Ultrafast studies of gold, nickel, and palladium nanorods

Abstract

Steady state and ultrafast transient absorption studies have been carried out for gold, nickel, and palladium high aspect ratio nanorods. For each metal, nanorods were fabricated by electrochemical deposition into approximately 6 microm thick polycarbonate templates. Two nominal pore diameters(10 and 30 nm, resulting in nanorod diameters of about 40 and 60 nm, respectively) were used, yielding nanorods with high aspect ratios (>25). Static spectra of nanorods of all three metals reveal both a longitudinal surface plasmon resonance (SPR(L)) band in the mid-infrared as well as a transverse band in the visible for the gold and larger diameter nickel and palladium nanorods. The appearance of SPR(L) bands in the infrared for high aspect ratio metal nanorods and the trends in their maxima for the different aspect ratios and metals are consistent with calculations based on the Gans theory. For the gold and nickel samples, time resolved studies were performed with a subpicosecond resolution using 400 nm excitation and a wide range of probe wavelengths from the visible to the mid-IR as well as for infrared excitation (near 2000 cm(-1)) probed at 800 nm. The dynamics observed for nanorods of both metals and both diameters include transients due to electron-phonon coupling and impulsively excited coherent acoustic breathing mode oscillations, which are similar to those previously reported for spherical and smaller rod-shaped gold nanoparticles. The dynamics we observe are the same within the experimental uncertainty for 400 nm and infrared (5 microm) excitation probed at 800 nm. The transient absorption using 400 nm excitation and 800 nm probe pulses of the palladium nanorods also reveal coherent acoustic oscillations. The results demonstrate that the dynamics for high aspect ratio metal nanorods are similar to those for smaller nanoparticles.

Vibrational Dynamics of Silver Nanocubes and Nanowires Studied by Single-Particle Transient Absorption Spectroscopy

“…The average damping time for the silver nanowires was (78.4 AE 22.3) ps, and the average quality factor was determined to be Q Ag;wire ¼ (23.2 AE 6.1) (errors equal standard deviations). The damping times measured in our experiments are much longer than those from ensemble measurements for the breathing mode of nanowires, [51,52] as expected from the broad distribution of widths in these samples.…”

Tuning the acoustic frequency of a gold nanodisk through its adhesion layer

“…Significant research efforts have been focused on the study of acoustic phonon modes in metallic nanoparticles using both ensemble [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and single-particle 23,[27][28][29][30][31][32][33][34][35][36] transient extinction measurements. These studies have shown that the elastic constants of the nanoparticles, obtained from the measured lattice vibrations, agree well with those of the corresponding bulk materials, suggesting that, generally speaking, there is no change in the elastic properties of nanoscale objects because of their smaller size 40 .…”

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

“…The other research group also reported the TAS studies on Au NRs at 410 nm excitation wavelength and observed that the transient bleaching of TSPR and LSPR absorptions show similar intensity results to previous studies. 9−11,17−20…”

“…The few experimental studies have been focused on the electron dynamics of the Au NRs by pump–probe transient absorption spectroscopy. 9−11,17−20…”