The present invention generally relates to nanoscale wires and, in particular, to nanoscale wires with heterojunctions, such as tip- localized homo- or heterojunctions. In one aspect, the nanoscale wire (10) may include a core (20), an inner shell (30), preferably insulating, surrounding the core, and an outer shell (40) surrounding the inner shell. The outer shell contacts the core at an end portion of the nanoscale core. In some cases, such nanoscale wires may be used as electrical devices. For example a p-n junction may be created where the inner shell is electrically insulating, and the core and the outer shell are p-doped and n-doped. Other aspects of the present invention generally relate to methods of making or using such nanoscale wires, devices, or kits including such nanoscale wires, or the like.