Introduction to aggregation induced emission (AIE) materials

Idea of introducing aggregation-induced emission (AIE) fundamentally altered the scientific community's perception of classical photophysical processes. Many exciting new possibilities have been coming into light due to the emergence of AIE, such as ability of rapid detection and in analyzing variety of bioactive substances required to monitor the complexed biological processes. This also became a handy tool in elucidating the essential physiological and pathological behaviors of organisms. AIE luminogens (AIEgens) are luminous substances that are either weakly or non-emissive in organic solvents or hydrophobic environment alone, but it gives strong emissive when aggregated along with transforming polarities upon aggregation. Owing to the their outstanding advantages such as rapid turn on/off of high brightness emission, big Stokes shift, excellent photostability, and strong biocompatibility AIEgens have become first choice among bio-inspired probes in biomedicine. In the view of providing basic information on AIE, this chapter give a brief overview of aggregation-caused quenching (ACQ) phenomenon, approaches to transform ACQ to AIE phenomenon, photo-physics of AIE phenomenon, followed by known and reportedly novel AIE active molecules and their biomedical applications.