@article{742e8c08a91d4c33a267f85b2d2c0416,
title = "Upconversion photoluminescence of CdS nanocrystals in polymeric film",
abstract = "We report on nonlinear upconversion photoluminescence (PL) of CdS nanocrystals (NCs) embedded in a polymeric film. The CdS NCs of 2 nm radius are synthesized by an ion exchange method and highly concentrated in the two layers near the surfaces of a freestanding Nafion film. We observed the differences between the two-photon and one-photon excited PL emissions. The two-photon absorption cross section and quantum yield of CdS NCs were measured with femtosecond laser pulses at 800 nm excitation. The origin of PL, optical nonlinearity, and the figure of merit for optical switching have been discussed.",
author = "Jun He and Scholes, {Gregory D.} and Qu, {Y. L.} and Wei Ji",
note = "Funding Information: This work was supported by the Natural Sciences and Engineering Research Council of Canada and the National University of Singapore (Grant No. R-144-000-097-112). FIG. 1. Experimental setup for PL and TPL measurements. FIG. 2. UV-visible transmission spectra of CdS-Nafion film (thick solid line) and pure Nafion film (dotted line). FIG. 3. Room temperature Raman spectrum of the CdS-Nafion film with excitation wavelength at 514 nm of Ar ion laser. FIG. 4. Intensity-dependent open-aperture Z-scans performed with 800 nm, 90 fs laser pulses at repetition rate of 82 MHz on (a) CdS-Nafion composite film and (b) CdS bulk crystal. The scatter graphs are experimental data, while the solid lines are theoretically fitting curves by employing the standard Z-scan theory. For clear presentation, the graphs in (a) are vertically shifted by 0.2, 0.1, and 0.0, respectively. FIG. 5. One-photon excited PL spectra of (a) CdS NCs and (b) CdS bulk crystal at different excitation intensities, where I 0 ∼ 1.2 GW / cm 2 . The insets show the log-log plots of the detected PL signal (counts/s) vs the excitation intensity. FIG. 6. TPL spectra of (a) CdS NCs and (b) CdS bulk crystal at different excitation intensities. The insets show the log-log plots of the detected TPL signal (counts/s) vs the excitation intensity. ",
year = "2008",
doi = "10.1063/1.2960536",
language = "English (US)",
volume = "104",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "2",
}