For the photothermal therapy of the tumor model (HepG2), an 808-nm laser with a power density of 2 W/cm 2 was used to irradiate the tumors in xenografted tumor-bearing mice once at 12 h after tailvein injection (dose of 6.7 μg/g) of the NPs. The status of the tumor after the laser irradiation was monitored by IVIS imaging system every two days (up to 10 days). Immediately after the laser irradiation for 10 min, some parts of the tumor in the PPD2-treated mice turned dark brown. Interestingly, the fluorescence of the PPD2 NPs disappeared in the tumor region after the laser irradiation. After 2 days, the tumor region developed eschars and turned black in the whole tumour region (Figure ). No obvious change was observed after 4 days, except for some slight recovery of the fluorescence in the tumour region. Some shrinkage of the tumor was observed after 8 days and 10 days, respectively. Similar results, except for some recurrence of the tumor of some mice, were observed in the group Please do not adjust margins Please do not adjust margins of mice treated with PPC5 NPs and the laser irradiation under the same condition as described above. (Figure ) The comparison suggests that the phototherapeutic effect of PPC5 NPs is not as good as that of PPD2 ones, which is consistent with the superior photothermal effect of the latter as shown in Figure . In contrast to the obvious phototherapeutic effect of PPD2 and PPC5 NPs, the control group of mice treated with PBS and the laser irradiation under the same condition did not show any phototherapeutic effect at all, and obvious growth of the tumor was observed over 10 days (Figure ). In addition, negligible changes were observed in the time dependence of body weight of mice (Figure ), suggesting the good biocompatibility of these NPs.