Sensors are analytical devices that quantify physical or chemical information. Recently, there has been an increasing demand for high performance sensors with high sensitivity, high resolution, short response/recovery time, long lifetime, multiplexity, disposability, etc. Nanomaterial-based sensors have been of great interest due to their high performance over the past two decades. This high performance is attributed to a high surface-to-volume ratio, size similarity to target macromolecules¹  and novel detection mechanisms.^2–4 

Among these, the high surface-to-volume ratio enhances the interaction between a sample analyte and the sensor's surface. However, it is not a good strategy to keep decreasing the size of nanomaterials since van der Waals forces become dominant at the nanoscale leading to aggregation of nanomaterials. Then, the free surface is screened by neighboring individual elements and the diffusion of target molecules into the inner part of aggregates is suppressed.⁵  Therefore, the target molecule can interact only with the outer surface of aggregates and the change in material properties is limited on the outer surface, which makes it difficult to observe. The effect of such behavior in aggregates is to decrease the sensitivity and/or resolution of nanomaterial-based sensors. Moreover, the restrained diffusion of the target molecule yields a sluggish response/recovery.