A luminescent zinc(II) coordination polymer as a highly selective and sensitive chemosensor for Fe(III) cation and Cr(VI) anions detection in aqueous solution

Rapidly and simply detecting Cr (VI) in aqueous media via a diketopyrrolopyrrole-based chemosensor with both high selectivity and low LOD

BACKGROUND

The high toxicity of hexavalent chromium [Cr (VI)] could not only cause harmful effects on humans, including carcinogenicity, respiratory issues, genetic damage, and skin irritation, but also contaminate drinking water sources, aquatic ecosystems, and soil, impairing the reproductive capacity, growth, and survival of organisms. Due to these harmful effects, detecting toxic Cr (VI) is of great significance. However, the rapid, simple, and efficient detection at a low Cr (VI) concentration is extremely challenging, especially in an acidic condition (existing as HCrO4-) due to its low adsorption free energy.

RESULTS

A diketopyrrolopyrrole-based small molecule (DPPT-PhSMe) is designed and characterized to act as a chemosensor, which allows a high selectivity to Cr (VI) at an acidic condition with a low limit of detection to 10-8 M that is two orders of magnitude lower than the cut of limit (1 μM) recommended by World Health Organization (WHO). Mechanism study indicates that the rich sulfur atoms enhance the affinity to HCrO4-. Combining with favorable features of diketopyrrolopyrrole, DPPT-PhSMe not only allows dual-mode detection (colorimetric and spectroscopic) to Cr (VI), but also enables disposable paper-based sensor for naked-eye detection to Cr (VI) from fully aqueous media. The investigation of DPPT-PhSMe chemosensor for the quantification of Cr (VI) in real life samples demonstrates a high reliability and accuracy with an average percentage recovery of 102.1 % ± 4 (n = 3).

SIGNIFICANCE

DPPT-PhSMe represents the first diketopyrrolopyrrole-derived chemosensor for efficient detection to toxic Cr (VI), not only providing a targeted solution to the bottleneck of Cr (VI) detection in acidic conditions (existing as HCrO4-) caused by its low adsorption free energy, but also opening a new scenario for simple, selective, and efficient Cr (VI) detection with conjugated dye molecules.

Multifunctional MOF-based probes for efficient detection and discrimination of Pb2+, Fe3+ and Cr2O72-/CrO42

Developing metal-organic framework (MOF)-based fluorescent probes for efficient detection and discrimination of polluting ions in groundwater is vital for environmental protection and human health. In this paper, we prepared two luminescence-active transition MOFs, namely, Zn-MOF and Cd-MOF, and conducted sensing experiments. The results show that they both exhibit multiple-target detection for Fe³⁺, Pb²⁺ and Cr(VI) with high sensitivity, good anti-interference ability and good recyclability even with different frameworks. In addition, Eu³⁺-incorporated samples, Eu³⁺@MOFs, with dual-emission have been fabricated via efficient encapsulation of Eu³⁺ ions into the MOF host. As expected, Eu³⁺@MOF hybrids also act as multi-target and self-calibrated probes to selectively detect Fe³⁺ and Cr(VI) ions. However, the quenching efficiencies of the original MOFs towards Fe³⁺ are higher than those of Eu³⁺@MOFs. Thus, we could differentiate Fe³⁺, Pb²⁺ and Cr(VI) ions by comparing the changes of fluorescence emission between Eu³⁺@MOFs and the original MOFs. The recognition mechanism may be attributed to the competitive energy absorption between MOFs or Eu³⁺@MOFs and the analytes.

Various carboxylates induced eight Zn(ii)/Cd(ii) coordination polymers with fluorescence sensing activities for Fe(iii), Cr(vi) and oxytetracycline

Eight new Zn(ii)/Cd(ii) coordination polymers constructed from a naphthalene-amide-pyridyl ligand and various carboxylates were synthesized and characterized, which show multifunctional fluorescence responses for cations, anions and antibiotics.