In this work, the sensitive detection of hydrogen sulfide (H2S) was realized at low cost and high efficiency through the application of silver–gold core–shell nanoprism (Ag@Au-np) combined with headspace single-drop microextraction (HS-SDME). After SDME, smartphone nanocolorimetry (SNC), with the aid of a smartphone camera and color picker software, was used to detect and quantify the H2S. The method took advantage of the inhibition of the ultraviolet–visible (UV–vis) signal caused by H2S etching of the Ag@Au-np preadded to the SDME solvent to measure the H2S concentration. The coating of the gold layer not only ensured the high stability of the nanomaterial but also enhanced the selectivity toward H2S. The HS-SDME method was simple to process and required only a droplet of solvent for analysis to be realized. This HS-SDME-SCN approach exhibited a calibration graph linearity of between 0.1 and 100 μM and a limit of detection of 65 nM (relative standard deviations of N% (n = 3) < 4.80). A comparison with UV–vis spectrophotometry was conducted. The practical applicability of HS-SDME-SNC was successfully demonstrated by determining H2S in genuine biosamples (egg and milk).

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Accurate recognition and speciation analysis of heavy-metal ions in complex hydrological environments is always a serious challenge. In this work, we proposed a small-molecule-based ultrasensitive colorimetric detection strategy and successfully applied it to the accurate detection of Fe 2+ , Fe 3+ , Co 2+ , and Hg 2+ in groundwater through the specific recognition of multiple ligands of different metal ions. The detection limits for Hg 2+ , Co 2+ , Fe 2+ , and Fe 3+ are calculated to be 6.51, 0.34, 0.49, and 1.01 ppb, respectively, which are far below the drinking water standards and superior to most of the reported colorimetric sensors. Remarkably, the speciation analysis of Fe 2+ /Fe 3+ also has been successfully realized by a one-step method without complex pretreatment. The speciation and concentration of Fe 2+ and Fe 3+ in actual water samples can be accurately identified and monitored. In addition, as an attempt of visual onsite detection, we have developed a simple test strip, which has been applied to visual monitoring of four metal ions with the detection limit estimated by the naked eye to be as low as ppb level. This proposed colorimetric method realizes the rapid, sensitive, and portable multiple metal ions recognition and Fe 2+ /Fe 3+ speciation analysis, displaying great potential for onsite rapid water quality analysis.

A novel 1-oxo-1H-phenalene-2,3-dicarbonitrile (OPD)-based fluorescent probe was developed to sense and image GSH in HeLa cells, different imatinib-resistant K562 cells, D. magna and zebrafish embryos.