CuS nanoparticles (CuS NPs) were synthesized by a simple precipitation method using rice starch water as a capping and reducing agent. The phase composition, morphology, absorbance, chemical bonds, and chemical states of the CuS NPs were investigated systematically and then examined for dye degradation catalytic activity with or without sulfite (SO 3 2− ) under dark conditions. Herein, we observed two reaction trends after the addition of SO 3 2− in a CuS NPs/dye system, first substantially enhanced dye degradation and second greater degradation activity between reaction time interval "t" 0−12 min. The redox cycling of Cu(II)/Cu(I) and oxidized sulfur (SO x 2− ) species on the surface of CuS NPs played a major role for the activation of SO 3 2− and generation and transformation of a sulfite radicalScavenging studies of reactive oxygen species (ROS) revealed that • SO 4 − was major reactive species involved in dye degradation. Our study showed that SO 3 2− acted as a source and CuS NP surface acted as an SO 3 2− activating agent for the generation of • SO 4 − , which degrades the dyes. The activation pathway of SO 3 2− and generation pathway of relevant ROS were proposed.

This paper implements the 5E instructional model to reveal authentic concepts in chemistry, in particular the ambiguous oxidation state formalism of copper sulfide (CuS) for pre-service science teachers (PSTs). We discuss the process and outcomes of learning phases of the 5E (engage, explore, explain, elaborate, and evaluate) for authentic chemistry learning. The puzzle activity of engage phase demonstrate PSTs prior-knowledge, understanding, problem-solving skills in the fundamental concepts of chemistry. However, we observed misconceptions in chemistry concepts, in particular the oxidation state formalism of CuS. Next, the explore phase describe how the scientific evidence from research literature give insight into whether the PSTs conceptions are in accordance with research evidence. The research evidence from collaborative literature review revealed the uncertainty in the oxidation state formalism of CuS. In the explain phase, we explained the complex electronic structure of CuS. In the fourth phase, the elaborate phase, we involve the PSTs in the book review to elaborate and analyze the uncertain concept. The results of the book review provide insight into the coverage of oxidation state formalism of CuS in nine chemistry textbooks. Finally, in evaluate phase, the results of questionnaire describe the PSTs perspectives and experiences in the student-centered chemistry learning.