Retained fluorescence of aggregation-caused quenched Rhodamine grafted in the hierarchical mesopores of silica MCM-41 at solid-state

Traditional organic compounds in dilute solutions exhibit different photophysical properties in comparison to their concentrated solutions. For example, organic materials which obey the aggregation-caused quench (ACQ) effect phenomena are known to have weak luminescence at solid-state (or in high concentration solutions) as compared to their dilute counterparts. This effect limits the application of ACQ compounds at solid-state. Herein, we report a way to overcome this phenomenon in Rhodamine B (RhB) by anchoring it to mesoporous silica having a hierarchical structure (referred to as MCM-41) with the help of 3-Aminopropyltriethoxysilane (APTES). Neat solid-state RhB suffers dynamic intramolecular rotations which results in non-radiative annihilation of its excited states and thus luminescence quenching. The strategy explored herein of employing APTES-MCM-41 exposes the cylindrical one-dimensional mesopores of silica for possible selective anchoring of RhB dyes, which helps to overcome the stacking interactions of the fluorophores-thus fluorescent retention. Finally, we went on to show the capabilities of the modified reserved-fluorescent ACQ RhB-grafted mesoporous silica as a possible concentration indicator for liquids and vapors. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.