Browsing by Author "Ramana Reddy, P."

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Effect of electrolyte concentration on morphological and photoluminescence properties of free standing porous anodic alumina membranes formed in oxalic acid
(Elsevier Ltd, 2020) Ramana Reddy, P.; Ajith, K.M.; Udayashankar, N.K.
The free-standing porous anodic alumina membranes (AAM) were prepared in oxalic acid by varying electrolyte concentration from 0.1 to 0.9 M with a constant potential of 40 V at 8 °C. The influence of electrolyte concentration on the morphological and optical features of AAM has been studied. Regularity ratio (RR) of AAM was measured using WSxM software, highest RR obtained for AAM formed in 0.3 M. From X-ray diffraction (XRD) analysis, it was found that prepared AAM were amorphous in nature. UV–Vis absorbance spectra reveal that absorbance bands slightly moves towards the higher wavelength side with increasing electrolyte concentration. Photoluminescence (PL) of AAM has been studied and related with RR of AAM. PL measurements of AAM exhibit strong PL peak in blue region, having a slight change with increasing electrolyte concentration. PL bands were originating from two kinds of oxygen-deficient defects (F and F+), their distributions were discussed on the basis of PL spectrum. © 2019 Elsevier Ltd
Effect of pore widening time on the structural aspects of self-organized nanopore arrays formed by anodization of aluminum in chromic acid
(Elsevier Ltd, 2016) Suchitra, S.M.; Ramana Reddy, P.; Udayashankar, N.K.
Anodic aluminium oxide (AAO) membranes were prepared by two-step anodization of aluminum formed in 0.3M chromic acid at the ambient temperature of ~ 30Â° C with anodization potential of 50 V. The radial average fast Fourier transform based study of nanopores has been carried out. The duration of the pore widening was varied from 0min to 60min in steps of 15 minutes. The effect of the pore widening time on the structural parameters of porous anodic alumina such as pore diameter (Dp), interpore distance (Dc), porosity (P) and pore density (n) were studied. It was observed that pore diameter and porosity increased with increasing pore widening time. Highly ordered and better nanopore array of AAO membrane was obtained for the sample anodized in chromic acid with 60 min pore widening time. Â© 2016 Elsevier Ltd.
Morphology and photoluminescence of nano-porous anodic alumina membranes obtained in oxalic acid at different anodization potentials
(Institute of Physics, 2020) Ramana Reddy, P.; K M, A.; Udayashankar, N.K.
Porous Anodic alumina (PAA) with highly ordered pore geometry serves as an ideal template for future development of nanodevices. In the present work, PAA was prepared by varying anodization potential from 10 to 50 V in oxalic acid at 8 °C with a constant electrolyte concentration of 0.3 M. The influence of anodization potential on the structural and photoluminescence (PL) properties of PAA has been studied. The effect of anodization potential on the main pore characteristics of PAA such as pore diameter, interpore distance, pore density, porosity and circularity was studied. It was observed that circularity of PAA was nearly equal to one in the case of anodization potential of 40 V. Highest regularity ratio (RR) obtained for PAA formed in 40 V and it was calculated by WSxM software. It was noticed that with increasing anodization potential there is a slight change in PL spectra of PAA and shows a strong PL peak in blue region. © 2020 The Author(s). Published by IOP Publishing Ltd
Structural and optical analysis of silver nanoparticles grown on porous anodic alumina membranes by electro-less deposition
(Elsevier Ltd, 2019) Ramana Reddy, P.; Ajith, K.M.; Udayashankar, N.K.
In this paper, we report our studies on silver nanoparticles which were synthesized inside the pores of porous anodic alumina (PAA) membranes by electro-less deposition method. The morphology of silver (Ag) nanoparticles was studied using FE-SEM. The result of FE-SEM showed that the Ag nanoparticles were spherical in shape and spread in uniform manner throughout the membrane. The elemental composition of Ag nanoparticles was investigated by Energy dispersive X-ray (EDX) spectroscopy. Structural characterization using X-ray diffraction pattern showed that PAA was amorphous and silver nanoparticles on PAA were crystalline in nature. Absorbance and luminescent behaviour of PAA and Ag-PAA were studied using UV-Visible and Photoluminescence (PL) spectra. PL spectra results revealed the presence of a strong peak at 392 nm in blue region, confirming the fact that the silver nanoparticles were embedded in the alumina template. Â© 2019 Elsevier Ltd.