Polyaniline embedded green copper oxide (Cu2O/PANI) nanocomposite has been synthesized through in situ chemical polymerization method in acidic medium at room temperature. The structural, optical, and magnetic properties of Cu2O/PANI nanocomposite were investigated through Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectra (UV-Vis spectra), scanning electron microscopy (SEM), photoluminescence spectra (PL), and vibrating sample magnetometer (VSM). FTIR spectra confirmed the formation of Cu2O/PANI composite through the shifting of vibrational peaks of PANI and green Cu2O nanoparticles at 825, 1142, 1299, 1499, 1573？cm？1 and 695？cm？1 respectively. SEM analysis revealed that many aggregations of well-separated irregular shape of Cu2O nanoparticles with diameter about 15–40？nm exist in the composite matrix. Optical absorbance studies further confirmed the formation of composite through the blue shift of absorption peaks of PANI and diminishing intensity peak of Cu2O. Cu2O/PANI nanocomposite demonstrates semiconducting as well as diamagnetic behavior like PANI and Cu2O nanoparticles. The nanocomposite exhibits high relative photoluminescence intensity in blue as well as green-yellow region of visible spectrum. The optical band gap value from absorption coefficient data is found to be 3.23？eV. 1. Introduction In recent years, polymers with special functional groups are used as specific stabilizers for the synthesis of polymer based nanocomposites with different properties [1, 2]. Polymer and its nanocomposites possess unique characteristics when compared to other bulk materials. The structure of its nanocomposites is improved and controls their size range [3]. The combination of conducting polymers with metal oxide is used as alternate materials for optoelectronic applications. Amongst the family of conducting polymers, polyaniline is the most studied conducting polymer for the past 20 years due to its facile synthesis [4], chemical and environmental stability [5], and excellent electronic properties. Semiconducting nature of polyaniline is used to produce nanocomposite with inorganic metal oxide and such materials facilitate optical measurements. However, the synthesis of monodispersed metal oxide nanoparticles into the polymer matrix of its nanocomposites with adjustable sizes and protected from photooxidation is a big challenge. In particular, it is difficult to generate highly enhanced luminescence in such polymer and its metal oxide nanocomposites systems. Luminescence from the polymer embedded Cu2O nanoparticles is greatly
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