Moreover, little change of the average diameter (56 nm) of NPs (Figure ) was observed by DLS after the heating process, suggesting good colloidal stability and integrity of the NPs. In the emission spectra of PPC15 NPs at 55 o C, the fluorescence (FL) intensity at 806 nm became 10-fold lower than the initial FL intensity at 25 o C. Notably, a full recovery of FL intensity was also observed after cooling down, further supported by the IVIS images (Figure ). The dramatic attenuation of emission at 55 o C may be due to the reabsorption phenomena of monomers confined in NPs. Similar phenomenon of enhanced FL intensity was also observed in Jaggregates of other molecular fluorophores, 4 resembling nature's strategy of circumventing concentration quenching in photosynthetic light-harvesting systems. Please do not adjust margins Please do not adjust margins