Selenium nanostructures: microbial synthesis and applications

Due to considerable impact on day-to-day life through the superior functions in energy, medicine, electronics, sensors and space industries, young researchers are being attracted towards the fields of nanotechnology and biotechnology. Selenium (Se) acts as an essential element in most organisms and is a beneficial nutrient in higher plants. Se nanostructures (NSs), i. e. nanospheres or nanoparticles (NPs) and nanowires (NWs), have unusual properties compared to their bulk counterparts. They have seven-fold lower toxicity than their other biologically utilizable materials. Several physical & chemical methods have been applied for the synthesis of Se NSs, but the development of eco-friendly routes is of considerable importance towards biological applications. Recently, microorganisms have been reported for the synthesis of Se NSs via the reduction of oxyions in anaerobic and aerobic environments. This review briefly proposes the recent developments in the microbial synthesis, characterization, and synthesis mechanism of Se NSs, along with their non-biological (solar, sensor, photocatalysis, etc.) and biological (anticancer, antioxidant, antiprotozoal, etc.) applications. Advantages of the Se NSs synthesized using green approaches, over the commonly used, are explored.