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Freshwater Diatoms from Deepor Beel - A Ramsar Site of Assam, India Revealed Potential Photoluminescence Properties for Nanotechnological Applications

Shamsun Nahar and Bhaben Tanti

Photoluminescence property of few freshwater diatoms was studied form Deepor Beel, a Ramsar site of Assam, India. Diatom, a unicellular, eukaryotic, photosynthetic alga of the class Bacillariophyceae has the natural ability biogeochemical cycling of natural silica and to deposit nanoporous silica over cell frustule. Nanoporous silica with excellent photoluminescence properties become suitable material for wider applications in IT based sector. Keeping view in mind, the present study was undertaken with some freshwater diatoms obtained from an important internationally recognized important freshwater wetland. Four diatom viz. Navicula sp., Thalassiosira sp., Nitzschia sp. and Achanthes sp., treated with acid digestion method were subjected to scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectroscopy analysis to characterize their structural properties of the frustules. Photoluminescence properties (PL) of diatom frustules excited at 250 nm, 285 nm and 329 nm showed a diverse range of PL spectra at ultraviolet, green and blue ranges that indicated their potential optoelectronic behaviours. Time-resolved photoluminescence (TRPL) analysis of the diatom frustules, excited at 375 nm revealed the decay time in the range between 3.85 eV to 2.67 eV suggesting the biexponential decay of natural diatoms.