Structural and optical characterization of WO3 and WO3/rGO nanocomposites synthesized by a simple chemical method

Fri, 28 Mar 2025 00:00:00 -0600

The chemical structure and morphology of inorganic metal oxides have attracted increasing interest because of these parameters directly influence their sensing properties. Additionally, the incorporation of reduced graphene oxide (rGO) favors an increase in the sensitivity of these composites. Tungsten oxide (WO₃) and tungsten oxide/reduced graphene oxide (rGO) nanocomposites with 3 w% (WO₃/rGO) were prepared via reflux method. X-ray Diffraction (XRD), Raman Spectroscopy and Scanning Electron Microscopy (SEM) techniques were used to study the crystalline structure and morphology properties of the prepared WO₃ and WO₃/rGO nanocomposites. The diffraction pattern of WO₃ shows the diffraction peaks of tungsten trioxide hydrate (WO₃(H₂O), tungstite) with orthorhombic structure; however, with the annealing at 500 °C occur a phase transformation to the monoclinic structure. The incorporation of rGO into the WO₃ matrix did not modify its monoclinic chemical structure. The crystallite size of the reduced composites increases as the percentage of rGO increases. Furthermore, the optical properties of WO₃/rGO nanocomposites were characterized by Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS). The band gap of WO₃/rGO composites varies between 3.32 and 3.35 eV. SEM images of WO₃ show structures of nanoplates with rectangular transversal section.

Self-organized gold nanoparticles on SiO2 surface nanopatterns induced by MeV ion implantation

Tue, 28 Jan 2025 00:00:00 -0600

Ion implantation at MeV energies leads to the formation of surface nano-patterns on diverse kinds of materials, such as metals, dielectrics, and semiconductors. Furthermore, under oblique irradiation, the implanted ions are preferentially deposited on the crests of such patterns. Based on previous experimental results, in this work the formation of gold nanoparticles is produced and found to be organized onto prepatterned surfaces as produced by 1.8 MeV Au ion implantation on SiO2 substrates at an impinging angle of 45°. The ion implantation was performed with an ion beam current of 400 nA for a total ion fluence between 0.2 ×10¹⁷ cm^-2 and 2.0 ×10¹⁷ cm^-2. After implantation, to assist gold nanoparticle nucleation, substrates were annealed at 1000 °C. The surface morphology and topography of the implanted substrates were analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. For the lowest fluences (0.4 - 0.8 ×10¹⁷ cm^-2), the formation of isolated surface structures on a flat background was observed whose morphology mimics the exoskeleton of a bug. According to SEM-EDS analysis, the formation of gold nanoparticles on the exoskeleton of the bugs was observed. For intermediate fluences (0.8 - 1.4 ×10¹⁷ cm^-2), a ripple background now appears and begins to surround the bugs. At the highest fluences (1.4 - 2.0 ×10¹⁷ cm^-2), the surface shows only a ripple pattern. In this last case, the gold nanoparticles are formed along the crests of the surface ripples. Finally, the optical absorption of the samples (except the one corresponding to the lowest fluence) shows the presence of a localized surface plasmon resonance (LSPR) in the wavelength region of 520 - 540 nm, suggesting the presence of gold nanoparticles.

Superficies y Vacío

Structural and optical characterization of WO3 and WO3/rGO nanocomposites synthesized by a simple chemical method

Self-organized gold nanoparticles on SiO2 surface nanopatterns induced by MeV ion implantation