10-Fold Quantum Yield Improvement of Ag₂S Nanoparticles by Fine Compositional Tuning

Abstract

Ag 2 S semiconductor nanoparticles (NPs) are near-infrared luminescent probes with outstanding properties (good biocompatibility, optimum spectral operation range, and easy biofunctionalization) that make them ideal probes for in vivo imaging. Ag 2 S NPs have, indeed, made possible amazing challenges including in vivo brain imaging and advanced diagnosis of the cardiovascular system. Despite the continuous redesign of synthesis routes, the emission quantum yield (QY) of Ag 2 S NPs is typically below 0.2%. This leads to a low luminescent brightness that avoids their translation into the clinics. In this work, an innovative synthetic methodology that permits a 10-fold increment in the absolute QY from 0.2 up to 2.3% is presented. Such an increment in the QY is accompanied by an enlargement of photoluminescence lifetimes from 184 to 1200 ns. The optimized synthetic route presented here is based on a fine control over both the Ag core and the Ag/S ratio within the NPs. Such control reduces the density of structural defects and decreases the nonradiative pathways. In addition, we demonstrate that the superior performance of the Ag 2 S NPs allows for high-contrast in vivo bioimaging.

A Theoretical Framework for Ratiometric Single Ion Luminescent Thermometers—Thermodynamic and Kinetic Guidelines for Optimized Performance

“…It is noteworthy that Equations (61) and (62) also account for the limiting cases that the decay from state |2⟩ can be either purely radiative or non-radiative, respectively. This case is translated to the presence of only one observable radiative transition in the luminescence spectrum.…”

“…This can pose a problem in the experimental determination of the decay time 2 (0) and the radiative decay rate k 2r (0). By knowledge of the pre-factor C and the easily obtainable radiative decay rate k 1r (0) of the lower excited state |1⟩, it is possible to independently determine k 2r (0), which in turn allows the determination of k nr (0) by Equations (61) and (62). Thus, luminescence thermometry also helps elucidate the different transition rates governing the kinetics of the two excited states of interest.…”

Synthesis and Bioapplications of Ag2S Quantum Dots with Near‐Infrared Fluorescence

“…The fluorescence lifetime of the Ag 2 S QDs was prolonged from 184 to 1200 ns and the absolute QY was increased by an order of magnitude (from 0.2% to 2.3%). [ 28 ] The advantages of this high‐temperature method for synthesizing Ag 2 S QDs are outstanding crystallinity, speed, high differentiation between nucleation and growth, and good size uniformity. However, high temperature is accompanied by high energy consumption and limited tunability of crystal type and bandgap (especially for some substable crystal types).…”

Gold Nanoclusters for NIR‐II Fluorescence Imaging of Bones

“…Therefore, this novel imaging strategy via NIR‐II would provide an approach for monitoring the bone, which is much attractive in comparison to other bone‐affinity fluorophores that require the removal of skin for in vivo imaging. [ 21 ]…”

“…Therefore, this novel imaging strategy via NIR-II would provide an approach for monitoring the bone, which is much attractive in comparison to other bone-affinity fluorophores that require the removal of skin for in vivo imaging. [21] To find out which components in bone were the target of the AuNCs, ex vivo fluorescence imaging of bone was performed. As shown in Figure 4a,b, after the removal of skin, the mice were shown very strong NIR-II fluorescence in spinal processes, vertebral bodies, ribs, etc.…”