Sriparna Chatterjee

Transport and magnetic properties of La0.7Pb0.3MnO3+x Ag (x=0−20 wt %) nanocomposites

Magnetization and transport properties of La0.7Pb0.3MnO3+x Ag (x=0−20 wt %) nanocomposites have been reported. In this Ag-containing colossal magnetoresistive (CMR) La0.7Pb0.3MnO3 composite (referred to as CMR-Ag), conductivity (σ) and metal–insulator transition temperature (Tp) increase with increasing Ag. Electron microscopy and elemental mapping indicated a uniform distribution of Ag nanoparticles/clusters. The enhancement of Tp is accompanied by a reduction of the c-axis lattice constant. Coexistence of interfacial tunneling with intrinsic transport behavior has been observed at the grain boundaries in the samples with a higher (⩾10 wt %) Ag content. Due to the presence of nonmagnetic Ag in the ferromagnetic La0.7Pb0.3MnO3 material, dc magnetization decreases but the corresponding Tp increases. In the low-temperature (T<Tp) phase, resistivity data follow a T2 dependent behavior for the samples with higher Ag concentration (x⩽5 wt %). On the other hand, for lower Ag (⩽5 wt %) containing samples, a T2.5...

Efficient photocatalytic degradation of rhodamine B dye by aligned arrays of self-assembled hydrogen titanate nanotubes

We show that an aligned array of hydrothermally grown, multiwalled hydrogen titanate (H2Ti3O7) nanotubes—anchored to both faces of a metallic Ti foil—acts as an efficient photocatalyst. We studied the degradation of rhodamine B dye in the presence of the nanostructured photocatalyst under UV irradiation, by monitoring the optical absorption of the dye. Rhodamine B was chosen as a representative—and particularly harmful—industrial pollutant dye. The inner and outer diameters of the H2Ti3O7 nanotubes were 5 nm and 10 nm, respectively. The nanotube array catalyst is recyclable and structurally stable. Most importantly, it shows comparable or higher photodecomposition rate constant than those of both H2Ti3O7 nanotube powder and P-25 (Degussa). The enhanced photocatalytic performance may be ascribed to the nanotube array having a superhydrophilic surface with a high accessible surface area.

Conjugation of cytochrome c with hydrogen titanate nanotubes: novel conformational state with implications for apoptosis

We show that hydrogen titanate (H(2)Ti(3)O(7)) nanotubes form strongly associated reversible nano-bio-conjugates with the vital respiratory protein, cytochrome c. Resonance Raman spectroscopy along with direct electrochemical studies indicate that in this nano-bio-conjugate, cytochrome c exists in an equilibrium of two conformational states with distinctly different formal redox potentials and coordination geometries of the heme center. The nanotube-conjugated cytochrome c also showed enhanced peroxidase activity similar to the membrane-bound protein that is believed to be an apoptosis initiator. This suggests that such a nanotube-cytochrome c conjugate may be a good candidate for cancer therapy applications.

Facile synthesis of single crystalline n-/p-type ZnO nanorods by lithium substitution and their photoluminescence, electrochemical and photocatalytic properties

Both n- and p-type single crystalline ZnO nanorods were successfully synthesized via a facile one step solvothermal method by lithium substitution. It was observed that substitution of Li is critical for the formation of n-type or p-type ZnO nanorods. The detailed formation mechanism indicates that the transition from n-type behavior to p-type behavior is due to the presence of defect states and lithium incorporation in the lattice. Using photoluminescence (PL) measurements, the role of defect states in generating the p-type or n-type nature of ZnO nanorods via Li substitution has been analyzed. Furthermore, the photocatalytic performances of the as-prepared ZnO nanorods have been investigated towards the degradation of rhodamine B and methyl orange, and the results demonstrate that the n-type ZnO nanorods behave as an excellent photocatalyst compared to the p-type ZnO nanorods owing to their higher charge carrier density.

