A polyethylenimine/salicylaldehyde modified cellulose Schiff base for selective and sensitive Fe3+ detection

We describe a new solid-state colorimetric sensor synthesized by micro-crystalline cellulose (MCC) in the presence of polyethylenimine (PEI) and salicylaldehyde (SA) via an oxidation process and two successive Schiff base reactions. The formation of the Fe3+ complex led to color change detectable by eye, as well as an absorption peak at 501 nm causing fluorescence quenching. The signal was linear with the concentration ranging from 4 to 20 ppm; the detection limit is 0.01 ppm, making this a sensitivity and reliable monitoring platform for Fe3+ detection. Orbital electron distribution and computational studies were also carried out using density functional theory (DFT) to better supplement the sensor's detection performance. Finally, the sensing mechanism is discussed in detail.