Photoluminescence Enhancement, Blinking Suppression, and Improved Biexciton Quantum Yield of Single Quantum Dots in Zero Mode Waveguides

Abstract

The capability of quantum dots to generate both single and multiexcitons can be harnessed for a wide variety of applications, including those that require high optical gain. Here, we use time-correlated photoluminescence (PL) spectroscopy to demonstrate that the isolation of single CdSeTe/ZnS core−shell, nanocrystal quantum dots (QDs) in Zero Mode Waveguides (ZMWs) leads to a significant modification in PL intensity, blinking dynamics, and biexciton behavior. QDs in aluminum ZMWs (AlZMWs) exhibited a 15-fold increase in biexciton emission, indicating a preferential enhancement of the biexciton radiative decay rate as compared to the single exciton rate. The increase in biexciton behavior was accompanied by a decrease in blinking events due to a shortening in the dark state residence time. These results indicate that plasmon mediated enhanced decay rates of QDs in AlZMWs lead to substantial changes in the photophysical properties of single quantum dots, including an increase in biexciton behavior.

Single Photon Source from a Nanoantenna-Trapped Single Quantum Dot

“…Besides, the on- and off-state probabilities are modified (Supporting Information Figure S11), leading to a more stable PL emission in the presence of the gold nanoantennas. This observation of QD blinking reduction goes in line with previous reports using conductive materials. ,,− Both the higher brightness of the on-state and the strongly suppressed blinking contribute to improve the PL emission of the QD trapped in the antenna.…”

“…This correlation at zero lag time is well below the 0.5 threshold that determines the boundary between single and multiple quantum emitters, demonstrating a plasmonic antenna-enhanced triggered single-photon emission. ,, For some selected QDs, we find an even lower antibunching with (Figure S12), yet this corresponds to less than 10% of all QDs tested. Importantly, it shows that the residual correlation found at zero lag time is limited by the QD sample and its biexciton quantum yield , and is not related to the nanoantenna trap.…”

“…2,51,68 For some selected QDs, we find an even lower antibunching with ≈ g (0) 0.2 (2) (Figure S12), yet this corresponds to less than 10% of all QDs tested. Importantly, it shows that the residual correlation found at zero lag time is limited by the QD sample and its biexciton quantum yield 22,51 and is not related to the nanoantenna trap. S1.…”

“…A major requirement for optical nanoantennas is that the quantum emitter must be positioned at the antenna hotspot with nanoscale precision in order to achieve the highest enhancement. Many approaches have been explored, relying on random dispersion, − two-step electron-beam lithography, , two-step nanofabrication, , DNA origami, , DNA self-assembly, , or atomic force microscopy . However, none of these techniques offer the simplicity and flexibility of plasmonic nano-optical tweezers where the trapped object is automatically positioned at the antenna hot spot. − Using the intense field gradients in plasmonic nanoantennas, − it becomes possible to manipulate single quantum emitters such as NV centers, , quantum dots, − erbium-doped nanocrystals, , or even a single atom .…”

Gold Ion Beam Milled Gold Zero-Mode Waveguides

“…As a result, ZMWs have found wide application in studies of genomic sequencing [ 47 , 48 , 49 , 50 ], protein–protein interaction [ 51 , 52 , 53 , 54 ], ligand–receptor binding [ 55 , 56 , 57 , 58 , 59 , 60 , 61 ], membrane-bound diffusion events [ 62 , 63 ] and the study of membrane proteins [ 64 , 65 ]. ZMWs have also been used to manipulate exciton behavior in quantum dots [ 66 ], and ZMWs have been shown to extend Förster Resonance Energy Transfer (FRET) distances from 10 to 13.6 nm [ 67 ]. A recent mini-review describes applications of these nanostructures for single molecule experiments [ 68 ].…”