Structural, Polymorph and Property Investigations of Realgar for Undergraduate Education

Abstract

An integrated research-style experiment on the preparation, characterization, and photoelectric properties of realgar (As4S4) is developed to enhance the interest, hands-on skills and innovative ability of undergraduates. Initially, students prepared red crystals of α-As4S4 by the solvothermal method and characterized via modern spectroscopic techniques including X-ray diffraction, X-ray photoelectron spectroscopy (XPS), UV–vis absorption and Raman spectroscopy. Then, they tested photoelectric properties of α-As4S4, revealing that it shows remarkable photocurrent response under visible-light illumination. Finally, students made DFT calculations to further illustrate the photoexcitation mechanism. Such experiment is beneficial to (a) deepen students’ comprehension of low oxidation state As(II), As–As bonds, As···S weak interactions, polymorph and cluster structure of α-As4S4, (b) improve their hands-on skills, scientific thinking and innovative ability, and (c) stimulate students to explore the new photoelectric materials via property study.