Temperature dependent, shape variant synthesis of photoluminescent and biocompatible carbon nanostructures from almond husk for applications in dye removal

This work reports the synthesis of water soluble and photoluminescent carbon nanostructures (wsFCNS) from almond husk, a bio-waste. Effect of carbonization temperature on morphology of the synthesized carbon nanostructures is illustrated. Carbonization was carried out at three different temperatures ranging from 750 degrees C to 950 degrees C. Carbonization at higher temperature resulted in carbon nanodots having spherical morphology, while lower temperature resulted in rod shaped carbon nanostructures. Further, oxidative treatment of the as-synthesized carbon nanostructures imparts water solubility as well as photoluminescent properties over the visible to near infrared (NIR) regions of the electro-magnetic spectrum. The synthesized wsFCNS are non-toxic in nature and on direct interaction with erythrocytes, show less than 2% hemolysis. The synthesized wsFCNS were further explored for the adsorptive removal of p-nitrophenol (PNP), a model dye pollutant. The removal of PNP with wsFCNS follows pseudo first order adsorption kinetics. The proposed synthesis method could be easily scaled up for gram scale synthesis of various carbon nanostructures.