S.N. Bose National Centre for Basic Sciences

About: S.N. Bose National Centre for Basic Sciences is a facility organization based out in Kolkata, India. It is known for research contribution in the topics: Black hole & Gauge theory. The organization has 852 authors who have published 3149 publications receiving 46148 citations.

‘Green’ synthesis of metals and their oxide nanoparticles: applications for environmental remediation

Abstract: In materials science, “green” synthesis has gained extensive attention as a reliable, sustainable, and eco-friendly protocol for synthesizing a wide range of materials/nanomaterials including metal/metal oxides nanomaterials, hybrid materials, and bioinspired materials. As such, green synthesis is regarded as an important tool to reduce the destructive effects associated with the traditional methods of synthesis for nanoparticles commonly utilized in laboratory and industry. In this review, we summarized the fundamental processes and mechanisms of “green” synthesis approaches, especially for metal and metal oxide [e.g., gold (Au), silver (Ag), copper oxide (CuO), and zinc oxide (ZnO)] nanoparticles using natural extracts. Importantly, we explored the role of biological components, essential phytochemicals (e.g., flavonoids, alkaloids, terpenoids, amides, and aldehydes) as reducing agents and solvent systems. The stability/toxicity of nanoparticles and the associated surface engineering techniques for achieving biocompatibility are also discussed. Finally, we covered applications of such synthesized products to environmental remediation in terms of antimicrobial activity, catalytic activity, removal of pollutants dyes, and heavy metal ion sensing.

Electronic structure, chemical bonding, and optical properties of paraelectric BaTiO 3

Abstract: The electronic-energy band structure, site, and angular-momentum decomposed density of states (DOS) and charge-density contours of perovskite ${\mathrm{BaTiO}}_{3}$ in the paraelectric phase are calculated by the first-principles tight-binding linear muffin-tin orbitals method with the atomic-sphere approximation using density-functional theory in its local-density approximation. The calculated band structure shows a direct band gap of 1.2 eV at the \ensuremath{\Gamma} point in the Brillouin zone. The total DOS is compared to the experimental x-ray photoemission spectrum. From the DOS analysis, as well as charge-density studies, we conclude that the bonding between Ba and ${\mathrm{TiO}}_{3}$ is mainly ionic and that the ${\mathrm{TiO}}_{3}$ entities bond covalently. Using the projected DOS and band structure we have analyzed the interband contribution to the optical properties of ${\mathrm{BaTiO}}_{3}.$ The real and imaginary parts of the dielectric function and hence the optical constants (such as the reflectivity, refractive index, extinction coefficient, absorption coefficient, and the electron energy-loss spectrum) are calculated. The calculated spectra are compared with the experimental results for ${\mathrm{BaTiO}}_{3}$ at room temperature in the ferroelectric phase and are found to be in good agreement with the experimental data in the low-energy regions. The role of band-structure calculation as regards the optical properties of ${\mathrm{BaTiO}}_{3}$ is discussed.

Temperature dependence of the resistance of metallic nanowires of diameter≥15nm: applicability of Bloch-Grüneisen theorem

Abstract: We have measured the resistances (and resistivities) of Ag and Cu nanowires of diameters ranging from $15\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}200\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ in the temperature range $4.2--300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ with the specific aim of assessing the applicability of the Bloch-Gr\"uneisen formula for electron-phonon resistivity in these nanowires. The wires were grown within polymeric templates by electrodeposition. We find that in all the samples the resistance reaches a residual value at $T=4.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and the temperature dependence of resistance can be fitted to the Bloch-Gr\"uneisen formula in the entire temperature range with a well-defined transport Debye temperature $({\ensuremath{\Theta}}_{R})$. The values of the Debye temperature obtained from the fits lie within 8% of the bulk value for Ag wires of diameter $15\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ while for Cu nanowires of the same diameter the Debye temperature is significantly less than the bulk value. The electron-phonon coupling constants (measured by ${\ensuremath{\alpha}}_{\mathit{el}\text{\ensuremath{-}}\mathit{ph}}$ or ${\ensuremath{\alpha}}_{R}$) in the nanowires were found to have the same value as in the bulk. The resistivities of the wires were seen to increase as the wire diameter was decreased. This increase in the resistivity of the wires may be attributed to surface scattering of conduction electrons. The specularity $p$ was estimated to be about 0.5. The observed results allow us to obtain the resistivities exactly from the resistance and give us a method of obtaining the exact numbers of wires within the measured array (grown within the template).

Copper quantum clusters in protein matrix: potential sensor of Pb2+ ion.

Abstract: A one-pot synthesis of extremely stable, water-soluble Cu quantum clusters (QCs) capped with a model protein, bovine serum albumin (BSA), is reported. From matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, we assign the clusters to be composed of Cu5 and Cu13 cores. The QCs also show luminescence properties having excitation and emission maxima at 325 and 410 nm, respectively, with a quantum yield of 0.15, which are found to be different from that of protein alone in similar experimental conditions. The quenching of luminescence of the protein-capped Cu QCs in the presence of very low hydrogen peroxide concentration (approximately nanomolar, or less than part-per-billion) reflects the efficacy of the QCs as a potential sensing material in biological environments. Moreover, as-prepared Cu QCs can detect highly toxic Pb2+ ions in water, even at the part-per-million level, without suffering any interference from other metal ions.