A novel highly luminescent LnMOF film: a convenient sensor for Hg2+ detecting

Abstract

A highly luminescent LnMOF {[Eu 2 (bqdc) 3 (H 2 O)(DMF) 3 ]$0.5DMF$H 2 O} n (1, bqdc ¼ 2,2 0 -biquinoline-4,4 0dicarboxylate) was designed and synthesized. It was characterized by single crystal X-ray diffraction, PXRD, TGA, EA and FT-IR. A new strategy for preparing mechanically robust MOF thin films was developed by electrodeposition in combination with subsequent solvothermal synthesis. A portable sensor device prototype consisting of a film of 1 was conveniently fabricated by using this new strategy and this sensor device exhibits a highly selective response to Hg 2+ . Its luminescence quenching can be distinguished clearly with the naked eye when illuminated by a handy UV banknote detector. The diffusion kinetics of Hg 2+ into the LnMOF film is first proposed.

A Terbium Metal–Organic Framework for Highly Selective and Sensitive Luminescence Sensing of Hg2+ Ions in Aqueous Solution

“…Although a few MOF fluorescence sensors have been reported to detect Hg 2+ species, challenges still remain in the design of functional MOFs for highly selective and sensitive sensing of Hg 2+ in environmental water samples. On the one hand, many MOFs are unstable in the aqueous solution which limits the quantitative detection of aqueous Hg 2+ . On the other hand, MOF‐based sensors that are designed for targeting with Hg 2+ may be cross‐sensitive toward other metal ions, such as Cu 2+ , Zn 2+ , Cd 2+ , and Pb 2+ (in fact, chemical properties of these metal ions are similar to that of Hg 2+ , such as the d 10 closed‐shell electronic configuration, which determines the absence of an intrinsic spectroscopic or magnetic signal) .…”

“…On the one hand, many MOFs are unstablei nt he aqueous solution which limits the quantitative detection of aqueous Hg 2 + . [11] On the other hand, MOF-based sensors that are designedf or targeting with Hg 2 + may be cross-sensitive toward other metal ions, such as Cu 2 + ,Z n 2 + ,C d 2 + ,a nd Pb 2 + (in fact, chemical properties of these metal ions are similar to that of Hg 2 + ,s uch as the d 10 closed-shelle lectronic configuration, which determines the absence of an intrinsic spectroscopic or magnetic signal). [12] Last but not the least, the previously reportedM OF-based Hg 2 + sensors usually exhibit an unsatisfactory detection limit, such as [Cd(2-NH 2 bdc)(tib)·4 H 2 O·0.5DMA] n [13] (42 nm)a nd the UiO-66-NH 2 / ssDNA hybrid system [14] (17.6 nm), which cannot satisfyt he maximum permitted level of 10 nm Hg 2 + in drinking water regulated by the U.S. EPA.…”

A luminescent Terbium-Succinate MOF thin film fabricated by electrodeposition for sensing of Cu2+ in aqueous environment

“…(3) The reaction process is more controllable and reproducible due to the nature of electrosynthesis [33]. Through the best of our knowledge, there have been relatively few reports on the Ln-MOF thin films prepared via electrodeposition method [29][30][31].…”

“…Recently our group reported a series of Ln-MOF thin films prepared via cathode electrodeposition under mild conditions [29][30][31]. Under electric field, conductive substances such as conductive glass can functionalize as electron reservoir to induce MOF crystallization [32].…”

Electrosynthesis of Metal–Organic Frameworks: Challenges and Opportunities

“…Costly metalssuch as europium can also be deposited as an oxide before being converted into aM OF.Y ang et al first electrodeposited Eu(OH) 2 , then turned it into at hin MOF film using as olvothermal step. [85] This film was then used for the luminescentd etection of lead ions.…”