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Nanoparticles of Dy3+ and Eu3+ doped YVO4 (core) have been prepared by urea-hydrolysis in ethylene glycol medium and further heated at 500 and 900 °C to grow particles as well as remove unwanted hydrocarbon/H2O, which acts as quencher in luminescence. Samples show emission peaks at 488 (blue), 537 (green), 572 (yellow), 592 (orange), and 617 nm (red). The emission intensity decreases when excitation wavelength changes from 300 [V–O charge transfer band (CTB)] to 255 nm (Eu/Dy–O CTB) and then to 355/395 nm (direct excitations of Dy3+/Eu3+). This is attributed to energy transfer from V–O to Eu3+/Dy3+, Eu/Dy–O to Eu3+/Dy3+. Energy transfer from Dy3+ to Eu3+ is more than that from Eu3+ to Dy3+. With heat-treatment temperature increases from 500 to 900 °C, emission intensity is improved due to the extent of decrease in nonraditive transition probability arising from surface. To the best of authors’ knowledge, local/site symmetry of Eu3+ and Dy3+ in same host is not detail discussed in literature. In the same host, asymmetric ratio of electric dipole allowed transition to magnetic dipole transition in both ions should be same but this was not happen. This study will give the origin of this. After covering core-nanoparticles with undoped YVO4 shell, luminescence intensity is further improved due to the extent of reduction in surface Eu3+/Dy3+ of particles and cross-relaxation reduction among Eu3+/Dy3+ ions.

Nanoparticles of Eu(3+) doped Y(2)O(3) (core) and Eu(3+) doped Y(2)O(3) covered with Y(2)O(3) shell (core-shell) are prepared by urea hydrolysis for 3 h in ethylene glycol medium at a relatively low temperature of 140 °C, followed by heating at 500 and 900 °C. Particle sizes determined from x-ray diffraction and transmission electron microscopic studies are 11 and 18 nm for 500 and 900 °C heated samples respectively. Based on the luminescence studies of 500 and 900 °C heated samples, it is confirmed that there is no particle size effect on the peak positions of Eu(3+) emission, and optimum luminescence intensity is observed from the nanoparticles with a Eu(3+) concentration of 4-5 at.%. A luminescence study establishes that the Eu(3+) environment in amorphous Y (OH)(3) is different from that in crystalline Y(2)O(3). For a fixed concentration of Eu(3+) doping, there is a reduction in Eu(3+) emission intensity for core-shell nanoparticles compared to that of core nanoparticles, and this has been attributed to the concentration dilution effect. Energy transfer from the host to Eu(3+) increases with increase of crystallinity.

Proteinases have the potential to effect partial solubilization of the proteinaceous gum sericin involved in binding the silk strands together in cocoon, an essential step in the silk cocoon cooking and reeling. Therefore, pineapple extract rich in cysteine proteinases was enzymologically characterized for its potential application in oak tasar (Antheraea proylei J.) silk cocoon cooking and reeling. Optimum sodium carbonate concentration (9.8 mM) and optimum temperature (60ºC) for the proteinase activity were determined. Though relatively thermostable, an enhanced activity loss was observed when the extract was incubated in the temperature range 70-90ºC with sodium carbonate. Bulk of the activity (80-83%) remained after 1 hr of time-dependent inactivation at 60ºC. The tasar cocoon extract neither caused inhibition of the activity nor enhanced its time-dependent loss by incubation at 60ºC. However, it caused an enhanced time-dependent loss of the activity by incubation at 60ºC *Corresponding author with sodium carbonate. Considering these enzymological characteristics, experimental cocooncooking media were constituted by taking the pineapple extract with or without sodium carbonate at room temperature or 60ºC. The results of the cocoon cooking and subsequent single silk filament reeling indicated for an applicability of pineapple extract as an effective agent for the oak tasar cocoon cooking and reeling.The fruit of pineapple, Ananas comosus (L.) Merr. is a rich source of a mixture of cysteine proteinases, the most abundant among them being the fruit bromelain (EC 3.4.22.33) which hydrolytically cleaves the internal peptide bonds in proteins with relatively broad specificity (Rowan and Buttle, 1994). The pineapple proteinases find uses in various industrial and medical applications including brewing, meat tenderization, prevention of diarrhea, digestive aids and treatment of edema (Takagi et al. 1992;Tanabe et al. 1996;Chandler and Mynott, 1998; Kelly, Singh L.R. et al. 1996;Maurer, 2001). The use of enzymes in the silk industry is relatively unexplored, has generated a lot of interest, and much research is being carried out internationally (Gulrajani et al. 2000). Against this background, pineapple fruit pulp extract (simply pineapple extract) having proteinase activity may also find application in tasar silk industry in general and tasar silk cocoon cooking and reeling in particular. The oak tasar (Antheraea proylei J.) silkworm is an important source of tasar silk (Singh and Singh, 1998). The larvae of the silkworm, reared on leaves of oak tree Quercus species (FamilyFagaceae), produce the cocoons from which the tasar silk is reeled (Singh and Singh, 1998). Unlike the mulberry (Bombyx mori L.) silk cocoons, the oak tasar silk cocoons cannot be satisfactorily softened by boiling in plain water (Jolly et al. 1979). The cocoons containing relatively higher amounts of protein-tannin complexes in the form of proanthocyanidins (Pandey and Goel, 1990;Pandey, 1997), have to be softened by more drastic boiling off tech...

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