Researchers have used powdered pigeon pea to synthesize zinc oxide nanoparticles that can degrade a harmful dye under ultraviolet and visible light1. In addition, these nanoparticles exhibit antibacterial properties and can be used to sense dopamine, a vital neurotransmitter in the brain. These nanoparticles are potentially useful for developing photocatalytic semiconductors, antibacterial agents and dopamine sensors.
The researchers synthesized the zinc oxide nanoparticles by heating a mixture of zinc nitrate solution and pigeon pea powder. After removing impurities from the heated mixture, they produced milky-white spherical zinc oxide nanoparticles with diameters in the range 40–80 nm. They then measured the efficiency of these nanoparticles to degrade methylene blue, a harmful dye, under ultraviolet and visible light.
The researchers found that the nanoparticles’ ability to degrade the dye decreased with increasing dye concentration. The nanoparticles could effectively break down the dye when its concentration was five parts per million. The ultraviolet light caused the nanoparticles to generate free radicals, such as hydroxyl radicals, which in turn degraded the dye molecules.
The nanoparticles also exhibited antibacterial properties when exposed to four disease-causing bacteria — Klebsiella aerogenes, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.
The free radicals generated by the nanoparticles killed these bacteria. Furthermore, the nanoparticles were able to electrochemically oxidize dopamine, a vital brain chemical whose levels are depleted in Parkinson’s disease. “These results demonstrate the versatility of zinc oxide nanoparticles, which could potentially be used to make efficient photocatalysts, antibacterial agents and electrochemical sensors,” says G. Nagaraju, a senior author of the study.
