A novel aggregation-induced emission (AIE) structure incorporating a tetraphenylethene (TPE) unit covalently linked to a spiropyran (SP) unit has been synthesized and investigated in semi-aqueous solutions with a 90% water fraction. The open-form red-emissive merocyanine (MC) unit, when combined with the TPE unit, functions as a bi-fluorophoric sensor for detecting lead(II) ions (Pb²⁺). This transformation occurs upon UV exposure, converting the nonemissive closed-form SP unit into the emissive MC form. In this system, the TPE unit serves as an energy donor with blue-green photoluminescence (PL) emission at 480 nm, while the MC unit acts as an energy acceptor with red PL emission at 635 nm. Due to Förster resonance energy transfer (FRET), the bi-fluorophoric sensor exhibits enhanced ratiometric PL behavior, resulting in stronger red emission compared to the monofluorophoric MC unit alone. Upon Pb²⁺ binding, the FRET-OFF process is triggered, turning off the red emission from the coordinated MC acceptor and restoring the blue-green emission from the TPE donor. This dynamic response enables highly sensitive detection, achieving a limit of detection (LOD) as low as 0.27 µM. The high red MC emission intensity coupled with optimal FRET efficiency was leveraged in cell viability tests, confirming the AIE sensor’s non-toxic nature and strong performance as a bio-marker for live-cell imaging of Pb²⁺. The developed FRET-OFF mechanism with ratiometric PL output offers significant potential for future applications in chemo- and biosensing.
The study highlights the importance of developing rapid, selective, and cost-effective methods for Pb²⁺ detection due to its widespread environmental presence and severe health risks.5786-21-0 Formula Traditional fluorescent sensors often suffer from aggregation-caused quenching (ACQ) in high-concentration or solid states. In contrast, the AIE phenomenon, particularly involving TPE derivatives, allows for intense fluorescence in aggregated states due to restricted intramolecular rotation. By integrating TPE with the photochromic MC unit, a dual-responsive system was created that combines both AIE and optical switching capabilities. UV irradiation induces the SP-to-MC isomerization, activating the FRET pathway. The spectral overlap between TPE emission and MC absorption ensures efficient energy transfer, enhancing the red signal. However, upon Pb²⁺ coordination, the MC unit’s ability to act as an acceptor is disrupted, leading to FRET inhibition and a visible shift from red to blue-green emission—ideal for visual detection.BTN1A1 Antibody medchemexpress
Characterization techniques such as dynamic light scattering (DLS), X-ray diffraction (XRD), and time-resolved photoluminescence (TRPL) confirmed structural changes and energy transfer dynamics.PMID:35021209 DLS revealed nanoparticle formation with average diameters consistent with aggregation behavior. TRPL measurements showed a dramatic reduction in TPE lifetime—from 5.10 ns in TPE-SP-P to just 0.44 ns in TPE-MC-P—indicating near-complete FRET efficiency (~91%). After Pb²⁺ binding, the lifetime increased to 1.48 ns, confirming FRET-OFF. Theoretical calculations using TD-DFT supported these findings, showing favorable orbital alignment and energy transfer pathways between TPE and MC units. Furthermore, pH and temperature studies demonstrated robustness under physiological conditions (pH 3–9, ≤45°C), although extreme conditions caused structural instability.
Confocal fluorescence imaging in HeLa cells validated the sensor’s biocompatibility and utility in live-cell monitoring. Cells treated with TPE-MC-P exhibited strong red emission, which switched to blue-green upon Pb²⁺ addition, enabling real-time tracking. Additionally, test paper-based detection was developed: a TPE-SP-P impregnated paper strip was converted to TPE-MC-P via UV exposure, then used to detect Pb²⁺ in contaminated water within seconds. The reversible color change allowed for reusable, on-site testing. Overall, this work presents a powerful, multifunctional platform for lead ion detection combining AIE, photochromism, and FRET in a single molecular design, offering high sensitivity, selectivity, and practical applicability across environmental, clinical, and biological settings.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
