Abstract: The present disclosure describes radiation-assisted, substrate-free, and solution-based nanostructure (e.g., a nanotube and/or a nanowire (NW)) growth processes. The processes use the high absorption coefficient and high density of free charge carriers in particle seeds (e.g., nanoparticles, metal nanoparticles, and/or metal nanocrystals) to photothermally drive semiconductor nanostructure growth. The processes can be performed at atmospheric pressure, without specialized equipment such as specialized heating equipment and/or high-pressure reaction vessels.