Point‐of‐Care Paper‐Based Sensors through Surface Etching of Gold Nanostars

Abstract Paper‐based analytical devices as a low‐cost and point‐of‐care sensing platform have attracted widespread research interest. However, the device fabrication and signal readout remain a challenge for their real‐world applications. Herein, a technically simple paper‐based sensor is developed by taking advantage of the easily accessible paper and the plasmonic property of gold nanomaterials. The sensing mechanism relies on the iodide‐mediated surface etching of gold nanostars that induces a color change from blue to red of the paper strip. The versatility of the paper substrate in size, shape, and materials allows for the facile immobilization of gold nanostars by a simple immersing method, which is easy to operate and free from specialized skills and equipment. In addition, the readout of the paper strip can be conveniently visualized by the naked eye or through a smartphone. This paper‐based sensor advantages in low cost, light weight, easy handling, and disposability that holds great promise as a point‐of‐care detection platform in resource‐constrained settings.