Synthesis and Characterization of Quantum Dots: A Case Study Using PbS Yi Pan, Yue Ru Li, Yu Zhao, and Daniel L. Akins* Department of Chemistry and the Center for Analysis of Structures and Interfaces (CASI), The City College of New York, New York, New York 10031, United States *S Supporting Information ABSTRACT: A research project for senior undergraduates of chemistry has been developed to introduce syntheses of a series of monodispersed semiconductor PbS quantum dots (QDs) and their characterization methodologies. In this paper, we report the preparation of monodispersed semiconductor PbS QDs with sizes smaller than the exciton Bohr radius using a simple, one-step process, and the characterization of the QDs using a range of instruments, including Fourier-transform infrared spectroscopy, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and energy-dispersive X-ray spectroscopy. Our synthesis approach involves dissolving powdered sulfur (as the S precursor) in 1-tetradecene and adding PbCl 2 as the Pb precursor to the suspension as well as oleylamine as a capping ligand. The PbS QD project represents, we believe, an almost ideal opportunity to provide exposure of undergraduate students to nanotechnology research via syntheses and characterization of semiconductor nanoparticles. KEYWORDS: Upper-Division Undergraduate, Physical Chemistry, Testing/Assessment, Crystals/Crystallography, IR Spectroscopy, Materials Science, Colloids, Nanotechnology, Synthesis, Semiconductors A dvances in nanotechnology in the past 20 years have resulted in enormous interest in introducing nanomateri- als and associated technologies into the undergraduate curriculum, especially in chemistry. 1-6 As examples, Pavel et al. 2 have reported experiments involving a scattering species, rhodamine 6G (R6G), adsorbed onto silver nanoparticles (AgNPs), with the purpose of quantitatively measuring the surface-enhanced Raman scattering (SERS) phenomenon for the system; this study also incorporated absorbance and emission measurements. Reid et al. 3 developed a laboratory experiment involving semiconductor ZnO quantum dots (QDs) focusing on band gap 3 and absorbance characterization. Also, Lisensky et al. 6 discussed a laboratory experiment involving absorbance and emission characterization of semi- conductor CdSe QDs. However, most of the reported studies involve theoretical issues that are somewhat sophisticated for undergraduate chemical education purposes. In this article, we present our recently developed research project of semi- conductor QD synthesis and characterization to help to promote and improve college-level education focusing on undergraduate research. We also demonstrate that an under- graduate research project can be conveniently utilized as a laboratory experiment for curriculum development purposes. The main reason we selected lead sulfide QDs to introduce nanoscience research to our undergraduates is that lead sulfide QDs can be conveniently synthesized under mild temperature in a simple, one-step noninjection process. Our approach significantly reduce burn risks to undergraduates that may occur when high-temperature syntheses are undertaken. In addition, undergraduates can gain some basic knowledge related to semiconductor QDs and their applications. Semiconductor lead chalcogenide (PbS, PbSe, PbTe) QD materials show strong quantum confinement effects due to their relative large exciton Bohr radii and dielectric constants. 7,8 The quantum confinement phenomenon 3 associated with lead chalcogenide QDs can be easily observed. 9-11 More specifically, PbS is a direct narrow band semiconductor with a bulk band gap of 0.41 eV and an exciton Bohr radius of 18 nm, 8,10 and its band gap can be tuned by changing its size. 12 PbS QDs have been widely investigated as nanocrystal QD- based solar cell materials and as sensor materials. Semi- conductor PbS QD-based photovoltaics (PVs) have the advantage of processability and tunability, the latter facilitating the maximizing of overlap of incident optical excitation with the Article pubs.acs.org/jchemeduc © XXXX American Chemical Society and Division of Chemical Education, Inc. A DOI: 10.1021/ed5009415 J. Chem. Educ. XXXX, XXX, XXX-XXX