Facile synthesis of fluorescent polysaccharides: Cytosine grafted agarose and κ-carrageenan

New fluorescent polymeric materials were synthesized by grafting the nucleobase cytosine on to the backbone of agarose and κ-carrageenan, employing a rapid water based method under microwave irradiation using potassium persulphate (KPS) as an initiator. The emission spectrum of the modified agarose and κ-carrageenan recorded in aqueous solution (5 × 10−5 M) exhibited emission maxima (λem,max) at 348 nm by excitation at 266 nm. The emission intensity was enhanced by ca. 104% and 60% compared to that of pure cytosine solution of the same concentration. When the concentration of the pure cytosine solution is made equivalent to the concentration of the cytosine molar component (3.09 × 10−5) and (3.5 × 10−5) present in 5 × 10−5 M solution of modified agarose and κ-carrageenan, respectively, then ca. 143% and 81% enhancement in emission intensity was observed. The remarkable fluorescent activity of the agarose–cytosine derivative may have potential uses as sensor in various applications.