Figure 4.

Characterization of etchable quantum dots containing zinc, mercury, selenide, and sulfide (ZHS-QDs). (a) Schematic of ZHS-QD etching. Ag-TS quenches ZHS-QDs by providing Ag⁺ in exchange for Zn²⁺ and Hg²⁺. (b) Photoluminescence spectra at 450 nm excitation of ZHS-QDs before and after treatment with [Ag(S₂O₃)₂]³⁻, an etchant consisting of silver ions (Ag⁺) stabilized with thiosulfate (TS) (Ag-TS). (n = 6 per group; Scale bars, 50 nm). (c) Hg²⁺ and Zn²⁺ release from ZHS-QDs with and without Ag-TS treatment. Columns represent fold-over non-etched group. n = 3 per group. (d) In vitro etching of ZHS-QDs by various chemicals. NIR images (upper panel) and the emission intensity of the ZHS-QDs before and after etching (bottom panel, n  =  4 per group). Each column corresponds to the tube above. (e) Peritoneal tumor imaging with ZHS-QDs. Mice-bearing peritoneal tumors created with MKN45P-luc luciferase-positive human gastric cancer cells received an intraperitoneal co-injection of iRGD or PBS with ZHS-QDs. Intraperitoneal etchant (1x Ag-TS) was given 90 min later. n  =  3 per group. Statistics, Student’s t-test (c); error bars, SEM; ns, not significant; ** p < 0.01; *** p < 0.001. This image has been adapted with permission from Liu et al. [93] © 2017, Springer Nature.