Sachil Sharma

Induction heating studies of Fe3O4 magnetic nanoparticles capped with oleic acid and polyethylene glycol for hyperthermia

Fe3O4 magnetic nanoparticles (Fe3O4-MN) capped with either oleic acid (Fe3O4-OA-MN) or polyethylene glycol (Fe3O4-PEG-MN) were prepared by a co-precipitation method. From X-ray diffraction studies, the average crystallite sizes of Fe3O4-MN, Fe3O4-OA-MN and Fe3O4-PEG-MN were found to be 12, 6 and 8 nm, respectively. A reduction in the agglomeration of particles was observed when the magnetic nanoparticles (MN) were capped with oleic acid (OA) and polyethylene glycol (PEG), as confirmed by a transmission electron microscopy study. Magnetization of these MN was almost zero at room temperature in the absence of an applied magnetic field, indicating their superparamagnetic behavior. Magnetization was lower and the superparamagnetic fraction was higher for Fe3O4-OA-MN and Fe3O4-PEG-MN compared to Fe3O4-MN studied using a Mossbauer spectrometer. Compared to the control, an increased killing (35%) was observed in human breast cancer cells (MCF7) after Fe3O4-OA-MN treatment, which was further enhanced (65%) under induction heating conditions. However, MCF7 cells treated with Fe3O4-MN or Fe3O4-PEG-MN showed 5–10% killing after induction heating. These results showed the characterization of MN with different lipophilicity and suggests their suitability for hyperthermia applications in cancer therapy.

Synthesis and self-assembly of monodisperse CoxNi100−x (x = 50, 80) colloidal nanoparticles by homogenous nucleation

Self-assembled monodisperse fcc Co(50)Ni(50) and Co(80)Ni(20) alloy nanoparticles with the average size of 25 and 8 nm respectively are synthesized by reductive thermal decomposition of Co(II)(acac)(2) and Ni(II)(acac)(2) in the presence of surfactants such as oleic acid, oleylamine and trioctylphosphine. The mechanism for formation of colloidal CoNi alloy nanoparticles is explored in this work. The CoNi nanoparticles with high atomic percentage of nickel are found to be more stable and non-interacting. The Co(50)Ni(50) nanoparticles are superparamagnetic at room temperature and exhibit superparamagnetic to ferromagnetic transition at the blocking temperature (T(b)) ∼130-160 K, whereas Co(80)Ni(20) nanoparticles are ferromagnetic at room temperature with low coercivity (∼20 Oe). The magnetization value of Co(80)Ni(20) nanoparticles is found to be high as compared to Co(50)Ni(50) nanoparticles due to high atomic percentage of cobalt. Interestingly, size of CoNi alloy nanoparticles with high nickel content is found to be large, which indicates that nickel nuclei act as catalysts for the growth of CoNi alloy nanoparticles in the reaction.

Synthesis of self-assembled monodisperse 3 nm FePd nanoparticles: Phase transition, magnetic study, and surface effect

Self-assembled monodisperse 3 nm face centered cubic (fcc) FePd particles are synthesized by modified polyol method using polyethylene glycol-600 as a reducing agent and oleic acid and oleyl amine as surfactants. As-synthesized FePd nanoparticles are superparamagnetic at room temperature and ferromagnetic below blocking temperature (TB=21 K). The significant enhancement in saturation magnetization is observed at 5 K. This is attributed to surface effect for 3 nm size particles. The nanoparticles are spherical with uniform dispersion as depicted in transmission electron microscopy study. The noninteracting behavior of as-synthesized FePd nanoparticles is verified through Langevin fit. The saturation magnetization (σs) and mean moment of (μm) particles are computed to be σs=22.73 emu/g and μm=4466μB, respectively. The ordered face centered tetragonal (fct) phase of composition Fe43Pd57 was obtained from disordered fcc FePd phase by annealing at 550 °C for 1 h under reducing atmosphere of (N2+H2) gas. The ha...

