Influence of Band Alignment on Electronic Relaxation in Plasmonic Metal–Semiconductor Hybrid Nanoparticles

Abstract

Recent advances in colloidal synthesis enable the generation of multicomponent metal−semiconductor nanoparticles that share a solid-state interface, thus providing a tunable platform for the tailored electronic and optical properties of nanoscale heterostructures. Here, the influence of size and material composition on electron−phonon scattering was investigated for a series of gold− metal chalcogenide (PbS, ZnS, and Cu 2−x S) hybrid nanoparticles using femtosecond time-resolved transient extinction spectroscopy. The influence of semiconductor size on electron−phonon coupling in the hybrid nanoparticles was studied using two Au−PbS systems having different PbS diameters, 6 ± 1 and 17 ± 3 nm. For Au−PbS (PbS = 6 ± 1 nm), an approximately 30% acceleration of the electron−phonon scattering rate was observed with respect to 5 ± 1 nm gold nanoparticles. In contrast, the system having the larger PbS domain size exhibited a decelerated rate when compared to gold nanoparticles. The nanostructure dependence of the electron− phonon scattering rates was attributed to differences in band edge alignment with respect to the Au Fermi level. Electron−phonon scattering was accelerated for Au−Cu 2−x S where the conduction band edge is in close alignment with the gold Fermi level. In contrast, the ultrafast response of Au−ZnS displayed no significant difference from pure AuNPs, which is consistent with minimal energy alignment between the two domains; the ZnS domain is an effective insulator in this case. These results demonstrate that controlled and selective modifications to both the size and composition of the semiconductor domain in metal−semiconductor hybrid nanoparticles impact band alignment, which in turn can be leveraged to modulate electronic thermalization in plasmonsupporting heterostructures.

Using Cation-Exchanged Nanorod Templates To Direct the Regioselective Growth and Plasmonic Coupling of Gold Nanoparticles

“…This value for the maximum absorbance is consistent with what we would expect to observe, as the ∼12 nm Au particles alone would exhibit a maximum absorbance near 520 nm that would red shift by ∼10 nm, to ∼530 nm, when coupled with ZnS. 38 For the ZnS nanorods that contain two Au particles separated by an average distance of 22 ± 9 nm, the maximum absorbance exhibited a further red shift to 542 nm, which is consistent with the red shift observed for DNA-linked Au nanoparticles having a comparable interparticle distance of 24 nm and a red shift of 15 nm. 10 We further validated that the observed red shift arises from the proximity of Au nanoparticles and not from other factors that influence the LSPR peak positions.…”

Influence of Halogen–Solvent Hydrogen Bonding on Gold Nanocluster Photoluminescence

“…Femtosecond transient absorption spectroscopy was performed using a setup that has been previously described. 35 Briefly, the 1040 nm fundamental from a 100 kHz ytterbium amplifier was used to seed a noncollinear optical parametric amplifier (NOPA) (Spectra Physics Spirit-NOPA). The NOPA was used to generate visible pulses at 575 nm with a full width at halfmaximum of 33 nm.…”

Rich Landscape of Colloidal Semiconductor–Metal Hybrid Nanostructures: Synthesis, Synergetic Characteristics, and Emerging Applications

“…Varying the size and type of the semiconductor segment in semiconductor−metal dimers resulted with an acceleration of the electron−phonon scattering rate for HNPs owing to the well-aligned semiconductor conduction band and metal Fermi level. 214 3.3.3. Charge Separation in Multiexciton Regime.…”

“…Energy band alignment was also reported to influence the electron–phonon relaxation processes. Varying the size and type of the semiconductor segment in semiconductor–metal dimers resulted with an acceleration of the electron–phonon scattering rate for HNPs owing to the well-aligned semiconductor conduction band and metal Fermi level …”