New properties arise as the size of a crystal reaches the Bohr radius of excitons. This phenomenon, known as quantum confinement, has enabled powerful synthetic strategies to control the optical and electronic properties of a material through size engineering. In this talk, we will discuss a fundamentally new approach that allows systematic tailoring of nanostructure excitons through covalently bonded surface functional groups that are themselves non-emitting. Specifically, we show that by varying the surface functional groups, a semiconducting carbon nanotube can be chemically converted to create a large series of distinct near-infrared quantum emitters that are molecularly specific, systematically tunable, and significantly brighter than the parent semiconductor. In contrast with quantum confinement, where size matters, this new property-tailoring capability arises from the creation of fluorescent quantum defects that can be chemically controlled at the molecular level. This new family of quantum emitters opens up exciting new opportunities for potential applications ranging from bioimaging and sensing to quantum information processing.