Seeing is believing: hot electron based gold nanoplasmonic optical hydrogen sensor

Area of Science:

• Nanophotonics
• Plasmonics
• Chemical Sensing

Background:

• Noble metal nanostructures exhibit unique optical properties due to localized surface plasmon resonance (LSPR).
• Hot electrons generated in plasmonic nanoparticles can drive chemical reactions.
• Optical detection of gases offers rapid and sensitive analysis.

Purpose of the Study:

• To report a novel method for rapid optical detection of gaseous hydrogen.
• To investigate the mechanism of hydrogen detection using plasmonically excited gold nanohemispheres.
• To explore the role of hot electrons and gold hydride formation in optical signal generation.

Main Methods:

• Fabrication of substrate-based gold nanohemispheres (Au NHs).
• Optical transmission measurements upon exposure to hydrogen gas.
• Excitation wavelength-dependent studies to identify optimal LSPR conditions.
• Numerical simulations including discrete dipole approximation (DDA) and finite-difference time-domain (FDTD) methods.

Main Results:

• Demonstrated rapid optical detection of hydrogen gas.
• Observed changes in optical transmission attributed to hot electron-induced H2 dissociation and metastable gold hydride (AuHx) formation.
• Maximized sensing response at the LSPR wavelength of Au NHs.
• FDTD simulations confirmed enhanced electric fields at the interface due to Au NHs, contributing to photocatalytic activity.

Conclusions:

• Gold nanohemispheres enable sensitive and rapid optical detection of hydrogen.
• The sensing mechanism involves plasmon-enhanced hot electron generation and subsequent chemical reactions.
• The geometry of nanohemispheres significantly enhances electric fields, improving sensing performance.