This paper describes the applicability of a modified polyol process in conjunction with a transmetallation reaction in synthesis of Co y Ag 100¡y nanocrystallites of a core-shell structure. The substitution Co ! Ag is varied as 20 y 95 by tuning the microstructure with functional magnetic and giant magneto resistance properties. The existence of core-shell structures was confirmed through transmission electron microscope and the size of Co-core increased from 8 to 50 nm with decrease in Ag-content of the sample. The magnetic behaviour of the sample changed from a pseudo-superparamagnetic nature to ferromagnetic with increase in Co-core size. Normalised saturation magnetisation values increased from 89.5 to 128.6 emu/g with increase in size of Co-core; however, none of the ferromagnetic samples exhibited any magneto resistance (MR). A value of 2.0% MR was observed in case of Co 20.6 Ag 79.4 which increased to a maximum of 3.6% MR for Co 36.6 Ag 63.4 sample when measured at 5 K.

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A complete green chemical reaction between aurochloric acid and tea polyphenols resulted in the reduction of Au 3? ? Au 0 . The reaction was carried out in a Teflon-coated bomb digestion vessel at 200°C. It was observed that with increasing the reaction time from 1 to 5 h, the shape of the nanoparticles changed from sphericalto rod-like structures. The reaction was followed with the help of UV-vis spectrometer, which showed a single absorption peak at 548 nm for 1-h reaction product and two peaks for a 5-h reaction product at 533 and 745 nm corresponding to the transverse and longitudinal surface plasmon resonance bands. Microstructures obtained from transmission electron microscope revealed that the samples obtained after 1-h reaction are predominantly spherical in shape with an average size of 15 nm. Whereas samples obtained after 5 h of reaction exhibited rod-like structures with an average size of 45 nm.

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