A novel “off-on-off” sensor for consecutive detection of Al3+ and H2PO4- as well as application in food and living cells

A novel julolidine based fluorescent sensor JBP was designed and synthesized for the sequential detection of Al3+ and H2PO4- in aqueous media. JBP exhibited high selectivity towards Al3+ with a Stokes shift of 132 nm. The fluorescence of the JBP-Al3+ complex could be quenched upon the addition of H2PO4-. The sequential detection of Al3+ and H2PO4- could be repeated up to three times. The detection limits for Al3+ and H2PO4- were calculated to be 5.7 × 10−8 M and 1.48 × 10−7 M, respectively. Additionally, JBP was effectively employed to detect Al3+ in environmentally relevant water samples, herbal teas, and various food samples (including edible alum, baking powder, fritters, and jellyfish) using only a smartphone. Importantly, JBP exhibited low toxicity and was capable of traversing cell membranes to detect Al3+ and H2PO4- within living cells.