Review on new horizons of aggregation induced emission: from design to development

An unusual behavior of some organic luminophores in which intensity of emission is enhanced in aggregated condition is known as aggregation induced emission (AIE). The exposure of this concept to the scientific community significantly changes the perception towards conventionally used photophysical phenomena. Due to the high quantum yield and tunable emission properties, AIE luminogens (AIEgens) have become promising candidates for biosensors, opto-electronics and energy applications. The excellent stimuli responsiveness of AIE luminogens (AIEgens) provides them with a key edge for sensitive measurements such as intracellular temperature, pH, etc. In recent times the immense research interest in the AIE phenomenon stems from the inherent solid-state emission as well as its constructive effect on many other phenomena such as mechanochromism, thermally activated delayed fluorescence and circularly polarized luminescence. Many AIE fluorophores readily exhibit mechanochromism but still their interaction with external stimuli results in aggregation caused quenching (ACQ). However, the latest reports shed some light on designing and developing mechanochromophores with enhanced emission. With the inclusion of bright emission, photostability, great signal to noise ratio and non-invasiveness into one package of aggregation induced emission, a significant contribution for the enrichment of the field of photodynamic therapy and theranostics can be foreseen. Hence, the aim of this review is to provide a comprehensive study on recent developments in AIE materials and their mechanochromic, photodynamic therapeutic and theranostic, sensing and electroluminescence applications which offers new possibilities to utilize AIE materials. This review article is devoted to future research perspectives and challenges towards the development of AIE materials for modern technological and therapeutic applications.