Locking the phenyl rings of tetraphenylethene step by step: understanding the mechanism of aggregation-induced emission

Stepwise locking of phenyl rings of tetraphenylethene increases the emission efficiency of luminogen solutions gradually, thus verifying the restriction of intramolecular rotation (RIR) mechanism of the aggregation induced emission phenomenon. The emission of the luminogen with one O bridge could be tuned reversibly in solid state through repeated heating and grinding.