By exploring whether nanotechnologies have the potential to generate green innovations, we consider the paradox between the negative and positive side-effects that could come with the development of nanotechnologies. Starting from the conceptual framework of green product innovation, the potential green innovation activity of more than 14,000 firms of the nanotech sector is investigated. Using a query-search method, their patenting activity is explored. Results first show that there is an increasing trend toward the creation of fundamental green knowledge by firms (...) involved in nanotechnologies; second, they demonstrate that energy efficiency is the main driver of green knowledge creation in the sector and third they reveal the main characteristics of nanotech firms creating green knowledge. Beyond their contribution to the debate between positive and negative outcomes of nanotechnology developments, these results also enrich the conceptual framework of green product innovation—a key route to achieving sustainability at the same time as growth. (shrink)