Amino-functionalized lanthanide metal-organic frameworks encapsulating boron-doped graphene quantum dots: A paper based fluorescent sensor to visual detection of salicylic acid

Abstract

Salicylic acid (SA), a widely distributed environmental pollutant, requires accurate detection for effective water quality monitoring and ecological protection. In this work, we developed a highly sensitive fluorescent sensor by encapsulating boron-doped graphene quantum dots (B-GQDs) within amino-functionalized lanthanum-based metal-organic frameworks (NH₂-La-MOFs). Upon 365 nm excitation, the composite exhibits strong blue emission peaking at 430 nm, which is significantly quenched and red-shifted to 560 nm as the SA concentration increases to 50 μM. This spectral shift is accompanied by a distinct color change visible to the naked eye, enabling intuitive visual detection. The quenching mechanism is attributed to static interactions and a reduction in the excited-state bandgap. Spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) confirms the uniform distribution of B-GQDs within the NH₂-La-MOFs matrix. Density functional theory (DFT) calculations reveal that hydrogen bonding and π–π stacking greatly enhance SA adsorption, which is consistent with the observed Zeta potential shift from −2.90 mV to −17.6 mV, indicating enhanced surface charge density and improved SA binding affinity. Selectivity tests demonstrate that the quenching efficiency (I₅₀/I₄₀ ≈ 0.15) remains stable even in the presence of 10 μM common interfering species such as Na⁺, K⁺, Mg²⁺, glucose, and alanine, indicating excellent anti-interference performance. By adopting the strategy of metal-organic frameworks coupled with boron-doped graphene quantum dots, this work provides a robust, portable, paper-based, flexible fluorescent sensor for efficient visual detection of salicylic acid in environmental applications.

Keywords

boron-doped graphene quantum dots / fluorescent sensor / metal-organic frameworks / salicylic acid / visual detection

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RIGHTS & PERMISSIONS

2026 The Author(s). FlexMat published by John Wiley & Sons Australia, Ltd on behalf of Nanjing University of Posts & Telecommunications.