Dynamics of hot carriers in plasmonic heterostructures

Abstract

Understanding and optimising the mechanisms of generation and extraction of hot carriers in plasmonic heterostructures is important for applications in new types of photodetectors, photochemistry and photocatalysis, as well as nonlinear optics. Here, we show using transient dynamic measurements that the relaxation of the excited hot-carriers in Au/Pt hetero-nanostructures is accelerated through the transfer pathway from Au, where they are generated, to Pt nanoparticles, which act as a hot-electron sink. The influence of the environment on the dynamics was also demonstrated. The time-resolved photoluminescence measurements confirm the modified hot-electron dynamics, revealing quenching of the photoluminescence signal from Au nanoparticles in the presence of Pt and an increased photoluminescence lifetime. These observations are signatures of the improved extraction efficiency of hot-carriers by the Au/Pt heterostructures. The results give insight into the time-dependent behaviour of excited compound nanoscale systems and provide a way of controlling the relaxation mechanisms involved, with important consequences for engineering nonlinear optical response and hot-carrier-assisted photochemistry.

Charge Separation between Pt Co-catalysts and Plasmonic Au in Pt–Au/C3N4 Photocatalysts

“…The lifetime of Pt–Au/C 3 N 4 ALD shows the lowest fluorescence decay, 7.90 ns, which is longer than that of Au–Pt/C 3 N 4 PD (6.64 ns) and Au/C 3 N 4 (5.80 ns), indicating that the carrier separation efficiency of Pt–Au/C 3 N 4 ALD is apparently improved. This result is consistent with the photoluminescence quenching study, suggesting the high carriers transfer rate when the Pt co-catalysts selectively deposited on the Au NPs by ALD. − The reduction in the photoluminescence intensity and the extension of carrier lifetime signify that Pt decreases the quantity of hot carriers in Au NPs which are available for radiative recombination through the charge transfer from Au to Pt.…”

Atomistic Theory of Hot-Carrier Relaxation in Large Plasmonic Nanoparticles

“…While the aforementioned modeling efforts allowed important insights into the relaxation dynamics of hot-carriers, it is important to note that they all employed highly simplified models of the NP electronic structure: they often use simple spherical well models or assume that the NP’s density of states is the same as that of a bulk-free electron gas. As a consequence, such models cannot capture hot-carriers generated in d bands, describe the dependence of the electronic structure on the exposed facets of the NP, or describe plasmonic heterostructures atomistically, all of which can play a critical role. − …”

Solvent-induced local environment effect in plasmonic catalysis

“…16 In addition, solvents, such as methanol as a hole scavenger, and solute species (e.g., OH − , O 2 ) dissolved in the solvents may also perturb the charge transfer at the interface. [17][18][19] Furthermore, the electrical double layer at the solid-liquid interface can also reduce the Schottky barrier to promote charge injection. 20 Apart from these mentioned multiple effects of the solvents in plasmonic catalysis, the effect of solvents on the interfacial excitation energy and charge transfer between the plasmonic metal and the molecular reactants remains to be explored.…”