Nibedita Paul

Rapid hydrothermal route to synthesize cubic-phase gadolinium oxide nanorods

An inexpensive fabrication route and growth mechanism is being reported for obtaining quality gadolinium oxide (Gd2O3) nanoscale rods. The elongated nanoscale systems, as produced via a hydrothermal process, were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), optical absorption spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and magnetic hysteresis measurements. XRD patterns of the nanorods, as-prepared from independent precursors of different pH, depict a cubic crystal phase and an average crystallite size of 5–6.5 nm. As revealed from HRTEM micrographs, diameter of the nanorods prepared at pH = 13.3 (∼ 7 nm) was much smaller than the rods prepared at pH = 10.8 (∼ 19 nm). However, the aspect ratio was more than double in the former case than the latter case. PL response was found to be dominated by defect mediated emissions, whereas Raman spectrum of a given specimen (pH = 10.8) has revealed characteristic Fg + Ag modes of cubic phase of Gd2O3 nanorods, apart from other independent modes. Furthermore, M ∼ H plot of the nanorod system (pH = 10.8) exhibited slight departure from the ideal superparamagnetic behaviour, with low remanence and coercive field values. The exploitation of one-dimensional Gd2O3 nanorods have immense potential in the production of advanced contrast agents, smart drives and also in making novel ferrofluids of technological relevance.

Characteristic spectroscopic properties of γ-irradiated rare-earth oxide-based ferrofluids

Ferrofluids are being considered as potential candidates both in basic and applied research owing to their novel optical and magneto-optical properties. We have synthesised surfactant (N-Cetyl-N,N,N-trimethylammonium bromide, CTAB)-coated nanoscale gadolinium oxide (Gd2O3) based ferrofluids and then irradiated by gamma (γ-) rays with doses in the range of 32 Gy–2.635 kGy. High-resolution transmission electron microscope (HRTEM) analysis shows that the particles have developed intragranular defects owing to γ-ray irradiation. Fourier transform infrared (FT-IR) and photoluminescence (PL) studies also support the formation of defect ordering upon irradiation. Further, PL study indicates abrupt change of the symmetry factor with increase in γ-dose. By viewing the nature of variation between relative intensity of the defect-related emission and dose-dependent symmetry factor, one can predict the tunability of PL response. A proper understanding of the PL response of the irradiated nanoscale rare-earth oxides would find new avenues for lasing and other optoelectronic/photonic devices.

Magnetically induced optical activity and dichroism of gadolinium oxide nanoparticle–based ferrofluids

The present work reports on magnetically induced optical activity (such as Faraday rotation and linear dichroism) of pristine and gamma-irradiated gadolinium oxide (Gd2O3) nanoparticle–based ferrofluids. The ferrofluids were produced by dispersing N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB)-coated ∼9-nm-sized Gd2O3 particles in a carrier fluid of ethanol. The ferrofluids were then irradiated with 1.25 MeV energetic gamma rays (dose: 868 Gy and 2.635 kGy). Irradiation-led formation of a number of point defects was revealed through high resolution electron microscopy. The interaction of light with the ionized point defects is believed to have caused substantial improvement in the magneto-optic response of irradiated magnetic fluids.

Augmented photocatalytic activity and luminescence response of Tb3+ doped nanoscale titania systems

The present work reports on the effect of Tb3+ doping on the luminescence and photocatalytic performance of nano-structured titania derived through a sol-gel route. X-ray diffraction patterns have revealed the existence of anatase phase with and without Tb3+ doping and with an improved orientation factor along (004) and (200) planes. Transmission electron microscopy and selective area electron diffraction studies, while exhibiting ample poly-crystallinity feature, have predicted an average particle size of ∼9 nm and ∼6 nm for the un-doped and 5% Tb3+ doped nano-titania samples; respectively. Apart from emissions accompanied by different types of defects, Tb3+ related transitions, such as, 5D3 → 7F5, 5D3 → 7F4, and 5D4 → 7F6 were identified in the photoluminescence spectra. Brunauer-Emmett-Teller surface area analysis, as carried out on a Tb3+ doped nano-titania system, has demonstrated a more-open hysteretic loop owing to significant difference of N2 adsorption/desorption rates. The photocatalytic activit...

Optical emission, vibrational feature, and shear-thinning aspect of Tb3+-doped Gd2O3 nanoparticle-based novel ferrofluids irradiated by gamma photons

The present work reports on the spectroscopic and rheological properties of un-exposed and gamma (γ-) irradiated rare earth (RE) oxide nanoparticle-based ferrofluids (FFs). The FFs were produced by dispersing surfactant coated terbium (Tb3+)-doped gadolinium oxide (Gd2O3) nanoparticles in the ethanol medium and later on they were subjected to energetic γ-irradiation (1.25 MeV) at select doses (97 Gy and 2.635 kGy). The synthesized RE oxide nanoparticles were of ∼7 nm size and having a cubic crystal structure, as predicted from transmission electron microscopy and x-ray diffraction studies. Fourier transformed infra-red (FT-IR) spectra showed an adequate blue shift of the Gd-O vibrational stretching mode from a wavenumber value of ∼558 cm−1, for the un-irradiated sample to a value of ∼540 cm−1 corresponding to the irradiated sample (2.635 kGy). In contrast, photoluminescence spectra have revealed modification of defect states along with Tb3+ assisted radiative transitions. The rheology measurements have il...

Temperature responsive gadolinium oxide nanoparticles for hyperthermia application

In this work we synthesized gadolinium oxide (Gd2O3) nanoparticles by a simple physico-chemical route. X-ray diffractogram (XRD) reveals cubic phase of Gd2O3 with preferred crystallographic orientation along (222) plane. The average crystallite size is found to be ∼ 3.5 nm. High resolution transmission electron microscopy (HRTEM) reveals particle size ∼9nm. UV-Vis spectra reveals two absorption peaks. The peak positioned at ∼285 and 350 nm is attributed to 8S7/2 → 6I7/2 transition of gadolinium (Gd) and the peak oxygen vacancy respectively. Room temperature PL spectra reveals various defect related emission. The prepared nanoparticles are also subjected to hyperthermia (cancer therapy) studies.