A method for fabricating porous wire-in-tube (WiT) nanostructures including forming a first porous core-shell nanostructure, forming a second porous core-shell nanostructure by increasing thickness and porosity of the porous core-shell nanostructure, and forming a porous WiT nanostructure by etching the second porous core-shell nanostructure. Forming the first porous core-shell nanostructure may include forming a porous layer on a semi-conductive core by depositing a first plurality of particles on the semi-conductive core and generating an initial porous semi-conductive core by etching the semi-conductive core simultaneously with forming the porous layer.