1：Experimental Design and Method Selection:

The study involved the fabrication of flexible plasmonic SERS substrates by decorating Ag NPs on regenerated cellulose from waste paper. The GTAC with positive charges was grafted onto the surface of the cellulose textile fibers through cationization under alkaline conditions. Plasmonic Ag NPs with negative charges were then decorated onto the fibers via electrostatic interactions.

2：Sample Selection and Data Sources:

Cellulose textile fibers recycled from waste paper through IONCELL-F technology were used. The Ag NPs were synthesized by citrate reduction method.

3：List of Experimental Equipment and Materials:

Materials included BPA, NaOH, GTAC, MBA, PDDA, thiram, AgNO3, Na3C6H5O7, PATP. Equipment included a portable Raman spectrometer, SEM, TEM, UV–Vis spectrophotometer, and X-ray powder diffractometer.

4：Experimental Procedures and Operational Workflow:

The process involved the preparation of Ag colloid, surface modification of cellulose textile fibers with GTAC, self-assembly of Ag NPs on the fibers, and SERS sensing of BPA in water and soft drinks.

5：Data Analysis Methods:

SERS spectra were processed and plotted using Origin software. The uniformity of SERS signals was evaluated by collecting spectra from different spots of the fiber-Ag substrate.