Structural and optical characterizations of (Cu, Ce) iso-co-doped ZnO aerogel structures grown in supercritical ethanol

Abstract

Undoped, Ce-doped, Cu-doped and (Ce, Cu) co-doped ZnO aerogels were synthesized by sol–gel process in supercritical conditions of ethanol. [Cu]/[Zn] and [Ce]/[Zn] atomic ratios were fixed at 0.02 (2%). The aerogels were investigated without any additional treatments by using X-ray diffraction (XRD), UV–visible spectrophotometry, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), Fourier transforms infrared spectroscopy (FTIR) and photoluminescence spectroscopy. XRD results revealed that all the samples are well crystallized in hexagonal wurtzite structure. TGA and EDS measurements showed that highly pure aerogels are prepared. SEM analysis indicated that the morphology of the samples is dependent on Cu and Ce dopants. From UV–visible spectroscopy analyses, it was shown that the absorption and the band gap of the aerogels are strongly affected by Ce and Cu dopants. FTIR spectra demonstrated that co-doping induces a shift of Zn–O bond vibration band toward low wavenumbers. The room temperature photoluminescence spectra put into evidence that Ce and Cu doping influence the visible emission intensity. In particular, the iso-codoping leads to the appearance of a blue emission band at 443 nm.