Xiaohong Cheng

A New Approach to Design Ratiometric Fluorescent Probe for Mercury(II) Based on the Hg2+-Promoted Deprotection of Thioacetals

On the basis of the protection reaction between ethanethiol and aldehyde, we designed and synthesized two new ratiometric fluorescent chemosensors, 3 and 4, by using intramolecular charge transfer (ICT) as a signaling mechanism. Upon the addition of Hg(2+) ion, both probes displayed apparent luminescence color changes, which could be observed by naked eyes under a UV lamp. Unexpectedly, both chemosensors also gave response to the addition of trace silver ions, making this kind of chemosensors as the first example of ratiometric fluorescent probe that showed dual channel fluorescence for both Hg(2+) and Ag(+). The test strips experiments suggested that 3 and 4 could serve as practical fluorescent probes for rapid detection of Hg(2+) ion.

New fluorescent and colorimetric probe for cyanide: direct reactivity, high selectivity, and bioimaging application.

Taking advantage of the special nucleophilicity of cyanide, a new ratiometric fluorescent and colorimetric probe (Coum-1) was designed by tuning the π-conjugated bridge to affect the intramolecular charge transfer efficiency. Upon the addition of CN(-) anion, the probe displayed very large blue-shift in both fluorescence (90 nm) and absorption (90 nm) spectra, with the detection limit of 800 nM. Other anions gave nearly no interference. Furthermore, Coum-1 was successfully applied to the fluorescent microscopic imaging for the detection of CN(-) in HeLa cells.

Azobenzene‐Based Colorimetric Chemosensors for Rapid Naked‐Eye Detection of Mercury(II)

Two new highly selective colorimetric chemosensors for Hg(2+), based on azobenzene and highly selective Hg(2+)-promoted deprotection of a dithioacetal have been designed and synthesized. In the presence of as little as 20 μM Hg(2+), the sensors change their color from light yellow to deep red, which can easily be observed by the naked eye. The underlying signaling mechanism is intramolecular charge transfer (ICT). The sensors have good selectivity for Hg(2+) with respect to several common alkali, alkaline earth, and transition metal ions. Furthermore, they can be used for in-the-field measurements by virtue of a dipstick approach without any additional equipment.

Fluorescent and Colorimetric Probes for Mercury(II): Tunable Structures of Electron Donor and π‐Conjugated Bridge

A new series of intramolecular-charge-transfer (ICT) molecules (compounds 1, 2, and 3) were synthesized by attaching various electron-donating thiophenes groups to a triphenylamine backbone with an aldehyde group as the electron acceptor. Based on the protection reaction between ethanethiol and aldehyde, the corresponding dithioacetals (compounds S1, S2, and S3) were prepared to serve as novel colorimetric and fluorescent chemosensors for Hg(2+) ions. Also, compound S1 was further utilized to construct the chemical-reaction-based conjugated polymer probe (PS1) towards Hg(2+) ions. In the presence of as little as 10 nM Hg(2+), compound PS1 displayed an apparent change in the fluorescent intensity. The sensing processes were revealed to be mediated by ICT, as confirmed by time-dependent DFT calculations. Furthermore, compound S1 was successfully applied to microscopic imaging for the detection of Hg(2+) in HeLa cells with ratiometric fluorescent methods.