A Highly Selective Turn-on and Reversible Fluorescent Chemosensor for Al3+ Detection Based on Novel Salicylidene Schiff Base-Terminated PEG in Pure Aqueous Solution.

The development of highly selective and sensitive chemosensors for Al3+ detection in pure aqueous solution is still a significant challenge. In this work, a novel water-soluble polymer PEGBAB based on salicylidene Schiff base has been designed and synthesized as a turn-on fluorescent chemosensor for the detection of Al3+ in 100% aqueous solution. PEGBAB exhibited high sensitivity and selectivity to Al3+ over other competitive metal ions with the detection limit as low as 4.05 × 10-9 M. PEGBAB displayed high selectivity to Al3+ in the pH range of 5⁻10. The fluorescence response of PEGBAB to Al3+ was reversible in the presence of ethylenediaminetetraacetic acid (EDTA). Based on the fluorescence response, an INHIBIT logic gate was constructed with Al3+ and EDTA as two inputs. Moreover, test strips based on PEGBAB were fabricated facilely for convenient on-site detection of Al3+.

A simple turn-on fluorescent chemosensor based on Schiff base-terminated water-soluble polymer for selective detection of Al3+ in 100% aqueous solution.

A simple water-soluble polymer PEGBHB based on polyethylene glycol bearing a Schiff base derivative moiety was successfully designed and synthesized. PEGBHB showed high selectivity and sensitivity towards Al3+ as a turn-on fluorescent chemosensor without influence by other competitive metal ions in 100% aqueous solution. The detection limit of PEGBHB for Al3+ was found to be 9.67 × 10-9 M. A 1:1 stoichiometry between PEGBHB and Al3+ has been confirmed by Job plot analysis. PEGBHB could detect Al3+ over a wide pH range from 4 to 10. The chemosensor was reversible by adding EDTA to the solution of PEGBHB-Al3+ complex. An INHIBIT molecular logic gate was constructed with the help of OFF-ON-OFF signal on alternate addition of Al3+ and EDTA to the chemosensor. Furthermore, test papers were fabricated facilely using PEGBHB for convenient and visual detection of practical Al3+.

A dual chemosensor for Cu2+ and Hg2+ based on a rhodamine-terminated water-soluble polymer in 100% aqueous solution.

A novel water-soluble polymer bearing a rhodamine receptor (PEGSRh) was synthesized as a dual chemosensor for the recognition of Cu2+ and Hg2+ in 100% aqueous solution. PEGSRh not only exhibited a sensitive colorimetric response towards Cu2+ and Hg2+ but also showed a selective turn-on fluorescence response towards Hg2+ over other metal ions. The binding stoichiometry for the complexation of PEGSRh with Cu2+ and Hg2+ was confirmed to be 1 : 1 by Job plot analysis. The low detection limits were found to be 5.92 × 10-7 M for Cu2+ and 2.85 × 10-6 M for Hg2+. The responses of PEGSRh to Cu2+ and Hg2+ were both stable over wide pH ranges. In addition, the fluorescence intensity changes of PEGSRh solution by the inputs of Hg2+, Cu2+ and EDTA have been used to construct a combinational logic gate. Again, an INHIBIT logic gate was also obtained by employing Cu2+ and EDTA as the chemical inputs and the absorbance signal as the output. Moreover, test papers were prepared facilely using PEGSRh for practical on-site detection of Cu2+ and Hg2+.