities. The parameters such as temperature and concentration of the silver nitrate and pH were chosen
to find the efficient synthesis of AgNPs. Extracts were prepared at 70 °C was added with 1, 2, 3, 4 and 5 mM AgNO3
and
incubated for 24 h at different pHs to prepare the AgNPs. The synthesised nanoparticles were characterized by the surface
plasmon resonance band at 430 nm. Highest absorbance band for nanoparticles synthesised from algal extract was obtained
at 70 °C and 5 mM silver nitrate at pH 11. The characteristic bands at 3300.93, 2107.30, 1640.74 and 1051.32 cm−
1 in FT-IR
suggested that the distinct functional groups, O–H, N–H and C = C are responsible for the reduction and capping of AgNPs.
The synthesised nanoparticles were also characterized with X-ray diffraction, energy-dispersive X-ray spectroscopy and scanning
electron microscopy. The X-ray diffraction study revealed the average size of the nanoparticles was 8.15 nm obtained
at pH 7, 51.11 nm at pH 9 and 40.64 nm at pH 11 and the peaks confirmed the face-centred crystalline lattice of the AgNPs.
AgNPs were further confirmed by EDX and SEM images. The synthesised nanoparticles were tested with gram positive
Staphylococcus aureus, Enterococcus faecalis and Bacillus circulans and gram-negative Escherichia coli and Pseudomonas
aeruginosa. The extract with AgNPs showed the highest antibacterial activity against Staphylococcus aureus. Hence, the
AgNPs from Turbinaria ornate was facile and innocuous synthesis which can serve as efficient antimicrobial agent against
human pathogens as well as water contaminating bacteria.
