Hybrid charge transfer complex–silver nanoparticles for portable colorimetric and fluorescence detection of aflatoxin B1 in contaminated peanuts

Abstract

Silver-incorporated charge-transfer complex nanoparticles (CTAg) were synthesized and evaluated as a highly sensitive chemosensor for the rapid detection of aflatoxin B1 (AFB1). The parent charge-transfer complex (CTC) was constructed via N⁺–H⋯O⁻ hydrogen bonding among 1,3,5-tri(m-pyridin-3-ylphenyl)benzene (BTy), chloranilic acid (ChA), and 6-hydroxypyridine-3-carboxylic acid (FA), followed by Ag⁺ incorporation to yield CTAg nanoparticles. Structural, morphological, and thermal characteristics were determined by FTIR, PXRD, UV-vis spectroscopy, fluorescence spectroscopy, SEM, TEM, TGA-DTA, ¹H NMR, and DFT/TD-DFT calculations. TEM and SEM confirmed the nanoscale granular morphology of CTAg with high surface area for interaction with the analyte. Fluorescence titration experiments showed significant quenching of CTAg by interaction with AFB1 through synergistic static and dynamic modes involving Förster resonance energy transfer (FRET) and Dexter electron transfer (DET). The chemosensor has a 0.1407 ppb detection limit and a fast response and is highly effective. Practical applicability was shown by monitoring AFB1 in Aspergillus flavus contaminated peanut samples with efficiency similar to pure AFB1 standards. Moreover, CTAg nanoparticles were inscribed into plain paper strips, allowing for naked-eye colorimetric fluorescence-based detection in daylight and UV light. The facile synthesis, strong sensitivity, and portability of CTAg demonstrate its potential as an effective on-site sensing platform for food safety monitoring.