Facile synthesis of size-tunable L-carnosine-capped silver nanoparticles and their role in metal ion sensing and catalytic degradation of <i>p</i>-nitrophenol

ʟ-Carnosine is a dipeptide with notable antioxidant, antiglycation, metal chelating, and neuroprotective properties. Despite its many biological roles, applying ʟ-carnosine as a capping agent in nanoparticle synthesis has remained underexplored. This study explores the potential of ʟ-carnosine in synthesizing tunable plasmonic silver nanoparticles (ʟ-car-AgNPs). The formation of ʟ-car-AgNPs was confirmed via UV-vis optical absorption spectroscopy, showing single and double plasmonic peaks, depending on the synthesis conditions. Physicochemical characterization using TEM, FTIR, and Raman spectroscopy, as well as EDX and XRD revealed controlled aggregation, successful capping, and crystalline growth of the ʟ-car-AgNPs. The ʟ-car-AgNPs exhibited promising sensing capabilities with limits of detection of 141.79 ppb (1.2 μM) for Cd²⁺, 131.33 ppb (0.63 μM) for Pb²⁺, 215.35 ppb (2.8 μM) for As³⁺, and 245.49 ppb (4.7 μM) for Cr³⁺. Additionally, these nanoparticles demonstrated catalytic activity regarding the degradation of <i>p</i>-nitrophenol (P-NP), achieving complete degradation of 0.25 and 1 mM solutions within 5 and 10 min, respectively. This study reveals the potential of ʟ-car-AgNPs for both heavy metal ion detection and catalytic degradation of P-NP, indicating their suitability for environmental monitoring and remediation applications. Further optimization and research are needed to expand their environmental applications and to understand their interaction mechanisms with various contaminants.