Influence of Electrolyte Composition on the Photoluminescence and Pore Arrangement of Nanoporous Anodic Alumina

Abstract

Influence of oxalic and sulfuric acid electrolyte-mixture on the morphological and photoluminescence (PL) properties of Nanoporous Anodic Alumina (NAA) is reported. Two-dimensional fast Fourier transform of the FESEM images was employed to investigate the pore-arrangement of mixed electrolyte NAA. Pore-properties increased with sulfuric ion concentration and pore-regularity was highest with 1.4M sulfuric acid. Pore regularity is a direct consequence of sulfuric acid concentration at a fixed oxalic acid concentration (0.3M). No obvious PL was observed for NAA prepared in sulfuric acid while those prepared using mixed electrolytes showed strong blue emission. This broad PL comprised of four Gaussian curves (273, 316, 360 and 460nm). First two bands could be ascribed to luminescent centers transformed from sulfuric and oxalic impurities, respectively while the latter two are attributable to oxygen vacancies (F + and F-centers). PL bands blue-shifted with increasing intensities at higher sulfuric acid concentration. Emission intensity and wavelength could be tailored by varying the electrolyte composition.

The microstructure and optical properties of novel Al2O3–Ag composite coating

“…It seems that the acid concentration has been decreased in the anodizing solution by addition of the colloidal solution of Ag/SDS/water. Subsequently, ion mobility has been decreased during the anodizing process [22]. According to Figure 2, SDS anionic surfactant changes the surface charge of Ag-nanoparticles into negative value.…”

Recent Progress in the Fabrication and Optical Properties of Nanoporous Anodic Alumina

“…Figure 10a shows typical PL emission spectra obtained from NAA prepared in oxalic and phosphoric acids. The observed PL depends characteristically on the electrolyte composition [253][254][255][256][257], pore etching treatments [227], and high-temperature annealing [211,221,258]. There exist mainly two ideas related to the origin of PL in NAA.…”

“…Recently, Choudhari et al studied the effect of mixing of oxalic acid and sulfuric acid electrolytes on the PL, and morphological properties of NAA prepared in the mixture electrolytes [254]. When excited by λ ex = 250 nm, the samples prepared in mixture samples showed PL in the range 350-500 nm due to F and F + centers, with additional peaks at 273 and 316 nm belonging to the luminescent centers transformed from sulfuric and oxalic ions, respectively.…”

Morphology and photoluminescence of nano-porous anodic alumina membranes obtained in oxalic acid at different anodization potentials

“…The best of our knowledge, the porous and compact alumina is formed by the anodization of aluminium in acidic solutions like H 2 SO 4 , H 2 C 2 O 4 and H 3 PO 4 [19][20][21] and in neutral solutions (boric, decanedioic, hexanedioic acid, etc) [22,23]. The effect of anodization process parameters such as anodization duration, temperature [24] and electrolyte composition [25] on the pore mechanism of PAA already studied. The main pore parameters of PAA such as pore diameter, interpore distance and porosity depends on the anodizing conditions like nature of the electrolyte concentration, anodization potential, duration and temperature [11].…”