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

Abstract

Well-defined and uniform double-walled Cu₇S₄ nanoboxes with an average edge length of about 400 nm have been successfully synthesized by using Cu₂O nanocubes as sacrificial template based on an inward replacement/etching method. The key step of the process involves repeated formation of Cu₇S₄ layer in Na₂S solution and dissolution of the Cu₂O core in ammonia solution for two consecutive cycles. Experiments show that the time of dissolving Cu₂O core with ammonia solution plays a key role in the preparation of double-walled Cu₇S₄. The as-prepared samples have been characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and photoluminescence analysis. NH₃ sensing properties of Cu₇S₄ 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 Cu₇S₄ nanobox sensor exhibited enhanced performances such as higher sensitivity and shorter response time in ammonia gas sensing compared with the single-walled one.