UV-Vis spectra of Cn HAT (n = 3, 8, 10, 11) SAMs were recorded by a V660 UV-Vis spectrophotometer (Brechbühler AG, Switzerland) and a Genesys 10S UV-Vis spectrophotometer (Thermo scientific, USA). The sample was prepared using the following method: a metal film of Au or Ag with a thickness of 10 nm was prepared on quartz by physical vapor deposition under high vacuum (MED 020, BAL-TEC, Leica microsystems GmbH, Switzerland). The UV-Vis spectrum of this metal substrate was collected first, and then it was immersed in an ethanoic Cn HAT solution for 2 h to obtain the Cn HAT SAM on the metal substrate. After immersion, the sample was rinsed with ethanol and dried under a flow of N 2 . The UV-Vis spectrum of the Cn HAT SAM on the metal substrate was then collected in the absorbance mode. The irradiation of the Cn HAT SAM was performed ex situ.