Nonblinking Colloidal Quantum Dots via Efficient Multiexciton Emission

Abstract

Nonblinking colloidal quantum dots (QDs) are significant to their applications as single-photon sources or light-emitting materials. Herein, a simple heatup method was developed to synthesize high-qualityWZ-CdSe/CdS core−shell colloidal QDs, which achieved a near-unity photoluminescence quantum yield (PLQY). It was found that the blinking behavior of such QDs was completely suppressed at high excitation intensities, and ultra-stable PL emission was observed. For this reason, a systematic investigation was conducted, revealing that the complete blinking suppression was attributed mainly to the efficient multiexciton emission at high excitation intensities. Such high-quality QDs with nonblinking behaviors and nearly ideal PL properties at high excitation intensities have massive potential applications in various robust conditions, including QD display screens, single-particle tracks, and single-photon sources.

Rational Tuning of Metal–Semiconductor Nano-Icosapods for Plasmon-Induced Photodetection

“…Here, Ag-CdS icosapods with uniform CdS arms ( D of 5.9 ± 1.3 nm and L of 50.6 ± 4.5 nm), prepared according to our recent report, were used as the seeds to adjust their diameter (Figure S5). With the aim to promote the lateral growth of the CdS arms, a new reaction system was developed by using ammonium thiocyanate (NH 4 SCN) as the sulfur precursor. , The D of the Ag-CdS icosapods has been successfully tuned from the original 5.9 ± 1.3 to 7.6 ± 1.0, 11.2 ± 1.2, 17.2 ± 1.5, and finally 20.5 ± 2.9 nm, respectively, while the L of the arms is almost kept the same (Figure a–d). The obtained Ag-CdS icosapods still show high monodispersity and uniformity after the secondary growth.…”

“…However, this method is complicated and time-consuming, as it involves consecutive and alternating injection of cationic and anionic precursors into the reaction mixture with core nanocrystals. , The modulation of the CdS arms on the tetrapods can also be achieved by adjusting the molar ratio of octadecylphosphonic acid to oleic acid, but the diameter and length can only be tuned in a narrow range . In our synthesis, pure CdCl 2 and OA are proposed to be the key for the continuous tuning of the arm diameter. ,− First, Cl – can form a complex with Cd 2+ with the assistance of OA, which can slow down the reactivity of the precursor, effectively suppressing the homogeneous nucleation and growth of CdS nanocrystals. Second, OA is considered to be the ligand weakly binding to the (100) facets of CdS, which would promote the lateral growth under optimal conditions.…”

Halide Ions Regulating the Morphologies of PbS and Au@PbS Core–Shell Nanocrystals: Synthesis, Self-Assembly, and Electrical Transport Properties

“…In our work, the PbS NCs were synthesized by hot-injection method, in which the solution of NH 4 SCN dissolved in oleylamine (OM) was quickly injected into the precursor solution of PbO, 1-octadecene (ODE), oleic acid (OA), and OM (see Methods for details). The reactive S 2– is released by means of thermal decomposition of SCN – ions ,, and then reacts with the Pb 2+ to generate PbS NCs. The as-prepared PbS NCs have rock-salt structure and sheet-like configuration with elongated hexagonal shape (Figure S1), which is distinct from the former report by direct decomposition of Pb­(SCN) 2 .…”

Scalable Synthesis of High‐Quality Core/Shell Quantum Dots With Suppressed Blinking

“…In our recent work, we have investigated the blinking behavior of single CdSe/CdS rod-in-dot QDs at various excitation intensities from 10 to 1000 W•cm −2 , whereas these QDs show obvious blinking behavior under excitation intensities less than 100 W•cm −2 (ref. [41]). Here, we study the blinking behaviors of as-prepared core/shell QDs under 450 nm pulsed laser excitation with a power density of 10 W•cm −2 , and the corresponding blinking behavior of these QDs can be visualized in Movies S1-S8, Supporting Information.…”