An inward replacement/etching route to synthesize double-walled Cu7S4 nanoboxes and their enhanced performances in ammonia gas sensing.

Well-defined and uniform double-walled Cu(7)S(4) nanoboxes with an average edge length of about 400 nm have been successfully synthesized by using Cu(2)O nanocubes as sacrificial template based on an inward replacement/etching method. The key step of the process involves repeated formation of Cu(7)S(4) layer in Na(2)S solution and dissolution of the Cu(2)O core in ammonia solution for two consecutive cycles. Experiments show that the time of dissolving Cu(2)O core with ammonia solution plays a key role in the preparation of double-walled Cu(7)S(4). The as-prepared samples have been characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and photoluminescence analysis. NH(3) sensing properties of Cu(7)S(4) nanoboxes with single and double walls have been investigated at room temperature with a simply adapted photoluminescence-type gas sensor. The results revealed that the double-walled Cu(7)S(4) nanobox sensor exhibited enhanced performances such as higher sensitivity and shorter response time in ammonia gas sensing compared with the single-walled one.