Cellulose/amylose derivatives bearing bulky substituents as reversible fluorescent sensors for detection of Fe.

Two novel cellulose and amylose derivatives bearing bulky tris(2-benzothienylformate) pendants (Cel-3 and Amy-3) were expeditiously prepared by one-step esterification. The fluorescent sensing performance of six polysaccharide derivatives, including Cel-3/Amy-3, and other four previously prepared benzothienyl- or benzofuranyl-phenylcarbamates of cellulose and amylose (Cel-1/Amy-1, Cel-2/Amy-2), were carefully evaluated using eight metal ions, including Co, K, Na, Li, Hg, Ni, Ca and Fe. All six derivatives exhibited excellent fluorescence quenching property to Fe ions with high sensitivity and selectivity. Especially, the limit of detection of Amy-2 with benzofuranylphenylcarbamates for Fe was 3.0 μM, much lower than the maximum contaminant level for Fe in the drinking water. Additionally, the six bulky derivatives displayed the interesting fluorescence "turn-off" and "turn-on" observation, indicating a desirable reversibility for Fe detection. The high anti-interference ability was also observed for detection of Fe on the benzothienyl/benzofuranyl derivatives of cellulose and amylose in the combined system containing Co, K, Na, Li, Hg, Ni and Ca. It suggested that the obtained polysaccharide derivatives with bulky chromophores possessed good potentials for detection of Fe as high-efficient fluorescent sensors in diverse applications. The sensing mechanism for detection of Fe was further proposed based on the Stern-Volmer plots and fluorescence titration analysis.