Research Article

Golden Layers: Advances and Challenges in Self-Assembled 2D Gold Monolayers

Abstract

Self-assembled two-dimensional (2D) Au monolayer films result from the self-organization of Au nanoparticles (Au-NPs) forming a single-layer film. This critical review analyzes the complexity in the field of self-assembled 2D Au monolayer films with focus on their preparation methods, tuning of the electronic and optical properties, and possible applications. First, fundamental concepts of self-assembled 2D Au monolayer films are introduced. Following that, different approaches are discussed to tune the electronic structures of self-assembled 2D Au monolayer films through chemical doping, substrate effects, and strain engineering. Each method contributes to changes in the electronic structures of these monolayers, which are crucial for various applications. Next, the optical properties of 2D Au-NP monolayer films are analyzed with focus on the resonance condition and electromagnetic enhancement associated with localized surface plasmon resonance (LSPR). Parameters affecting the LSPR phenomenon and their optical responses are investigated, which can be quantitatively described under specific circumstances. In addition, the applications of 2D Au monolayer films in surface-enhanced Raman scattering (SERS) and photoelectric devices are explored. The significance of 2D Au monolayer films in improving the sensitivity of SERS sensors and performances of photoelectric devices is emphasized. The main challenges involved in the design of self-assembled 2D Au monolayer films, such as stability, homogeneity, environment responsiveness, and large-scale fabrication, are pointed out. Finally, promising solutions to these challenges, advanced characterization techniques, and the incorporation of 2D Au monolayers into sophisticated devices are anticipated. This review concludes by proposing the future direction for self-assembled 2D Au monolayer films to ensure further robustness and functionalities and biomedical applications.