Water-Soluble Ag Nanoclusters Exhibit Strong Two-Photon-Induced Fluorescence

摘要

The constraints imposed by high sensitivity cellular and medical imaging, especially through tissue, have fueled efforts in developing red and near-infrared (NIR) fluorophores. Ideal for excitation and emission within the optical window from 630-1100 nm, two-photon excited fluorescence offers high spatial resolution owing to its inherent quadratic intensity dependence, while also providing spectral selectivity and improved sensitivity resulting from decreased NIR absorption, scattering, and fluorescence in tissue. Many fluorophores have been created and characterized for multi-photon bioimaging. Push-pull organic dyes have been created with high absorption cross sections, but water-soluble organic dyes are plagued by low two-photon absorption (TPA) cross sections and rapid photobleaching.