Aggregation Induced Emission Enhancement (AIEE) of Naphthalene‐ Appended Organic Moiety: An Al³⁺ Ion Selective Turn‐On Fluorescent Probe

Abstract

An example of an aggregation‐induced emission enhancement (AIEE)‐active new naphthalene appended Schiff base (H2L) as an Al3+ ion selective fluorescent sensor has been successfully designed and synthesized. H2L showed turn‐on fluorescence at high concentration in DMF only, and at low concentration in DMF‐H2O mixtures having high water content (more than 20%). But at very low concentration of H2L and in DMF/H2O solutions with low water fraction (fw ≤ 20%), the fluorescence was turned ON in presence of Al3+ ions, which helps to detect Al3+ ions as low as 4.9×10−7 M with high selectivity in an DMF solution without any interference of other competitive metal ions. The fluorescence of H2L in different conditions and in solid state due to AIE effect has been established with the help of detailed spectroscopic studies, dynamic light scattering (DLS), scanning electron microscope (SEM), life time using time‐resolved photoluminescence and optical fluorescence microscope. The experimentally observed H‐type aggregation nature of the probe H2L has also been supported by the theoretical (DFT studies and TDDFT) studies. This probe (H2L) has also been employed for on‐site Al3+ ions detection in solid state.

Smart-Phone-Assisted Optical Biosensors Based on Silk-Fibroin-Decorated Reduced Graphene Oxide Quantum Dots for Fluorescent Turn-On Recognition of l-Dopa

“…This effect is demonstrated in Figure S5a,b. All of these solvent effects are responsible for the AIEE mechanism through the formation of J/H type aggregation . Furthermore, in the presence of saturated KCl solution (2 M), the fluorescence intensity of the sensing mixture decreased significantly.…”

“…In a non-aggregated state, molecules undergo intramolecular motions (vibration and rotation) against their molecular axis that serves as a relaxation pathway for excited-state molecules to decay. − On the other hand, in the aggregated state, all non-radiative pathways are blocked due to the restriction in intramolecular rotation as well as vibration, and H/J aggregate formation followed the radiative path with induced emission. , As both are reliant on solvent polarity, AIEE and AIE have different relative intensities in solution states. The AIE effect is when the solvent allows for no fluorescence of the material prior to aggregation and displays an increase in PL intensity after aggregation, whereas the AIEE effect is when the materials initially produce low PL intensity in the selected solvent and increase their relative intensity after aggregation with the analytes. − Several factors can interfere with the AIE/AIEE process such as the viscosity of the solvents, temperature effect on sensing media, and polarity of the solvents. Viscosity and polarity have a similar effect as their increment promotes the RIR effect favoring AIE/AIEE, while the reverse effect is observed for an increase in temperature of the sensing media .…”

Red-Emitting AIEE-Active Rhodamine-Based Ionic Liquid for the Ultrasensitive and Selective Detection of Mercury Ions

“…Nevertheless, in mixtures containing a high water content, the solute molecules quickly agglomerate in a random way to form highly emissive amorphous particles. Therefore, an increase of the volume percentage of water facilitates the aggregation of RhB-IL in favor of AIEE …”

Understanding a Thermoemissive ESIPT-Based Solid-State Off–On Switch as a Dual-Channel Chemosensor in Solid and Solution Phases: Detailed Experimental and Theoretical Study

“…So the probe HL has a better limit of detection as well as a binding constant with Al 3+ and Zn 2+ ions in solution phases compared to previously reported works (Table S2). − …”