M. Deepa

Bio: M. Deepa is an academic researcher from All Saints' College. The author has contributed to research in topics: Crystal structure & Crystal. The author has an hindex of 7, co-authored 17 publications receiving 127 citations. Previous affiliations of M. Deepa include University of Kerala.

Structural, optical, photocatalytic, and antimicrobial activities of cobalt-doped tin oxide nanoparticles

Abstract: In this study, pure and Co-doped tin oxide (SnO2) nanoparticles were synthesized by sol–gel method, and the effect of Co-doping on the structural, optical, photocatalytic, and antimicrobial activities was studied. The prepared samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, UV–visible diffuse reflectance spectroscopy, and N2 adsorption/desorption analysis. The XRD patterns of all the samples are identified as tetragonal rutile-type SnO2 phase which is further confirmed by TEM analysis. The optical spectra showed redshift in the absorption edge of doped samples, which enhances their absorption toward the visible light region. The photocatalytic activity of all the samples was assessed by monitoring the degradation of methylene blue solution under daylight illumination, and it was found that the photocatalytic activity significantly increases with the increase in dopant concentration, which is due to the effective charge separation of photogenerated electron–hole pairs. The antimicrobial studies investigated against standard bacterial and fungal strains showed enhanced antimicrobial activity in doped samples, which can be attributed to the production of reactive oxygen species and large surface area of the nanoparticles.

Band gap narrowing and photocatalytic studies of Nd 3+ ion-doped SnO 2 nanoparticles using solar energy

Abstract: Pure and Nd3+-doped tin oxide (SnO2) nanoparticles have been prepared by the sol–gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive spectroscopy and UV–visible spectroscopy. The XRD patterns of all the samples are identified as tetragonal rutile-type SnO2 phase which is further confirmed by TEM analysis. Neodymium doping introduces band gap narrowing in the prepared samples and enhances their absorption towards the visible-light region. The photocatalytic activity of all the samples was evaluated by monitoring the degradation of methylene blue solution under day light illumination and it was found that the photocatalytic activity significantly increases for the samples calcined at 600 than 400°C, which is due to the effective charge separation of photogenerated electron–hole pairs. The efficiency of photocatalysts was found to be related to neodymium doping percentage and calcination temperature.

Influence of Fe dopant concentration and annealing temperature on the structural and optical properties of ZnO thin films deposited by sol–gel method

Abstract: Nanostructured Fe doped ZnO thin films were deposited onto glass substrates by sol–gel spin coating method. Influence of Fe doping concentration and annealing temperature on the structural, compositional, morphological and optical properties were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–Vis spectroscopy and photoluminescence (PL) measurements. XRD analysis showed that all the films prepared in this work possessed a hexagonal wurtzite structure and were preferentially oriented along the c-axis. Pure ZnO thin films possessed extensive strain, whereas Fe doped films possessed compressive strain. In the doped films, least value of stress and strain was observed in the 0.5 at.% Fe doped thin film, annealed at 873 K. Average crystallite size was not significantly affected by Fe doping, but it increased from 15.57 to 17.79 nm with increase in annealing temperature from 673 to 873 K. Fe ions are present in +3 oxidation state as revealed by XPS analysis of the 0.5 at.% Fe doped film. Surface morphology is greatly affected by changes in Fe doping concentration and annealing temperature which is evident in the SEM images. The increase in optical band gap from 3.21 to 3.25 eV, with increase in dopant concentration was attributed to Moss–Burstein shift. But increase in annealing temperature from 673 to 873 K caused a decrease in band gap from 3.22 to 3.20 eV. PL spectra showed emissions due to excitonic combinations in the UV region and defect related emissions in the visible region in all the investigated films.

Synthesis of nanocrystalline SnO2 powder byamorphous citrate route

Abstract: Nanocrystalline SnO2 has been synthesized by liquid mix technique using citric acid as the complexing agent. The tin oxide powder obtained at different calcination temperatures (773–1223 K) is characterized using powder X-ray diffraction (XRD), SEM, TEM, TG-DTG and UV spectroscopic techniques. The material obtained is nanocrystalline, having particle size in the range of 10–14 nm. The technique is cost-effective and yields the desired product at temperatures as low as 773 K.

Tin oxide nanostructured materials: an overview of recent developments in synthesis, modifications and potential applications

Abstract: Tin oxide nanostructures represent an important class of crystalline semiconducting nanomaterials. Being wide band gap (3.6 eV) n-type semiconductors, these materials have the inherent potential to be used as catalysts, sensors, anode materials etc. Moreover, these materials have permitted rational structure design and control over the band gap by suitable modifications. This structure–property relationship can be readily explored by taking advantage of the knowledge of their detailed electronic environment, which enables fine-tuning of their functionalities for desired applications.