Plasmonic Cavity-Catalysis by Standing Hot Carrier Waves

Plasmon Hot Carriers: Cognizing, Utilizing, and Regulating

The localized surface plasmon resonance (LSPR) effect can effectively utilize and transform solar energy, which is an ideal candidate to solve the energy crisis. In particular, plasmon hot carriers generated by LSPR effect are the focus of current research because their energy characteristics are higher than the Fermi level, which can easily promote the chemical reaction on the catalysts and improve the photoelectric performance of the optoelectronic devices. In this review, the generation of hot carriers and their decay pathways under different nano-structured models are discussed, and their unique significance is highlighted. Meanwhile, recent research advances in cognizing the plasmon hot carriers, the role of hot carriers in various applications, and the regulating mechanism of hot carriers in the nanostructure are discussed in depth. In addition, the limitations and challenges of the current research on plasmon hot carriers are presented, and prospects for the future are proposed.

Manipulating Nonadiabatic Dynamics by Plasmonic Nanocavity

In recent years, plasmonic nanocavities have emerged as powerful tools for controlling and enhancing light-matter interactions on the nanoscale. This study explores the role of plasmonic nanocavities in manipulating nonadiabatic dynamics, particularly in systems where fast electronic transitions are crucial. By coupling molecular states to the plasmonic resonances of metallic nanocavities, we demonstrate that the local electromagnetic fields generated by plasmons can significantly influence the rates and pathways of nonadiabatic transitions, including electron transfer and excitation relaxation processes. Using the Floquet quantum master equation (FQME) and Floquet surface hopping (FSH) methods that we previously developed, we find that plasmonic nanocavities can enhance nonadiabatic effects by tuning the plasmonic coupling strength, the molecule-metal interaction strength, and the material properties. These approaches offer a new perspective for predicting molecular dynamics in ultrafast processes. Our findings pave the way for designing novel plasmonic devices capable of controlling electron and energy transfer in chemical reactions, optoelectronic applications, and quantum information processing.

Asynchronous wide-field transient absorption microscopy

We have developed a new, to the best of our knowledge, femtosecond laser spatiotemporal imaging technique, named asynchronous wide-field transient absorption microscopy (AWTAM), which does not require phase synchronization between an optical chopper and a complementary metal-oxide-semiconductor (CMOS) camera. By presenting a theoretical scheme, an image reconstruction algorithm, and experimentally imaging the photocarrier diffusion process in a 2D layered semiconductor, our technique has been comprehensively demonstrated. Our technique is widely applicable for fundamental photo-physical research and industrial applications, with the advantages of lower hardware cost as well as higher imaging speed.

Quantifying Ultrafast Energy Transfer from Plasmonic Hot Carriers for Pulsed Photocatalysis on Nanostructures

Photocatalysis with plasmonic nanostructures has lately emerged as a transformative paradigm to drive and alter chemical reactions using light. At the surface of metallic nanoparticles, photoexcitation results in strong near fields, short-lived high-energy "hot" carriers, and light-induced heating, thus creating a local environment where reactions can occur with enhanced efficiencies. In this context, it is critical to understand how to manipulate the nonequilibrium processes triggered by light, as their ultrafast (femto- to picoseconds) relaxation dynamics compete with the process of energy transfer toward the reactants. Accurate predictions of the plasmon photocatalytic activity can lead to optimized nanophotonic architectures with enhanced selectivity and rates, operating beyond the intrinsic limitations of the steady state. Here, we report on an original modeling approach to quantify, with space, time, and energy resolution, the ultrafast energy exchange from plasmonic hot carriers (HCs) to molecular systems adsorbed on the metal nanoparticle surface while consistently accounting for photothermal bond activation. Our analysis, illustrated for a few typical cases, reveals that the most energetic nonequilibrium carriers (i.e., with energies well far from the Fermi level) may introduce a wavelength-dependence of the reaction rates, and it elucidates on the role of the carriers closer to the Fermi energy and the photothermally heated lattice, suggesting ways to enhance and optimize each contribution. We show that the overall reaction rates can benefit strongly from using pulsed illumination with the optimal pulse width determined by the properties of the system. Taken together, these results contribute to the rational design of nanoreactors for pulsed catalysis, which calls for predictive modeling of the ultrafast HC-hot adsorbate energy transfer.

Nanoscale Manipulation of Exciton-Trion Interconversion in a MoSe2 Monolayer via Tip-Enhanced Cavity-Spectroscopy

Emerging light-matter interactions in metal-semiconductor hybrid platforms have attracted considerable attention due to their potential applications in optoelectronic devices. Here, we demonstrate plasmon-induced near-field manipulation of trionic responses in a MoSe2 monolayer using tip-enhanced cavity-spectroscopy (TECS). The surface plasmon-polariton mode on the Au nanowire can locally manipulate the exciton (X0) and trion (X-) populations of MoSe2. Furthermore, we reveal that surface charges significantly influence the emission and interconversion processes of X0 and X-. In the TECS configuration, the localized plasmon significantly affects the distributions of X0 and X- due to the modified radiative decay rate. Additionally, within the TECS cavity, the electric doping effect and hot electron generation enable dynamic interconversion between X0 and X- at the nanoscale. This work advances our understanding of plasmon-exciton-hot electron interactions in metal-semiconductor-metal hybrid structures, providing a foundation for an optimal trion-based nano-optoelectronic platform.