Thermal-induced formation of a three-dimensional nanoplasmonic sensor from Ag nanocubes with high stability and...

Nanoplasmonic sensors based on the localized surface plasmon resonance (LSPR) of noble metal nanoparticles have many advantages, such as real-time detection, no need for reagent labelling, and no use of complicated equipment. However, the nanoplasmonic sensors with two dimensional structures usually suffer from a low LSPR signal and thus low sensitivity due to the low density of the nanoparticles. In addition, complicated surface functionalization is always required to suppress the non-specific binding of the analyst to the substrate of the sensor, because the two types of surface, that is, metal and substrate surfaces, are simultaneously exposed to the reaction medium. To overcome these problems, an innovative thermal-induced method has been proposed in the present work, to construct three dimensional (3D) nanostructure of Ag nanocubes on both surfaces of the substrate by using the unique amphiphilic property of 2-diethylaminoethanethiol. The prepared nanoplasmonic sensor is highly sensitive due to the high density of 3D structure of the nanoparticles and the low non-specific binding since only one type of surface is exposed. To enhance the stability of the sensor, a thin SiO2 overlayer was formed on the surface without using an additional coupling agent. Furthermore, the Ni(II)-nitriloacetic acid (Ni(II)-NTA) complex was covalently bound on the surface, so that the regeneration and reuse of the sensor becomes easy. Therefore, the easy fabrication, high stability, and good reusability of this 3D LSPR sensor makes our method competitive for the development of nanoplasmonic sensors.