The application relates to a nanovesicle comprising a bilayer of at least 15 mol % porphyrin-phospholipid conjugate, wherein the conjugate comprises a porphyrin, porphyrin derivative or porphyrin analog covalently attached to the phospholipid side chain. The nanovesicle can be used for photothermal therapy, photoacoustic imaging, and fluorescence imaging. The application also discloses a method of preparing the said nanovesicle.