Sm3+ doped spinel cobalt ferrite nanoparticles with a generic formula CoSmxFe2−xO4 (x = 0.00, 0.06, 0.12 and 0.18) were prepared using wet chemical co-precipitation technique. The structural, optical, magnetic and dielectric characteristics of the samples were investigated carefully. The phase purity and growth of spinel cubic structure was verified by room temperature x-ray diffractograms. Mean crystallite size was observed within the range of 6 nm to 15 nm as calculated from Scherrer’s formula. A blue shift in the indirect optical band gap was noticed with increasing Sm percentage as observed in UV–vis spectra due to the nanosize effect. Superparamagnetic nature at 300 K was detected for all Sm doped ferrite samples. Field cooled (150 kOe) M-H loops obtained at 5 K revealed a large amount of exchange bias field (≈4 kOe) together with high coercivity for the sample having smallest sized particles. Dielectric responses of all samples showed that the hopping of electrons was the fundamental charge conduction mechanism and grain boundaries play a crucial role in determining the dielectric properties.

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Vanadium doped ZnS quantum dots (QDs) were synthesized with the generic formula Zn 1-x V x S (where x=0, 0.05, 0.10 and 0.15). Polyvinylpyrrolidone capped QDs were prepared by chemical co-precipitation technique. The phase purity of the samples were confirmed by x-ray diffraction. Crystallite size of 1.7-2.2 nm was obtained from the Scherrer's formula. Optical absorption studies revealed a band gap varying from 3.9 to 4.1 eV. Photoluminescence studies revealed a strong blue shift due to the strong quantum confinement in the particles. Magnetic studies indicated a ferromagnetic ground state for the doped samples.

Low frequency under-water acoustic signal detections are challenging, especially for marine applications. A Mach-Zehnder interferometric hydrophone is demonstrated using polarization-maintaining photonic-crystal-fiber (PM-PCF), spliced between two single-mode-fibers, operated at 1550 nm source. These data are compared with standard hydrophone, single-mode and multimode fiber. The PM-PCF sensor shows the highest response with a power shift (2.32 dBm) and a wavelength shift (392.8 pm) at 200 Hz. High birefringence values and the effect of the imparted acoustic pressure on this fiber, introducing the difference between the fast and slow axis changes, owing to the phase change in the propagation waves, demonstrate the strain-optic properties of the sensor.

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