In an era of dramatic changes, enterprises tend to rely on tracking the main trends of technological evolution to maintain a competitive advantage when confronted with the impact of competing new and old technologies and disruptive innovation. This paper explores the evolution of nanotechnology via an analysis of the patent co-classification from the database at the United States Patent and Trademark Office (USPTO). A total of 518 patents on nanotechnology were analyzed. The trend of nanotechnology and the patents of high betweenness centrality were identified. It was found that the technical classifications of "semiconductor device manufacturing" and "chemistry of inorganic compounds" have the highest potential for future growth. These classifications have shown a stable number of filed patents and have become the mainstream in nanotechnology development since the 1980s. Furthermore, this study also showed that the patents owned by the US comprise a significant portion of the applications in the major technical classifications, which has played an important role in the evolution of nanotechnology. The results demonstrated that an analysis of the patent network can be a useful tool for both understanding and predicting the trend of an emerging technology.