The development of highly sensitive and selective fluorescent chemosensors for metal ions has attracted significant attention due to their applications in environmental monitoring, clinical diagnostics, and biological imaging. Among various metal ions, copper (Cu²⁺) is particularly important because of its essential role in physiological processes and potential toxicity at elevated concentrations. Conventional fluorescent probes often suffer from limitations such as poor solubility in water, low stability, interference from other ions, and limited reusability. To overcome these challenges, researchers have turned to hybrid organic-inorganic materials that combine the advantages of both components.
In this study, a novel organosiloxane precursor, (E)-3-hydroxy-4-((2-(2-hydroxy-4-(3-(3-(triethoxysilyl)propyl)ureido)benzoyl)hydrazono)methyl)phenyl(3-(triethoxysilyl)propyl)carbamate (AHBH-Si), was synthesized and used together with tetraethyl orthosilicate (TEOS) as mixed silicon sources. Through a co-condensation reaction, bridged periodic mesoporous organic silica (AHBH-PMOs) nanoparticles were successfully fabricated. These hybrid materials exhibit unique fluorescence properties derived from two key mechanisms: Aggregation-Induced Emission (AIE) and Intramolecular Charge Transfer (ICT). The molecular structure of AHBH contains critical functional groups—CvN bonds and ortho-hydroxyl groups—that enable efficient ICT and facilitate AIE behavior when restricted within a rigid silica matrix.
Upon incorporation into the silica framework, the mobility of AHBH molecules is significantly restricted, suppressing non-radiative decay pathways and enhancing fluorescence emission via the AIE effect. This results in a strong “off-on” transition where previously weakly fluorescent AHBH becomes highly emissive inside the PMO network. Upon exposure to Cu²⁺, however, the fluorescence is quenched again, forming an “off-on-off” response pattern. This dual-switch mechanism offers superior sensitivity and selectivity compared to traditional “on-off” or “off-on” systems. The detection limit for Cu²⁺ reaches as low as 3.26 × 10⁻⁹ M, demonstrating exceptional performance even in complex aqueous environments.
Extensive characterization techniques including FTIR, ¹H NMR, HRMS, and DFT calculations confirmed the coordination interaction between AHBH and Cu²⁺.GNAS Antibody Data Sheet The data reveal that Cu²⁺ binds through nitrogen and oxygen donor atoms from the deprotonated imine and hydroxyl groups, forming a stable 1:2 complex.SLC45A3 Antibody Technical Information Density functional theory (DFT) simulations further demonstrated a significant reduction in the HOMO-LUMO energy gap upon complexation, which stabilizes the system and facilitates electron transfer, leading to fluorescence quenching.PMID:34510007
Importantly, AHBH-PMOs maintain excellent performance across a wide pH range (5–12), showing minimal interference from common cations such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Zn²⁺, Pb²⁺, Fe³⁺, and others. Competitive experiments confirm that Cu²⁺ can effectively quench fluorescence even in the presence of interfering ions. Furthermore, the sensor exhibits reversible behavior: adding EDTA restores the original fluorescence intensity, confirming its reusability and practical applicability.
Solvent effects were also investigated. In THF-water mixtures, AHBH and AHBH-Si display pronounced AIE behavior, with maximum fluorescence observed at 60% water content. Additionally, increasing solvent polarity induces a red shift in emission due to enhanced ICT effects. These findings underscore the multifunctional nature of the material, integrating multiple luminescent mechanisms for robust sensing.
In conclusion, the AHBH-PMO nanomaterials represent a promising class of solid-state fluorescent sensors capable of detecting Cu²⁺ in pure aqueous solutions with high sensitivity, selectivity, low detection limits, and excellent recyclability. By leveraging the synergistic interplay between AIE and ICT within a rigid silica host, this work advances the design principles of next-generation chemosensors for real-world environmental and biomedical applications.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com