Abstract:
Graphene oxide is widely used to produce an antibacterial silver composite, but mostly
required toxic chemicals for production and they are comparatively expensive. The
present study was focused on synthesizing cost-effective less hazardous antibacterial
composite using vein graphite and silver. Silver graphite composites can be made using
various methodologies and those methods can affect the antibacterial property. Therefore,
in this study, silver graphite composite was synthesized by ultrasonication associated
chemical reduction method. Sri Lankan vein graphite was purified by the patented acid
leaching method, then surface modified with patented mild chemical oxidation method.
The silver-graphite composite was synthesized from an AgNO3 silver precursor with a
concentration of 0.00025 M, 0.001 M, 0.002 M by using tri-sodium citrate as a reducing
agent. X-ray Diffractometry analysis indicated that composite only consists of silver
nanoparticles and carbon in pure crystalline form. The composite was characterized by
Scanning Electron Microscopy. Nano-scale silver particles were seen deposited on the
surface of graphite. Antibacterial efficiency of the synthesized composites was analysed
using Escherichia coli and the test was carried out using the shake flask method. For
positive and negative controls, modified graphite and commercial antibiotic ofloxacin
were used respectively. The samples were drawn out with a one-hour time interval from 0
to 6 hours and the number of surviving colonies on Eosin Methylene Blue agar was
counted after 24 hours of incubation. The removal of the Colony Forming Unit for all
samples gave efficiency over 99 %. The Kruskal-Wallis test suggests that colony removal
depends on the time and concentration of AgNO3 used in the synthesized composite.
Therefore, this study suggested that silver-graphite composite synthesized via
ultrasonication associated chemical reduction can be used for E. coli as an effective
antibacterial agent.
Keywords: Graphite, Silver nanoparticles, Ultrasonication, Chemical reduction, Trisodium citrate
