A mixed polydiacetylenes (PDAs) vesicle with a phospholipid unit is functionalized by entrapping fluorescent benzoxazole (BZ) molecules inside the PDA vesicles. Upon photo-polymerization and heat-treatment of the self-assembled vesicles, a weak red fluorescence can be observed. Excitation of BZ molecules enables the amplification of PDA vesicle fluorescence resonance energy transfer (FRET) to more than four times that of the direct excitation of red-phase PDA vesicles. The backbone of the PDA vesicles act as energy acceptors, which absorb energy from embedded BZ donor molecules inside the PDA vesicle, which emit blue fluorescence. The amplified red emission from the PDA vesicle can be altered by pH changes in the aqueous solution and thus the PDA vesicle mixed with a phospholipid and entrapped molecules inside can be a promising candidate as a pH sensor. (C) 2012 Elsevier Ltd. All rights reserved.