Hybrid nanomaterials YVO4:Eu/Fe3O4 for optical imaging and hyperthermia in cancer cells

YVO4:xEu nanoparticles having a spherical shape at different concentrations of Eu (x = 0.02, 0.05, 0.07 and 0.10 at%) are prepared by a polyol method at 120 °C and their luminescence properties at different annealing temperatures (as-prepared, 500 and 900 °C) are studied. In the luminescence study, the typical emission peaks of Eu3+ ion at 590 and 612 nm are observed for all samples. The intensity of the emission peak increases with the increase of annealing temperature due to the decrease of the contribution from the non-radiative process arising from the surface dangling bond/OH. The crystallite size calculated from the X-ray diffraction is found to increase with annealing from 500 to 900 °C but the as-prepared sample has a larger crystallite size than the 500 °C annealed sample. This can be explained by the incorporation of C in the interstitial sites of the lattice after heating the as-prepared sample at 500 °C. The C residue remains after decomposition of ethylene glycol at 500 °C. Luminescence decays for the 5D0 level of Eu3+ are studied under 395 nm (direct excitation) and 270, 320 nm (indirect excitation). The energy transfer process from V–O to Eu3+ is studied from decay curves. The quantum yields for as-prepared, 500 and 900 °C annealed samples of 5 at% Eu3+ doped YVO4 nanoparticles are 1, 14 and 46%, respectively. We have also synthesized YVO4:10Eu/Fe3O4 hybrid nanocomposites and determined their intracellular localization as well as hyperthermia efficacy in tumor cells. These materials will have potential application in the diagnosis as well as therapy of cancer cells.

Structural and electrical resistivity studies on Bi1.6Pb0.4Sr2Ca4Cu5O y composition synthesized by different routes

Since the discovery of superconductivity in the Bi-Sr-Ca-Cu-O system [1], several experimental investigators have verified that Bi-Sr-Ca-Cu-O systems synthesized by different routes possess phases with Tc of 20, 80 and 110 K. Studies of disproportionation reaction by varying the doping concentration of Pb [2-4] in this system have also been reported. In this investigation we varied the synthesis conditions in Bi2_xPbxSr2Ca4CusOy composition in order to investigate the formation of superconducting phases, their disproportionation reaction and possible textured growth. We attempted synthesis of the above composition by three different routes: matrix ceramic (MC), glass ceramic (GC) and melt texture (MT). The resultant samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAD) and resistivity [p(T)] measurements and the results are reported.

Electron-molecular vibration interactions in undoped fullerene films. A micro-Raman study

Abstract A detailed micro-Raman study of the various crystallites in undoped fullerene films, comprising C 60 with inclusions of other fullerenes, has been carried out. Raman spectra of some of the crystallites exhibited a broad background scattering and a superposed asymmetric band shape for some of the optical phonons. These spectral features are qualitatively similar to those observed in doped fullerenes like K 3 C 60 . In the present case electron transfer from higher fullerenes to C 60 is envisaged to explain the observation.

Effect of Annealing on Magnetic Properties of FePd and FePdPt Nanoparticles

Nanoparticles of FePd and FePdPt with the average size of ∼3 nm have been prepared by modified polyol route. As‐prepared nanoparticles are crystallized in fcc phase, whereas, 550–600° C annealed nanoparticles are crystallized in fct phase. As‐prepared samples are superparamagnetic at 300 K, whereas, annealed samples are strongly ferromagnetic at 300 K. As compared to fct FePd nanoparticles (Hc = 1180 Oe), the fct FePdPt nanoparticles show significantly high coercivity (Hc = 4675 Oe) and squareness ratio (σr/σs = 0.71) and thus, the addition of Pt in FePd nanoalloy improves the magnetic anisotropy significantly. The Curie temperature of FePd nanoalloy increases with increasing annealing temperature because of increase of atomic ordering in fct phase.

Incommensurate periodic lattice modulation in carbon cluster composite films

Abstract The splitting of electron diffraction spots from carbon cluster composite films is assigned to incommensurate periodic lattice modulation indicating the formation of a common crystal lattice due to intermixing of constituent clusters on a molecular scale.