title: Metastable tetragonal Cu2Se hyperbranched structures: large-scale preparation and tunable electrical and optical response regulated by phase conversion.
abstract: Despite the promising applications of copper selenide nanoparticles, an in-depth elucidation of the inherent properties of tetragonal Cu(2)Se (β-Cu(2)Se) has not been performed because of the lack of a facile synthesis on the nanoscale and an energy-intensive strategy is usually employed. In this work, a facile wet-chemical strategy, employing HCOOH as reducing agent, has been developed to access single-crystalline metastable β-Cu(2)Se hyperbranched architectures for the first time. The process avoids hazardous chemistry and high temperatures, and thus opens up a facile approach to the large-scale low-cost preparation of metastable β-Cu(2)Se hyperbranched architectures. A possible growth mechanism to explain the formation of the β-Cu(2)Se dendritic morphology has been proposed based on time-dependent shape evolution. Further investigations revealed that the metastable β-Cu(2)Se can convert into the thermodynamically more stable cubic α-Cu(2-x)Se maintaining the dendritic morphology. An increase in electrical conductivity and a tunable optical response were observed under ambient conditions. This behavior can be explained by the oxidation of the surface of the β-Cu(2)Se hyperbranched structures, ultimately leading to solid-state phase conversion from β-Cu(2)Se into superionic conductor α-Cu(1.8)Se, which has potential applications in energy-related devices and sensors.
authors.affiliation: Department of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, PR China.
authors.forename: Jinbao
authors.initials: J
authors.lastname: Zhu
authors.forename: Qiuyang
authors.initials: Q
authors.lastname: Li
authors.forename: Liangfei
authors.initials: L
authors.lastname: Bai
authors.forename: Yongfu
authors.initials: Y
authors.lastname: Sun
authors.forename: Min
authors.initials: M
authors.lastname: Zhou
authors.forename: Yi
authors.initials: Y
authors.lastname: Xie