Plasmonic platforms for colorimetric sensing of cysteine

Cysteine plays a crucial role in physiological processes, as well as in the food, pharmaceutical, and even personal care industries, which is of great significance to control its concentration. Plasmonic nanomaterials have attracted increasing interest in colorimetric sensing, due to their outstanding optical, chemical, and catalytic properties. Their colors, derived from the absorption of the localized surface plasmon resonance (LSPR), strongly depend on the shape, size, constituent, and aggregates states, which could be tuned by cysteine. This review highlights the recent advances in cysteine detection with plasmonic nanoparticles as colorimetric platforms, wherein the colors of nanomaterials change upon the introduction of cysteine, which could be easily followed by the naked eye without requiring any instrumentation. The selective and sensitive detection mechanisms are discussed. The presence of cysteine could adjust the shape, size, constituent, and interparticle distance of nanomaterials, leading to the color transformation. In addition, the introduction of cysteine could adjust the catalytic capability of nanomaterials, resulting in the color variance. Based on those mechanisms, the colorimetric detection of cysteine could be achieved in a facile way. Finally, challenges and future perspectives are outlined.