With the support of the Chemical Mechanism, Function, and Properties Program of the Division of Chemistry, Professors Kristin Wustholz and Elizabeth Harbron of the Department of Chemistry at the College of William and Mary are developing new fluorescent dyes with unique properties for single molecule spectroscopy (SMS) applications. SMS is renowned for its ability to visualize complex materials and biological structures that are important in technology and medicine. Current SMS studies focus on brightly fluorescent materials that emit light continuously until they fail and become dark. However, some fluorescent dyes can switch between bright, dim, and dark states, with these fluctuations containing important information about the molecule, its location, and its environment. By combining expertise in chemical synthesis, SMS, and advanced statistical analysis, the team of Wustholz and Harbron is creating new dyes engineered to produce dim states and deploying them to reveal otherwise inaccessible structural and dynamic information at the single-molecule level. Students supported by this project gain a range of technical expertise. Considerable effort has been devoted to designing fluorophores that exhibit ideal fluorescence properties such as high quantum yield, which requires minimizing nonradiative deactivation pathways. Minimizing twisted intramolecular charge transfer (TICT), where an internal donor-acceptor charge transfer occurs upon molecular twisting, has improved qu