The invention relates to a multifunctional nanomaterial comprising a nanorod comprising 1) a noble metal, wherein the nanorod exhibits surface plasmon resonance absorption in the near-infrared spectrum; 2) an up-conversion phosphor that absorbs infrared light and emits visible luminescence; and optionally 3) a biomolecule targeting moiety. The invention further relates to methods of detecting and treating cancer using the multifunctional nanomaterials of the invention.