Bifunctional Sensors Based on Phosphomolybdates for Detection of Inorganic Hexavalent Chromium and Organic Tetracycline

Exploring effective sensors for detecting possible hazards in a water system are greatly significant. This work proposed a strategy for stable and effective bifunctional sensors via incorporating hourglass-type phosphomolybdates into metal- organic fragments to construct a high-dimensional framework. Two hourglass-type phosphomolybdate-based electrochemical sensors toward heavy metal ion Cr(VI) and tetracycline (TC) detection were designed with the formula [Co-2(II)(H2O)(4)NaI2]- [Co-II(Hbpe)] [NaI(bpe)1 .5]{Co-II[PV4MoV6O31H6](2)}middot9H(2)O (1) and [Co-II(H2O)(4)NaI3] [Co-II(Hbpe)] [Co-II(bpe)]-{Co-II[PV4MoV6O31H6](2)}middot9H(2)O (2) [bpe = 1,2-di(4-pyridyl)-ethylene]. Structural analysis showed that hybrids 1 and 2 possess three-dimensional POM-supported network features with favorable stability and exhibit reversible redox properties. Experiments found that this kind of hybrids as efficient sensors have excellent electrochemical performance toward Cr(VI) detection with high sensitivities of 0.111 mu Amiddot mu M-1 for 1 and 0.141 mu Amiddot mu M-1 for 2, fast response time of 1 s, and low detection limits of 30 nM for 1 and 27 nM for 2, which far meet the standard of WHO for drinking water. Moreover, hybrids 1-2 also exhibit fast responses to TC detection with sensitivities of 0.0073 and 0.022 mu AmiddotmM(-1) and detection limits of 0.426 and 0.084 mM. This work offers a novel strategy for the purposeful design of efficient POM-based electrochemical sensors for accurate determination of contaminants in a practical water system.

Automated summary

This study proposed a strategy to construct stable and effective bifunctional sensors by incorporating hourglass-type phosphomolybdates into metal-organic fragments. Two electrochemical sensors were designed for detecting heavy metal ion Cr(VI) and tetracycline (TC). The experiments showed that these sensors exhibited excellent electrochemical performance with high sensitivities, fast response time, and low detection limits, meeting the drinking water standards. The study offers a novel approach for designing efficient sensors for accurate determination of contaminants in water systems.