The influence of surface topography on the field emission of nanostructured copper oxide thin films grown by oblique incidence deposition

We report the surface morphology dependent enhanced field electron emission properties of copper oxide thin films, which are sputter deposited at two different incidence angles. The turn-on field is as low as 1.3 V μm−1 for obliquely deposited thin film, with an enhancement factor of ∼5144. The emission current also shows good stability. With the help of finite element method analysis, we show that the enhanced field emission behaviour is due to the special surface topography of obliquely deposited film. While for the normally deposited film the screening effect plays an important role and thereby condemning the electron emission performance. We expect to have a general applicability of this study in the design of thin film based electron emitters.

Array of Cu2O nano-columns fabricated by oblique angle sputter deposition and their application in photo-assisted proton reduction

Nano-columnar arrays of Cu2O were grown by the oblique angle sputter deposition technique based on the self-shadowing principle. The as-grown nano-columnar samples are oriented along {111} direction, and they are highly transmitting in the visible range with a low reflectance. In this work, we show the photo-electrochemical activity of nano-columnar array of Cu2O, which shows a higher (∼25%) photocurrent density and a two-fold enhancement in the incident-to-photon conversion efficiency as compared to continuous thin film of Cu2O in photo-assisted proton reduction type reaction. The improvement in electrochemical activity of nano-columnar Cu2O photocathode can be attributed to the change in morphology, crystal structure, as well as electrical property, which shows a higher degree of band bending, increased donor carrier (e−) density and lower width of space charge region as revealed by capacitance measurements and Mott-Schottky analysis.

Field emission from hydrogen titanate nanotubes

Hydrothermally synthesized hydrogen titanate (H2Ti3O7) nanotube meshes and arrays exhibit excellent field emission characteristics. The turn-on field is as low as 1.4 V μm−1 for the mesh and 2.6 V μm−1 for the array, while the electric field corresponding to an emission current density of 10 μA cm−2 is 2 V μm−1 (mesh) and 3.8 V μm−1 (array). The H2Ti3O7 nanotube mesh has one of the lowest reported turn-on voltages and highest enhancement factors. The emission current also shows good long term stability. We attribute the efficient field emission to the presence of mid-gap states arising from the negative surface charge on the H2Ti3O7 nanotubes.

Multifunctional behavior of ZnO supported Bi1−xDyxFeO3 nanorods

We have shown that it is possible to realize multifunctional Bi1−xDyxFeO3 (BDFO) nanorods by coating BDFO film on ZnO nanorods. These BDFO coated ZnO (BDFO/ZnO) nanorods are obtained by depositing BDFO on vertical ZnO nanorods grown on Si substrate by using pulsed laser deposition technique. The BDFO/ZnO rods exhibit coexistence of ferroelectric and ferromagnetic properties with significant coupling between two order parameters at room temperature. Moreover, the piezoresponse of these nanorods is found to be even superior to pure ZnO nanorods. The unique multifunctional behavior of these nanorods at room temperature could find different applications in nanodevices like sensors, power generators, etc. with ease and flexibility in operation.

Temporal wetting property of “Micro” versus “Nano” rods of ZnO grown using the pressure dependent aqueous solution method

We report the role of pressure dependent growth of micro and nanorod arrays of zinc oxide by an aqueous solution route. Initially, both micro- and nano-ZnO surfaces show hydrophobicity with water contact angles of 140° ± 3° and 130° ± 3°, respectively. We find that the temporal decay in water contact angle is faster in the case of the nanorod surface compared to that of the microrod surface. While for the microrod surface, the small change in contact angle happens due to water droplet evaporation, the significant change in the particular case of the nanorod surface is attributed to the capillary action.

A facile approach for the synthesis of copper(II) myristate strips and their electrochemical activity towards the oxygen reduction reaction

The usage of an inexpensive and non-noble metal-based material as the electrocatalyst in the oxygen reduction reaction has gained great attention for fuel cell application. In this report, a facile approach has been developed for the synthesis of copper myristate strips. The as-synthesized material has demonstrated its electrocatalytic activity towards oxygen reduction reaction. This study opens up a new scope for the use of straight chain copper complexes as electrocatalysts. The interesting performance of the copper myristate strips holds promising application in energy conversion devices.