Improvement of the optical and photocatalytic properties of ZnAl2O4: 1% La3+, x% Pb2+ nanoparticles synthesized by citrate sol-gel route

Abstract

Samples of pure zinc aluminate (ZnAl2O4) and doped both with lead (Pb2+) at different ratios (0, 0.5, 1, 1.5, 2 and 2.5% mol) and a constant amount of lanthanum (La: 1% mol), were prepared by the citrate sol-gel technique, and then annealed at 900°C for 2h. In order to study the structural, optical and thermal properties; different characterization methods were used, such as: powder X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC), TGA, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The Analyzes by XRD revealed the presence of the cubic single phase ZnAl2O4 for all samples, with a crystallites size between 19 and 25 nm. These results were confirmed using FTIR, Raman spectroscopy and SEM. Also, photocatalytic study for different samples of ZnAl2O4 shows that they can be used like as photocatalyst and good adsorbents for degradation of Hexamethyl crystallized violet dye in aqueous solution.

Insight into the crystalline structure, morphology, luminescence, and electrical conductivity of ZnAl2O4:xMn2+ (0 ≤ x ≤ 2.0 mol%) nanostructures

“…A small peak around 815 cm −1 and 808 cm −1 is related to vibrations modes of Al 3+ ion occupied at tetrahedral sites [10]. The band lies between 450 and 700 cm −1 certify the formation of the cubic structure of ZnAl 2 O 4 which is analogous to the XRD results [12]. The sharp peak at 681 cm −1 may correspond to the Al-O stretching type mode of vibrations in a tetrahedral coordination [16].…”

“…It may be due to the formation of impurities phase during their sample synthesis. Filali et al [12] noticed a similar band gap energy in transition metal ion (Pb 2+ ) doped ZnAl 2 O 4 samples and the absorption edge shift towards large wavelength with reported that increase in dopants concentration. Radha et al [17] reported the detailed characterization of Zn 1-x Cu x Al 2 O 4 (0.0 x 0.1) samples after synthesis by hydrothermal method.…”

“…The study suggests that Fe doping generates many empty and occupied energy states in between the valence and conduction band of host oxide. Filali et al [12] prepared the pure and 1% La 3+ ion (Lanthanum ions) with x% Pb 2+ doped ZnAl 2 O 4 after annealing the samples at 900 °C. They investigated the photocatalyst character of the prepared samples and showed that samples could be used as adsorbents from the degradation of many dyes.…”

“…These features are also depending upon the synthesis conditions and particular method of preparation. Nowadays many physical and chemical routes like co-precipitation, solid-state method, ball milling, sol-gel, combustion, and hydrothermal, are available in the literature to produce phosphorescence materials [7][8][9][10][11][12]. The citrate sol-gel approaches are free from all the above-mentioned drawbacks of the conventional methods and generate nanomaterials with enhanced features [19].…”