Cholesterol (C 27 H 46 O) is the most abundant and best-known steroid in the animal kingdom. The in vitro crystallization of this important biomaterial has been attempted by few researchers. Here we are reporting crystallization of pure cholesterol monohydrate crystals in gel medium. It is found that the morphology of the crystals depends on various parameters. The effect of solvent has been studied in detail. The different morphologies observed are fibrous, needle, platelet, dendrite etc. Micro topographical studies have been made and it is found that the crystals grow, at least in the last stage, by spreading of layers. However, at initial stage microcrystals formed and developed into dendrite or needle forms. These one-dimensional crystals developed into platelets and finally thickened. Further studies reveal that micro impurities play a vital role in the development of these crystals as seen by dissolution figures on the crystals. These crystals are characterized by using the XRD and IR spectroscopic methods.
Calcium Tartrate crystals were synthesized using sol-gel technique. Linear optical studies of the crystals were carried out in the UV-Vis-NIR spectral range. Nonlinear optical open aperture z-scan studies were done using high sensitive z-scan experimental technique. Both saturable absorption and reverse saturable absorption behaviour were observed at different input fluences. Reverse saturable absorption characteristic of the crystals make them suitable for optical limiting applications. Our analysis revealed that the novel crystal has the optimum values for the optical limiting parameters which are required for a high-performance optical limiter.
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