Castor oil derivatives in the environmentally friendly one-pot synthesis of silver nanoparticles: application in cysteine sensing

Natural products-mediated synthesis has become quite an interesting route for the ecofriendly production of nanomaterials. However, products employed in nature may require long reaction times and high temperatures that lead to non-ideal particle-size distribution. In this work, we developed an optimized one-pot synthesis of silver nanoparticles using isolated ricinoleic acid (extracted from castor bean plant) and its epoxidized form as both reducer and stabilizer agents to convert silver ions into silver nanoparticles at room temperature. Through a design of experiments, we discovered that the epoxidized form of the ricinoleic acid is far more effective than its unmodified counterpart in terms of reaction time and homogeneity of nanoparticles. The silver nanoaparticles were then evaluated as functional chromogenic probes for cysteine sensing, allowing for direct naked-eye detection and a limit of detection of 25.37 mu mol L-1. Cysteine sensing mechanisms are also discussed in this work. This approach reinforces the advantages in using purified natural products over their direct natural sources.