Mechanistic study of colorimetric and absorbance sensor developed for trivalent yttrium (Y³⁺) using chlortetracycline-functionalized silver nanoparticles

The presence of hazardous, radioactive, and rare earth metal such as yttrium (Y³⁺) in water poses a serious health concern to the public health, thus, exploring novel Y³⁺-binding molecules and colorimetric indicators are desired. Chlortetracycline (CTC)-functionalized silver nanoparticles (AgNPs–CTC) were synthesized, purified by centrifugation and then characterized by UV–vis spectroscopy, XPS, XRD, and HR-TEM. Functionalization of AgNPs with CTC molecules enabled the rapid and sensitive detection of trivalent yttrium ion (Y³⁺). A decrease in the intensity of the original surface plasmon resonance peak at 420 nm was observed within the fraction of a min, with the simultaneous appearance of a new peak at a longer wavelength (540 nm); thus, a novel colorimetric and ratiometric absorbance probe was achieved. The free-O-containing moieties of CTC on the AgNPs surface coordinate with Y³⁺. Thus, CTC molecules led to the bridging of the AgNPs and subsequent aggregation. A good linear relationship (R² = 0.933) in the range of 18 to 243 nM for Y³⁺ was observed, and the limit of detection (LOD) for ratiometric results was approximately 57.7 nM. The AgNPs–CTC sensor exhibited better colorimetric performance in terms of excellent sensitivity, LOD, and rapid formation of the AgNPs-CTC complex towards Y³⁺. The Y³⁺ spiked water samples from different sources and fetal bovine serum suggest that the developed method is practically useful and essentially portable for on-site monitoring. The AgNPs–CTC sensor can be also applied as a common colorimetric indicator for the detection of trace levels of Y³⁺ and lanthanides.