View article

By means of ab initio calculations, a new concept of the mixed π-conjugated bridge is identified to significantly improve the first hyperpolarizability of a D–π–A system based on carbon nanotubes (CNTs). This mixed π-conjugated bridge is constructed through applying a –(CHCH)x–NH2 chain to modify the end of the CNT system, which can effectively increase the degree of charge transfer and decrease the transition energy. This further results in a considerable first hyperpolarizability, much larger than that of the corresponding directly NH2-modified CNT system with the same conjugated length. In particular, the first hyperpolarizabilities of these tube–chain (CNT–(CHCH)x–NH2) systems can exhibit a monotonous increase with lengthening the –(CHCH)x–NH2 chain. This overcomes the bottleneck encountered with pure CNT serving as the π-conjugated bridge: that further extending the CNT will not produce any …