Size-dependent photoemission study by electrochemical coarsening of nanoporous gold

The generation and utilization of hot charge carriers in plasmonic materials have emerged as a topic of significant importance with profound implications across multiple disciplines, including optoelectronics, photovoltaics, photocatalysis, and sensing. In this study, we investigate the hot electron transfer from nanoporous gold (npAu) dependent on the structure size, utilizing both the nanoscale feature size and the interconnected nature of this material. We employed photoelectron injection from nanoporous gold into the electrolyte under UV illumination as a test electron transfer process. Nanoporous gold thin films with sub-10 nm initial ligament diameter are stepwise coarsened by potential cycles in a photoelectrochemical setup, thereby allowing us to precisely probe the influence of the ligament diameter on the photocurrent response. The resulting ligament diameter variations are confirmed by scanning electron microscopy (SEM) analysis. As the ligament diameter increased from 8 to 16 nm, there was a corresponding decrease in quantum efficiency proportional to the inverse ligament diameter squared. Such a dependency is expected for electrons excited by surface collisions. For the small ligament diameter of 10 nm, we estimate an emission efficiency of excited 6sp electrons as 3.14%, reaching 23% for the surface-excited electrons.

Subjects

Absorption

Gold

Hot electrons

Photoemission

Quantum efficiency

DDC Class

621.3: Electrical Engineering, Electronic Engineering

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Size-dependent photoemission study by electrochemical coarsening of nanoporous gold