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We have deposited magnetite thin films using the pulsed laser deposition technique from a α-Fe2O3 target on different substrates (Si (1 1 1), GaAs (1 0 0), Al2O3 (0 0 1) and amorphous float glass (FG)) without any buffer layer at a substrate temperature of 450 °C. These films have been characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, ac magnetic susceptibility and four-probe resistivity. The XRD results of these films show highly (1 1 1) oriented growth and single phase nature of Fe3O4 films on all substrates. Fe 2p core level x-ray photoelectron spectra and Raman spectra reveal the formation of Fe3O4 throughout the thickness of the films. All films show a Verwey transition at or around 120 K. It is observed that the oriented growth of Fe3O4 films takes place along the [1 1 1] direction on these substrates, which have either a huge lattice mismatch or no matching at all (as in FG) with Fe3O4.

We present a Raman study of Fe3O4 (100) thin films across the Verwey transition in the temperature range of 85–300K. These films are epitaxially grown on MgO (100) substrate by pulsed laser deposition technique. X-ray diffraction and low temperature resistivity measurements reveal that these films exhibit high structural order and perfect stoichiometry with Verwey transition at 121K. The frequency of different Raman modes [A1g and T2g(2)] changes abruptly around the Verwey transition temperature (TV). Below TV we observe a splitting in T2g(3) mode. Using Allen’s formula [Solid State Commun. 14, 937 (1974)] the strength of the electron-phonon coupling (λ) is estimated from the observed line shape parameters, and our estimates show that in epitaxially grown Fe3O4 thin films strong electron-phonon coupling is present. This coupling parameter is larger for T2g(3) mode as compared with that of A1g and T2g(2) modes. It is also observed that the coupling parameter corresponding to A1g mode remains invariant going from bulk single crystal to thin film while that of T2g(2) and T2g(3) modes are almost doubled. An attempt has been made to correlate the observed behavior with the presence of antiphase boundary in epitaxial thin films.

In this study, hepatitis B surface antigen (HBsAg) loaded poly(lactic-co-glycolic acid) (PLGA) microparticles were prepared and coated with chitosan and trimethyl chitosan (TMC) to evaluate the effect of coating material for nasal vaccine delivery. The developed formulations were characterized for size, zeta potential, entrapment efficiency, and mucin adsorption ability. Plain PLGA microparticles demonstrated negative zeta potential. However, coated microparticles showed higher positive zeta potential. Results indicated that TMC microparticles demonstrated substantially higher mucin adsorption when compared to chitosan-coated microparticles and plain PLGA microparticles. The coated and uncoated microparticles showed deposition in nasal-associated lymphoid tissue under fluorescence microscopy. The coated and uncoated microparticles were then administered intranasally to mice. Immune-adjuvant effect was determined on the basis of specific antibody titer observed in serum and secretions using enzyme-linked immunosorbent assay. It was observed that coated particles showed a markedly increased anti-HBsAg titer as compared to plain PLGA microparticles, but the results were more pronounced with the TMC-coated PLGA microparticles.