We report here file study of two-photon induced luminescence of 11- mercaptoundecanoic acid functionalized quantum-sized Au nanodots (11MUA-Au nanodots). The X-ray absorption near- edge structure (XANES) measurement at the gold L-m edge indicates that the oxidation state of the surface of 11MUA- Au nanodots is best described as Au+ The two-photon absorption (TPA ) property of 11MUA-Au nanodots was then investigated via an open aperture Z-scan method. Together with a precise extinction coefficient (i.e. one- photon absorption) extracted from inductively Coupled plasma mass spectrometry, the TPA cross section, sigma, was deduced to be 8761 175 GM (800 nm) for 11MUA-Au nanodots (diameter 1 33 +/- 0.12) in water. Upon dextran encapsulation, 11MUA-Au nanodols was proved to be highly water- soluble, stable, and low ill toxicity, which demonstrated its power in two -photon imaging toward human mesenchymal stem cells (hMSCs) in vitro. ; 附設醫院影像醫學部 ; 醫學院附設醫院 ; 期刊論文