Interfacial polymerisation and functionalization of Cu-doped ZnO/polyaniline nanocomposites for optoelectronic application

Abstract

Copper-doped zinc oxide (5 % and 15 % Cu-doped ZnO) nanoparticles have been synthesised and incorporated into the polyaniline (PANI) matrix in an in-situ interfacial polymerisation of aniline with ammonium persulphate (APS) to obtain solution processable PANI/5 % and 15 % Cu-doped ZnO nanocomposites, without the aid of surfactants. The samples were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV–Vis spectroscopy, scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDX), and Four-point probe method. The XRD patterns of the nanoparticles revealed that they possess hexagonal wurtzite crystal structure of ZnO with slight shift of the diffraction peaks to higher 2θ values, and their estimated crystallite sizes were 27.165 and 32.450 nm, respectively. The estimated optical bandgaps of the nanoparticles decreased with Cu doping (3.09 and 2.85 eV at 5 and 15 % Cu doping, respectively) when compared with the standard value of pure ZnO (3.30 eV), consistent with the redshift in the absorption wavelength observed in the UV–Vis absorption spectra. In contrast to the significant reduction observed in the bandgaps of the nanoparticles, marginal changes were observed in the optical bandgaps of the PANI/Cu-doped ZnO nanocomposites with increasing nanoparticles loading ranging from 2.29 eV to 2.46 eV. The FTIR of the nanocomposite depicted the same characteristic peaks of PANI but were slightly shifted to higher wavenumbers attributed to the interaction between PANI and the nanoparticle, while the XRD patterns of the nanocomposites revealed the orthorhombic crystal structure of PANI and weak diffraction peaks of the nanoparticles. From the SEM/EDX, the observed elemental composition of the nanocomposite confirmed the presence of the nanoparticles within the PANI matrix. The electrical measurement revealed that the PANI/Cu-doped ZnO nanocomposites exhibited enhanced electrical conductivity, which reached maximum values at specific nanoparticles loadings. The obtained results and the solution processability of these nanocomposites make them suitable for applications in optoelectronics.