Journal of Nano Research Vol. 24

Abstract: Cd_1-xCo_xS (0 x 0.5) thin films have been deposited by liquid phase chemical bath deposition method on glass substrate from a complex liquid phase formed by equimolar volumes of cadmium sulphate, thiourea and cobalt sulphate. For deposition various preparative parameters, such as speed, temperature, pH, and time were optimized and found to be 70 ± 2 rpm, 56 ^°C, 11±0.2 and 80 min. respectively. The samples were thin, uniform and tightly adherent with colour changing from orange red to dark chocolate as x was varied from 0 to 0.5. The films were characterized to evaluate the surface morphology, composition and optical measurements. The surface morphologies of these films revealed random orientation of the crystallites of elongated rhomboids with sharp and clear edges having leaf like appearance. The grain size is found to be enhanced continuously from x = 0 to x = 0.1 with fine and more clear grain boundaries and decreased for higher x values. Energy Dispersive X-ray analysis suggests that the deposits are Cd rich. The optical studies were performed on these samples in the range of wavelengths between 500 nm to 1300 nm and yield a high absorption coefficient (α 10⁴-10⁵ cm^-1) with a direct type of transitions. The estimated band gap decreased from 2.42 eV to 1.94 eV as x was varied from 0 to 0.5.

Abstract: The experimental conditions play an important role in particle size and in their properties in multifunctional magnetic nanoparticle synthesis. In the present study, magnetite nanoparticles of various sizes were synthesized by microwave irradiation method. The synthesized powder samples were characterized using XRD and SEM which substantiated the formation of magnetic nanoparticle in cubic phase. The particle sizes obtained were 40 nm, 31 nm and 27 nm from TEM micrographs. The FTIR studies confirmed the characteristic band of Fe-O within the range of 574 - 580 cm^-1. The magnetic properties of the samples were measured by vibration sample magnetometer that confirmed ferrimagnetic behavior of magnetite nanoparticles at room temperature. From the present study, it is observed that the microwave irradiation method is a convenient method to produce a wide range of magnetite nanoparticles of desired size for a variety of novel biomedical applications.

Abstract: A series of core-shell type nanoparticle samples of Mn_xZn_1-xFe₂O₄ were prepared by auto-combustion technique with x=0.3, 0.5, 0.7, 1.0. Subsequent to the structural and electrical property investigation the samples were irradiated with gamma radiation for different time intervals using ⁶⁰Co source. A significant decrease in lattice parameter and particle size was observed in gamma irradiated samples. Electrical resistivity of irradiated samples was found to decrease with the increase in γ-radiation dose. Frequency and temperature dependent dielectric constant and dissipation constant measurements carried out showed multifold enhancement of dielectric constant with pragmatic increase in dielectric loss, in γ-irradiated samples.

Abstract: The structures of silicon doped gold clusters Au_nSi (n = 1-10 and 19) have been investigated using first principle calculations based on density functional theory (DFT). Calculations indicate that the stability of a gold cluster increases with the introduction of a Si atom. In all the low lying geometries, Si prefers peripheral positions. For every ground state configuration with n > 3 (n = 6 and 9 being exceptions) Si has tetra-coordination. In almost all of the tetra coordinated geometries the coordination unit including Si, is in the form of a square pyramid with gold atoms forming the square base. Electronic properties such as HOMO-LUMO gap, ionization potential and electron affinity have also been calculated and support the relative stability of clusters with even n. The study of Au₂₀ cage doped with Si atom has been done .Similar to smaller Si doped gold clusters; the Si atom prefers an exohedral position. The doping of Si atom has enhanced the stability and chemical reactivity of Au₂₀ cluster.

Abstract: La_1-xBa_xTa (O,N)₃ oxynitrides were synthesized by ammonolysis of oxide precursors, prepared by a complex polymerization method. The absorption edge of the solid-solutions did not show a blueshift with an increase of x, in spite of the increase of O/N ratio, but rather the edge was redshifted. The substitution of La³⁺ by Ba²⁺ was thought to cause the bandgap to be redshifted due to the improved symmetry in (O,N)-Ta-(O,N) linkages in the perovskite structure. Addition of a NaCl flux during the ammonolysis of oxide precursors suppressed agglomeration of primary particles to inhibit the deterioration in the reflectivity after the longer wavelength region of the absorption edge.