Herein, we carefully investigated the Fe³⁺ doping effects on the structure and electron distribution of Cr₂O₃ nanoparticles using X-ray diffraction analysis (XRD), maximum entropy method (MEM), and density functional theory (DFT) calculations. We showed that increasing the Fe doping induces an enlargement in the axial ratio of c/a, which is associated with an anisotropic expansion of the unit cell. We found that as Fe³⁺ replaces Cr in the Cr₂O₃ lattice, it caused a higher interaction between the metal 3d states and the oxygen 2p states, which led to a slight increase in the Cr/Fe–O1 bond length followed by an opposite effect for the Cr/Fe–O2 bonds. Our results also suggest that the excitations characterize a well-localized bandgap region from occupied Cr d to unoccupied Fe d states. The Cr₂O₃ and Fe-doped Cr₂O₃ nanoparticles behave as Mott–Hubbard insulators due to their band gap being in the d−d gap, and Cr 3d orbitals dominate the conduction band. These findings suggest that the magnitude and the character of the electronic density near the O atom bonds in Cr₂O₃ nanoparticles are modulated by the Cr–Cr distances until its stabilization at the induced quasi-equilibrium of the Cr₂O₃ lattice when the Fe³⁺ doping values reaches the saturation level range.

In this work, silver atoms were deposited by ion sputtering on the surface of diglycidyl ether of bisphenol A (DGEBA) epoxy resin cured at 150 °C for 6 hours in air. The films of DGEBA and its precursors were characterized by Raman spectroscopy to identify the main functional groups and their relationship with the deposited silver atoms. Silver thin films of 5, 10, 15 and 20 nm were deposited on the epoxy resin at room temperature. Both the initial film of DGEBA and the subsequent silver thin film were analyzed by Atomic Force Microscopy (AFM) in the non-contact mode. Silver thin films were also analyzed using X-ray diffraction (XRD) at room temperature. The AFM results showed the formation of silver crystallites on the surface of DGEBA at very low coverage whereas XRD indicated that most of them had their main axis aligned to the normal of the surface. An increase in the coverage led to an increase in the grain size as indicated by AFM. However, XRD results indicated that the crystallite size remained almost constant while the appearance of peaks corresponding to other crystalline orientations suggests the coalescence of the original crystallites and an increase in size of the more dense planes, namely [111].

Nanocrystals of Zn _1−x M _x O ( M =Mn, Co, or Ni) were grown using proteic sol-gel process, and the crystalline phases were identified by X-ray diffraction and Rietveld refinement. The nanocrystals have hexagonal wurtzite structure, with space group P 63 mc . The insertion of Mn ²⁺ in the place of Zn ²⁺ provoked an increase in the size of the nanocrystals, and the insertion of Co ²⁺ or Ni ²⁺ caused a reduction in the sizes of the nanocrystals, as compared to pure ZnO. This occurred because these three transition metals have very different ionic radii (Co ²⁺ =0.58 A˚, Mn ²⁺ =0.66 A˚, Ni ²⁺ =0.55 A˚, and Zn ²⁺ =0.60 A˚).

ZnO nanocrystals with three different morphologies have been synthesized via a simple sol-gel-based method using Brosimum parinarioides (bitter Amapá) and Parahancornia amapa (sweet Amapá) latex as chelating agents. X-ray diffraction (XRD) and electron diffraction patterns (SAED) patterns showed the ZnO nanocrystals were a pure hexagonal wurtzite phase of ZnO. XRD-based spherical harmonics predictions and HRTEM images depicted that the nanocrystallites constitute pitanga-like (~15.8 nm), teetotum-like (~16.8 nm), and cambuci-like (~22.2 nm) shapes for the samples synthesized using bitter Amapá, sweet Amapá, and bitter/sweet Amapá chelating agent, respectively. The band gap luminescence was observed at ~2.67–2.79 eV along with several structural defect-related, blue emissions at 468–474 nm (V_O, V_Zn, Zn_i), green emissions positioned at 513.89–515.89 (h-${\mathrm{V}}_{\mathrm{O}}^{+}$), and orange emission at 600.78 nm (${\mathrm{V}}_{\mathrm{O}}^{+}$–${\mathrm{V}}_{\mathrm{O}}^{++}$). The best MB dye removal efficiency (85%) was mainly ascribed to the unique shape and oxygen vacancy defects found in the teetotum-like ZnO nanocrystals. Thus, the bitter Amapá and sweet Amapá latex are effective chelating agents for synthesizing distinctive-shaped ZnO nanocrystals with highly defective and remarkable photocatalytic activity.