Department of Chemistry, School of Physical Sciences, Sikkim University, Sikkim 737102, India.
Department of Biomedical Sciences, University of Hull, Hull, HU6 7RX, UK.
Dalton Trans. 2020 Nov 10;49(43):15425-15432. doi: 10.1039/d0dt02974b.
Aqueous-stable, Cd- and Pb-free colloidal quantum dots with fluorescence properties in the second near-infrared region (NIR-II, 1000-1400) are highly desirable for non-invasive deep-tissue optical imaging and biosensing. The low band-gap semiconductor, silver chalcogenide, offers a non-toxic and stable alternative to existing Pd, As, Hg and Cd-based NIR-II colloidal quantum dots (QDs). We report facile access to NIR-II emission windows with Ag2X (X = S, Se) QDs using easy-to-prepare thio/selenourea precursors and their analogues. The aqueous phase transfer of these QDs with a high conservation of fluorescence quantum yield (retention up to ∼90%) and colloidal stability is demonstrated. A bimodal NIR-II/MRI contrast agent with a tunable fluorescence and high T1 relaxivity of 408 mM-1 s-1 per QD (size ∼ 2.2 nm) and 990 mM-1 s-1 per QD (size ∼ 4.2 nm) has been prepared by grafting 50 and 120 monoaqua Gd(iii) complexes respectively to two differently sized Ag2S QDs. The size of the nanocrystals is crucial for tuning the Gd payload and the relaxivity.
具有荧光性质的水稳定、无镉和无铅胶体量子点在近红外二区（NIR-II，1000-1400nm）中是非常理想的，可用于非侵入式深层组织光学成像和生物传感。低带隙半导体银硫属化物为现有的基于 Pd、As、Hg 和 Cd 的近红外二区胶体量子点（QD）提供了一种无毒且稳定的替代品。我们使用易于制备的硫脲/硒脲前体及其类似物，轻松地获得了具有 Ag2X（X = S、Se）QD 的近红外二区发射窗口。这些 QD 的水相转移具有高荧光量子产率（保留率高达约 90%）和胶体稳定性。通过分别将 50 和 120 个单 Aqua Gd（iii）配合物接枝到两个不同尺寸的 Ag2S QD 上，制备了具有可调荧光和高 T1弛豫率的双模态近红外二区/MRI 对比剂，其弛豫率分别为 408 mM-1 s-1/每个 QD（尺寸约为 2.2nm）和 990 mM-1 s-1/每个 QD（尺寸约为 4.2nm）。纳米晶体的尺寸对于调节 Gd 载药量和弛豫率至关重要。
