Large‐Area Nanosphere Self‐Assembly Monolayers for Periodic Surface Nanostructures with Ultrasensitive and Spatially Uniform SERS Sensing

Abstract Colloidal lithography provides a rapid and low‐cost approach to construct 2D periodic surface nanostructures. However, an impressive demonstration to prepare large‐area colloidal template is still missing. Here, a high‐efficient and flexible technique is proposed to fabricate self‐assembly monolayers consisting of orderly‐packed polystyrene spheres at air/water interface via ultrasonic spray. This “non‐contact” technique exhibits great advantages in terms of scalability and adaptability due to its renitent interface dynamic balance. More importantly, this technique is not only competent for self‐assembly of single‐sized polystyrene spheres, but also for binary polystyrene spheres, completely reversing the current hard situation of preparing large‐area self‐assembly monolayers. As a representative application, hexagonal‐packed silver‐coated silicon nanorods array (Si‐NRs@Ag) is developed as an ultrasensitive surface‐enhanced Raman scattering (SERS) substrate with very low limit‐of‐detection for selective detection of explosive 2,4,6‐trinitrotoluene down to femtomolar (10 −14 m ) range. The periodicity and orderliness of the array allow hot spots to be designed and constructed in a homogeneous fashion, resulting in an incomparable uniformity and reproducibility of Raman signals. All these excellent properties come from the Si‐NRs@Ag substrate based on the ordered structure, open surface, and wide‐range electric field, providing a robust, consistent, and tunable platform for molecule trapping and SERS sensing for a wide range of organic molecules.