A series of 4-N,N-dimethylaminoaniline salicylaldehyde Schiff-base derivatives (DAS) were facilely prepared. They exhibit typical AIE properties with various fluorescence emissions and high fluorescence quantum yields in an aggregated state. DAS exhibit unique pH-dependent optical properties, which indicated their potential applications in pH sensing.

Luminescent molecules with photochromic properties show strong potential in molecular switches, molecular logic gates, photo-controllable materials, bio-imaging, anti-counterfeiting, photo-patterning, etc. However, research is still scarce in such molecules exhibiting reversible photo-controllable color and fluorescence changes in solid states, which is due to the aggregation-caused quenching (ACQ) effect of most luminogens. In this work, a reversible photochromic molecule (1) with aggregation-induced emission (AIE) properties was developed. Compound 1 exhibits typical AIE properties as a result of restricted intramolecular rotation (RIR) and excited-state intramolecular proton transfer (ESIPT) processes. As a photochromic molecule, compound 1 shows reversible color and fluorescence changes upon UV light irradiation with good fatigue resistance. More importantly, the conversion rate from its irradiated form to its initial form is controllable by temperature and long wavelength light irradiation, which makes it suitable for photo-patterning materials with erasable properties.

In this work, a novel photo-controllable third-order nonlinear optical (NLO) switch based on a rhodamine B salicylaldehyde hydrazone metal complex was developed.

Aggregation-induced emission luminogens (AIEgens) have been widely used in the development of functional materials due to their excellent luminescence properties in the solid state. The development of new AIEgens is of great significance. In this work, a novel o-phthalimide-based AIEgen of 2,3-diphenylquinoxaline-6,7-dicarboimide (2) is reported, which exhibited multifunctional sensing applications. Interestingly, compound 2 exhibited ultrafast photo-response properties upon UV light irradiation in both the dissolved state and solid state, which was attributed to a unique photo-induced rearrangement reaction. This property of 2 makes it suitable for UV sensing and photo-patterning materials with a significant fluorescence change. Meanwhile, based on the highly specific interaction between Hg(II) and the o-phthalimide moiety of 2, a complex of 2-Hg-2 formed in the presence of 0.5 equiv. Hg(II), resulting in a strong fluorescence change of 2. The active hydrogen in the o-phthalimide moiety also makes the fluorescence of 2 sensitive to the pH of aqueous solutions. Due to these characteristics, 2 was successfully used in the detection of UV light, Hg(II) and the pH of aqueous solutions, in which 2 exhibited satisfactory detection performance.