Nanocomposite of bismuth ferrite and activated carbon for photocatalytic disinfection of microbe

Abstract

Microbial pathogenic contaminants such as bacteria, viruses and protozoa pose a major threat to environment human health that can cause deadly infectious diseases. One promising way of disinfection activity is by photocatalysis. Bismuth ferrite (BFO) has been regarded as an efficient visible-light driven material for photocatalyst due to its narrow band gap value. However, rapid recombination of photogenerated electron (e-) – hole (h+) pairs has limits its application as photocatalyst. To overcome this, BFO-activated carbon nanocomposites (BFO-AC) was synthesized by ultrasonication method with various ratio of activated carbon. Characterization using X-Ray diffraction analysis showed no change in crystallinity of BFO nanoparticles when activated carbon was incorporated into nanoparticles. By using the UV-Vis diffuse reflactance spectroscopy (UVDRS), the emission band of all BFO and BFO-AC nanocomposites were found within visible light range (400-700 nm) and BA (1:1.5) was having the lowest band gap value of 1.86 eV. Interestingly, after the addition of AC, the Brunauer–Emmett–Teller (BET) surface area of BA (1:0.5), BA (1:1) and BA (1:1.5) dramatically increased ie., 267.51 m2/g, 351.82 m2/g and 862.99 m2/g, respectively. BET results indicate BA (1:1.5) has the highest surface area due to its porous property. The field emission scanning electron micrograph has shown that BA (1:1.5) possess a better distribution and less agglomeration. The photoluminescence analysis demonstrated the intensity of all BFO-AC nanocomposites decreases compared to pristine BFO. The decrease of photoluminescence indicate the lower rate of electron (e-) – hole (h+) pairs recombination. Photocatalytic disinfection of S.aureus by AC, BFO, BA (1:0.5) and BA (1:1) were obtained within 150 min, 120 min, 120 min and 90 min, respectively. BA (1:1.5) exhibited the strongest bactericidal activity as a complete inactivation of S.aureus was achieved within 60 min. The surface and morphology of S.aureus were characterized by transmission electron microscopy analysis. Bacterial cell had a smooth and spherical shape before being irradiated under visible light. However, the bacterial cell were severely damaged and ruptured as the irradiation time increased, implying that S.aureus was killed. It is herein worth noting that the incorporation of AC onto BFO significantly improved the performance of photocatalytic disinfection of S.aureus under visible-light irradiation.