The present invention relates to the formation and processing of nanostructures including nanotubes. Some embodiments provide processes for nanostructure growth using relatively mild conditions (e.g., low temperatures). In some cases, methods of the invention may improve the efficiency (e.g., catalyst efficiency) of nanostructure formation and may reduce the production of undesired byproducts during nanostructure formation, including volatile organic compounds and/or polycylic aromatic hydrocarbons. Such methods can both reduce the costs associated with nanostructure formation, as well as reduce the harmful effects of nanostructure fabrication on environmental and public health and safety.