Structural and fluorescence studies of B,N-codoped carbon dot@UiO-66 MOF nanocomposites for rapid and selective detection of cefixime in biological and environmental samples

Abstract

This study reports the development of a novel and sensitive fluorescence sensor for the detection of cefixime (CFX), a widely used antibiotic. The sensor is based on a highly stable B,N-codoped carbon dot@UiO-66 metal-organic framework (MOF) nanocomposite, which exhibits a BET surface area of 35.63 m2/g, a pore volume of 0.03105 cm3/g, and an average pore size of 3.49 nm, consistent with mesoporosity. ImageJ analysis revealed polyhedral-like particles ranging from 5.85 to 22.8 nm, with an average size of 15.3 nm, aligning with BET results. FE-SEM analysis confirmed a well-dispersed, heterogeneous structure, where B,N-CD nanoparticles are uniformly distributed over the UiO-66 MOF framework. EDS analysis validated the presence of C (19.65 wt.%), O (36.46 wt.%), Zr (31.71 wt.%), B (3.63 wt.%), and N (8.54 wt.%). XPS further confirmed successful element incorporation. The fluorescence of the nanocomposite was effectively quenched by CFX via static quenching and inner filter effects. The sensor exhibited a low detection limit (LOD) of 4.21 nM (1.907 ng/mL), a quenching constant of 0.0842-3.51 M-1, and a wide linear range (0-100 nM). It demonstrated high selectivity for CFX over other antibiotics and metal ions. The sensor retained stability, with only a 2.23 % fluorescence intensity decrease after 60 days at 12 degrees C, and maintained performance over multiple cycles. Recovery rates of 96.9 %-101.63 % in real-world samples (honey, tap water, seawater) further validated its applicability. These findings highlight the potential of B,N-CD@UiO-66 as a reliable sensor for CFX detection in biological and environmental matrices.