Studies of Ultrafast Transient Absorption Spectroscopy of Gold Nanorods in an Aqueous Solution

Herein, ultrafast transient absorption spectroscopy is performed to probe the electron transfer studies between aqueous solution and gold nanorods (Au NRs). The seed-mediated growth method is used to synthesize crystalline cylindrical Au NRs having longitudinal plasmon resonance peak maximum at 825 nm. The as-synthesized Au NRs show average width and length of ∼10 ± 2 and ∼50 ± 2 nm, respectively, with an aspect ratio in the range of ∼5. The time-resolved decay profiles have been studied in a subpicosecond resolution range using pump wavelength at 410 nm excitation and probe wavelengths from visible to near-infrared region. The plasmon dynamics studies of Au NRs depend on the electron heating phenomena, coherent acoustic phonon vibration and electronic transient behavior, i.e., electron-phonon coupling, and homogenous dephasing processes. Thus, the obtained results highlighted that the ultrafast charge transfer dynamics studies in Au NRs could play an important role to elucidate their electronic, photothermal, and optical properties for molecular imaging, photothermal therapy, and optoelectronic and light-harvesting devices.