Luminescent polymer nanomaterials and thin films have a range of applications as sensing and imaging probes. Properties such as deep red or near-infrared (nir) emission or absorption, long lifetime emission, or nonlinear optical effects can further extend the capabilities of these systems. Using all-organic molecules exhibiting thermally activated delayed fluorescence i have prepared polymeric emitters with long (μs) lifetime emission in the deep red/nir. These emitters can be incorporated into water-soluble polymer dots, retaining their desirable emissive properties giving nir-emissive nanoparticles suitable for time-resolved imaging. My work has also explored materials with red emission but higher-energy absorption as two-photon excited fluorescence imaging probes.