NIR Excitation in Atomically Precise Nanoclusters via Two-Photon and Three-Photon Absorption.

ConspectusGold nanoclusters exhibit unique optical properties, with absorption similar to that of molecular systems, ranging from the UV to near-infrared (NIR) region with tunable photoluminescence. Nanoclusters also present outstanding multiphoton properties, with the possibility of excitation in the NIR-I and NIR-II ranges via two- or three-photon absorption. Multiphoton microscopy, which relies on multiphoton excitation, offers additional advantages such as the selective excitation of molecules only at the focal point, enabling true 3D optical sectioning and reducing photobleaching and phototoxicity compared with one-photon microscopy. Our review organizes the current knowledge on the multiphoton absorption of noble metal nanoclusters, highlighting key recent advances in the field and addressing current challenges, with particular emphasis on the potential of these nanostructures in biological NIR imaging applications. The Account starts with an introduction to the basis of multiphoton absorption and multiphoton microscopy advantages, followed by examples of applications of nanoclusters as two- and three-photon absorbers and NIR emitters. Thus, current trends and further perspectives clearly show that the application of multiphoton excitation and noble metal nanoclusters provides a highly beneficial approach for efficient NIR bioimaging.