Sub-Diffraction Correlation of Quantum Emitters and Local Strain Fields in Strain-Engineered WSe2 Monolayers.

Strain-engineering in atomically thin metal dichalcogenides is a useful method for realizing single-photon emitters (SPEs) for quantum technologies. Correlating SPE position with local strain topography is challenging due to localization inaccuracies from the diffraction limit. Currently, SPEs are assumed to be positioned at the highest strained location and are typically identified by randomly screening narrow-linewidth emitters, of which only a few are spectrally pure. In this work, hyperspectral quantum emitter localization microscopy is used to locate 33 SPEs in nanoparticle-strained WSe2 monolayers with sub-diffraction-limit resolution (≈30 nm) and correlate their positions with the underlying strain field via image registration. In this system, spectrally pure emitters are not concentrated at the highest strain location due to spectral contamination; instead, isolable SPEs are distributed away from points of peak strain with an average displacement of 240 nm. These observations point toward a need for a change in the design rules for strain-engineered SPEs and constitute a key step toward realizing next-generation quantum optical architectures.

Conversion of Classical Light Emission from a Nanoparticle-Strained WSe2 Monolayer into Quantum Light Emission via Electron Beam Irradiation.

Solid-state single photon emitters (SPEs) within atomically thin transition metal dichalcogenides (TMDs) have recently attracted interest as scalable quantum light sources for quantum photonic technologies. Among TMDs, WSe2 monolayers (MLs) are promising for the deterministic fabrication and engineering of SPEs using local strain fields. The ability to reliably produce isolatable SPEs in WSe2 is currently impeded by the presence of numerous spectrally overlapping states that occur at strained locations. Here nanoparticle (NP) arrays with precisely defined positions and sizes are employed to deterministically create strain fields in WSe2 MLs, thus enabling the systematic investigation and control of SPE formation. Using this platform, electron beam irradiation at NP-strained locations transforms spectrally overlapped sub-bandgap emission states into isolatable, anti-bunched quantum emitters. The dependence of the emission spectra of WSe2 MLs as a function of strain magnitude and exposure time to electron beam irradiation is quantified and provides insight into the mechanism for SPE production. Excitons selectively funnel through strongly coupled sub-bandgap states introduced by electron beam irradiation, which suppresses spectrally overlapping emission pathways and leads to measurable anti-bunched behavior. The findings provide a strategy to generate isolatable SPEs in 2D materials with a well-defined energy range.

Nanoparticle surfactants for kinetically arrested photoactive assemblies to track light-induced electron transfer.

Nature controls the assembly of complex architectures through self-limiting processes; however, few artificial strategies to mimic these processes have been reported to date. Here we demonstrate a system comprising two types of nanocrystal (NC), where the self-limiting assembly of one NC component controls the aggregation of the other. Our strategy uses semiconducting InP/ZnS core-shell NCs (3 nm) as effective assembly modulators and functional nanoparticle surfactants in cucurbit[n]uril-triggered aggregation of AuNCs (5-60 nm), allowing the rapid formation (within seconds) of colloidally stable hybrid aggregates. The resultant assemblies efficiently harvest light within the semiconductor substructures, inducing out-of-equilibrium electron transfer processes, which can now be simultaneously monitored through the incorporated surface-enhanced Raman spectroscopy-active plasmonic compartments. Spatial confinement of electron mediators (for example, methyl viologen (MV2+)) within the hybrids enables the direct observation of photogenerated radical species as well as molecular recognition in real time, providing experimental evidence for the formation of elusive σ-(MV+)2 dimeric species. This approach paves the way for widespread use of analogous hybrids for the long-term real-time tracking of interfacial charge transfer processes, such as the light-driven generation of radicals and catalysis with operando spectroscopies under irreversible conditions.

Effect of age and pathologic Gleason score on PSA recurrence: analysis of 2911 patients undergoing radical prostatectomy.

OBJECTIVES: To clarify the relationship between age and pathologic Gleason score and their effect on prostate-specific antigen recurrence (PSAR). METHODS: The data from a cohort of 2911 men who had undergone radical prostatectomy from 1988 to 2006 were retrieved from the Duke Prostate Center database. Patient age was divided into 3 groups: <60, 60-64, and >or=65 years. The pathologic Gleason score was divided into 5 groups: 7. PSAR was defined as the prostate-specific antigen level increasing to >0.2 ng/mL >30 days after radical prostatectomy. The associations between age and pathologic Gleason score on PSAR and the time to PSAR were analyzed using parametric, nonparametric, Kaplan-Meier, and Cox regression techniques. RESULTS: Patient age and interval to PSAR had no significant association (P > .05). Kaplan-Meier analysis demonstrated a significant difference in PSAR among age groups. The pathologic Gleason scores of 3 + 3, 3 + 4, 4 + 3, and >7 were significant in determining the incidence of PSAR. Age was not significant for PSAR in patients with a pathologic Gleason score of 7, a statistically significant difference was observed among the age groups. Men <60 years old with a pathologic Gleason score >7 had a lower incidence of PSAR than did older men with a similar pathologic Gleason score. A pathologic Gleason score of >or=6 was significant in predicting PSAR. CONCLUSIONS: Age alone was an independent factor in predicting PSAR, but not in predicting the interval to PSAR. The pathologic Gleason score remained a predictor of PSAR, and patient age should be considered in patients with a pathologic Gleason score >7.