Green synthesis of palladium mixed with PdO nanoparticles by chemical bath deposition

Abstract

In this paper, we present preliminary experimental results in the synthesis of Pd mixed with PdO nanoparticles, grown by chemical bath deposition at ~80 °C. These samples were subjected to further thermal annealing treatment at ~1000 °C in air atmosphere. The properties of these compounds were investigated using the scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), X-ray diffraction (XRD), optical absorption and photoluminescence (PL) techniques. The SEM images for the grown sample show small dense and compact crystals. The FTIR spectra shows absorption bands associated with the OH− and CO32− ions. XRD diffractograms identified a face-centred cubic structure for metallic Pd, and traces of PdO in the tetragonal structure. The grain size ranges between ~33.91 nm and 86.92 nm, and ~33.96 nm–86.94 nm, respectively. The bandgap energy (~3.7 eV) showed a shift towards higher energy linked with the quantum confinement effect. PL spectrum displayed eight emission bands at the UV–Vis range (~363–524 nm). The time-resolved (delayed) PL spectra were achieved ~13.0 ns after excitation. PL signals presented two blue emission bands in the Vis region, and they were associated with native crystalline defects. These blue emission bands are explained by the vacancies and interstitial defects, mostly associated with surfaces or grain boundaries. Likewise, emission bands were investigated, applying the Maxwell–Boltzmann theoretical model and contrasting them with the experimentally registered signals. The PL dependence on trap density and the surface recombination velocity is discussed in the light of calculated lifetimes, PdA1 ~2.04 cm3 s−1 and PdA2 ~9.65 cm3 s−1.