Thermally robust and blinking suppressed core/graded-shell CdSe/CdSe1-xSx/CdS 'giant' multishell semiconductor nanocrystals.

Abstract

We demonstrate that core/graded-shell CdSe/CdSe1-xSx/CdS giant semiconductor nanocrystals (g-NCs) have robust photoluminescence (PL) temperature response. At a size of 10.2 nm in diameter, these g-NCs undergo a PL drop of only 30% at 355 K relative to their PL intensity at 85 K. In comparison, the core/step-shell CdSe/CdS g-NCs at the same diameter exhibit 80% PL drop at 355 K. Spectral shifting and broadening were found to be, respectively, 5-10 times and 2-4 times smaller than those observed in standard CdSe core and CdSe/CdS core/shell NCs. These core/graded-shell g-NCs are largely blinking suppressed and have insignificant photoluminescence decay even after excitation at very high irradiance (44 kW cm(-2)) for over an hour. These types of g-NC have potential applications as the active medium for thermally robust laser devices (in the visible range) or as temperature-insensitive bioprobes for biomedical imaging.

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