A targetable nanoconstruct capable of simultaneously serving as a therapeutic platform for photodynamic therapy as well as an MR molecular imaging agent, free of heavy metal atoms. F3-cys targeting agent nanoconstructs, including 8PEGA-Ce6 NCs. A label-free 8PEGA nanoconstruct that can be directly and selectively imaged by MRI, using standard spin-echo imaging sequences with large diffusion magnetic field gradients to suppress the water signal.