Photochemical synthesis of silver nanoprisms via green LED irradiation and evaluation of SERS activity

Silver nanoprisms (AgNPrs) are promising candidates for surface-enhanced Raman scattering (SERS) due to their strong localized surface plasmon resonance and sharp tip geometry. In this study, AgNPrs were synthesized through a photochemical method by irradiating spherical silver nanoparticle seeds with 10 W green light-emitting diodes (LEDs; 520 ± 20 nm) for various periods of time up to 72 h. The growth mechanism was investigated through ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, X-ray diffraction, and transmission electron microscopy analyses, confirming the gradual transformation of spherical seeds into AgNPrs. Optimal conversion was observed after 72 h of irradiation, producing well-defined AgNPrs with an average size of 78 nm. The SERS activity of the AgNPrs was evaluated using 4-mercaptobenzoic acid as a probe molecule. Compared to spherical AgNPs, AgNPrs exhibited a significantly higher SERS enhancement factor of 1.15 × 10⁶, enabling detection limits down to 10^-9 M. These findings demonstrate that green LED-mediated synthesis provides a simple, environmentally friendly route to fabricate high-yield AgNPrs with superior SERS capabilities, suitable for ultrasensitive chemical and biological sensing applications.