We report a portable and highly sensitive Hg 2+ nanosensor, where the CuS nanozyme functions as an Hg 2+ recognition unit, a Hg 2+ enrichment/preconcentration carrier, and a signal amplifier/output unit. The as-designed enrichmentdetection integration strategy is customizable and endows the sensor with both a wide detection range from 50 ppt to 400 ppb and a high sensitivity with a minimum detectable Hg 2+ concentration of 50 ppt. In order to make the Hg 2+ nanosensor portable and cost-effective, a commercial RGB sensor is employed here in conjunction with the Hg 2+ -dependent colorimetric reaction. More importantly, the as-developed Hg 2+ nanosensor is feasible for analysis of real samples with satisfactory accuracy (deviation <10%) and reproducibility (recovery ∼82%). Thus, this portable Hg 2+ nanosensor appears to be a viable solution to meet the actual needs of on-site and real-time mercury contamination analysis and may also pave the way to colorimetric nanosensors for other metal ions.

No abstract

The drop-tube technique was used to solidify droplets of the Ni-25.3 at.% Si alloy at high cooling rates. XRD, SEM and TEM analysis revealed that the metastable phase, Ni 25 Si 9 , formed as the dominant phase in all ranges of the droplets, with -Ni 31 Si 12 and 1 -Ni 3 Si also being present. Three different microstructures were observed: the regular and anomalous eutectic structures and near single phase structure containing small inclusions of a second phase, termed here a heteroclite structure. Both eutectic structures comprise alternating lamellae of Ni 25 Si 9 and 1 -Ni 3 Si, which, we conjecture, is a consequence of an unobserved eutectic reaction between the Ni 25 Si 9 and 1 -Ni 3 Si phases. The matrix of the heteroclite structure is also identified as the metastable phase Ni 25 Si 9 , in which twined growth is observed in the TEM. As the cooling rate is increased (particle size decreased) the proportion of droplets displaying the entire heteroclite structure tends to increase, with its fraction increasing from 13.91% (300-500 µm) to 40.10% (75-106 µm). The thermodynamic properties of the Ni 25 Si 9 phase were also studied by in-situ heating during XRD analysis and by DTA. This showed the decomposition of Ni 25 Si 9 to 1 and -Ni 31 Si 12 for temperatures in excess of 790 K (517°C).

No abstract