Teals Inspired Label-Free and Two-Colored Imprinting Probes for the Ratiometric Detection of Levofloxacin in Aqueous Solution

Inspired by the color patterns of blue-winged teals' feathers, a new biomimetic imprinting (IM) probe with chemical fluorescent (CF) color and physical structural (PS) color was developed for the label-free and ratiometric detection of levofloxacin (LOF). The probe is defined by a periodic photonic crystal structure formed by monodisperse imprinting microspheres that incorporate LOF-binding nanocavities, similar to the color emission structure of teals. With the increase of the LOF solution, the probe can selectively bind LOF molecules and demonstrate a two-color response without the use of labels: the CF color emerged from the entering of CF color-emissive LOF molecules, further enhanced by the Purcell effect, while the PS color resulted from the periodic photonic crystal structure. As the concentration of LOF increases, the CF color becomes brighter (turn on), while the PS color becomes darker (turn off). These color changes are perceptible to the naked eye. The probe demonstrated label-free, sensitive (down to 2.77 nmol/L), rapid (10 min), selective, and stable detection of the LOF, utilizing a self-correction function of colors. In addition, the probe was successfully applied in real sample detection.