Design, Preparation And Properties Of Copper Chalcogenides With Hollow Nanostructures

Copper chalcogenides, as an important kind of semiconductors, have been considered for potential applications in solar cells, nanoswitches, thermo electric converters, electrode materials, catalysts and superionic conductors.In our previous work, double-walled Cu7S4 and Cu2-xSe nanotube arrays have been successfully prepared through an elaborate strategy. Based on the previous work of our group, in the present dissertation, a variety of copper chalcogenides with hollow nanostructures have been fabricated, including single- and double-walled Cu7S4 nanoboxes, Cu7S4 18-facet nanopolyhedra, single-walled Cu2-xSe hollow nanospheres, Cu2-xSe/Cu7S4 heterogeneous hollow nanospheres and Ag3CuS2 nanocages. Properties related with the double-walled as well as heterogeneous hollow nanostructures have been investigated. Main points are summarized as follows:1. Double-walled Cu7S4 nanostructures are fabricated through an inward lithography method and their gas sensing properties are investigated in this thesis. Single-walled Cu7S4 nanoboxes with wall thickness of about 20 nm and average edge length of about 400 nm are fabricated based on template of Cu2O nanocubes. Furthermore, double-walled Cu7S4 nanoboxes with the same wall thickness and size are prepared. Photoluminescence (PL) spectra of both samples are analyzed. Ammonia sensing properties of Cu7S4 nanoboxes with single and double walls have been investigated at room temperature with a simply adapted PL-type gas sensor. Results reveal that double-walled Cu7S4 nanobox sensor exhibits enhanced performance such as higher sensitivity, better stability and shorter response time in ammonia gas sensing compared with single-walled one. Double-walled structures and the distinct architectures of the nanoflakes on inner box are believed to be responsible for their enhanced ammonia sensing performance. A possible sensing mechanism is proposed.2. Cu2-xSe/Cu7S4 heterogeneous hollow nanospheres are obtained based on an extended inward lithography method and their optical and electrochemical properties have been investigated in detail. Cu2-xSe hollow nanospheres with wall thickness of around 20 nm are synthesized based on the Cu2O nanosphere templates. Furthermore, Cu2-xSe/Cu7S4 heterogeneous hollow nanospheres with same thickness as that of Cu2-xSe nanospheres are prepared. UV-vis and PL spectra of Cu2-xSe/Cu7S4 heterogeneous hollow nanospheres have been analyzed. Results indicate that there are obvious red-shift of their UV-vis adsorption peak and blue-shift of their PL emission peaks, compared with those of Cu2-xSe single component. Electrochemical analysis implies their promising application in detecting trace amounts of Rhodamine B. A possible mechanism is discussed with respect to the changes of their optical and electrochemical properties, compared with those of single component Cu2-xSe.3. Ag3CuS2 with novel hollow nanostructures is synthesized and applied in gas sensing. Cu7S4 18-facet nanopolyhedra with average size of about 400 nm are obtained first through the direct reaction of Cu2O nanocubes and Na2S solutions without any help of heating and surfactants. Ag3CuS2 with novel morphology of nanocages are obtained via a facile ion-exchange route by AgNO3 reacting with these Cu7S4 hollow nanostructures. PL spectra and ammonia sensing performances of Ag3CuS2 nanocages have been investigated. Compared with solid shape counterparts, hollow Ag3CuS2 exhibits distinct PL characteristic and improved ammonia sensing performances, such as higher sensitivity, shorter response and recovery time. Hollow structures are believed to be responsible for the improved ammonia sensing performances.