Laser reshaping of gold nanoparticles for highly sensitive SERS detection of ciprofloxacin

Laser reshaping of hexagonal gold plates is demonstrated to generate particles with different size and shape, which is further used for highly sensitive label-free surface-enhanced Raman scattering detection of synthetic antibiotic ciprofloxacin. A nanosecond laser can be used to reshape gold particles to 120-nm diameter and form a spherical-hexagonal combined structure, while a femtosecond laser can reshape the particles into spherical and triangle shapes with an average size of 6 nm. The nano-sized particles can help to enhance the Raman signal and demonstrate a superior performance with a lowest detection limit of 7.5 × 10⁻⁸ M for the ciprofloxacin sensing in milk. The presented ultrafast laser reshaping of gold nanoparticles can be exploited in a wide range of plasmonic enhanced sensing applications for a simple, fast, flexible, and portable biomaterial detection.