**Appendix A**

**Figure A1.** TEM, HAADF, and EDS characterization of the prepared nanoparticles with different amounts of Ag seeds: (**a1**–**a5**) 40 µL, (**b1**–**b5**) 80 µL, (**c1**–**c5**) 160 µL, and (**d1**–**d5**) 500 µL.


**Table A1.** Characteristic vibrations of fentanyl.
