Anushree Roy

Bio: Anushree Roy is an academic researcher from Indian Institute of Technology Kharagpur. The author has contributed to research in topics: Raman spectroscopy & Raman scattering. The author has an hindex of 19, co-authored 103 publications receiving 1187 citations. Previous affiliations of Anushree Roy include Indian Institutes of Technology.

Optical Properties of Nanocrystalline Y2O3:Eu3+

Abstract: Optical properties of nanocrystalline red-emitting phosphor, Europium doped Yttria (Y$_{2}$O$_{3}$:Eu$^{3+})$, of average particle size 15 nm are investigated. The intensity of the strongest emission line at 612 nm is found to be highest in the nanocrystalline sample with 4 at. wt. % of Europium. The narrow electronic emission spectrum suggests a crystalline surrounding in this nanomaterial. We have estimated the strength of the crystal field parameter at the dopant site, which plays a crucial role in determining the appearance of the intense emission line. The equilibrium temperature of this system has also been calculated from the intensity ratio of Stokes and anti-Stokes Raman scattering. Though known for the bulk samples, our approach and consequent results on the crystalline nanomaterial of Y$_{2}$O$_{3}$:Eu$^{3+}$ provide a unique report, which, we believe, can be of considerable significance in nanotechnology.the intensity ratio of Stokes and anti-Stokes Raman scattering. Though known for the bulk samples, our approach and consequent results on the crystalline, defect/disorder free nanomaterial of Y2O3:Eu3+ provides a unique report which, we believe, can be of considerable significance in nanotechnology.

Quantitative analysis of hydrogenated diamondlike carbon films by visible Raman spectroscopy

Abstract: The correlations between properties of hydrogenated diamondlike carbon films and their Raman spectra have been investigated. The films are prepared by plasma deposition technique, keeping different hydrogen to methane ratios during the growth process. The hydrogen concentration, sp3 content, hardness, and optical Tauc gap of the materials have been estimated from a detailed analysis of their Raman spectra. We have also measured the same parameters of the films by using other commonly used techniques, such as sp3 content in films by x-ray photoelectron spectroscopy, their Tauc gap by ellipsometric measurements, and hardness by microhardness testing. The reasons for the mismatch between the characteristics of the films, as obtained by Raman measurements and by the above mentioned techniques, have been discussed. We emphasize on the importance of the visible Raman spectroscopy in reliably predicting the above key properties of diamondlike carbon films.

Optical properties of nanocrystalline Y2O3:Eu3+

Abstract: Optical properties of nanocrystalline red-emitting phosphor, europium-doped yttria (Y2O3:Eu3+), of average particle size of 15nm are investigated. The intensity of the strongest emission line at 612nm is found to be highest in the nanocrystalline sample with 4at.wt% of europium. The narrow electronic emission spectrum suggests a crystalline surrounding in this nanomaterial. We have estimated the strength of the crystal-field parameter at the dopant site, which plays a crucial role in determining the appearance of the intense emission line. The equilibrium temperature of this system has also been calculated from the intensity ratio of Stokes and anti-Stokes Raman scattering. Though known for the bulk samples, our approach and consequent results on the crystalline nanomaterial of Y2O3:Eu3+ provide a unique report, which, we believe, can be of considerable significance in nanotechnology.

Quantitative Analysis of Hydrogenated DLC Films by Visible Raman Spectroscopy

Abstract: The correlations between properties of hydrogenated diamond like carbon films and their Raman spectra have been investigated. The films are prepared by plasma deposition technique, keeping different hydrogen to methane ratio during the growth process. The hydrogen concentration, sp$^3$ content, hardness and optical Tauc gap of the materials have been estimated from a detail analysis of their Raman spectra. We have also measured the same parameters of the films by using other commonly used techniques, like sp$^3$ content in films by x-ray photoelectron spectroscopy, their Tauc gap by ellipsometric measurements and hardness by micro-hardness testing. The reasons for the mismatch between the characteristics of the films, as obtained by Raman measurements and by the above mentioned techniques, have been discussed. We emphasize on the importance of the visible Raman spectroscopy in reliably predicting the above key properties of DLC films.

Core/Shell semiconductor nanocrystals.

Abstract: Colloidal core/shell nanocrystals contain at least two semiconductor materials in an onionlike structure. The possibility to tune the basic optical properties of the core nanocrystals, for example, their fluorescence wavelength, quantum yield, and lifetime, by growing an epitaxial-type shell of another semiconductor has fueled significant progress on the chemical synthesis of these systems. In such core/shell nanocrystals, the shell provides a physical barrier between the optically active core and the surrounding medium, thus making the nanocrystals less sensitive to environmental changes, surface chemistry, and photo-oxidation. The shell further provides an efficient passivation of the surface trap states, giving rise to a strongly enhanced fluorescence quantum yield. This effect is a fundamental prerequisite for the use of nanocrystals in applications such as biological labeling and light-emitting devices, which rely on their emission properties. Focusing on recent advances, this Review discusses the fundamental properties and synthesis methods of core/shell and core/multiple shell structures of II-VI, IV-VI, and III-V semiconductors.

Raman spectroscopy of biological tissues

Abstract: This article reviews some of the recent advances in Raman spectroscopy, in areas related to natural tissues and cell biology. It summarizes some of the most widely used peak frequencies and their assignments. The aim of this study is to prepare a database of molecular fingerprints, which will help researchers in defining the chemical structure of the biological tissues introducing most of the important peaks present in the natural tissues. In spite of applying different methods, there seems to be a considerable similarity in defining the peaks of identical areas of the spectra. As a result, it is believed that preparing a unique collection of the frequencies encountered in Raman spectroscopic studies can lead to significant improvements both in the quantity and quality of spectral data and their outcomes. This article is the first review of its kind to provide a precise database on the most important Raman characteristic peak frequencies for researchers aiming to analyze natural tissues by Raman ...

A First Principles Study

Abstract: The electronic density of states (DOS) and magnetic moments of rare-earth antimonides (NdVSb3) has been studied by the first principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange-correlation potential, the GGA+U method is used. The effective moments of NdVSb 3 B was found to be 4.50 . The exchange-splittings of V-3d state electrons and 4f-states of Nd atoms were analyzed to explain the magnetic nature of these systems. The V atom plays a significant role on the magnetic properties due to the hybridization between V-3d and Sb-5p state orbitals. The results obtained are compared and found to be in qualitative agreement with the available results.