Two-photon absorption (2PA) offers several advantages for bio-oriented applications, such as intrinsic three-dimensional resolution and increased penetration depth in biological materials such as tissue. The essential background theory needed for an understanding of 2PA is described, the key experiments to quantify 2PA merit and molecular design to optimise material performance are discussed and the existing challenges in the use of 2PA in imaging, therapy and theranostics are reviewed.

The overview and progress of the selection of substrate and template, immobilization methods and thickness controlling strategy in surface imprinting is emphasized. Furthermore, immobilization methods such as ligand, metal ion, covalent interaction and physical adsorption are introduced.