Excitation wavelength based reversible multicolour photoluminescence by a single chromophore upon aggregation: Detection of picric acid-application in bioimaging

In an attempt to achieve photo switching of multicolour photoluminescence on a unimolecular platform, herein we report a benzothiazole based probe as an excitation wavelength sensitive multicolour emitter in its aggregated state. Though in solution the blue emission overwhelms others, but in the dry state the emission in blue, green and red with intermediate yellow could be achieved. Further, the probe in its aggregated state detects picric acid in solution, solid and live cells, where blue emission is quenched in all the three working media while the red emission is activated in solid state and live cells. TD-DFT (time dependent density function theory) calculations were performed to understand the electronic properties and sensing behaviour of the probe. This probe constitutes a first example of detection of picric acid in human cancer cells to the best of our knowledge. The tuneable multicolour emission of the probe suggests its possible implementation in applications related to OLEDs.