In situ scanning electrochemical microscopy (SECM) was used to study N-isopropoxypropyl-N'-ethoxycarbonyl thiourea (iPOPECTU) adsorption on chalcopyrite. The in situ SECM images indicated a preferential adsorption of iPOPECTU on chalcopyrite surfaces, resulting in a decrease in the probing electrochemical current response. The surfaces after iPOPECTU adsorption were analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS).ToF-SIMS results provided a strong evidence of iPOPECTU binding with copper only. XPS analysis showed the reduction of cupric to cuprous on chalcopyrite surfaces as a result of iPOPECTU adsorption. Our results shed light on adsorption mechanism of iPOPECTU on the surface of chalcopyrite samples. (c) 2014 Elsevier Inc. All rights reserved.