Cotton swabs wrapped with three-dimensional silver nanoflowers as SERS substrates for the determination of food colorant carmine on irregular surfaces

A lightweight, portable, low-cost, and accessible cotton swab was employed as surface enhanced Raman spectroscopy (SERS) matrix template. The silver nanoflowers were in situ grown on the surface of cotton swabs to form three-dimensional Ag nanoflower@cotton swabs (AgNF@CS) SERS substrate with high-density and multi-level hot spots. The SERS performance of AgNFs@CS substrates with various reaction time was systematically studied. The optimal AgNF-120@CS SERS substrate exhibits superior detection sensitivity of 10⁻¹⁰ M for methylene blue, good signal reproducibility, high enhancement factor of 1.4 × 10⁷, and excellent storage stability (over 30 days). Moreover, the AgNF-120@CS SERS substrate also exhibits prominent detection sensitivity of 10⁻⁸ M for food colorant of carmine. Besides, the portable AgNF-120@CS SERS substrate is also capable of detecting food colorant residues on irregular food surfaces. Graphical abstract: (Figure presented.).