Synthesis, Structural and Optical Properties of CUO Nanocrystals Embedded in Polyvinyl Chloride (PVC) Thin Films
Metal oxides constitut the most diverse class of materials having properties covering almost all aspects of
materials science and physics. Among these materials, copper oxide CuO is very promising. It is a p-type semiconductor
material with a band gap of about 1.8 eV. The growing interest granted to CuO is due to many potential applications that it
offers in the conversion of solar energy, optoelectronics and photocatalytic degradation of organic pollutants. It is also used
in consumer products such as pillowcases and socks because of its cosmetic and antimicrobial properties. In this work, we
studied the structural and optical properties of hybrid nanocomposite consisting of Polyvinyl chloride (PVC) as a matrix and
the nanocrystallites of the semiconductor CuO as a filler. The samples in the form of thin films were deposited on glass
substrates by the dip-coating technique using a colloidal solution prepared by dissolving the Polyvinyl chloride and
dispersing the CuO nanocrystallites. The CuO nanoparticles have been previously synthesized by the hydrothermal method.
The characterization of the films of the CuO-PVC nanocomposite by the X-ray diffraction (XRD ) has shown the
incorporation of the CuO nanocrystallites with monoclinic phase in the amorphous matrix or PVC. The resolution and
intensity of the diffraction peaks indicate a good crystallinity and a random orientation of the nanocrystallites of CuO. The
CuO nanocrystallite size was determined using the Debye-Scherrer formula and it was estimated to about 15 nm. Analysis
of the CuO-PVC nanocomposite by infrared spectroscopy confirmed the presence of the CuO cristallites in the PVC matrix
by revealing vibration modes which are specific to the Cu-O bond. The characterization by the measurement of the optical
absorption in the UV-Visible domain has allowed to observe a band at 372 nm which is attributed to the CuO
nanocrystallites because the PVC is optically transparent in the UV-Visible domain. The optical gap of the CuO-PVC
nanocomposite was estimated to 3.50 eV. Some discrepancies with respect to the gap of PVC and of bulk CuO are due to the
nanometric size of the CuO crystallites and to the effect of the interaction between the CuO nanocrtstallites and the PVC
matrix. This variation of the gap is a result of the new optical behavior of PVC when it is doped with CuO nanocrystallites.
Photoluminescence (PL) spectrum has showed two strong emission bands in the visible domain at 500 nm (green emission)
and 695 nm (red emission).
Keywords: CuO nanocrystals, Hydrothermal synthesis, CuO-PVC nanocomposite, Dip-coating, XRD, AFM, Infrared
spectroscopy, Optical absorption, Photoluminescence.