Transient Absorption: A New Modality for Microscopic Imaging of Nanomaterials in Living Cells

Transient absorption is a secondary absorption that happens after a material has been excited through primary absorption. Different mechanisms can contribute to transient absorption. This universal photophysical process exists in almost all types of nanomaterials, making it an ideal modality to monitor the location, dynamics, and interactions of nanomaterials in living cells, tissues, or animals. With two beams of lasers and a scanning microscope, transient absorption microscopy is able to acquire high‐resolution, 3D images at high speed, without the need for labeling. Through time‐delay adjustments of pulse trains, this novel method can also reveal background‐free images of specific nanomaterials, even with the interference of high concentrations of fluorophores.