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Mercury poses a significant threat to human health and the environment, and the United States Environmental Protection Agency has set a drinking water threshold of mercury (10 nM). Therefore, developing an environmentally friendly, on-site mercury ion (Hg2+) detection is highly desirable. Based on the synergetic catalysis of gold nanoparticles (AuNPs) and mercury, a simple and ultrasensitive colorimetric method for the determination of Hg2+ was established. The innovation of this work is to propose a strategy based on the self-assembly of two-dimensional (2D) AuNPs for colorimetric detection of Hg2+. The AuNPs are self-assembled into a densely arranged 2D AuNP layer at the liquid/liquid interface between dimethyl carbonate and water, which converts from the disordered distribution of AuNPs in 3D space to an orderly 2D AuNP layer distribution. This avoids the shortcomings of poor repeatability and weak detection signals caused by the uneven sampling before and greatly plays the catalytic role of each AuNP. In this work, gold amalgam catalyzes colorless 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) to yield blue-green oxidized TMB (oxTMB), realizing the colorimetric quantitative detection of Hg2+ in water systems. In this process, the formation of gold amalgam greatly improves the catalytic ability of AuNPs, and the detection limit of mercury ions is as low as 0.021 nM. The practical application of this sensor in the determination of Hg2+ in tap water samples has also been successfully verified, providing an effective method for environmental monitoring. [ABSTRACT FROM AUTHOR]

Nanocrystals (NCs) of cesium lead halide perovskites are optically unstable, which prevents their use in optical sensors. The combination of perovskite NCs and metal single atoms (SAs) may be a good solution to this issue. Unfortunately, depositing metal SAs on perovskite NCs remains a challenge due to relative weak metal-halide bonds. Herein, we present that, via a photo assisted method using cesium lead halide perovskite NCs as host material to anchor Y single atoms, we successfully synthesize Y SA anchored CsPbBr3 NCs (Y-SA/CsPbBr3 NCs) with outstanding fluorescence stability through the formation of two Y−O bonds and two Y−Br bonds. In comparison to bare CsPbBr3 NCs, Y-SA/CsPbBr3 NCs possess more stable optical characteristics. The as-synthesized Y-SA/CsPbBr3 NCs can be employed as a colorimetric platform to perform rapid CH3I sensing. Detection limit of 0.044 ppm is exhibited in this approach with excellent anti-interference performance. The Y-SA/CsPbBr3 NCs-based system has been applied to the detection of CH3I in sweet potato samples with satisfying results. [ABSTRACT FROM AUTHOR]

Owing to the unique coordination environment and high atom utilization efficiency, single atom catalysts have been considered as an ideal artificial enzyme to mimic natural enzymes. Herein, single-atom Fe nanozyme anchored on N-doped Ti3C2Tx (Fe SA/N-Ti3C2Tx) with asymmetrically coordinated Fe-N1C2 configuration is synthesized by vacancy capture and heteroatom doping strategy, which exhibits excellent peroxidase-like activity. Based on the results of peroxidase catalytic kinetics and X-ray adsorption fine spectroscopy, the Fe-N1C2 active sites in Fe SA/N-Ti3C2Tx are responsible for the excellent performance. Furthermore, the developed Fe SA/N-Ti3C2Tx can be employed to quantitative detection of melatonin (MT), which shows a wide linear detection range (0.01–100 µM) and an excellent detection limit (7.3 nM) in buffer, 0.01–100 µM and 7.8 nM in serum samples. Our work proves that MXene-based single atoms can be promising nanozyme in the field of bioassays. [ABSTRACT FROM AUTHOR]