Layer-By-Layer Deposition for 2D Nanoparticle Superlattices Stabilized by Schiff Base Reaction for a Recyclable SERS Application

Abstract

2D nanoparticle superlattices (NPSLs) are of great interest for their unique collective properties that are highly desirable for potential applications such as electronic devices, sensing, and catalyst. Here, a layer-by-layer deposition method is reported for fabricating 2D NPSLs stabilized by Schiff base reaction that provides high structural stability in solvents of different polarities. 2,5-hexanedione and hexagonal closed packed spherical gold nanoparticle (Au NP) monolayer film with micrometer-sized single crystalline domains formed at the air-liquid interface are sequentially deposited on a functionalized Si substrate. Schiff base reaction is induced between amine group (─NH₂) on Au NP monolayer and ketone group (─C═O) in 2,5-hexanedione by thermal treatment, resulting in Au NP monolayer stabilized on Si substrate. By repeating the same procedure, Au NP bilayer and trilayer stabilized on Si substrate are successfully formed. These 2D Au NPSLs show highly enhanced Raman intensities that significantly increase with the number of layers. The high structural stability of the 2D Au NPSLs on a Si substrate enables its repeated use as a surface-enhanced Raman scattering substrate for 10 consecutive cycles. The method developed in this study provides new opportunities for potential applications of 2D NPSLs which require robust structural stability in solvents.