Insights into the Exciton Dynamics of Functionalized 2D Nanomaterials for Robust Photoelectrochemical Sensing Applications

Summary

Photoelectrochemical sensing is a robust analytical tool for rapid, selective, and sensitive monitoring of chemical and biochemical substances. In contrast to conventional sensing techniques, the photoelectrochemical sensing method employs two separate energy sources: light for excitation and current for detection, thereby enhancing the catalytic activity and sensitivity. The superiority of photoelectrochemical sensing depends greatly on the design and engineering of photoactive materials. Visible light‐harvesting ability is a prerequisites for an efficient photoelectrochemical sensor. Furthermore, the charge separation of photogenerated excitons (electron‐hole pairs) also plays a crucial role in the efficacy of photoactive materials. Therefore, the design and development of engineered materials with enhanced light‐harvesting capacity and improved exciton lifespan are of prime importance for robust photoelectrochemical sensing applications.

Two‐dimensional nanomaterials are promising candidates for photoelectrochemical sensors owing to their intriguing properties, such as high surface‐to‐volume ratio, good stability, high electron mobility, and exciting mechanical and interfacial properties. Recently, 2D materials such as graphene, reduced graphene oxide (rGO), graphitic carbon nitride (gC₃ N₄), molybdenum disulfide (MoS₂), and boron nitride (BN) have been extensively utilized as photoactive materials for the photoelectrochemical sensing of target molecules with enhanced sensitivity and selectivity. Semiconducting 2D nanomaterials can generate excitons (electron‐hole pairs) under visible light excitation owing to their compatible narrow‐band structures. In addition, some 2D nanomaterials can enhance the life span of photogenerated excitons by lowering the charge recombination owing to the extensive π‐architecture. Moreover, charge confinement in one dimension leads to extraordinary exciton dynamics in 2D nanostructures, which can be fine‐tuned by controlled structural and morphological modifications. Surface modification of 2D nanomaterials with element doping, hybridization with noble metals, nanoheterojunction with semiconducting metal oxide/ metal sulfide nanomaterials, surface functionalization with organic ligands, and metal‐organic frameworks, have also been reported to have immense potential to synergistically alter exciton dynamics and enhance photoelectrochemical sensing performance.

Therefore, this chapter attempts to summarize and compare the recent progress in the use of 2D nanomaterials in the field of photoelectrochemical sensors and their applications, starting from the features of their synthesis and concluding remarks on the perspectives of photoelectrochemical sensing applications.