We present a method to separately tune the multiphoton absorption (MPA) and multiphoton excited photoluminescence using semiconductor core/enlarged-shell quantum dots (QDs), where the enlarged shell greatly enhances the MPA cross-sections while varying the core size facilitates emission wavelength selectivity. Following two-photon absorption (2PA) primarily in the shell and ultrafast charge-carrier localization to the core, luminescence occurs. We exemplify the validity of this method with CdSe/CdS nanorod heterostructures and find that the 2PA cross-section is enlarged to ∼1.4×106 GM for 180 nm nanorods (with 800 nm, 150 fs laser pulse excitation) which is two to four orders larger than that of CdSe QDs.
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Xing et al. (2010) studied this question.