Copper nanoparticle biosynthesis and characterization utilizing a bioflocculant from Kytococcus sedentarius

Abstract The application of microbial flocculants in nanoparticle synthesis is attracting scientists to utilize them due to their eco-friendliness. This study was mainly focused on biosynthesizing and characterizing copper nanoparticles from a non-pathogenic microorganism Kytococcus sedentarius to produce bioflocculant. The formed copper nanoparticles (CuNPs) were analyzed using UV–vis spectroscope (UV–vis), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD) and thermo-gravimetric analysis (TGA). After extraction and purification, 2.4 g was produced from bioflocculant in a 1 L culture fermentation mixture. During CuNP biosynthesis, a blue color change was obtained after 24 h of incubation indicating their successful formation. A variety of elements namely, C, O, Cu, P, Ca, Mg and Al were found in the as-synthesized CuNPs with 25.23 % (wt) carbon, 20.13 % (wt) of oxygen and 23.37 % (wt) of Cu element. SEM and TEM images of the product depicted it to be agglomerated with different size and shapes. The TGA showed the CuNPs to be thermal stable as 70 % weight was retained at 900 °C with 30 % weight lost. FT-IR spectrum of the biosynthesized CuNPs contains a variety of functional groups related to sugar and proteins namely, hydroxyl, amine, carboxyl groups and a typical Cu–O bond at 559 cm −1 . The crystallite size was estimated to be 28.3 nm, which is in line with JCPDS card no. 89–5899 of copper standard confirming the correct peak orientation. UV–vis analysis revealed the absorption peak to be 275 nm which confirms synthesis of the CuNPs using a bioflocculant.