Abstract: Disclosed herein are fusion peptides comprising a fluorescent domain and a rare earth element detection domain capable of binding to a rare earth element and fluorescing when exposed to light when a rare earth element is bound and compositions thereof. The fusion peptide may further comprise a leader domain and a tail domain. The fusion peptide acts as a biosensor to detect and quantify rare earth elements. Methods for imaging internal body structures, detecting rare earth elements in a biosample or environmental sample, and cleaning an environmental site are also presented.