Double Schiff base from thiophene-2,5-dicarboxylic acid as an “off–on–off” fluorescence sensor for the sequential detection of In3+ and PPi†
a
Guangyou
Zhang
*a
Abstract
A double Schiff base T as acceptor for metal ions derived from thiophene-2,5-dicarboxylic acid was designed and synthesized, and showed a high selectivity for In3+ in a DMF/H2O buffer solution. T exhibited a 300-fold fluorescence enhancement upon the addition of In3+, accompanying a visual color change from dark (Φ = 0.009) to bright yellow (Φ = 0.197). The complex T–In3+ could serve as a secondary sensor for PPi, which displayed recyclability upon the sequential addition of In3+ and PPi. The detection limits were calculated to be 4.48 × 10−8 M for In3+ and 4.4 × 10−6 M for PPi, respectively. According to Job's plot, T and In3+ tended to form 1 : 2 complexes with the binding affinity of 2.3 × 109 M2. The fluorescence behavior of T towards In3+ was primarily explained by the photoinduced electron transfer (PET) process based on theoretical calculations using Gaussian 09. Moreover, T could be applicable for indium detection in tap water with satisfactory recovery and RSD.
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